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CatalogⅠ Introduction Ⅱ What is a PNP Transistor?Ⅲ PNP Transistor SymbolⅣ PNP Transistor ConstructionⅤ How a PNP Transistor WorksⅥ PNP Transistor ConfigurationⅦ PNP Transistor CircuitⅧ Applications of PNP TransistorsⅨ Benefits of PNP TransistorsⅩ How to Identify a PNP Transistor Ⅺ PNP vs NPN TransistorⅫ Frequently Asked Questions About PNP Transistor Ⅰ IntroductionPNP transistors are Bipolar Junction Transistors (BJT). The PNP transistor has a completely different structure than the NPN transistor. In the PNP transistor structure, the two PN-junction diodes are reversed with regard to the NPN transistor, so that two P-type doped semiconductor materials are separated by a thin layer of N-type doped semiconductor material. The majority current carriers in a PNP transistor are holes, while electrons are the minority  current carriers  . The polarity  of all supply voltages  applied to the PNP transistor are inverted. The current sinks into the base terminal in PNP,  Because the PNP is a current-controlled device, the modest base current may regulate the huge emitter-collector current. Ⅱ What is a PNP Transistor?PNP transistors are transistors that have one n-type material doped with two p-type materials. It is a device that is powered by current. The modest quantity of base current regulated both the emitter and collector currents. In the PNP transistor, two crystal diodes are linked back to back. The emitter-base diode is on the diode's left side, while the collector-base diode is on the diode's right side. The majority of the carriers in the PNP transistors make up the current in the hole. The movement of holes inside the transistor generates current, while the flow of electrons in the transistor's leads generates current. The PNP transistor switches on when a tiny current flows through its base. In a PNP transistor, current passes from the emitter to the collector. The letter of the PNP transistor indicates the voltage required by the transistor's emitter, collector, and base. The base of a PNP transistor has always been negative in proportion to the emitter and collector. In a PNP transistor, electrons are drawn from the base terminal. Before reaching the collector ends, the electricity that enters the base is amplified. Ⅲ PNP Transistor SymbolThe letters PNP stand for PNP Transistor. The symbol for a PNP transistor is illustrated in the diagram below. The current flows from the emitter to the collector in a PNP transistor, as represented by the inward arrow. PNP Transistor Symbol Ⅳ PNP Transistor ConstructionThe diagram below depicts the structure of a PNP transistor. The emitter and base junctions are biased forward, whereas the collector and base junctions are biased reverse. Electrons are drawn to the battery by the forward biased emitter, causing current to flow from the emitter to the collector. Doped semiconductors can be found in three different parts of a transistor. There is an emitter on one side and a collector on the other. The term "base" refers to the area in the center. The three components of the transistor are detailed in detail below. PNP Transistor Construction EmitterIt is the emitter's responsibility to provide charge carriers to the receiver. In order to supply a large number of charge carriers, the emitter is constantly forward biased when compared to the base. BaseThe base of a transistor is the part in the middle that connects the emitter and collector via two PN-junctions. Because the base-emitter junction is forward biased, the emitter circuit has a low resistance. The collector circuit has a high resistance due to the reverse bias of the base-collector junction. CollectorThe collector is the portion of the emitter on the opposite side that gathers the charges. The collector is always prejudiced in the opposite direction when it comes to collecting. Because it has two PN-junctions, the transistor is comparable to two diodes. The junction between the emitter and the base is referred to as an emitter-base diode or emitter diode. A collector-base diode, also known as a collector diode, is the junction between the collector and the base. Ⅴ How a PNP Transistor WorksA voltage source (VEBpositive )'s terminal is connected to the Emitter (P-type), while the negative terminal is connected to the Base terminal (N-type). As a result, the Emitter-Base junction is biased forward. Furthermore, the positive terminal of a voltage source (VCB) is linked to the Base terminal (N-type), while the negative terminal is attached to the Collector terminal (P-type). As a result, the Collector-Base junction is biased in reverse. How a PNP Transistor Works Because it is connected in forward bias, the depletion region at the Emitter-Base junction is narrow as a result of this sort of bias. Because the Collector-Base junction is in reverse bias, the depletion zone at the Collector-Base junction is quite large. The Emitter-base junction is biased forward. As a result, a substantial number of holes from the emitter pass through the depletion region and enter the Base. At the same time, only a few electrons reach the Emitter from the base and recombine with the holes. The amount of electrons present in the Base layer is equal to the number of holes lost in the emitter. However, the amount of electrons in the base is relatively modest due to the fact that it is a very lightly doped and thin region. As a result, practically all Emitter holes will cross the depletion area and penetrate the Base layer.  The current will flow via the Emitter-Base junction due to the movement of the holes. This current is referred to as Emitter current (IE). To flow the Emitter current, the holes are the predominant charge carriers.  The leftover holes that do not recombine with electrons in the Base will proceed to the Collector. Because of the perforations, the Collector current (IC) travels via the Collector-Base area. Ⅵ PNP Transistor Configuration(Note: For a PNP transistor, the arrow represents the emitter and the typical current flow, "in.") The accompanying diagram depicts the structure and terminal voltages of an NPN transistor. The PNP Transistor has characteristics that are very similar to their NPN bipolar cousins, except that the polarities (or biasing) of the current and voltage directions are reversed for any of the three possible configurations discussed in the first tutorial, Common Base , Common Emitter, and Common Collector. Because the Base terminal of a PNP transistor is always biased negatively with respect to the Emitter, the voltage between the Base and Emitter (VBE) is now negative at the Base and positive at the Emitter. In addition, the Emitter supply voltage is positive in relation to the Collector ( VCE ). As a result, for a PNP transistor to conduct, the Emitter must always be more positive than both the Base and the Collector. PNP Transistor Connection As depicted, the voltage sources are coupled to a PNP transistor. This time, the Emitter is connected to the supply voltage VCC via a load resistor, RL, limiting the maximum current flowing through the device attached to the Collector terminal. The Base voltage VB is biased negative in relation to the Emitter and is connected to the Base resistor RB, which is utilized to limit the maximum Base current once again. In order for the Base current to flow in a PNP transistor, the Base must be more negative than the Emitter (current must leave the base) by approximately 0.7 volts for a silicon device or 0.3 volts for a germanium device, with the formulas used to calculate the Base resistor, Base current, or Collector current being the same as those used for an equivalent NPN transistor and is given as. IC = IE -IBIC = β·IBIB = IC / β The basic difference between an NPN and a PNP transistor is the proper biasing of the transistor junctions, as current and voltage polarities are always opposed to each other. So, in the aforementioned circuit, Ic = Ie - Ib since current must leave the Base. In general, PNP transistors may substitute NPN transistors in most electronic circuits; the main difference is the polarity of the voltages and current flow directions. Ⅶ PNP Transistor CircuitThe Output Characteristics Curves of a PNP transistor are essentially similar to those of an equivalent NPN transistor, with the exception that they are rotated by 180o to accommodate for reverse polarity voltages and currents (that is for a PNP transistor, electron current flows out of the base and collector towards the battery). To determine the operating points of PNP transistors, the same dynamic load line can be drawn onto the I-V curves. Ⅷ Applications of PNP TransistorsPNP transistors are used to source current, i.e. current flows out of the collector.PNP transistors are used as switches.These are used in the amplifying circuits.PNP transistors are used when we need to turnoff something by push a button. i.e. emergency shutdown.Used in Darlington pair circuits.Used in matched pair circuits to produce continuous power.Used in heavy motors to control current flow.Used in robotic applications. Ⅸ Benefits of PNP TransistorsTo source current, PNP Transistors are used.Because it generates a signal that is referenced to the negative power supply rail, it simplifies the circuit design.In comparison to NPN Transistors, they produce less noise.It's smaller than other transistors and can be used in Integrated Circuits, just like the others. Ⅹ How to Identify a PNP Transistor PNP transistors are generally identified by their structure. When comparing the structures of NPN and PNP transistors, we see various discrepancies. Another way to recognize a PNP transistor is that it is normally in OFF for positive voltage and ON for tiny output current and negative voltage at its base with respect to the emitter. However, to identify them most efficiently, we use another technique that involves calculating the resistance between the three terminals, such as the base, emitter, and collector. For recognizing both NPN and PNP transistors, we have some standard resistance values. Each pair of terminals must be tested for resistance values in both directions, resulting in a total of six tests. This method is quite beneficial for quickly identifying the PNP transistor. We can now observe how each pair of terminals operates. Terminals for Emitter-BaseThe emitter-base area functions like a diode, but it only conducts in one direction. Terminals for Collector-BaseThe collector-base area also functions as a diode, conducting current in only one way. Terminals for Emitter-CollectorThe emitter-collector area has the appearance of a diode, yet it does not conduct in any direction. Let us now look at the resistance value table to identify both NPN and PNP transistors, as illustrated in the table below. Between Transistor TerminalsPNPNPNCollectorEmitterRHIGHRHIGHCollectorBaseRLowRHIGHEmitterCollectorRHIGHRHIGHEmitterBaseRLowRHIGHBaseCollectorRHIGHRLowBaseEmitterRHIGHRLow Then we can define a PNP Transistor as generally "OFF," but a modest output current and a negative voltage at its Base (B) relative to its Emitter (E) will turn it "ON," allowing a big Emitter-Collector current to flow. When Ve is substantially bigger than Vc, PNP transistors conduct. In other words, a Bipolar PNP Transistor will only conduct if both the Base and Collector terminals are polarized against the Emitter. Ⅺ PNP vs NPN TransistorThe following table summarizes the main distinctions between PNP transistors and NPN transistors: PNP TransistorNPN TransistorStructureIt has one N-type and two P-type semiconductors.It has two N-type and one P-type semiconductor.Direction of currentThe current will flow through the emitter to the collector.The current will flow through the collector to the emitter.Majority charge carrierHolesElectronMinority charge carrierElectronsHolesSwitching time SlowerFasterJunction biasingEmitter-base junction is in reverse bias and collector-base junction is in forward bias.Emitter-base junction is in forward bias and collector-base junction is in reverse bias.Collector-emitter voltageNegativePositiveEmitter arrowPointed inPointed out Ⅻ Frequently Asked Questions About PNP Transistor1. Where are PNP transistors used?Amplification circuits employ PNP transistors. Darlington pair circuits employ PNP transistors. Robotic applications make advantage of PNP transistors. PNP transistors are used to control current flow in high-power applications. 2. How can PNP transistor be controlled?To begin, in order to switch on the PNP transistor, the voltage on the base must be lower than the voltage on the emitter. It's customary for a basic circuit like this to connect the emitter to the plus from your power supply. This manner, you can tell what voltage is on the emitter. 3. How does a PNP transistor turn on?PNP and NPN Transistors' Terminal Resistance Values Then we can define a PNP Transistor as generally "OFF," but a modest output current and a negative voltage at its Base (B) relative to its Emitter (E) will turn it "ON," allowing a big Emitter-Collector current to flow. 4. Can I replace PNP with NPN?If you remember one simple rule, you can use NPN and PNP transistors interchangeably. A bipolar transistor is effectively two diodes connected back to back, with the base serving as the common connection. 5. How does a PNP junction work?A PNP transistor is a bipolar junction transistor composed of an N-type semiconductor sandwiched between two P-type semiconductors. A PNP transistor has three terminals: a Collector (C), an Emitter (E), and a Base (B) (B). The PNP transistor functions similarly to two PN junction diodes connected back to back. 

Comprehensive understanding of TVS diode operating principles, types, selection and applications1 Introduction: What is a TVS DiodeIn today's era of increasingly miniaturized and complex electronic devices, Transient Voltage Suppression (TVS) diodes have become indispensable components in the protection of electronic systems. Transient voltage threats—such as Electrostatic Discharge (ESD), Electrical Fast Transients (EFT), and induced lightning strikes—can cause catastrophic damage to sensitive electronic components within microseconds, leading to equipment failure or even safety hazards.TVS diodes are semiconductor devices specifically designed to protect electronic circuits from these transient voltage threats. As the name suggests, they effectively suppress transient voltages by diverting excess energy and limiting the voltage across the protected device. According to the latest market data, the global TVS diode market is projected to grow from $2.44 billion in 2025 to $3.45 billion by 2033, with a compound annual growth rate of 4.37%."The annual loss in electronic equipment due to electrostatic discharge (ESD) and voltage transients is estimated to be approximately $5 billion. Proper transient protection measures can reduce this loss by more than 80%." — Electronic Manufacturers AssociationThis article will comprehensively introduce the working principles, types, parameter selection, application scenarios, and comparisons with other protection devices of TVS diodes, helping electronic engineers and enthusiasts correctly understand and apply this important circuit protection component. Whether you are an experienced designer or a beginner, this guide will provide you with in-depth insights and practical knowledge about TVS diodes.2 Working Principle of TVS Diodes2.1 Basic ConceptsTVS diodes are essentially specially designed avalanche breakdown diodes, specifically used for handling transient overvoltage events. Their working principle is based on the avalanche breakdown characteristics of semiconductor PN junctions. Under normal operating conditions, TVS diodes present a high impedance state, barely affecting the normal operation of the protected circuit. When the applied voltage exceeds its preset breakdown voltage (VBR), the diode rapidly enters a conduction state, diverting excess current while maintaining its terminal voltage at a safe level (known as the clamping voltage VC).TVS diodes need to satisfy three key characteristics to work effectively:Fast response time: TVS diodes typically respond at the sub-nanosecond level (<1ns), which is crucial for capturing extremely brief voltage spikes.High surge current capability: Ability to withstand large currents (typically from a few amperes to hundreds of amperes) for short periods without degradation or damage.Precise clamping characteristics: Maintaining a relatively fixed voltage in the conducting state to ensure the protected circuit is not damaged.2.2 Internal StructureStructurally, TVS diodes differ fundamentally from standard PN junction diodes. They typically employ larger chip areas and thicker epitaxial layers to withstand higher transient power. The typical structure of TVS diodes includes:Unidirectional TVS: Basically a large-area PN structure, optimized for single-direction overvoltage protectionBidirectional TVS: Usually consisting of two back-to-back unidirectional TVS structures, providing bidirectional protectionThe electrical characteristics of TVS diodes are controlled by their semiconductor doping concentration and junction area, thereby achieving the desired breakdown voltage and clamping voltage.2.3 Protection MechanismThe protection mechanism of TVS diodes can be broken down into the following stages:Normal Operating State: When the circuit operates within its nominal voltage range, the TVS diode is in a high impedance state with minimal leakage current (typically in the microampere range or even lower).Transient Event Occurrence: When a transient voltage appears and reaches the reverse breakdown voltage (VBR) of the TVS diode, the diode quickly enters the avalanche breakdown state.Current Diversion: In the conduction state, the TVS diode diverts excess transient current while maintaining its terminal voltage at the clamping voltage (VC) level.Energy Absorption: The TVS diode absorbs the energy from the transient event and dissipates it as heat.Return to Normal: After the transient event ends, the TVS diode automatically returns to its high impedance state without requiring reset or replacement.Professional TipThe response speed of TVS diodes (typically <1ns) is much faster than traditional protection devices like fuses or varistors (typically at the microsecond level). This makes them particularly suitable for protecting modern semiconductor devices that are extremely sensitive to transient events, such as MOSFETs, microcontrollers, and communication interfaces.3 Types of TVS Diodes3.1 Unidirectional TVS DiodesUnidirectional TVS diodes are primarily used in direct current (DC) circuits to protect against transient voltages in either the positive or negative direction (depending on the installation direction). They provide standard diode forward conduction characteristics (typically around 0.7V forward voltage drop) in one direction and avalanche breakdown protection in the opposite direction.Key characteristics include:Suitable for unipolar signal lines and DC power linesLower clamping voltage compared to equivalent bidirectional TVSTypical applications include DC power lines, MOSFET gate protection, etc."When selecting a unidirectional TVS diode, ensure its reverse working voltage is slightly higher than the maximum operating voltage of the system, which ensures it won't conduct under normal operating conditions." — Circuit Protection Design Manual3.2 Bidirectional TVS DiodesBidirectional TVS diodes are essentially two unidirectional TVS connected back-to-back in series, providing similar protection characteristics in both directions. They are particularly suitable for alternating current (AC) signal lines and data lines that require protection in both positive and negative directions.The main applications of bidirectional TVS diodes include:AC signal and power linesBipolar signals (such as audio signals)Data communication lines (such as RS-232, RS-485, CAN bus, etc.)I/O port protectionCompared to unidirectional TVS, bidirectional TVS typically have symmetrical breakdown voltages in both directions, making them particularly suitable for protecting AC signals and bipolar data lines.3.3 TVS Diode ArraysTVS diode arrays are devices that integrate multiple TVS diodes in a single package, designed specifically for protecting multi-line interfaces (such as USB, HDMI, Ethernet, etc.). They typically come in small packages suitable for space-constrained applications.The main advantages of TVS arrays:Multi-channel protection, reducing PCB space usageSimplified design and layoutMore consistent protection characteristicsReduced overall wiring complexity and parasitic effectsCommon TVS array packages include SOT-23-6/8, SOIC-8, QFN, and ultra-small DFN/CSP packages designed for portable electronic devices and high-density PCB designs.Important NoteWhen selecting TVS arrays, consider the coupling effects between channels. High-quality TVS array designs should ensure that a transient event on one channel does not affect other channels through parasitic coupling.4 TVS Diode Selection Parameters4.1 Key ParametersSelecting suitable TVS diodes requires consideration of multiple key parameters, which collectively determine the device's protection capability and application range:ParameterSymbolDefinitionSelection ConsiderationReverse Working VoltageVRWMMaximum reverse voltage that the device can continuously withstandShould be greater than the system's maximum operating voltageReverse Breakdown VoltageVBRVoltage at which the device begins to enter avalanche stateTypically 1.1~1.5 times VRWMClamping VoltageVCMaximum voltage at specific test currentShould be lower than the voltage tolerance of the protected componentPeak Pulse CurrentIPPMaximum transient current the device can withstandShould be greater than the current of expected transient eventsPeak Pulse PowerPPPMaximum transient power the device can absorbDepends on application scenario and expected threat levelReverse Leakage CurrentIRLeakage current at VRWMShould be low enough to not affect normal operationJunction CapacitanceCJParasitic capacitance of TVS diodeLow capacitance types should be selected for high-speed signal linesProfessional TipFor high-speed data lines (such as USB 3.0, HDMI, PCIe, etc.), selecting low-capacitance TVS diodes is crucial. Higher parasitic capacitance can lead to signal integrity issues and data transmission errors. Modern low-capacitance TVS diodes typically have capacitance values as low as 0.5pF.4.2 Selection GuideSelecting appropriate TVS diodes is key to ensuring effective protection. Here is a systematic selection process:Determine the system's maximum operating voltage: Analyze the normal voltage range of the protected circuit, including possible fluctuations.Select reverse working voltage (VRWM): Should be slightly higher than the system's maximum operating voltage, ensuring the TVS doesn't conduct during normal operation.Determine the voltage tolerance of the protected device: This will determine the required upper limit of clamping voltage (VC).Evaluate transient threat types and levels: Determine the required protection level based on application environment (industrial, automotive, consumer electronics, etc.) and applicable standards (IEC 61000-4-2/4/5, etc.).Determine peak pulse current/power requirements: Should be based on worst-case transient event analysis.Consider signal bandwidth requirements: High-speed signals require low-capacitance TVS devices.Evaluate space limitations and heat dissipation conditions: Select appropriate packaging.Reference selection criteria for different applications:Power line protection: Select VRWM slightly higher than maximum power supply voltage, consider higher power handling capabilityData line protection: Prioritize low-capacitance models, ensure signal integrityAutomotive electronics: Select TVS diodes that comply with AEC-Q101 certification, wide operating temperature range, and high energy handling capabilityPortable devices: Consider small package size and low leakage current characteristics4.3 Package TypesTVS diode packages are diverse, ranging from power devices to miniature surface-mount packages. Selecting the appropriate package is crucial for meeting space, power, and heat dissipation requirements:Package TypeSize CharacteristicsPower Handling CapabilityTypical ApplicationsDO-214 (SMA, SMB, SMC)Medium-sized SMD package400W - 5000WPower lines, industrial interface protectionSOD-123/SOD-323Small SMD package150W - 500WMedium to low power applications, space-constrained scenariosSOT-23/SOT-363Small multi-pin package100W - 300WMulti-channel protection, data linesDFN/CSPUltra-small package50W - 200WMobile devices, wearable devicesQFN/SOICMulti-channel array packageVaries by number of channelsMulti-line interface protection (USB, HDMI, etc.)Important NoteWhen selecting a package, consider power dissipation capability simultaneously. For high-power applications, ensure the PCB design provides sufficient heat dissipation paths, such as increasing copper foil area, adding thermal vias, etc. Improper heat dissipation can significantly reduce the actual protection capability of TVS diodes.5 TVS Diode Application Areas5.1 Industrial ApplicationsIndustrial environments typically face harsh electrical conditions, including induced lightning, motor switching transients, power surges, etc. TVS diodes play a crucial role in these applications:Industrial automation systems: Protecting PLC inputs/outputs, sensor interfaces, and communication busesFactory equipment: Protecting motor drivers, frequency converters, and control circuitsMeasuring instruments: Ensuring stability and accuracy of precision measurement circuitsFieldbus systems: Protecting industrial communication interfaces such as RS-485, PROFIBUS, DeviceNet, etc.Industrial applications typically require TVS diodes with high power handling capability and wide operating temperature range. In these applications, reliability and durability are primary considerations.5.2 Automotive ElectronicsAutomotive electronic systems are exposed to harsh electrical and environmental conditions, requiring special protection measures. Automotive-grade TVS diodes typically need to meet AEC-Q101 standards and withstand a wide range of temperatures and electrical transients.Major automotive applications include:Engine Control Units (ECUs): Protecting sensor inputs and actuator control linesIn-vehicle networks: CAN bus, LIN bus, and FlexRay communication line protectionPower management systems: Protecting power conversion and distribution circuitsSafety systems: Airbag controllers, ABS, and ADAS systemsInfotainment systems: Protecting audio/video interfaces and USB connections"As the level of automotive electronics continues to increase, especially with the popularization of 48V systems and electric vehicles, TVS protection in automotive environments has become more important than ever before." — Automotive Electronics Design Magazine5.3 Consumer ElectronicsIn consumer electronic products, TVS diodes are mainly used to protect interface circuits and sensitive components from ESD and power transients. These applications typically have strict requirements for size, cost, and performance.Mobile devices: Protection for charging interfaces, audio interfaces, and data ports in smartphones and tabletsPersonal computers: Protection for USB, HDMI, Ethernet, and other I/O interfacesHome appliances: Protection for control circuits and power inputsWearable devices: Protection for battery management and communication interfacesIn consumer electronics applications, small size, low capacitance, and low cost are important selection factors. As interface speeds continue to increase, low-capacitance TVS diodes are becoming increasingly important.5.4 Telecommunications EquipmentCommunications equipment is frequently exposed to harsh outdoor environments and is susceptible to lightning strikes and power transients. These applications require robust protection solutions:Base station equipment: Protection for RF paths, power inputs, and control linesNetwork switching equipment: Protection for Ethernet ports and backplane connectionsLine interface protection: DSL, T1/E1 line interface circuitsPower line protection: AC/DC converter input protectionCommunication applications typically require compliance with specific standards such as IEC 61000-4-5 (surge), GR-1089-CORE, and ITU K.20/K.21 standards, which influence the selection of TVS diodes.TVS Diode AdvantagesNanosecond-level response timeLow clamping voltageNo degradation design (can withstand thousands of overvoltage events)Bidirectional protection capability (bidirectional type)No follow current (auto-recovery)TVS Diode LimitationsLimited power handling capability (compared to large varistors)Higher cost (especially high-power models)Parasitic capacitance may affect high-speed signalsDifficulty handling extremely high-energy eventsInstallation direction sensitive (unidirectional type)6 TVS Diode Market TrendsThe TVS diode market is experiencing significant growth and technological evolution, driven by multiple factors:According to market research data, the global TVS diode market is expected to grow from $2.45 billion in 2025 to $3.45 billion by 2033, with a compound annual growth rate of 4.37%. The following are the main trends affecting the market:Miniaturization and Low Capacitance: As electronic devices continue to miniaturize, demand for ultra-small package TVS diodes is rapidly growing. Simultaneously, high-speed interfaces (such as USB 3.2, HDMI 2.1, PCIe 5.0, etc.) are driving a surge in demand for low-capacitance TVS diodes.Automotive Electronics Growth: The rise of electric vehicles, autonomous driving features, and advanced driver assistance systems (ADAS) has greatly promoted the demand for high-performance automotive-grade TVS diodes. According to forecasts, automotive electronics will be the fastest-growing segment in the TVS diode market, with an expected growth rate of 13% between 2025-2033.Proliferation of IoT Devices: With over 75 billion IoT devices expected to be deployed globally by 2026, there is a massive demand for low-power, small-form-factor TVS protection solutions.Integrated Protection Solutions: There is an increasing trend toward multifunctional protection components that integrate TVS diodes with other protective elements (such as PTCs, fuses, common mode chokes, etc.) into a single package, providing comprehensive protection.New Material Technologies: Wide bandgap semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) are emerging in high-performance TVS diodes, offering higher temperature tolerance and greater energy handling capabilities.In terms of regional market distribution, the Asia-Pacific region (especially China, South Korea, and Taiwan) is expected to account for the largest market share, primarily due to the region's strong electronics manufacturing industry and rapidly developing automotive industry. North American and European markets will be driven by high-end applications and stringent regulatory environments."As electronic devices become smaller and more complex, there is growing demand for 'one-stop' integrated protection solutions. This is driving the development of multifunctional TVS devices that not only provide overvoltage protection but also integrate EMI filtering and surge limiting functions." — Semiconductor Industry AnalystTechnological development directions include TVS diodes with higher energy density, lower clamping ratio (ratio of clamping voltage to reverse working voltage), and specialized protection solutions for fast charging applications. The industry is also focused on manufacturing process innovations to reduce production costs and improve reliability.7 Comparison of TVS Diodes with Other Protection Devices7.1 TVS Diodes vs VaristorsTVS diodes and varistors (MOVs) are two commonly used overvoltage protection devices, each with their own advantages and disadvantages:TVS Diode AdvantagesFaster response time (<1ns vs. MOV's ~25ns)More precise and stable clamping voltageNo performance degradation (can withstand thousands of overvoltage events)Lower leakage currentSmaller size (especially modern SMD packages)Varistor AdvantagesCan handle higher transient energy (under comparable volume conditions)Generally lower costHigher voltage ratings available (up to several kilovolts)Inherently bidirectional operationBetter suited for AC line protectionApplication scenario comparison:TVS diodes are suitable for: Protecting sensitive electronic equipment, high-speed data lines, applications requiring precise clamping voltageVaristors are suitable for: AC power line protection, high-energy surge protection, cost-sensitive applications, primary/secondary surge protection7.2 TVS Diodes vs Zener DiodesAlthough TVS diodes and Zener diodes operate based on similar physical principles, they have fundamental design differences and application scenarios:CharacteristicTVS DiodeZener DiodePrimary FunctionTransient overvoltage protectionVoltage regulation and referenceChip DesignLarge area PN junction to handle transient powerSmall area structure optimized for stabilityPower HandlingHigh peak power, low continuous powerLow peak power, moderate continuous powerResponse TimeExtremely fast (sub-nanosecond)Fast (nanosecond level)Temperature CoefficientTypically higherCan be very low (temperature compensated types)While Zener diodes can serve as simple protection elements in some low-power applications, TVS diodes are optimized specifically for handling high-energy transient events, providing more reliable protection capabilities.Important NoteDo not use Zener diodes for protection scenarios requiring high energy handling capability. Transient events exceeding their power handling capacity, even for short durations, will cause permanent damage to the Zener diode, leaving the protected circuit exposed to danger.7.3 Protection Device Comparison TableThe following table summarizes the key characteristics comparison of common overvoltage protection devices:CharacteristicTVS DiodeVaristorGas Discharge TubeMultilayer Varistor CeramicResponse Time< 1ns (extremely fast)~25ns (fast)>100ns (slow)~1ns (extremely fast)Clamping PrecisionHighMediumLowMedium-highPower CapacityMediumHighVery highLowLeakage CurrentVery lowHigherExtremely lowRelatively lowLifespan/DurabilityVery longSignificant degradationLimited number of operationsRelatively longCapacitanceMedium to low (special models)MediumVery lowHigherMain ApplicationsData lines, DC power, secondary protectionAC power, primary protectionCommunication lines, primary protectionLow-power signal linesIn practical applications, multi-layer protection strategies are often adopted, combining different types of protection devices to achieve optimal performance. For example, using gas discharge tubes or varistors as primary protection, followed by TVS diodes as secondary protection, to achieve the best protection effect.8 PCB Design Practical TipsProper use of TVS diodes in PCB design is critical for effective protection. Here are some key design considerations:Placement: TVS diodes should be placed as close as possible to the interface or device being protected. Ideally, the TVS should be the first component "seen" by signals or power lines coming from external connections.Layout Best Practices:Keep TVS connections to ground as short and direct as possible to reduce parasitic inductanceUse wider PCB traces to reduce impedanceAvoid connecting TVS to ground planes through narrow viasUse multiple parallel vias when necessary to lower impedanceGrounding Strategy: For high-speed signal protection, TVS diodes should be connected to a low-impedance ground plane, avoiding shared current return paths with sensitive analog or digital grounds.Thermal Management: High-power TVS diodes may require additional thermal management measures. Design sufficient copper area for heat dissipation, and when necessary, use thermal vias to connect to inner or bottom layer copper.Pro TipWhen protecting high-speed differential pairs (such as USB 3.0, HDMI, PCIe, etc.), select differential pair TVS diodes specifically designed for these applications, and ensure that the layout maintains symmetry to preserve signal integrity.For particularly sensitive circuits or applications in harsh environments, consider multi-stage protection schemes:Use high-power TVS or varistors as the first stage of protection to handle most of the energyUse precision TVS diodes as the second stage of protection to precisely control residual voltageAdd RC filters if necessary to further attenuate high-frequency components9 Frequently Asked QuestionsQ: What's the difference between TVS diodes and regular diodes?A: While both are semiconductor devices based on PN junctions, TVS diodes are specifically designed to handle high-energy transient events, featuring larger junction areas, higher power handling capabilities, and precise breakdown voltage characteristics. Regular diodes are primarily used for rectification or signal processing and are not suitable as protection devices.Q: How do I determine the power requirements for a TVS diode?A: Power requirements depend on the characteristics of the expected transient events. Consider the peak voltage of the transient, its duration, and possible energy levels. Typically, you should refer to industry standards applicable to your specific application (such as IEC 61000-4-5 surge standard or IEC 61000-4-2 ESD standard) to determine worst-case energy levels, then select a TVS diode with sufficient safety margin.Q: Do TVS diodes affect high-speed signal integrity?A: Yes, the parasitic capacitance of TVS diodes can affect high-speed signal integrity. For high-speed interfaces such as USB 3.0, HDMI 2.0, PCIe, etc., specialized low-capacitance TVS diodes (typically <1pF) should be selected. Additionally, PCB layout is critical for minimizing signal integrity issues.Q: How do I choose between unidirectional and bidirectional TVS diodes?A: For unipolar signal lines and DC power lines, unidirectional TVS diodes are typically used, offering lower clamping voltage in one direction. For signal lines that may experience voltage in both directions (such as AC signals, data lines, audio lines, etc.), bidirectional TVS diodes should be used. If uncertain, bidirectional models are generally the safer choice, although unidirectional types can provide lower clamping voltage.Q: Do TVS diodes have a "service life"? Do they degrade over time?A: Unlike varistors, TVS diodes do not significantly degrade when used within their rated parameters. They can withstand thousands of transient events within their rated range without performance deterioration. However, transient events exceeding their ratings may cause damage or performance degradation to the TVS diode.10. Conclusion and Future OutlookTVS diodes, as key components in the protection of modern electronic devices, provide effective defense against transient voltage threats. Their fast response time, excellent clamping performance, and reliability make them ideal for protecting increasingly sensitive and complex electronic systems.As electronic devices continue to evolve toward higher speeds, smaller sizes, and lower power consumption, TVS protection technology continues to evolve as well. Future trends in TVS diode technology include:Lower clamping ratio: Allowing protection of low-voltage circuits with smaller voltage marginsUltra-low capacitance designs: Supporting next-generation ultra-high-speed interfaces (such as USB4, PCIe 6.0, etc.)Higher power density: Providing more protection in smaller packagesMultifunctional integrated protection: Combining EMI filtering, common mode suppression, and ESD protection functionsWide bandgap semiconductor materials: Using SiC and GaN to provide better temperature performance and reliabilityWhen selecting and applying TVS diodes, a comprehensive understanding of key parameters, awareness of the specific application requirements and constraints, and adherence to good design practices are crucial for achieving effective circuit protection. As electronic systems become more complex and sensitive, professional circuit protection design will continue to be a key factor in ensuring product reliability and durability."In electronic design, neglecting transient protection is often a major source of system reliability issues. Proper selection and application of TVS diodes is not just a technical consideration but a critical investment in ensuring product quality and customer satisfaction." — Electronic System Reliability HandbookThrough this comprehensive introduction to TVS diodes, we hope to provide electronic engineers and designers with the necessary knowledge for selecting and using these critical protection devices to create more reliable and durable electronic systems.About the AuthorElectronics engineer with over 10 years of experience in circuit design and electronic protection. Specializing in power management, signal integrity and circuit protection, he has assisted many companies in designing reliable electronic systems.Extended ReadingDiodes Understanding Switching Diodes: Principles, Advantages, and Applications5 Items You Need to Know About DiodesDiode Rectifier Basics and Circuit Types OverviewLast Updated: 2025-04-28 body { font-family: 'Arial', sans-serif !important;; line-height: 1.6 !important; color: #333; background-color: #f9fafb; } .container { max-width: 1200px; margin: 0 auto; padding: 20px; } h2, h3, h4 { font-weight: 700; margin-top: 1.5em; margin-bottom: 0.5em; color: #1a56db; } } h2 { font-size: 2rem; border-bottom: 2px solid #e5e7eb; padding-bottom: 0.5rem; } h3 { font-size: 1.5rem; color: #2563eb; } h4 { font-size: 1.25rem; color: #3b82f6; } p { margin-bottom: 1.5rem; } .quote { background-color: #e0f2fe; border-left: 4px solid #3b82f6; padding: 1rem; margin: 1.5rem 0; border-radius: 0 6px 6px 0; } table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; } table, th, td { border: 1px solid #e5e7eb; } th, td { padding: 0.75rem 1rem; text-align: left; } th { background-color: #f3f4f6; font-weight: 600; } tr:nth-child(even) { background-color: #f9fafb; } ul, ol { margin-bottom: 1.5rem !important;; padding-left: 2rem !important;; } ul li, ol li { margin-bottom: 0.5rem !important;; } .pro-tip { background-color: #d1fae5; border-radius: 6px; padding: 1rem; margin: 1.5rem 0; border-left: 4px solid #10b981; } .important-note { background-color: #fee2e2; border-radius: 6px; padding: 1rem; margin: 1.5rem 0; border-left: 4px solid #ef4444; } .toc { background-color: #f3f4f6; padding: 1.5rem; border-radius: 6px; margin-bottom: 2rem; } .toc ul { list-style-type: none; padding-left: 0; } .toc ul ul { padding-left: 1.5rem !important;; } .toc li { margin-bottom: 0.5rem !important;; } .toc a { text-decoration: none; color: #2563eb; } .toc a:hover { text-decoration: underline; } .author-section { background-color: #f3f4f6; border-radius: 6px; padding: 1.5rem; margin-top: 3rem; display: flex; align-items: center; } .author-section img { width: 80px; height: 80px; border-radius: 50%; margin-right: 1.5rem; margin-top: 0; margin-bottom: 0; } .pros-cons { display: flex; gap: 20px; margin: 1.5rem 0; } .pros, .cons { flex: 1; padding: 1rem; border-radius: 6px; } .pros { background-color: #d1fae5; } .cons { background-color: #fee2e2; } .faq-item { margin-bottom: 1.5rem; } .faq-question { font-weight: bold; color: #1e3a8a; margin-bottom: 0.5rem; }

Ⅰ Introduction In this project, we will use hardware ultrasonic sensor and  Raspberry Pi 3, Software Python code. Not everyone is familiar with ultrasonic sensor and Raspberry Pi3. Therefore, in the front part ,we will introduce some basic knowledge about ultrasonic sensor and Raspberry Pi3. This is conducive to understanding the project better. And then, we will have a look at the project of wiring Ultrasonic Sensor  (HC-SR04) with Raspberry Pi3 Catalog Ⅰ Introduction Ⅱ Ultrasonic Sensor Related Video Ⅲ Basic Guide to Ultrasonic Sensor  3.1 What is an ultrasonic sensor? 3.2 How Ultrasonic Sensors Work？ 3.3 Using Multiple Sensors & Avoiding Disruption 3.4 How are Ultrasonic Sensors Used? Ⅳ Basic Guide to Raspberry Pi3 4.1 What is  Raspberry Pi3? 4.2 What Is the Raspberry Pi3 Capable of？ 4.3 How do I Get Started With the Raspberry Pi 3? 4.4 How Is the Raspberry Pi 3 Different From Its Predecessors? Ⅴ Ultrasonic Sensor (HC-SR04) + Raspberry Pi3 5.1 Hardware 5.2 Wire Setup 5.3  Breadboard  5.4 Software Ⅵ FAQ     Ⅱ Ultrasonic Sensor Related Video   Ultrasonic Sensor Video Description: Connecting the Ultrasonic Sensor( HC-SR04) to the Raspberry Pi to measure distance. Equipment you need One 1 kilo-Ohm resistor One 2 kilo-Ohm resistor 8 Female-Male Jumper Wire   Ⅲ Basic Guide to Ultrasonic Sensor  3.1 What is an ultrasonic sensor? An ultrasonic sensor is a device that uses ultrasonic sound waves  to determine the distance between two objects. An ultrasonic sensor employs a transducer to send and receive ultrasonic pulses that relay information about the proximity of an object. High-frequency sound waves  reflect off boundaries, resulting in distinct echo patterns. Fihure1: Ultrasonic Sensor   3.2 How Ultrasonic Sensors Work？ Ultrasonic sensors  operate by emitting a sound wave at a frequency  that is above the range of human hearing. To receive and transmit an ultrasonic sound, the sensor's transducer functions as a microphone. Like many others, our ultrasonic sensors  use a single transducer to send a pulse and receive the echo. The sensor calculates the distance to a target by measuring the time elapsed between sending and receiving the ultrasonic pulse. Figure2:How Ultrasonic Sensors Work This module's operation is straightforward. It emits a 40kHz ultrasonic pulse that travels through the air and, if it encounters an obstacle or object, bounces back to the sensor. The distance can be calculated by multiplying the travel time by the speed of sound. Ultrasonic sensors  are an excellent solution for detecting clear objects. Because of target translucence, applications that use infrared sensors.  for example, struggle with this particular use case for liquid level measurement. Ultrasonic sensors  detect objects regardless of color, surface, or material for presence detection (unless the material is very soft like wool, as it would absorb sound.) Ultrasonic sensors  are a reliable choice for detecting transparent and other items where optical technologies may fail.   3.3 Using Multiple Sensors & Avoiding Disruption When putting multiple sensors  into an application, it's critical to connect them in a way that prevents crosstalk and other interference. To prevent the ultrasonic signals from your sensor from being disrupted, keep the face of the ultrasonic transducer clear of any obstructions. Common obstructions include: DirtSnowIceOther Condensation We recommend our Self Cleaning sensors  for this application. Our self-cleaning function is designed to run continuously for the self-cleaning feature to be active. They are intended specifically for applications requiring condensation resistance in high moisture environments. Please keep in mind that the Self Cleaning function is not intended to remove dirt from the transducer's surface. Its purpose is to clear the transducer's face of moisture so that it can operate normally.   3.4 How are Ultrasonic Sensors Used? Our ultrasonic distance, level, and proximity sensors  are frequently used in conjunction with microcontroller platforms such as Raspberry Pi,  ARM , PIC,  Arduino , Beagle Board, and others. Ultrasonic sensors send sound waves  toward a target and measure the time it takes for the reflected waves to return to the receiver to determine their distance. This sensor is an electronic device that transmits ultrasonic sound waves  to measure the distance to a target and then converts the reflected sound into an electrical signal. Our sensors are frequently used as proximity detectors. Ultrasonic sensors are also used in obstacle detection systems and in manufacturing. Our ShortRange sensors provide the option for closer range detection in situations where a sensor that ranges objects as close to 2cm is required. These are also designed with very low power requirements in mind, as well as environments requiring noise rejection.   Ⅳ Basic Guide to Raspberry Pi3 4.1 What is  Raspberry Pi3? The  Raspberry Pi 3 Model B is the most recent model of the $35 Raspberry Pi computer. The Pi isn't your typical machine; in its most basic form, it lacks a case and is simply a credit-card-sized electronic board, similar to those found inside a PC or laptop but much smaller.   4.2 What Is the Raspberry Pi3 Capable of？ Surprisingly large. For starters, the Pi 3 can be used as a low-cost desktop, media center, retro gaming console, or router, as shown below. That, however, is only the tip of the iceberg. There are hundreds of projects where people have used the Raspberry Pi to build tablets, laptops, phones, robots, smart mirrors, take pictures on the edge of space, and run experiments on the International Space Station.   Figure3:The Raspberry Pi 3.   4.3 How do I Get Started With the Raspberry Pi 3? One thing to keep in mind is that the Pi is merely a bare board. You'll also need a power supply, a monitor or TV,  HDMI  cables to connect to the monitor, and a mouse and keyboard. After connecting all of the cables, the simplest way for new users to get up and running on the Pi is to download the NOOBS (New Out-Of-Box Software) installer. Once the download is complete, follow the instructions to learn how to install an operating system on the Raspberry Pi. The installer makes it simple to install various operating systems, though the official OS Raspbian is a good choice for first-time users—other operating systems are listed below. Raspbian's appearance and feel should be familiar to any desktop computer user. The operating system, which is constantly being updated, recently received a graphical makeover and now includes an optimized web browser, an office suite, programming tools, educational games, and other software.   4.4 How Is the Raspberry Pi 3 Different From Its Predecessors? The Raspberry Pi 3 quad-core processor is both faster and more capable than its predecessor, the Raspberry Pi 2. For those interested in benchmarks, the Pi 3's CPU—the board's main processor—outperforms the Pi 2 by roughly 50-60% in 32-bit mode, and is 10x faster than the original single-core Raspberry Pi (based on a multi-threaded CPU benchmark in SysBench). Real-world applications will see performance increases ranging from 2.5x for single-threaded applications to more than 20x when video playback is accelerated by the chip's NEON engine when compared to the original Pi. Unlike its predecessor, the new board can play 1080p MP4 video at 60 frames per second (with a bitrate of around 5400Kbps), further enhancing the Pi's media center credentials. That's not to say that all videos will playback this smoothly; performance will vary depending on the source video, the player used, and the bitrate. With built-in Wi-Fi and Bluetooth, the Pi 3 also supports wireless internet right out of the box. The most recent board can also boot directly from a USB-attached hard drive or a pen drive, as well as from a network-attached file system via PXE, which is useful for remotely updating a Pi and sharing an operating system image between multiple machines.   Ⅴ Ultrasonic Sensor (HC-SR04) + Raspberry Pi3 A distance measurement is required or advantageous for many (outdoor) projects. These small modules, which start at 1-2 dollars and can measure distances of up to 4-5 meters using ultrasound, are surprisingly accurate. The connection and control are demonstrated in this tutorial. 5.1 Hardware Raspberry pi 3Ultrasonic Sensor(s) - HC-SR04A set of resistors for each sensor you are connecting330Ω and 470ΩJumper wires to connect the sensor(s) to the piBreadboard to connect the sensor(s) to the pi   5.2 Wire Setup Pins The sensor has four (labeled) pins that must be connected to the Raspberry Pi's pins. Pin 2 to VCC (5v - power)Pin 6 to GND (ground)Pin 12 receives a TRIG signal (GPIO18) The ECHO resistor 330 - Attach it to Pin 18 at one end (GPIO24) - Connect it to Pin6 as well, using a 470 resistor (ground). - This is done because GPIO pins can only withstand a maximum voltage of 3.3V.   5.3  Breadboard  As shown in the circuit diagram, connect the sensor to the pi using a breadboard. By replicating this exact setup on the other half of the breadboard, an additional sensor can be connected to the pi. Connect the VCC and GND pins together (2 and 6) For the TRIG and ECHO connections, use any two GPIO pins. Just make sure to include the correct GPIO pins in your code. Figure4: Connecting resistors and jumper wires between sensors and pi       5.4 Software Python Create a new script Figure5:Creating a new script in Python 3 Choose Menu → Programming → Click on Python 3 to create a new scriptWhen you run the code, the script below will print the distance of the object in front of the sensor.Because this code is easily manipulated to add another sensor, all variables have a "1" after them.Simply copy and paste each section of code, renaming variables with a "2."Make sure to connect a TRIG2 and an ECHO2 to the pi's two new GPIO Pins and to mirror the circuit diagram on the other half of the breadboard. import  RPi.GPIO  as GPIO import time GPIO.setmode(GPIO.BCM) TRIG1 = 18 ECHO1 = 24 #print ("Distance Measurement In Process") GPIO.setup(TRIG1, GPIO.OUT) GPIO.output(TRIG1, False) GPIO.setup(ECHO1, GPIO.IN) #print ("Waiting For Sensor1 To Settle") time.sleep(.1) GPIO.output(TRIG1, True) time.sleep(0.00001) GPIO.output(TRIG1, False) while GPIO.input(ECHO1) == 0:     pass     pulse_start1 = time.time() while GPIO.input(ECHO1) == 1:     pass     pulse_end1 = time.time() pulse_duration1 = pulse_end1 - pulse_start1 distance1 = pulse_duration1 * 17150 distance1= round(distance1, 2) print ("Distance1:",distance1, "cm") time.sleep(10) GPIO.cleanup()   Make a copy of your script and save it as ultrasonic distance.py. Go to File and click on Save as In the Save in field, navigate to the C: drive and then select a folder to save in. In the File name field, enter ultrasonic distance.py. Select All Files in the Save as type field. Click the Save button. To run the script, use the terminal. Clicking on the monitor icon at the top of the screen will launch the terminal. Enter cd "folder name" to change directory to your pythonpractice folder, then enter ultrasonic distance.py to run your program. Ⅵ FAQ 1. Does HC-SR04 need resistor? If you are using the ultrasonic transmitter from a HC-SR04 , I think you will find it needs between 5 and 12V to drive it. So you don't need a resistor you actually need a transistor circuit to provide the greater voltage under the control of the gpio. 2. What is the range of HC SR04? 2 cm to 400 cm The HC-SR04 ultrasonic sensor uses SONAR to determine the distance of an object just like the bats do. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package from 2 cm to 400 cm or 1” to 13 feet. 3. Is ultrasonic sensor digital or analog? The output of the Ultrasonic Sensor is digital. Two of the four pins are forsupplying power to it, one is for sending an echo signature to it, and the other is for getting output from it. 4. What is ultrasonic sensor HC-SR04? The HC-SR04 Ultrasonic Distance Sensor is a sensor used for detecting the distance to an object using sonar. ... The HC-SR04 uses non-contact ultrasound sonar to measure the distance to an object, and consists of two ultrasonic transmitters (basically speakers), a receiver, and a control circuit. 5. What are the types of ultrasonic sensor? All together there are four types of ultrasonic sensors, classified by frequency and shape: the drip-proof type, high-frequency type, and open structure type (lead type and SMD type). 6. Is HC SR04 analog or digital? One of them is digital and the other is analog. We choose to use two sensors that measure: The UltraSonic Sensor (HC-SR04): Digital Sensor.

CatalogIntroductionⅠ What is a Microcontroller（MCU）?Ⅱ The History of the Microcontroller (MCU)Ⅲ The Classification and Application of MCUⅣ China MCU Technology and Well-known ManufacturersⅤ  The Basic Functions of MCUⅥ Learning Methods - Using MCUⅦ Six Main Dimensions of MCU Products for Future ImprovementⅧ Programming of MCUⅨ Summary of the MCU Programming EngineerⅩ How to Develop MCU Ⅺ 5 Tips to Solve the Questions About the MCU CrystalⅫ Summary of Chip OperationFAQIntroductionA microcontroller (MCU) is a small computer built on a single metal-oxide-semiconductor (MOS) integrated circuit (IC) chip. A microcontroller is made up of a CPU  (processor core), memory, and programmable input/output peripherals. On chip, a small amount of RAM, as well as ferroelectric RAM, NOR flash, or OTP ROM , is commonly included. Microcontrollers  , in contrast to microprocessors  used in personal computers  or other general-purpose applications, are designed for embedded applications and are made up of a number of discrete chips. This article will delve deeper into the MCU.Ⅰ What is a Microcontroller（MCU）? Microcontroller UnitThe microcontroller unit (MCU) appropriately reduces the frequency and specifications of the CPU  and integrates peripheral interfaces such as memory, counter, USB, A/D conversion, UART, PLC, and DMA. At the same time, even the LCD driver circuit is integrated on a single chip to form a chip-level computer, which can be controlled in different combinations for different applications, such as mobile phones, PC peripherals, remote controls, automotive electronics, industrial stepping motors, machines The control of the arm, etc., can be seen in the MCU.Figure 1 MCU componentsⅡ The History of the Microcontroller (MCU)Microcontroller Unit has a short history, but it has evolved quickly. Its generation and development are roughly synchronized with that of microprocessors  (CPUs). Since Intel Corporation of the United States first introduced 4-bit microprocessors  in 1971, its evolution can be roughly divided into five stages. The following is an overview of the development of Intel's MCU.1971-1976  The initial stage of MCU developmentIn November 1971, Intel introduced the Intel 4004, a 4-bit microprocessor with an integration level of 2000 transistors/chips and equipped with RAM, ROM, and shift registers, which served as the first MCS-4 microprocessor. The Intel 8008 8-bit microprocessor was introduced, followed by other 8-bit microprocessors  from various companies.1976-1980  Low-performance MCU stageThe MCS-48 series, introduced by Intel Corporation in 1976, has a monolithic structure that integrates an 8-bit CPU.  an 8-bit parallel I/O interface, an 8-bit timer/counter, RAM, and ROM on a semiconductor chip. Its addressing range is limited (no more than 4 KB), there is no serial I/O, the RAM and ROM capacity is limited, and the interrupt system is simple, but its functions can meet the needs of general industrial control and intelligent instruments and meters.1980~1983  High-performance MCU stageHigh-performance 8-bit microcontrollers introduced at this stage typically include serial ports, multi-level interrupt processing systems, and multiple 16-bit timers/counters. The capacity of the on-chip RAM and ROM  is increased, and the addressing range can reach 64 KB. A/D conversion interfaces are also available on individual chips. 1983~late 1980s  16-bit microcontroller stage.In 1983, Intel introduced a high-performance 16-bit microcontroller MCS-96  series. The chip integration level was as high as 120,000 transistors/chips due to the use of the most recent manufacturing process.1990sCPUs are developing to a higher level in all directions, such as integration, function, speed, reliability, and application fields. Ⅲ The Classification and Application of MCUMCUs are classified into two types based on their memory type: those with no on-chip ROM  and those with on-chip ROM,  The chip without on-chip ROM  must be used externally with EPROM (typically 8031); the chip with on-chip ROM  is classified as on-chip EPROM (typically 87C51), MASK on-chip mask ROM  (typically 8051), on-chip Flash (typically 89C51), and other types.MCUs are classified into two types based on their intended use: general-purpose and special-purpose. It is classified into4, 8, 16, and 32-bit MCUs based on the width of the data bus and the number of data bytes that can be processed at the same time.Figure 2 MCU product category At present, the most widely used MCU market in China is in the consumer electronics  field, followed by the industrial field and the automotive electronics  market. Consumer electronics  include home appliances, televisions, game consoles, and audio and video systems. Industrial fields include smart homes, automation, medical applications, and new energy generation and distribution. The automotive field includes automotive powertrains and safety control systems. Industrial MCU Industrial MCU products  are primarily used for motor control operation, data acquisition control, and other functions in motor control, instrumentation, low-voltage power distribution, power tools, industrial robots, and other application scenarios.Figure 3 Electric-Vehicle-ChargerThe number of MCU devices is increasing as the complexity of industrial equipment increases. Consider industrial robots: at least ten MCU products  are used in a single industrial robot.Home Appliance MCU MCU is widely used in household appliances, mainly used to realize system control, motor control, panel display control, and other functions.The home appliance market is mainly divided into small household appliances and everyone electricity, small household appliances including kitchen appliances (microwave oven, induction cooker, soybean milk machine, etc.), household appliances (vacuum cleaner, electric fan, electric heater, etc.), personal life small household appliances (electric toothbrush, hairdryer, etc.), everyone electricity mainly for air conditioning, refrigerator, washing machine, and other white appliances.Figure 4 Induction-heating-cooker-app-block-diagramAt the moment, 32-bit MCUs have become the market's mainstream due to their higher specifications and performance, as well as their constantly decreasing cost, and are widely used in automotive electronics.  industrial control/medical, and other fields; however, there are still a large number of application scenarios requiring simple control, and low-value MCUs have cost advantages, so they continue to occupy a large market.BitApplication4Calculator, auto instrument, auto anti-theft device, pager, wireless phone, CD player, LCD dynamic controller, children's toys, scales, chargers, Tire gauge, thermometer, remote control, etc8Electrical appliances, ammeter, motor controller, electric toy machine, pager, fax machine, telephonograph, keyboard and USB, etc16Mobile phones, digital cameras and video recorders, etc32Smart home, IoT, motor and frequency conversion control, security monitoring, fingerprint identification, touch keys, Modem, GPS, STB, Workstation, ISDN telephone, laser printer and color fax machine, etc64Advanced workstation, multimedia interactive system, advanced TV game instrument, advanced terminal, etc.According to IC Insights, the global MCU market is about 16.4 billion dollars in 2019 and could reach about 20 billion dollars by 2023.The scale of China's MCU market was about 25.6 billion yuan in 2019, accounting for about 26% of the global market, with a compound growth rate of 9% from 2015 to 2019.In terms of the global market, the auto circuit accounts for 33% of the global MCU market. According to IC Insights data, the automotive MCU market space will reach $8.1 billion in 2023, the overall growth rate is considerable; At the moment, 32-bit MCUs have become the market's mainstream due to their higher specifications and performance, as well as their constantly decreasing cost, and are widely used in automotive electronics.  industrial control/medical, and other fields; however, there are still a large number of application scenarios requiring simple control, and low-value MCUs have cost advantages, so they continue to occupy a large market.Figure 5  MCU Market StructureFrom the perspective of pattern, the top five global automotive MCU market shares in 2020 were Renesas, NXP, Infineon, Texas Instruments and Microchip, accounting for 87% in total.Ⅳ China MCU Technology and Well-known ManufacturersMCU market is still dominated by overseas leaders, and Chinese high-quality manufacturers are gradually making breakthroughs in the segmented fields, and their share is expected to increase rapidly under the background of accelerated localization in China.The global MCU market is expected to grow further, with the global MCU market size reaching $16.4 billion in 2019 and $20 billion in 2023.On the demand side, improvements in automotive electrification, accelerated IoT  penetration, increased demand for intelligent frequency conversion in home appliances, rapid iteration of wearable devices, and steady growth in industrial control continue to drive the rapid growth of the MCU industry. (Using MCU as an example, the global market compound growth rate from 2020 to 2023 is 7.7 percent, and the market space is expected to be 8.1 billion dollars by 2023)On the supply side, the MCU industry is experiencing a continuous shortage due to the epidemic in 2020. Infineon, NXP.  and ST  , as well as other overseas MCU large factories, have appeared several times to dozens of times the price, with delivery times of more than 50 weeks; persistent shortages are expected to last at least through the end of 2021 and the first quarter of 2022.In terms of circuit barriers, the requirements of automobile circuits in the MCU downstream field are the highest, followed by industrial and home appliance circuits, and the relative requirements of consumer electronics  are slightly lower, according to MCU product environmental temperature, yield, and service life, and other parameters.According to the industry competition pattern, Chinese MCU manufacturers have a low market share, benefit from accelerated replacement due to stock shortages in the short term, and have ample room for improvement in the long term:The global MCU market is more concentrated, with a microchip, ST  MICROELECTRONICS, Renesas, TI, NXP  , Infineon, and other manufacturers occupying more than 80% of the market share; China's MCU market is approximately 25 billion yuan, and the total market share of domestic MCU manufacturers is less than 12%, primarily concentrated in the consumer market, which has ample room for expansion.The shortage of goods leads to the acceleration of the pace of China's MCU manufacturers, in the automotive, industrial, and consumer circuit, the pace of China's MCU certification continues to accelerate. Renesas Electronics - the world's first automotive MCU manufacturer Renesas was founded in 2003 by the merger of Hitachi Semiconductor division and Mitsubishi Electric Semiconductor division. Its main business covers automotive, industrial, communications, and other fields. Renesas is the world's first automotive MCU manufacturer, accounting for 30% of the automotive MCU market in 2020.Renesas MCU has a complete product line covering EV/HEV, powertrain, electric vehicle, vehicle dashboard, vehicle network, chassis control, ADAS, and other application fields.Microchip technology -8 bit MCU main features, acquisition of Atmel to supplement the strength of 32 bit MCUMicrochip Technology Corporation (Microchip) was founded in 1989, Microchip technology is the world's leading supplier of single-chip and analog semiconductors. The company's main business is the microcontroller, memory products, analog interface, and mixed information products, technology licensing, and so on.The products are mainly used in embedded control systems and IoT-related industries, including data processing, Medical Internet + (IoT), smart city, Industry 4.0, intelligent healthcare, etc. Major customers include Intel, Dell, Lockheed Martin, HP, Boeing, etc. STST -ARM architecture MCU king ST was founded in 1987, its products are mainly used in automotive products, computer peripherals, communication systems, consumer products, industrial automation control systems, and other aspects. Its major customers include Apple, blackberry, Bosch, Cisco, Conti, HP, Nokia, Obata, Samsung, and Western Digital.MCU vehicle grade products accounted for 32.13% of the company's revenue. St holds 8.5% of the current MCU market and is the leader in the segmented 32bitMCU  market.ST has been deeply engaged in the automotive semiconductor field for many years, and the company has a complete industrial chain, its products have a very high-cost performance ratio, and occupy a dominant position in the MCU of vehicle regulation level. Its customers include Nissan, Audi, SAIC, Tesla, and many other companies. NXP - the world's leading automotive MCU manufacturer NXP Semiconductor was founded in 2006. It was formerly the semiconductor division of Philips. NXP's main business is MCU, MPU, and other products, which can be widely used in automotive electronics  , industrial control, smart city, smart home, and wearable products. Its MCU/MPU based on the S32 automotive platform has obvious advantages in safety and efficiency and has been adopted by mainstream OEMs around the world.The industry's first crossover MCU was independently developed by NXP: I. MX RT series. Such products have been recognized by many Internet platforms (such as Amazon) for their high integration, cost performance, and security.NXP's acquisition of Freescale (founded by MOTOROLA) in 2015 gives it a deeper presence in the automotive industry. In 2020, 47% of its revenue came from vehicle MCU. At present, the company accounts for 27.8% of the global automotive MCU industry, ranking second in the world. NXP  provides complete semiconductor solutions for intelligent vehicles including automotive entertainment systems, Advanced Driver Assistance Systems (ADAS). Sino Wealth Electronics - China's largest home appliance MCU manufacturer Sino Wealth Electronic Ltd. is an MCU integrated circuit design company, the main products include 8-bit Flash MCU, 8-bit OTP/Mask MCU, 16-bit  DSP , 4-bit OTP/Mask MCU, widely used in household appliances, automotive, industrial control, security, and other fields;In the field of small household appliances, the company's competitors are mainly ABOV from Korea and Holtek from Taiwan. In the field of white household appliances, the company's competitors are mainly from Europe and America, including Renesas, NEC, TI, STM, and so on. Ⅴ The Basic Functions of MCUInternal-function diagramFor most MCUs, the following functions are the most common and basic. The description methods for different MCUs may differ, but the essence is essentially the same.1. Timer: Although there are many different types of Timers, they can be divided into two categories. The first is a Timer with a fixed time interval, which means that its timing is set by the system and cannot be controlled by the user program. The system only provides a few different types of Timers. The user program is given a fixed time interval, such as 32Hz, 16Hz, 8Hz, and so on. Because Timers of this type are relatively common in 4-bit MCUs,they can be used to implement clock, timing, and other related functions.The other type is Programmable Timer. The timing of this type of Timer can be controlled by the user's program. The control methods include the selection of the clock source, the selection of the prescale number, and the setting of the preset number, etc. There are Most MCUs have all three at the same time, and some may have one or both of them. This kind of Timer application is very flexible, and the actual use is also ever-changing. One of the most common applications is to use it to achieve PWM  output.Since the clock source can be freely selected, such Timers are generally combined with the Event Counter.2. IO port: Any MCU has a certain number of IO ports. Without IO ports, the MCU will lose the channel of communication with the outside world. According to the configurable situation of the IO port, it can be divided into the following types:Pure input or pure output : This type of IO port is determined by the MCU hardware design, and can only be input or output, and cannot be set in real-time by software.3. Directly read and write IO port: For example, the IO port of MCS-51 belongs to this type of IO port. When the read IO port command is executed, it is an input port; when the write IO port command is executed, it is automatically an output port.Program programming to set the direction of input and output: the input or output of this type of IO port is set by the program according to the actual needs, the application is more flexible, and can realize some bus-level applications, such as12C bus, various LCD, LED Driver control bus, etc.When using the IO port, this point must be kept in mind: for the input port, there must be a clear level signal to ensure that it cannot be floated (this can be achieved by adding a pull-up or pull-down resistor); and for the output port, the output state level must be Considering its external connection, it should be ensured that there is no source current or sink current in Standby or static state.External interrupts: External interrupts are a basic function of most MCUs. They are commonly used for real-time signal generation, data sampling, and state detection. Rising edge, falling edge, and level triggering are all interrupting methods. In most cases, the external interrupt is handled via the input port. If it is an IO port, the interrupt function will only be enabled when it is set as an input port; if it is set as an output port, the external interrupt function will be automatically closed (with some exceptions in ATMEL's ATiny series, where the output port can also trigger the interrupt function). The application of external interrupt is as follows:Detection of external trigger signals: One is based on real-time requirements, such as thyristor control, detection of sudden signals, and so on, while the other is based on power savings.Measurement of signal frequency:: To ensure that the signal is not missed, an external interrupt is the best option.Decoding data: To reduce design costs in the field of remote control applications, it is frequently necessary to use software to decode various encoded data, such as Manchester and PWM encoding.Button detection and system wake-up: In order for the MCU to enter the Sleep state, it must be woken up via an external interrupt. The most basic form is a button, and the level change is caused by the button's action.4. Communication interface: The communication interface provided by MCU generally includes SPI interface, UART. I2C interface, etc., which are described as follows:SPI interface: This type of interface is the most basic communication method provided by most MCUs. Its data transmission is controlled by a synchronous clock. The signals include SDI (serial data input), SDO (serial data output), SCLK (serial clock), and Ready signal; in some cases, there may be no Ready signal; this type of interface can work in Master mode or Slave mode, the popular saying is to see who provides the clock signal, the party providing the clock is the Master, and the opposite party It is Slaver.UART（Universal Asynchronous Receive Transmit）：It belongs to the most basic asynchronous transmission interface. Its signal lines only have two Rx and Tx lines. The basic data format is: Start Bit + Data Bit(7-bits/8-bits) + Parity Bit(Even， Odd or None) + Stop Bit(1~2Bit). The time occupied by one bit of data is called Baud Rate .For most MCUs, the length of data bits, data check mode (odd check, even check or no check), Stop Bit length and Baud Rate can be flexibly set through program programming. Certainly. The most common way of this type of interface is to communicate with the serial port of the PC.I2C interface: I2C  is a data transmission protocol developed by Philips. It also uses two signals to implement: SDAT (serial data input and output) and SCLK (serial clock). The biggest advantage is that multiple devices can be attached to this bus, and they can be identified and accessed through addresses; one of the biggest advantages of the I2C  bus is that it is very convenient to use software to implement through the IO port, and the data rate of its transmission is completely controlled by SCLK. To control, it can be fast or slow, unlike the UART  interface, which has strict rate requirements.5. Watchdog: Watchdoga basic configuration of most MCUs, can only allow the program to reset it but not close it (some are set when the program is burned in, such as Microchip PIC  series MCUs), while some MCUs are It is determined by a specific method whether it is turned on or not. For example, in Samsung's KS57 series, as long as the program accesses the Watchdog  register, it is automatically turned on and cannot be turned off again. Generally speaking, the reset time of the watchdog can be set by the program. The most basic application of Watchdog  is to provide a self-recovery ability for the MCU to crash due to unexpected failure.Ⅵ Learning Methods - Using MCUThe basic principles and functions of any MCU are similar. The only difference is the configuration and quantity of its peripheral function modules and the instruction system.For the instruction system, although it seems to be different in form, it is only a difference in symbols, and the meanings it represents, the functions to be completed, and the addressing modes are similar.To learn about an MCU, the first thing you need to know is its ROM space, RAM space, number of IO ports, number of timers and timing methods, peripheral function modules (Peripheral Circuit) provided, interrupt sources, operating voltage, and power consumption, etc.After understanding these MCU Features, the next step is to compare the functions of the selected MCU with the required functions of the actual project development and clarify which resources are currently required and which are not used in this project.For the functions that need to be used in the project but are not provided by the selected MCU, it is necessary to carefully understand the relevant information of the MCU, to use an indirect method to achieve it. For example, the developed project needs to communicate with the COM port of the PC, and If the selected MCU does not provide a UART  port, it can be implemented through external interrupts.For the resources needed for project development, you need to carefully understand and read the Manua*, while for the unneeded function modules, you can ignore or browse. For MCU learning, the application is the key and the main purpose.For beginners or designers who use this MCU for the first time, they may encounter a lot of ambiguous descriptions of the functions of the MCU. For this kind of problem, there are two ways to solve it, one is to write a special verification program to understand the functions described in the data; the other can be ignored for the time being. Leave it to modify and improve when debugging. The former method is suitable for projects with loose time and beginners, while the latter method is suitable for those who have some experience in single-chip development or when the project schedule is more urgent.Don't take the time to learn the command system in particular. The instruction system is simply a logical description symbol. During programming, you can only check the relevant instructions in accordance with the logic requirements of the program. As your programming skills improve, you will become more proficient in the instruction system.Ⅶ Six Main Dimensions of MCU Products for Future ImprovementStronger computing performance: MCU towards 500Mhz main frequency, MPU increase more processor cores;Additional wireless connection functions: More RF modules have been integrated.Low power consumption, high energy efficiency ratio: integrated analog chip, and low power analog peripheralsContinued support for hardware accelerators: high integration of algorithms and toolsSafety: improve anti-interference ability and safetyCost-effective: reduce costⅧ Programming of MCUThe programming of MCUs and PCs differ significantly. Although C-based MCU development tools are becoming more popular, assembly language remains the most concise and efficient programming language for designers who are efficient program code and like to use assembly.Circuit diagram to build your own microcontroller programmerThe basic framework for MCU programming is roughly the same, divided into the initialization part (the biggest difference between MCU programming and PC programming), the main program loop body, and the interrupt handler. as shown below:1.Initialization: The most basic and important step in the design of all MCU programs is an initialization, which generally includes the following:Mask all interrupts and set the stack pointer to In general, the initialization section does not want any interruptions to occur.Clearing the system's RAM and displaying the Memory: Although it is not always necessary, it is recommended to develop good programming habits for the sake of reliability and consistency, particularly to avoid accidental errors.IO port initialization: Set the input and output modes of the relevant IO port based on the project's application requirements. Set the pull-up or pull-down resistance for the input port, and the initial resistance for the output port.Interrupt setup: Enable and set interrupt trigger conditions for all interrupt sources required by the project, and close unnecessary interrupts that are not used.Initialization of other functional modules: For all peripheral functional modules of MCU that need to be used, corresponding Settings must be carried out according to the application requirements of the project. For example, Baud Rate, data length, verification mode and Stop Bit length should be set for communication of UART  , and clock source should be set for Programmer Timer. Frequency and Reload Data, etc.Initialization of parameters: after completing the initialization of MCU hardware and resources, the following is the initialization of some variables and data used in the program. This part of initialization needs to be designed according to the specific project and the overall arrangement of the program. For some applications that use EEPROM to store the number of prefab items, it is recommended to copy the relevant data to THE RAM of MCU during initialization to improve the speed of data access and reduce the power consumption of the system (in principle, access to the external EEPROM will increase the power consumption of the power supply).2.Main program loop body: Most MCUs run continuously for a long time, so their main program bodies are basically designed in a looping manner. For applications with multiple working modes, there may be many Each loop body is converted between each other through state flags. For the main program body, the following modules are generally arranged:Calculation procedures: Calculation procedures are generally time-consuming, so it is strongly opposed to processing in any interrupt, especially multiplication and division operations.Processing programs with low or no real-time requirements;Display transfer program: mainly for applications with external LED and LCD Driver.3. Interrupt handler: The interrupt program is mainly used to handle tasks and events with high real-time requirements, such as detection of external sudden signals, detection, and processing of buttons, timing counting, LED display scanning, etc.Under normal circumstances, the interrupt program should keep the code as concise as possible. For functions that do not need to be processed in real-time, the trigger flag can be set in the interrupt, and then the main program executes the specific transaction - this is very important, especially for low-power, low-speed MCUs, is necessary to ensure timely responses to all interrupts.4. There are various MCU processing methods for various task bodies.For example, for low-speed, low-power MCU (Fosc=32768Hz) applications, considering that such projects are handheld devices and use ordinary LCD, the response to buttons and display response requires high real-time performance, so generally Timed interrupts are used to process button actions and data display; for high-speed MCUs, such as Fosc>1MHz applications, since the MCU has enough time to execute the main program loop body at this time, it can only be interrupted at the corresponding Various trigger flags are set in the program, and all tasks are executed in the main program body.5. In MCU programming, special attention should be paid to:Avoid situations where the same variable or data is accessed or set in both the interrupt and the main body. The effective prevention method is to arrange the processing of such data in a module, and decide whether to execute the relevant operation of the data by judging the trigger flag; In other bodies (mainly interrupts), only the trigger flag is set where the processing of the data is required. This ensures that data execution is predictable and unique.Ⅸ Summary of the MCU Programming EngineerTo develop a good habit of summarizing, summarizing is not only a summary of their learning, but also a review and deepening of the learning process, but also to avoid the second error.Before writing the program, we should have a solid understanding of the project so that we can start with a solid idea and a general framework. It is critical to consider the layout and what makes the most sense. To determine which module should be completed first, specific steps for the module, how to name each function, and the relationship with other modules. Take a piece of paper and scribble down significant progress.For C language modular programming, we should first divide each module, a module programming, determine a sequence, and then write the next module based on the success of the previous one. When it comes to header files, write the module's header file after you've finished writing the module.Do not ignore the fact that the program must be unreasonable to comprehend its origins and find a solution. When looking for a source, it should be pertinent; you can search for relevant data on the Internet or consult with others. For example, the primary function of another project was incorporated into this project. Some functions are named multiple times. Step by step analysis of the cause, also according to the experimental phenomenon. When defining the port, the incorrect interface was selected. When you can't solve a problem, it's sometimes good to take a break. Things can go wrong no matter how simple they seemThe problems of code utilization efficiency, anti-interference, and MCU reliability continue to plague MCU application development. Ⅹ How to Develop MCU 1How to reduce program bugsThe following are the over-arching management parameters that should be considered during system operation in order to reduce program bugs.Physical parameters: These are primarily system input parameters that include excitation parameters, acquisition and processing operating parameters, and result parameters at the end of processing.Resource parameters: These are primarily the resources of the system's circuits, devices, and functional units, such as memory capacity, storage unit length, and stacking depth.These application parameters are frequently expressed as the application conditions of some single-chip microcomputers and functional units. The term "process parameter" refers to a parameter that changes in an orderly manner during the system's operation.2How to improve the efficiency of C language programming codeIt is an inevitable trend of the development and application of MCU to use C language to design MCU. If you are programming in C, it is best to be familiar with the C compiler you are using to achieve maximum efficiency. First test the number of statement lines in the assembly language corresponding to each C language compilation, so that you can clearly know the efficiency. When programming in the future, use the statement with the highest compilation efficiency. Each C compiler will have certain differences, so the compilation efficiency will also be different. The code length and execution time of an excellent embedded system C compiler is only 5-20% longer than the same functional degree written in assembly language.C language can be used for complex and time-critical projects, but the premise is that you are very familiar with the C language and C compiler of the MCU system and that you pay special attention to the data types and algorithms that the C compiler system can support. Although C is the most commonly used high-level language, the C language compilation system varies due to MCU manufacturer differences, particularly in the operation of some special function modules. As a result, if you don't understand these features, you'll have a lot of trouble debugging, which will result in lower execution efficiency than assembly language.3 How to Solve the MCU Anti-Interference ProblemThe most effective way to prevent interference is to remove interference sources and cut off interference paths, but this is often difficult to do, so we can only conclude that MCU's anti-interference ability is insufficient. While improving the anti-interference capability of hardware systems, software anti-interference has received increasing attention due to its flexible design, ability to save hardware resources, and high reliability.As for the program run fly, in fact, can also use software trap and watchdog to pull the program back to reset state, so the MCU software anti-interference is the most important to deal with the reset state.In most cases, MCU will have some sign registers that can be used to determine the reason for the reset; alternatively, you can bury some tokens in RAM yourself. Different reset causes can be determined in each program reset by judging these signs. You can also use different flags to jump directly to the corresponding program. In this manner, the program will run indefinitely, and the user will be unaware that it has been reset.4How to test the reliability of the MCU systemWhen a MCU system design is completed, there will be different test items and methods for different MCU system products, but some must be tested:lTest the completeness of the software functions of the MCUlPower-on and power-off testlAging testlTests such as ESD and EFT Sometimes, we can also simulate the damage that may occur in human use. For example, the contact port of the MCU system is intentionally rubbed with the human body or clothing fabric, thereby testing the antistatic ability. Use a high-power electric drill to work close to the MCU system to test the anti-electromagnetic interference ability.To sum up, the MCU has become an important aspect of the development and application of the computer.Most of the functions that must be realized by analog circuits or digital circuits in the past can now be realized by software methods using a single-chip microcomputer. This control technology in which software replaces hardware is also called micro-control technology, which is a revolution of traditional control technology.In addition, in the process of development and application, we must master the skills and improve the efficiency, so as to facilitate its wider use.Ⅺ 5 Tips to Solve the Questions About the MCU CrystalCrystal oscillator for MCUCommon causes of the crystal can not vibratePCB wiring error;Microcontroller quality issues;Crystal vibration quality issues;The load capacitance or matching capacitance does not match the crystal oscillator or the capacitor quality is incorrect;PCB board damp, resulting in impedance mismatch and inability to vibrate;The crystal oscillator circuit is too long;There is a line between the feet of crystal;Influence of peripheral circuit.You are advised to rectify faults one by one as follows: 1Remove the possibility of circuit error so that you can compare the recommended circuit of the corresponding type of microcontroller.2 Rule out the possibility of poor peripheral components; because peripheral components are nothing more than resistance and capacitance.3Rule out the possibility of using a crystal oscillator as a stop oscillator because you will not be experimenting with just one or two crystal oscillators.4Try changing the capacitor at both ends of the crystal; perhaps the crystal oscillator will begin to vibrate; please refer to the crystal oscillator capacitor size instructions.5In PC  B wiring, crystal oscillator circuit wiring should be as short as possible and as close to IC as possible, not between crystal oscillator feet. Ⅻ Summary of Chip OperationThe operation of the chip is mainly the operation of the registers in the chip. The registers in the chip have their unique address mapped on the memory, which is the operation of the corresponding address. To learn the chip, first look at the sequence diagram, then understand the corresponding registers, understand how to operate, define the required port (the program can recognize), write and read the operation program.Cross-sectional-views-of-chip-operationHow data is written to the chip, how it is read out, and through which port it is input or read.When connecting a chip through a bus, the first step is to understand the protocol of the bus. The chip connected to the I2c bus is controlled by the bus.1One 74HC595 lattice is used for column selection, and the other two are used for color selection. The lattice is equivalent to a set of diodes.The diode lights up only when one end is switched to a high level and the other to a low level. Just one end of the selection of different, bright different colors.Timer working mode selection: Set timer T1 in the high four digits and timer T0 in the low four digits. Then the last two characters of each mode set the working mode. When using interrupts, note that after entering the interrupt, the reset should be reset.2Serial port transceiver: Baud rate is generally set in mode 2 (automatic reloading initial value) because different devices have different data processing capabilities, the baud rate is set mainly to take care of low-speed devices and for communication between each other. The interrupt flag bit should be cleared by the software. When setting the serial port interrupt, either sending or receiving can enter the interrupt function, so pay attention to setting the interrupt function. (Self-sense generally sets a function, as the upper machine or lower machine).If you send interrupts, you have to figure out how to enter interrupts the first time, so you send them once and then you can enter interrupts. Only one byte can be sent at a time, and only after TI is set to one can the next byte be sent.3Pcf8591ad conversion, there are four channels of input, read PC  F8591, which channel, read is that channel input voltage, after the conversion of data stored in the chip, then read. Read to write the address of the chip, the son writes device address (0 x40 | channel number) and then reads the data.4Da conversion is to write the device address into the chip first, then write the sub-address (0x40) and then write the digital quantity to be converted. Device address chip information is introduced.5For the liquid crystal display, write data display, he will always display, do not continue to refresh, to change, only re-input.6For THE DS1302 clock chip, reading data is read out of the first data at the falling edge of the eighth clock when writing data, and then prepare for the next output. Pay attention to the writing of the program, but also pay attention to the position of the return value.7In Ds1302, the register is specified first, and then data is written to it. The registers on the chip data indicate the address. 8Initialization is best to write, in case you forget later. When reading or writing, the first operation is the lowest or highest bid, which can be judged according to the sequence diagram.9For the infrared transceiver, receiving, he is according to the length of time between the two falling edges to determine the high level or low level, write a program, first with the timer to determine the length of time, save, and then into binary (the program written to see more, very good).10Stepper motor: mainly used as switches, stepper motor torque decreases with the increase of speed. It is mainly used for automatic feeding of parts processing on machine tools. It can also be used in high-precision control places.Stepper motor is an open-loop control element stepper motor that converts electric pulse signal into angular displacement or linear displacement. In the case of the overload, motor speed, stop position depends only on the pulse signal frequency and pulse number, and are not affected by load change, when the stepper driver receives a pulse signal, it is driving a stepper motor according to set the direction of a fixed Angle, known as the "step Angle", its rotation is based on the Angle of the fixed step by step. The angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning. At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency, achieving the purpose of speed regulation.11Servo motor : Servo motor refers to the engine that controls the operation of mechanical components in a servo system. It is an indirect transmission device for auxiliary motors. Servo motors can control speed, position accuracy is very accurate, voltage signal can be converted into torque and speed to drive the control object. Servo motor rotor speed is controlled by the input signal, and can respond quickly, in the automatic control system, used as an executive element, and has the characteristics of mechanical and electrical time constant is small, high linearity, starting voltage, etc., can receive the electrical signal into the motor shaft angular displacement or angular velocity output. It is divided into DC and AC servo motors. Its main characteristic is that when the signal voltage is zero, there is no rotation phenomenon, and the speed decreases uniformly with the increase of torque.12Chinese Characters overview: To output Chinese characters on display or printer, Chinese characters are designed into a dot matrix graph according to graphic symbols, and corresponding dot matrix codes (glyphs) are obtained.The unified encoding for the representation of Chinese characters in the computer is called the internal code (such as national code), and the internal code is unique (equivalent to the id number of the character). The encoding of Chinese characters formed to facilitate the input of Chinese characters is the input code, which belongs to the external code of Chinese characters. The input code varies with the encoding mode and is diverse. The Chinese character code formed for displaying and printing Chinese characters is the character code, and the computer finds the character code in the character library through the character code and realizes its conversion.Machine code: According to the GB code, each Chinese character has a certain binary code, but this code will conflict with THE ASCII code when handled internally by the computer. To solve this problem, the first byte of each GB code is incremented by 1. Because ASCII code only uses 7 bits, the "1" on the first digit can be used as a symbol to identify Chinese character codes. When the computer processes the code with the first digit of "1", it will be interpreted as the information of Chinese characters, and when it processes the code with the first digit of "0", it will be interpreted as the ASCII code. After such processing, the national code (internal code) is the machine's internal code.If put this "mouth" word graphic "." With "0" instead, you can very vividly get the "mouth" glyphs :0000H 0004H 3FFAH 2004H2004H 2004H2004H 2004H2004H 2004H2004H 2004H 3FFAH 2004H 0000H 0000H. Computer to output "mouth", find shows that character first address, according to the "mouth" machine code after calculation, to find a "mouth" glyph code, and then according to the glyph code (to) in binary character generator, in turn, scan control on the screen, which is where the "0" of the binary empty, is a place where "1" swept out of the window, Then you get the character graph of the mouth.Chinese characters are arranged according to the order of national standard codes and stored in the memory in the form of binary files, which constitute the Chinese character font library, also known as the Chinese character font library, called the Chinese character library1312864 liquid crystal: Each display point corresponds to a binary number, with 1 indicating on and 0 indicating off. The RAM that stores this lattice information is called the display data memory. To display a graph or Chinese character is to write the corresponding lattice information into the corresponding storage unit.When the horizontal address = 0FH, it will be reset to 00H, but it will not automatically add one to the vertical address. Therefore, when writing multiple data in a row, the program needs to determine whether the vertical address needs to be reset14GDRAM: Drawing display RAM provides 128×8 bytes of memory space. When changing the drawing RAM, the horizontal and vertical coordinate values are successively written, and then two bytes of data are written to the drawing RAM. The address counter (AC) will automatically increment the horizontal address (X address) and reset to 00H when the horizontal address is 0XFH. Vertical addresses will not be carried automatically plus 1. The drawing display must be turned off during writing to the drawing RAM,For C, a defined variable is automatically allocated space and its address is the name of the variable. Through this name, the data can be recruited in memory, and the new data can be obtained through an operation. In assembly, the programmer needs to define the storage space and send the data to the accumulator for operation, and the programmer needs to operate every step. In C, this is done by the compiler.FAQ1. What is the main function of microcontroller?Microcontroller is a compressed micro computer manufactured to control the functions of embedded systems in office machines, robots, home appliances, motor vehicles, and a number of other gadgets. A microcontroller is comprises components like - memory, peripherals and most importantly a processor.2. What is an example of a microcontroller?The examples of 8-bit microcontrollers are Intel 8031/8051, PIC1x, and Motorola MC68HC11 families. The 16-bit microcontroller performs greater precision and performance as compared to the 8-bit.3. What are the elements of a microcontroller?Therefore, the microcontroller must also satisfy the five basic elements of input, calculation, storage, output, and control. These are called five elements of microcontrollers.4. Which is best microprocessor or microcontroller?If you need access to large amounts of really fast memory then a microprocessor is likely your best option. A microcontroller is already embedded with memory so the memory choices are fewer than with a microprocessor. The maximum amount of FLASH memory available with most microcontrollers is usually around 2MB.5. What is difference between BIOS and CMOS?The BIOS is the program that starts a computer up, and the CMOS is where the BIOS stores the date, time, and system configuration details it needs to start the computer. ... CMOS is a type of memory technology, but most people use the term to refer to the chip that stores variable data for startup.6. Is CMOS a RAM or ROM?RAM and ROM are the products, but Complimentary Metal Oxide Semiconductor (CMOS) is the process they are built in. CMOS uses two different types of transistors to achieve a lower overall power consumption.7. Whats an RTC battery?The Real Time Clock (RTC) battery provides power for the internal clock/calendar and for maintaining system configuration settings. This error can occur when a machine has been left turned-off for an extended period of time (approximately one to four months), and it is the result of a depleted RTC battery.            

This article is a collection of 5 frequently asked questions about blower motor resistor. Catalog I. What is a Blower Motor Resistor? II. How Does the Blower Motor Resistor Work? III. How Do I Know If My Blower Motor Resistor is Bad or Broke? IV. How to Test a Blower Motor Resistor? V. Can I Fix the Blower Motor Resistor by Myself? FAQ I. What is a Blower Motor Resistor? The blower motor resistor is the blower motor component that regulates the speed. When you raise the thermostat on the air conditioner, the resistor sends a signal to the blower motor to speed up and blow more air. When you turn it down, the opposite happens. It is an electronic component that sends electronic pulses corresponding to the information you send through the adjustment dial. The electrical signal increases or decreases, which affects the overall motor speed of the fan. As far as electrical systems are concerned, they are simple, but as you might see, if something interrupts the flow of power, problems can occur.   Behind these vents in the dashboard, there is a blower motor that starts when you need heating or air conditioning. Usually, it is located in the dashboard on the other side of the steering wheel. You can't see it because it is inside the vehicle, but there it is.   A digital speed controller controls a variable speed motor. The controller typically receives a digital input from the speed switch or HVAC control head. The control head then sends a command to the motor controller to adjust the speed to the driver's requirements.   The motor controller rapidly pulses the ground circuit on and off to achieve the desired speed. So a half-speed driver request will result in the blower motor controller pulsing the ground connection off twice as often as when the fan is running at full speed.   The blower motor resistor or control module is often positioned within one of the ducts in the HVAC system, close to the blower motor, in most modern vehicles. This is done so that the resistor or control module can be cooled by passing air. A blower motor resistor was fitted on the firewall of some older vehicles, with access from under the hood.  II. How Does the Blower Motor Resistor Work? This video will give a detailed explanation of blower motor circuit to help you better understand how eactly it works. III. How Do I Know If My Blower Motor Resistor is Bad or Broke? There are a few indications that your car's blower motor resistor has failed. Because the symptoms may overlap with difficulties in other systems in your vehicle, you may require the assistance of a specialist to help you diagnose them. These are some of the most typical warning signs. (1)  No air. As simple as it may sound, one of the most noticeable indicators to look for is a lack of air moving through the vents when trying to get the heater or air conditioner to function. If nothing comes out when you turn the knob or press the button and it's intended to start blowing air, it's a good clue that the blower motor resistor has failed. This can be a sign of a variety of different issues, so don't take it as a given if this is the only signal you're receiving.   (2)  High speeds only. As previously stated, a blower motor resistor is not required in two situations. When the fan is totally turned off or when it is running at high power. Because the current does not need to be modulated at high power, it bypasses the resistance. So, if you discover that your heat and air conditioning can only switch from being completely off to being on at high power, it's almost certain that you have a broken blower motor resistor.   (3)  Low speeds only. When your fan only works at low speed, this may be a signal of poor blower motor resistance as well. However, when there is a wiring problem between the blower motor resistor and the blower motor itself, it may only work at low speeds.   (4)  The fan will not turn off. If you can't turn off the fan no matter what you do, and no matter how you try to go up, down, or turn off the fan, the fan is constantly running, which means that the blower motor resistor cannot properly regulate the current.   (5)  The blower motor works under certain settings, but does not work under other settings. The blower motor should have a series of settings, from low to high, which can be set in a variety of intermediate ranges. If you find that some of these intermediate settings are working and some of them do nothing at all, it probably means that there is a problem with the switch, and how the switch sends a signal about your settings to the blower motor resistor blower motor.   (6)  Smoking vents. This is an unusual signal of a faulty blower motor resistor, though it is not unheard of. If there is a short around the blower motor resistor and wires begin to melt, the fan may spew smoke from those melting wires back into your car's cabin.   A solid rule of thumb is that if smoke starts flowing in via your car's vents, you should pull over immediately and figure out what's wrong. If it isn't the blower motor resistor, it could be something more serious, and you should get it checked out as soon as possible.   (7)  Burning Smell. Similarly to the smoking vent issue, it is not always as dangerous as actual smoke billowing into the car's cabin, but you will detect the distinct burning smell that indicates that some metal or plastic is overheated somewhere in the vehicle. This is frequently associated with one of the other signals we've already mentioned above. IV. How to Test a Blower Motor Resistor? Blower motor resistor test V. Can I Fix the Blower Motor Resistor by Myself? Whether you can repair the blower motor resistor yourself obviously depends on how much you know about blower motor resistors and general car maintenance. If you are reading a guide on blower motor resistance and its functions, you may not be familiar with them. Therefore, we recommend that you do not try to fix this problem yourself, as this is not a beginner-level fix.   This is not to say that you cannot replace the blower motor resistance yourself, but it will be a complicated task. But we provide you with some basic methods to diagnose and repair some simple blower motor problems, for reference only. For specific steps, please consult professionals or check related videos on youtube.   (1) The blower only works in high speed. This is a sure sign of a bad blower motor resistor, not a faulty speed switch. Change the resistor.   (2) The blower only works in low speed. Check for a blown fuse or a faulty high-speed relay. Replace the high-speed relay with a relay of the same part number. Check the fuse for the high speed relay's control side as well. Verify that the high speed relay's ground side is good.   (3) Repeated failures of the blower motor resistor Check for full airflow at the vents. If airflow appears to be restricted or lower than typical, a blocked cabin air filter is to blame. Examine the cabin air filter. If everything is ok, look for debris on the evaporator or heater. When the airflow is reduced, the blower motor resistor overheats and fails. Reduced airflow forces the blower motor to work harder and draw more current, which might result in repeated blower motor resistor failures. FAQ 1. What does a resistor do on a blower motor? Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. 2. Can I bypass blower resistor? Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. 3. What can cause a blower motor to stop working? In a situation where the motor doesn't work on any speed, the most likely causes are: a blown power supply fuse, a bad motor ground connection, bad motor speed control module or a failed motor. On all systems, a failed blower motor is least likely. ... Start by checking the blower fuse and HVAC controller fuse. 4. How do you test a blower motor resistor with a multimeter? Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications. 5. Is the blower motor resistor supposed to get hot? Yes that resistor will get very hot. Most people don`t know this but it is faster to defrost the windshield on low or medium fan speed due to that resistor putting off heat. Also that resistor needs to be cooled off with the air flow or it will burn up . 6. What is the function of a blower motor resistor? A blower motor resistor is an adjustable resistor. This electrical component is used to control the air conditioning system of a vehicle. It is the part that controls the fan speed of the fan motor according to settings that can be changed by turning the knob to the left or right, thereby increasing or decreasing the resistance of the electric current flowing to the rotating fan motor connected to the fan. 7. Where is the blower motor resister? A blower motor resistor, typically located beneath the passenger side dashboard, contains three resistors, or sets of terminals designed to generate voltage in proportion to electrical current. 8. How do you replace a blower motor resistor? Safety Tip: Always wear safety glasses when working on your motor. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or closed toe shoes. 1.Remove the negative battery terminal.2.Locate the blower motor resistor on the passenger side under the dash board. It is mounted to the the blower housing near the blower motor.3.Disconnect the electrical connector to the blower motor resistor.4.Remove the screws or bolts to the blower motor resistor and remove the resistor.5.Installation is the reverse of the removal. 9. Can you test a blower motor resistor? Yes. Set your multimeter to Diod or continuity and place leads on either side of the resistor. If no tone and infinite resistance it is bad. If tone but no resistance it is bad. If you have continuity to ground, something has shorted to ground look for heat damage. If you have tone and resistance it is good.  10. Why does a blower motor resistor keep going out? If you are constantly blowing that part. You ether have the motor pulling to much amps. If it is home unit it could also be a inline control board cap.

Warm hints: The word in this article is about 3500 words and  reading time is about 15 minutes.   Based on the heat balance principle, the basic theory for the calculation of steady and transient temperature rise of transformer is discussed.   The calculation of transformer temperature rise is mainly used to make sure that the steady-state temperature rises produced by the transformer with rated load in long-term continuous operation will not exceed the limit specified in the standard or technical contract. In addition, the data of overload operation capacity of transformer running under various rated loads are also used to offer support to the measures taken to ensure safe overload operation of electrical systems.   However, from the author's current reading of recent info on transformer principles, design, and calculation theories available, it may be due to the limitation of space or different aspects of emphasis that they are always making an introduction to various practical formulas for transformer temperature rise calculation in a practical way. As to the involved thermal principle of calculating the transformer temperature rise is always a bit of an oversimplification I think, especially the thermal analyses demonstrating how heat energy be absorbed(or dissipate) and the temperature goes up(or goes down) during a heating process. In this article, therefore I would like to make some theoretical discussions to solve this problem and add some extra explanations needed.   Catalog   I. Brief Introduction II. Heating & Cooling Process 2.1 Heating process when the thermal power is constant 2.2 The cooling process in which the heated body is no   longer supplied with heat 2.3 Just as same as the situation of 2.1, but Τ≠0 when   t=0 III. Further Analysis of Some Formula 3.1 Mechanism of temperature-rising process of heated   body 3.2 Properties and applications of Τu in formula 2 3.3 Definition, function and derivation of the thermal   time constant Τ IV. Conclusion FAQ I. Brief Introduction   It is well known that heat is always transferred automatically from a high-temperature object to a low-temperature object. Heat can transfer (or move) in three ways: conduction, convection, and radiation, usually a combination of two or three of them may cause the transmission (also known as heat dissipation).   Before formally describing this section, I would like to quote two conclusions from laboratory research that are fundamental to thermal science:   1) the temperature rise of an object is directly proportional to the heat (heat) supplied by the outside world and inversely proportional to its own mass and Specific Heat Capacity.   2) the heat energy (calorific energy) that a heating object disperses into a cooler object(cooling medium) within a unit of time is directly proportional to the area of its radiating surface, the temperature difference, and the Heat Transfer Coefficient between the heating object and cooling medium.   Specific heat capacity: the ratio of the heat added to (or removed from) an object to the resulting temperature change per unit mass of material.   Heat transfer coefficient: when the temperature difference between the heating object and the cooling object is 1K, the heat from the unit dissipation surface area to the cooler object within a unit of time.   For the convenience of discussion, the heating object is referred to as the heated body in this paper, and the object which gets the heat released from the heated body is called the cooling body (or the cooling medium).   Take a dry transformer, for example, its winding and core are heating bodies, and the cooling body refers to the air around the transformer. For oil-immersed transformers, in addition to the winding and core known as heating bodies, the oil-filled in the transformer can also be called a heating one in relation to ambient air or cooling water. However, relative to the winding and core, oil is also called a cooling body(cooling medium).   Fig. 1 Transformers are found everywhere alternating current is used   II. Heating & Cooling Process   2.1 Heating process when the thermal power is constant Suppose that in the heating process (that is, the heat is still in a transition state, not reaches a stable state yet), the temperature rise by Τ relative to the cooling medium, the temperature rise increases dΤafter a tiny time unit dt.   The heat supplied by the outside during this dt period is a constant thermal power of Pdt(P. For windings in oil-immersed transformers, it refers to load loss; for oil, it refers to total loss). Let the heat supplied by the outside surroundings during this dt period be Pdt(P is the constant thermal power; for windings in oil-immersed transformer, P refers to load losses, and for oil, the total losses). Some of the Pdt is the heat absorbed when the temperature rise of the heated body increases by dΤ, and the other part is dispersed into the cooling medium.   In order to understand the nature of this physical phenomena in the heating process better, suppose the heated body is an isothermic one, therefore the density, specific heat capacity, and any other parameters being the same, including the heat dissipation capacity of each point on the surface.   According to the principle of thermal balance (it comes down to the law of energy conservation), the states of the heating process described above can be represented by the following equations:   Where   P——Constant value of thermal power c——Specific heat capacity of the heated body G——the mass of the heated body F——Heat dissipation surface area of the heated body k——Heat transfer coefficient  Τ——Temperature difference (or temperature rise) between the heated body and cooling body at a certain time   The first item on the right of Equation (1) indicates the heat energy absorbed by the heated body when it increases the temperature of dΤ; The second item indicates that the heat energy is dispersing to the cooling body while the heated body is storing heat.   When the temperature rise of the heating body does not go up, that is, when the temperature rise reaches a stable state, then there is dΤ=0 and Τ=Τu (Τu means the steady-state temperature rise).   At this point, from formula (1) there is:   According to the above analyses we can see: formula (1) is the mathematical expression of the heat balance principle under the transient state; formula (2) is the mathematical expression of the heat balance principle under steady-state.   From Formula (1) and Formula(2) we can get a first-order differential equation of Τ:   Where: From formula (4), the parameters on the right side of the equation are the physical parameters of the object itself, so Τ is a constant and has a dimension of time, so it is called the thermal time constant. In the physical sense, Τ is the ratio of the heat storage capacity of the heated body to the heat dissipation capacity per unit time of the heating system studied, which is an attribute of the heated body. Therefore formula (4) is considered to be the definition of Τ and the formula (4') is another expression for calculation.   To obtain the solution of formula (3) we let t=0 and Τ=0, then this is what we get:   Note that sometimes it is easier to express the formula (5) with temperature θ instead of temperature rise Τ, so it is reworded as follows: Where:   θ——The temperature of heated body at any given moment and there is θ-θа=Τ θа——The temperature of cooling body θu——The steady state temperature of the heated body that reaches a steady state Δθu——θu-θа=Τu   The rising curve in Fig. 1 shows the temperature rise of heated body changes with time t.   In order to visually see how the Τ changes with the temperature rise, Fig. 1  shows two curves with different Τ and same Τu. Fig. 2 Relation between temperature-rise(Τ)of heated body and time(t) As can be seen directly from formula (5), formula (5') and Fig. 1, the process of temperature rising of a heated body is characterized by the fact that it changes fast at the very start, then gradually slows down, and when the time t becomes equals to (4～6)Τ, it remains almost unchanged, at this point it can be assumed that Τ reaches Τu (theoretically t reaches ∞).   2.2 The cooling process in which the heated body is no longer supplied with heat   When the temperature rise of the heated reaches Τu and no heat will be emitted, the temperature rise begins to go down from Τu to zero, which we call the cooling process. At this point, its transient process equation can still be deduced by formula (1), in which you need only to let P be equal to zero.   Therefore the first-order differential equation of its temperature rise is as follows:   The solution is: All the symbols of parameter in the formula above are identical with those in formula (5), except that Τu is the initial value of temperature rise when t=0; when (4～6)Τ later, Τ≈0.   Why would we worry about Formula 6?    This is because the temperature rise of winding got at the end of the current transformer temperature rise test, is still the value of temperature rise calculated through measurements of the resistance value of the winding which will change with the temperature. The resistance value measurement is still carried out in the temperature rise test under a way of supply voltage been removed, thus the formula (6) should be used to calculate.     2.3 Just as same as the situation of 2.1, but Τ≠0 when t=0 When the heating body is supplied with constant heat power and Τ=Τ0 (≠0) when t=0 satisfied, the whole process of deduction of temperature rise calculation, with the exception of the situation of Τ=Τ0 when t = 0, is the same as 2.1, in other words, the formula of temperature rise can still be deduced from formula (5) as follows: Comparing this with the formula (5) we notice that there is a new second item occurs. Considering the physical meaning of the expression is not obvious enough, it is now rewritten (which will not change the result of the calculation) as: These two formulas above show a case that the transformer is suddenly asked to conduct a overload operation running beyond the steady load.   III. Further Analysis of Some Formula   3.1 Mechanism of temperature-rising process of heated body Formula (5) and Fig. 1 describe the rising process of heated body temperature from a mathematical point of view. This process is characterized by a rapid start and then a gradual slow down until it finally stops rising and reaches a stable temperature rise of Τu .   In this section, characteristics of heating and cooling mechanism in this process will be described from a physical point of view. So we divide the t into n small and equal time periods when t=Τu, that is Δt1=Δt2=……=Δtn=Δt (theoretically t=∞, but in practice, it is desirable to suppose that t=(4～6)T, considering the value required of Tu with a higher accuracy). Therefore, the derivative symbol "d" in this article is replaced with a increment sign "Δ".   Please note that the heat energy supplied by surroundings in each time period is equal to P·Δt (P is the constant thermal power).   Now let us take a look in the first time period Δt1. Since the temperature of heated body has already made be equal to the cooling body when t=0, that is Τ=0, according to the second item of formula (1), we can assume the heat energy emitted is also equal to 0 during the period of Δt1 until the end of present stage. Therefore, during the Δt1 period, the final increments of the temperature rise of the heated bodyΔΤ1 is determined by the total external heat energy (P·Δt). So the temperature rise at the end of first time period Δt1 is Τ1=ΔΤ.    According to the same analytical principle, we continue with the second time period Δt2. Since the initial temperature rise at the beginning of Δt2 is the that of the first time period Δt1, it can be included that Τ1=ΔΤ1. The heat emitted during Δt2 is no longer zero, but . At the end of the Δt2, the increment value of temperature rise of heated body ΔΤ2 is determined by , so there we have ΔΤ2<ΔΤ1 (That is, the increment of temperature rise in the second period is smaller than that in the first period).   Finally, at the end of the second time period Δt2, the temperature rise Τ2 is equal to ΔΤ1+ΔΤ2. The rest may be deduced by analogy, at the end of Δtn time period, the temperature rise is , also ΔΤn=0 has been illustrated at the same time.   According to the changes of temperature increment ΔΤn in each of time period above, there always are: ΔΤ1>ΔΤ2…>ΔΤn-1>ΔΤn (ΔΤn=0), therefore demonstrating the trend that all the heat absorbed by heated body in each time period gradually goes down from P·Δt absorbed in the time period of Δt1 to 0 absorbed in the time period of Δtn. The heat energy emitted in each of the corresponding time periods is gradually increased from 0 to (from the first time period Δt1 to the end of the NO.n time period Δtn). That also means the final temperature rise (steady temperature rise) is: After the temperature rise reaches the stable value of Τu, the heated body no longer absorbs external heat energy, which indicates that all the external heat energy has been dispersed to the cooling body.   3.2 Properties and applications of Τu in formula 2 Formula 2 is a theoretical formula derived from the heat balance principle for calculating the steady-state temperature rise of the heated body. It is difficult to calculate the temperature rise directly for complex heated bodies such as transformers.   Therefore, various manufacturers and scientific research institutions have respectively obtained many practical formulas, according to their own practical experience or scientific research results and the characteristics of the heated body structure and three different heat dissipation forms, including conduction, convection, and radiation.   Furthermore, a heated body such as a transformer having a complex structure does not always have the characteristics of the homogeneous isothermal body assumed in formula 2, and the heat-dissipation capability at each point on the surface is not equal, either.   Therefore, the steady-state temperature rise (Τu) calculated from formula 2 (including the relevant practical formula based on formula 2) on the whole indicates the average value of temperature rise at different points in the heat source.   The calculation of the maximum temperature rise (temperature) of an object at a "hot spot" of concern has so far could only be mainly estimated by experience and the use of temperature rise measurements in certain heaT tests (for example, confirming the difference between the maximum temperature rise and the average value or confirming the multiple values between them to estimate).   3.3 Definition, function and derivation of the thermal time constant Τ Formula 4 is the definition expression of thermal time constant. It is obtained in the derivation of formula 5 from formula 2 and formula 1. Therefore, it is possible to think that equation 4 is obtained under the admission that when t=∞ it has dΤ=0 and Τ=Τu, the latter of which is obtained under the boundary conditions of objective reality. Because the definition of "Τ" and some functions have been described in section 2.1, here i only do some additional analyses to formula 7 which shows applications of transformer temperature rise under a short-time overload operation. Fig. 3 What is a Transformer   The basic theory of transformer and working principle of transformer   Fig. 4 Large power transformers have their core and windings submerged in an oil bath to transfer heat and muffle noise, and also to displace moisture which would otherwise compromise the integrity of the winding insulation. Heat-dissipating "radiator" tubes on the outside of the transformer case provide a convective oil flow path to transfer heat from the transformer's core to ambient air.   First of all, according to the statistics of a large number of dry and oil-immersed power transformers with different capacities, which have been manufactured at home and abroad, the value of Τ is generally not less than 1h (for oil-immersed transformer, although the T of winding is quite low, about 5 min-20 mins, the T of oil is 1h～5h.    Noting that the oil actual temperature rise is generally not lower than the temperature difference between the winding and the oil and that the thermal time constant of the oil should therefore be considered to control the temperature rise of the winding during the overload operation, that is, the temperature difference between winding and ambient air or temperature of cooling water still plays a decisive role.    Although the Τu of the transformer will obviously exceed the temperature rise limit of rated-load operation, as long as the time t has been controlled within T, it can still make the actual temperature rise running in short-time overload not excess the temperature rise limit of short-time overload operation. These permissible limits, according to the standard of the load guide of the oil-immersed power transformer, is related to the operation type within nameplate capacity, namely, normal periodicity, long-term or short-term emergency, and generally higher than that of rated temperature rise.   It can be seen from this that the function of the thermal time constant T is relatively large, so it is necessary to pay close attention to its definition, various affecting factors, and derivation of its formula. However, I have seen some people added another boundary condition except dΤ=0 during the derivation of the expression of Τ: in extreme cases, the heat will not be transferred into the surrounding medium at all, which is also called "adiabatic condition". In this regard, I would like to put forward the following different views for discussion.   (1) In this article, the derivations of formula 4 and formula 5 have only used a "boundary condition" of dΤ=0 (Τ=Τu) when t=∞, so there is no need to add another adiabatic condition for derivation.   It is said that without heat dissipation, the time required to reach a stable temperature is called time constant (Τ), but that will only be true when the second item (dissipated heat) on the right of the equation meets a condition of , now that to reach a steady temperature Τ must be equal to Τu, which is at variance with objective reality of electric accessories including transformers.   Some might say that when people calculate the temperature of a transformer at a short-circuit current, don't they also use the formula obtained under the "adiabatic condition" to calculate the temperature of the transformer? Yes, but the case being considered is only the "short time" one, that is, the formula only applies when short-circuit durations never exceed 10s (actually 2s).    The time is very small compared with the thermal time constant of winding in oil-immersed power transformer (about 5min-20mins) and that of oil (about 1lh～5h). This is still true when compared with the thermal time constant of the windings of dry-type transformers (about or above 30min). In section 3.1 of this article, such a short duration makes it is possible to consider it as an adiabatic transient system. In a broad sense, if the heat energy emitted accounts for only a very small part of the heat supplied by the outside world during a same period, it can be roughly regarded as adiabatic process. At this point, it is precisely because of the recognition of  that it is in line with objective reality.   This proves that adiabatic conditions should not be used as the basis in the derivation of expression of Τ (formula 4) and that of transient temperature rise (formula 5).   (3) From the details of the derivation process in this article, I would like to say that the true expression of temperature rise of the heated body still has not been obtained yet in the end. Think about that, a task for you, my readers.   IV. Conclusion   (1) Starting from the principle of heat balance, this article expounds the model of the heating mechanism in the rising process of temperature rise of the heated body with concise mathematics and physical language.   (2) It is clearly pointed out in this paper that the steady temperature rise of the heated body can be calculated by using formula 2, and formula 5 and formula 7 are the formulas for calculating the temperature rise of the heated body during the transient process.   (3) It is pointed out that to obtain the expression of the transient temperature rise of the thermal time constant Τ and the heated body, the adiabatic condition should not be used for the process of derivation, which is not necessary either.   (4) Due to space constraints, this article has not covered the heat dissipation mechanism of heated body, but you readers can refer to other references about heat loss or transfer in Kynix and other sites.   FAQ   1. How hot is too hot for a power transformer? Transformers designed with high-temperature insulation systems can run safely at temps up to 200°F. But remember, a hot-running transformer is an angry transformer.    2. What is ambient temperature of transformer? The average ambient temperature for a transformer over a 24 hour period should not exceed 30 degrees Celsius. For instance, if the transformer ambient temperature was 40 deg. C for 12 hours, then the transformer must not exceed 20 deg.   3. Should doorbell transformer be hot? Transformers are always going to produce some heat. It's a part of the step-down process. It should only be warm to the touch, however.   4. What is maximum ambient temperature? In general, a safe range is between 60 and 75 degrees Fahrenheit or 15 and 25 degrees Celsius, although the cooler end of that range is better. Ambient temperatures above those ranges make it difficult for a computer's cooling system to keep it at a safe operating temperature.   5. What is the name of oil used in transformer? Mineral oil and Synthetic oil are the majorly used transformer oil. These are the petroleum products, like Naphthenic based transformer oil and Paraffinic based transformer oil. Naphthenic based transformer oils are known for their heat distribution, which is one of the main problems with transformer.   6. What will happen if the regulation of a transformer is poor? If the transformer supplies a very low lagging power factor, large secondary currents will flow resulting in poor voltage regulation due to greater voltage drops in the winding. ... Therefore positive regulation produces a voltage drop in the winding while a negative regulation produces a voltage rise in the winding.   7. What is high transformer temperature? Standard Ratings and Overload Capacity：Dry-type transformers are available in three standard temperature rises: 80C, 115C, or 150C. Liquid-filled transformers come in standard rises of 55C and 65C. These values are based on a maximum ambient temperature of 40C.   8. What is hot spot temperature in transformer? Modern transformers make use of thermally upgraded paper that has been chemically treated to improve the stability of cellulose structure. The rated hot spot temperature for this kind of paper is 110°C and it can be seen that an increase of 7°C will double the aging acceleration factor.   9. How much heat does a 75 kVA transformer give off? According to Cutler-Hammer, a 75-kVA, 150°F-rise, dry-type transformer has an efficiency of 97.2% at 1/4 load and 96.7% at full load. So, figure 3% loss at 75 kVA, which would represent 2,250 W.   10.What happens when transformer is overloaded? The weakening of the system will happen faster if the transformer is frequently overloaded. The net result of small, incremental increases in loading capacity over time is a weakened insulation system. Overloading causes overheating, and eventually thermal degradation that acts thrrough cracks in the insulation.   You May Also Like: Some suggestions about protecting transformers Learn Some Basic Knowledge about Capacitor Voltage Transformer