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body { font-family: Arial, sans-serif; line-height: 1.6; color: #333; } h2 { border-bottom: 2px solid #3598db; padding-bottom: 10px; margin-top: 30px; } h3 { color: #2c3e50; margin-top: 25px; } img { max-width: 100%; height: auto; } .note { background-color: #f9f9f9; border-left: 5px solid #3598db; padding: 15px; margin: 20px 0; } .faq-item { margin-bottom: 20px; } .question { font-weight: bold; font-size: 16px; color: #236fa1; }IntroductionThe Q factor (quality factor) serves as a critical metric telling us how close a real-world inductor is to an ideal inductor. Inductors are ubiquitous components in power electronics converters, filter networks, and communication systems, where they are frequently used in resonant networks. While theoretical studies often treat inductors as having pure inductance, in reality, they possess inherent resistance and parasitic elements. The Q factor is defined as the ratio of the inductive reactance of the coil to its effective resistance.While the most obvious constituent of this resistance is the standard DC resistance (DCR) of the wire, high-frequency AC losses often play a more significant role. So, what is the true relationship between resistance and quality factor? Why is the Q factor so vital?Video: What is Q-Factor?Ⅰ Why is Q Factor Important for an Inductor?When selecting components, engineers must rely on the manufacturer's datasheet and product line cards after calculating the required inductance for the specific application. However, the Inductance value alone is not enough. It is crucial to consider the Quality Factor (Q) of the inductor, particularly for RF (Radio Frequency) circuits and precision analog applications.A high Q factor indicates that the inductor has low energy losses relative to the energy it stores. In resonant circuits, a high Q leads to a sharper resonance peak and narrower bandwidth, which is essential for selectivity in radio tuners. In power applications, a higher Q generally implies lower power dissipation (heat), leading to higher overall system efficiency.Ⅱ Inductor Q Factor Analysis2.1 There Are No Ideal InductorsIn practice, a "perfect" component does not exist. Inductors are constructed by winding conductive coils around cores made of various magnetic materials (ferrite, iron powder, air, etc.). The actual inductance value depends on physical parameters: the number of turns, the permeability of the core material, flux density, and the core's cross-sectional area.Furthermore, in real-world operation, the effective inductance and performance can fluctuate based on the applied current (saturation), signal frequency, aging, and operating temperature. To ensure consistent output accuracy across a wide range of frequencies and environmental conditions, specific parameters must be quantified. The Q-Factor is the primary parameter used to measure the "purity" and consistency of the coil's performance.2.2 What is Q-Factor?Figure 1. Q Factor in InductorsIdeally, an inductor would only exhibit inductance. However, a functional inductor includes fixed DC resistance, variable AC resistance, and parasitic capacitance. These parasitic elements reduce the inductor's efficiency. The Quality Factor (Q) is a dimensionless figure of merit that quantifies the inductor's performance regarding its losses. It is essentially the ratio of Energy Stored to Energy Dissipated per cycle.Let's explore the parasitic resistances that lower the Q Factor in depth:(DCR or RDC) DC ResistanceThe wire used to wind the coil has internal resistance, known as "DC resistance." This value is usually found in the "DCR" or "RDC" column of a datasheet. DCR depends on the total length of the wire and its cross-sectional area (gauge). To achieve a higher inductance, more turns are required, which increases wire length and, consequently, DCR. Designers often have to balance wire thickness and physical size. Larger diameter wires (lower gauge number) yield lower DC resistance but increase the component's size.Note: How to calculate the resistance of copper wire?Engineers often use the standard resistivity formula:Where:R is the resistance in Ohms (Ω)l is the length of the conductor in metersρ is the electrical resistivity of the material (e.g., Copper)A is the cross-sectional area in square millimeters (derived from wire diameter)Skin Effect Due to AC Resistance (Rac)When the frequency increases (roughly above 50 kHz for standard copper wire, though the effect starts earlier), AC resistance (Rac) becomes dominant over DCR. This is due to the "Skin Effect."At higher frequencies, alternating current tends to flow only near the surface (or "skin") of the conductor rather than through the entire cross-section. This effectively reduces the usable cross-sectional area of the wire, significantly increasing resistance. To mitigate this in high-Q applications, engineers often use Litz wire (multistrand insulated wire) to increase surface area.Core Hysteresis Losses (Modeled as Resistance)In magnetic cores, the magnetic domains must align and realign with the changing magnetic field (H). This realignment is not frictionless; energy is lost as heat during each cycle. This is known as Hysteresis Loss. Ideally, the B-H curve (Magnetic Flux Density vs. Magnetic Field Intensity) would be linear. In reality, it forms a loop. The area inside this loop represents energy lost per cycle.As frequency increases, these losses occur more often per second, increasing the effective resistance. This loss appears in the equivalent circuit as a resistor in series (or parallel, depending on the model) with the inductor, lowering the Q factor.Figure 2. BH Curve and Hysteresis LoopDielectric Losses (Rd)Inductors use insulation on the wire (enamel) and sometimes between layers. The core material itself is also a dielectric. These materials have finite resistance and dielectric constants. While often modeled as a parallel resistance (leakage), dielectric absorption causes losses that add to the total system energy loss, further reducing the Q factor at very high frequencies.Calculating Total Resistance and QThe total effective series resistance (ESR) in a functional inductor is the sum of these components:The Quality Factor (Q) is calculated as the ratio of Inductive Reactance ($X_L$) to this Total Resistance ($R_{total}$):Where $ omega = 2pi f $ (frequency).The Q factor can also be expressed in terms of power:Conclusion: If DCR, Skin Effect, or Core Losses increase, the denominator ($R$) increases, causing the Q-Factor to drop. A lower Q means higher power loss and broader bandwidth. Conversely, a high Q value implies that the inductor behaves more like an ideal reactance with minimal energy loss.Ⅲ What is the Role of Q Factor in a Circuit?The Q factor plays a dominant role in the **Filter Bandwidth** of practical circuits.Narrow Bandwidth (High Q): For Radio Frequency (RF) applications—such as police wireless communication or distinct radio channels—filters must be highly selective. They need to accept a specific frequency while rejecting everything else. An inductor with a High Q factor (Red line in theoretical plots) produces a sharp resonant peak, allowing for a narrow bandwidth.Wide Bandwidth (Low Q): Other applications may require a wider frequency range to pass through. An inductor with a lower Q factor (Orange line) produces a flatter, broader curve with less voltage gain at the peak but a wider passband.Additionally, designers must remember the Self-Resonant Frequency (SRF). Every inductor has parasitic capacitance between its windings. At a certain high frequency (SRF), the inductor resonates with its own capacitance and acts as a resistor. Beyond this frequency, it behaves like a capacitor, and the Q factor concept as an inductance metric becomes invalid.Frequently Asked Questions about Q Factor in Inductors1. How do you find the Q factor of an inductor?The quality factor Q of the inductor is defined by the formula $Q = frac{omega L}{R}$, where $omega$ is the angular frequency ($2pi f$), $L$ is the inductance, and $R$ is the effective series resistance (ESR). Since $R$ changes with frequency (due to skin effect and core losses), Q is frequency-dependent. It is usually measured using an LCR meter or an Impedance Analyzer at the specific operating frequency of the circuit.2. How is Q factor calculated from a bandwidth perspective?In a resonant circuit, the Q factor can be determined by the frequency spectrum. It is defined as $Q = frac{f_r}{Delta f}$, where $f_r$ is the resonant frequency (where impedance is maximum or minimum depending on circuit topology) and $Delta f$ is the -3dB bandwidth (the width of the peak at half-power). A narrower peak indicates a higher Q.3. How do I lower the Q factor of a circuit?Sometimes a high Q is undesirable because it causes ringing or oscillation. To lower the Q factor (dampen the circuit), you can add resistance to the circuit. Adding a resistor in series with the inductor increases the denominator in the $Q = frac{omega L}{R}$ equation, thereby reducing Q. Alternatively, placing a resistor in parallel with the inductor can also widen the bandwidth and lower the Q.4. Does a higher Q factor always matter?It depends on the application. Yes: In RF tuning, oscillators, and filter circuits, a high Q is essential for sharp selectivity and frequency stability. No (or less so): In some power supply chokes or wideband filtering, a moderate Q is acceptable. In fact, if the Q is too high in a switching power supply filter, it might cause transient ringing spikes that damage components. In these cases, designers might intentionally choose a lower Q or add damping.5. What is the physical meaning of Q factor?In physics and engineering, the quality factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is. A higher Q indicates a lower rate of energy loss relative to the stored energy of the resonator. In simple terms, a high-Q pendulum would swing for a long time (low friction), while a low-Q pendulum would stop quickly (high friction).

IntroductionSeries Circuits and Parallel Circuits are main circuit connections, also a third type of circuit involves the dual use of series and parallel connections in a circuit. Circuit connection is a kind of principle for layout diagram that shows the relationship between components drawn by physical and electrical standardized symbols for research and engineering planning. As we all know, there are two types of circuit we can make, called series and parallel. They provide solutions for analyzing performance, installing electronic and electrical products.CatalogIntroductionⅠ Series Circuits and Parallel CircuitsⅡ Series Circuits and Parallel Circuits Calculation2.1 Resistors2.2 Capacitors2.3 Inductor2.4 Switch2.5 Power Supply2.6 Series and Parallel Circuits RulesⅢ Six Circuit Design Software Tools Introduction3.1 Protel PCB Design Platform3.2 Altium Designer3.3 Quartus II3.4 Electronics Workbench (EWB)3.5 NI Multisim3.6 Allegro PCBⅣ Frequently Asked Questions about Series and Parallel CircuitsⅠ Series Circuits and Parallel CircuitsWhat is the difference between series and parallel circuits? Just have a look of the following video and words description about series circuits and parallel circuits to get the basics and differences of them.Series vs Parallel CircuitsSeries connection is one of the basic ways to connect circuit elements. The circuit formed by connecting various electrical parts in series. In the series circuit, the current through each part is equal.Parallel connection is another connection method between electrical components. Components connected in parallel are connected in multiple paths so that the current can split up, and the same voltage is applied to each component.Ⅱ Series Circuits and Parallel Circuits Calculation👉 Resistors in Series and Parallel Circuits2.1 ResistorsResistors in SeriesAs shown in the figure, n resistors connect in series. Now connect the power supply to both ends of this series circuit. According to Kirchhoff’s current law, the current given from the power supply is equal to the current through each resistor, so .According to Ohm’s law, the voltage across the k-th resistor is equal to the current through multiplied by its resistance .According to Kirchhoff’s voltage law, the voltage across the power supply is equal to the algebraic sum of the voltage across all resistors.Therefore, the equivalent resistance Req of n resistors in series is .According to Ohm’s law, the voltage across the power source is equal to the given current times the equivalent resistance .Pay attention to the voltage shared by the resistors of the series circuit is proportional.Conductance G is the reciprocal of resistance R, so the equivalent conductance of n resistors in series is Among them, Gn is the conductance of the n-th resistor.For the simple case of two resistors in series, the equivalent conductance is .Resistors in ParallelWhen linear resistors connect in parallel, the conductance (the reciprocal of resistance) is equal to the sum of the conductances of the parallel resistors, which is called the equivalent conductance, and the reciprocal is called the equivalent resistance. For example, the resistances of R1, R2, and R3, their conductances are G1, G2, and G3, respectively. The total resistance R and total conductance G of the parallel circuit are calculated according to the formula .Note: Calculate the total series and parallel resistance of a circuit using Apogeeweb's Parallel and Series Resistor Calculator. 👉 Capacitors in Series and Parallel Circuits2.2 CapacitorsCapacitors in SeriesAs shown in the figure, n capacitors are connected in series. From the definition of capacitor, it can be obtained that the current passing through the k-th capacitor is equal to its capacitance multiplied by the voltage change rate across it:According to Kirchhoff’s current law, the current i given from the power source (ac or dc) is equal to the current passing through each capacitor, so According to Kirchhoff’s voltage law, the voltage across the power supply is equal to the algebraic sum of the voltage across all capacitors:The voltage change rate of the power supply end is .Therefore, the equivalent capacitance Ceq of n capacitors in series is Each capacitor has a “voltage rating” set by its manufacturer. Assuming that the working voltage exceeds the voltage rating of the capacitor, it may cause capacitor failure. In order to avoid it, several similar capacitors can be connected in series to make the algebraic sum of the voltage rating greater than the operating voltage. However, this will also reduce the equivalent capacitance of the circuit.Capacitors in ParallelAs shown in the figure, n capacitors are connected in parallel. From the definition of capacitor, it can be obtained that the current ik through the k-th capacitor is equal to its capacitance Ck multiplied by the voltage change rate across it:According to Kirchhoff’s voltage law, the voltage across the power supply is equal to the voltage across each capacitor:According to Kirchhoff’s current law, the current given from the power source (dc or ac) is equal to the algebraic sum of the current through each capacitor: Therefore, the equivalent capacitance Ceq of n capacitors in parallel is .Note: Calculate the total series and parallel capacitance of a circuit using Apogeeweb's Series and Parallel Capacitance Calculator. 👉 Inductors in Series and Parallel Circuits2.3 InductorInductor in SeriesAs shown in the figure, n inductors are connected in series. According to the method described above, the equivalent inductance can be calculated as .Among them, Ln is the inductance of the n-th inductor.The magnetic field generated by the inductor will be coupled with the winding coil of the adjacent inductor. So it is difficult to avoid the mutual influence of the adjacent inductors. The mutual inductance M of physical quantities can give a measure of this influence.A series circuit composed of two inductors L1 and L2, and the mutual inductance Ms.1) Assuming that the magnetic fields or fluxes generated by two inductors are in the same direction, the equivalent mutual inductance Leq is expressed by the equation: 2) Assuming that the magnetic fields or fluxes generated by two inductors are in opposite directions, Leq is expressed by the equation:For a parallel circuit with three or more inductors, it is necessary to consider the self-inductance of each inductor and the mutual inductance among the inductors, which makes the calculation more complicated. The equivalent inductance is the algebraic sum of all self-inductance and mutual inductance.For example, a series circuit composed of three inductors will involve three self-inductances and six mutual inductances. The self-inductances of the three inductors are M11, M22, and M33, and the mutual inductances are M12, M13, M21, M23, M31, and M32.Equivalent inductance is .Since the mutual inductance between any two inductors is equal to each other, the latter two sets of mutual inductance can be combined:Inductors in ParallelN ideal inductors without mutual inductance are connected in parallel. Similar to the method described above, the equivalent inductance Leq can be calculated as .Among them, Li is the inductance of the i-th inductor.The above equation describes an ideal case where n inductors are connected in parallel without mutual inductance.A parallel circuit composed of two inductors with inductances L1 and L2 and mutual inductance M:1) Assuming that the magnetic fields or fluxes generated by two inductors are in the same direction, the equivalent mutual inductance Leq is expressed by the equation: 2) Assuming that the magnetic fields or fluxes generated by two inductors are in opposite directions, Leq is expressed by the equation:For a parallel circuit with three or more inductors, it is necessary to consider the self-inductance of each inductor and the mutual inductance among the inductors, which makes the calculation more complicated. 👉 Switch in Series and Parallel Circuits2.4 SwitchSwitch in SeriesTwo or more switches are connected in series to form an or gate circuit. Assuming a power supply is connected to both ends of the circuit, current will only flow when all switches are closed.Switch in ParallelTwo or more switches are connected in parallel to form an or gate circuit. Assuming that a power supply is connected to both ends of this circuit, even though any one of the switches is closed, current will flow. 👉 Power Supply in Series and Parallel Circuits2.5 Power SupplyPower Supply in SeriesFor example, assuming that several cells in the battery pack are connected in series to form a power source, the voltage across the power source is the algebraic sum of the voltages across all cells.Power Supply in ParallelFor example, assuming that a battery pack uses several single batteries with the same voltage connected in parallel as a power source, the voltage across the power source is equal to the voltage across the single battery.Note: Get more info from Switching Power Supply Circuit Diagram with Explanation. 2.6 Series and Parallel Circuits RulesHow to judge whether the electrical circuits are connected in series or in parallel? Series and parallel are the two most basic forms of circuit connection, and there are certain differences between them. So get to know their basic characteristics well according to the following specific methods.(1) Visual CheckLook at the connection form of electrical parts in the circuit. The one by one in sequence is series; the one paralleled between two points of the circuit is parallel.(2) Current FlowWhen the current flowing from the positive pole of the power supply to each element in turn shows that the circuit is in series; when the current flows to two branches and get together at a certain place finally, it indicates that the circuit is in parallel.(3) Removing ComponentsRemove one electrical part at will to see whether other electrical components are working normally. If the circuit can continue to work, then the connection relationship of this circuit is in parallel, otherwise, it is in series. Ⅲ Six Circuit Design Software Tools Introduction3.1 Protel PCB Design PlatformProtel PCB is a CAD software for the circuit industry launched by Protel Systems Pty Ltd in 1985, and has rebranded to Altium Designer. It has many advantages compared with many EDA software for circuit designers. Almost all circuit companies use it. The early Protel PCB was mainly used as a printed board automatic wiring tool. It ran in DOS and had fewer hardware requirements. It can run under the 1M memory of a 286 machine without a hard disk. However, it’s less functional, only electrical schematic drawing and printed board design functions, and the PCB layout rate of automatic wiring is also low.It is a professional circuit board drawing tool. It includes electrical schematic drawing, analog circuit and digital circuit mixed signal simulation, multilayer PCB design, programmable logic device design, chart generation, circuit table generation, and supports macro operations, etc. And it has a client/server architecture. PROTEL is also compatible with some other design software file formats, such as ORCAD, PSPICE, EXCEL, etc. Using automatic routing of multi-layer can achieve 100% layout rate of high-density PCBs.3.2 Altium DesignerAltium Designer is one of the most popular of the high end PCB design software packages on the market today. It provides a single, unified application that incorporates all the technologies and capabilities necessary for complete electronic products, which mainly runs on the Windows operating system. This software provides designers with brand-new design solutions through the perfect integration of schematic design, circuit simulation, PCB drawing editing, topology logic automatic routing, signal integrity analysis and design output, etc. When using this software, the quality and efficiency of circuit design can be greatly improved.Fully inheriting the functions and advantages of the previous series of versions of Protel 99SE and Protel DXP, Altium Designer has many improvements and many high-end features. The platform broadens the traditional interface of board-level design and fully integrates FPGA design functions and SOPC design implementation functions, allowing engineers to integrate FPGA in system design with PCB design and embedded design. With these advantages, Altium Designer requires higher computer system performance than the previous version. 3.3 Quartus IIThe Altera Quartus II design software is a multiplatform design environment that easily adapts to your specific needs in all phases of FPGA and CPLD design. In other words, Quartus II software delivers the highest productivity and performance for Altera FPGAs, CPLDs, and HardCopy ASICs. It is a comprehensive CPLD/FPGA development software, and supports schematics, VHDL, VerilogHDL and AHDL (Altera Hardware supports Description Language) and other design input forms. Quartus II embedded with its own synthesizer and simulator, can complete the process of design input to the hardware configuration. It can run in Windows, Linux and Unix. Use Tcl scripts to complete the design process, and it also provides a complete user graphical interface design method. Quartus II has the characteristics of fast running speed, unified interface, centralized function, easy to learn and easy to use.Quartus II provides a fully integrated development which independent of circuit structure, with all the features of digital logic design, including:1. You can use the schematic diagram, structural block diagram, VerilogHDL, AHDL and VHDL to complete the circuit description, and save it as a design entity file.2. Chip (circuit) plane layout wiring editing3. With LogicLock region, users can build and optimize the system, and add subsequent modules that have little or no impact on the performance of the original system.4. Powerful logic synthesis tool5. Complete circuit function simulation and sequential logic simulation6. Timing analysis and critical path delay analysis7. Signaltap ii logic analyzer can be used for embedded logic analysis.8. Support the addition and creation of software source files, and link them to generate programming files.9. Use the combined compilation method to complete the overall design process at one time.10. Automatically locate compilation errors.11. Efficient period programming and verification12. Read into standard EDIF, VHDL and Verilog netlist files.13. It can generate VHDL and Verilog netlist files used by third-party EDA software.3.4 Electronics Workbench (EWB)EWB is is a mixed-mode SPICE-based electronics design and simulation tool, launched by Interactive Image Technology Co., Ltd. in the early 1990s. It is used for mixed simulation of analog circuits and digital circuits. With this powerful software, you can directly see the output of various circuits on the screen.Compared with other EDA software, EWB is a smaller software, and its function is relatively single. However. its simulation function is very powerful, almost 100% simulation results of real circuits. It provides parts such as multimeters, oscilloscopes, signal generators, frequency sweepers, logic analyzers, digital signal generators, logic converters, etc., and its device library contains many transistor components, integrated circuits and digital gate circuit chips from large companies.  In addition, components that are not in the device library can also be imported externally. Among many circuit simulation software, EWB is the easiest to use. Its working interface is very intuitive. The schematic diagram and various tools are in the same window. People who have never touched it can use the software proficiently with a short-time learning. For electronic designers, it is an excellent EDA tool. For many circuits, you can know its results without using a soldering iron. If you want to change components or change parameters, you only need to click the mouse. It can also be used as an auxiliary teaching software for electrical knowledge.3.5 NI MultisimMultisim is a Windows-based simulation tool launched by National Instruments (NI) Co., Ltd.. It is industry standard SPICE simulation and circuit design software for analog, digital, and power electronics in education and research. It includes graphical input of circuit schematics, circuit hardware description language input, and has rich simulation analysis capabilities. Engineers can use it to interactively build circuit schematics and simulate the circuit.With SPICE simulation, designers can quickly capture, simulate and analyze new designs without knowing SPICE deeply, which also makes it more suitable for electronics education. Through Multisim and virtual instrument technology, PCB designers and electronics educators can complete a complete integrated design process from theory to schematic capture and simulation to prototype design and testing.NI Multisim software is an EDA tool software specially used for electronic circuit simulation and design. As a personal desktop electronic design tool running in Windows, NI Multisim is a complete integrated design environment. Its computer simulation and virtual instrument technology can solve the problem of disconnection between theoretical teaching and actual reality experiment. Students can easily reproduce the theoretical knowledge they have learned through computer simulation, and can use virtual instrument technology to create their own instruments. It has an intuitive graphical interface, abundant components, powerful simulation capabilities, abundant testing instruments and complete analysis methods. NI Multisim software is a not bad teaching tool.3.6 Allegro PCBAllegro PCB is an advanced PCB design routing tool introduced by Cadence. It provides a good and interactive working interface, and powerful and complete functions. Provide the most perfect solution for the current high-speed, high-density, multi-layer complex PCB design and wiring, with the combination of its front-end products Cadence, OrCAD, and Capture. Allegro has a complete constraint setting. Users only need to set the wiring rules as required. The wiring design requirements can be met without violating DRC, thus saving tedious manual inspection time and improving work efficiency. It can also define parameters such as minimum line width or line length to meet the various requirements of today's high-speed circuit board wiring. Allegro PCB enables you to do high-speed design, RF antenna, flex-circuitry, and design for manufacturing (DFM) technology.For the drawing and modification functions of copper foil that the industry attaches great importance to, Allegro provides a simple and convenient inner layer division function, as well as the ability to review the inner layer of the positive and negative film. For copper paving, it can also be divided into dynamic copper or static copper, which can be used for different applications. Dynamic copper parameters can be divided into different levels of settings for all copper, single copper or single object, so as to meet the requirements of different connection effects or spacing values to match the special settings due to design requirements. Ⅳ Frequently Asked Questions about Series and Parallel Circuits1. What is the difference between parallel and series circuits?In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents flowing through each component. ... In a series circuit, every device must function for the circuit to be complete. If one bulb burns out in a series circuit, the entire circuit is broken. 2. What are the rules for series and parallel circuits?Rules regarding Series and Parallel CircuitsVoltage drops add to equal total voltage.All components share the same (equal) current.Resistances add to equal total resistance. 3. What are the similarities and differences between series and parallel circuits?Series circuits are designed so that the current through each component is the same, whereas parallel circuits are designed so that the voltage through each component is the same. 4. Why is resistance different in series and parallel?In a series circuit, the output current of the first resistor flows into the input of the second resistor; therefore, the current is the same in each resistor. In a parallel circuit, all of the resistor leads on one side of the resistors are connected together and all the leads on the other side are connected together. 5. Which software is best for circuit design?Based on Proto-Electronics client preferences, we have drawn up the top 10 best electronics CAD software programmes.EagleAltiumProteusKiCadCadence OrCAD PCB DesignerDesignSparkProtelCadstar

IntroductionAlarm Circuits and Control Circuits are pretty common in daily life. A control circuit is a special type of circuit used to control the operation of a completely separate power circuit. Alarm circuit is a security circuit to reduce life loss and poverty under the excepted prevailing conditions. Both are quite famous and you probably could have seen plenty of different versions of them. Here, we will introduce several available home/office hobby circuits for smoking alarm, temperature controlling and timing, with their design principles, and component selection. They will provide more convenience for your daily life.A Simple Guide to Electronic Components in CircuitsCatalogIntroductionⅠ Indoor Monitoring Circuit DesignⅡ Smoke Alarm Circuit DesignⅢ Temperature Controlled Circuit Using NE555Ⅳ Temperature Sensor Circuit for Temp MeasuringⅤ Water Tank Temperature Controlled ProjectⅥ Cyclic Timing Circuit DiagramⅦ Indoor Overvoltage Protection Circuit DesignⅧ Temperature Fan Controller DiagramⅨ Water Boiling Alarm Circuit DesignⅩ FAQEvery alarm circuit and control circuit is composed of a number of basic components connected together to achieve the desired performance. The following lists some common and simple alarm and control circuits diagrams to share different ideas for protecting your home/office and making your life more easier.Ⅰ Indoor Monitoring Circuit DesignThe monitor can detect infrared rays emitted by the human body, and when a person enters the monitoring area, it can sound for alarm. It is suitable for homes, offices, warehouses, laboratories and other important occasions.👍 Circuit Working ModelFigure 1. Infrared Detection Alarm CircuitThe device consists of an infrared sensor, a signal amplifier circuit, a voltage comparator, a delay circuit and an audio alarm circuit. When the sensor IC1 detects the infrared signal radiated by the human body in front, it outputs a weak electrical signal from the pin②. It is amplified by the first-stage amplifying circuit formed by the transistor VT1, and then input to the operational amplifier IC2 through C2 with high gain and low-noise amplification. IC3 acts as a voltage comparator. Its pin⑤ reference voltage is provided by R10 and VD1. When the signal voltage output by IC2 pin① pass to the IC3 pin⑥, the voltages of the two input terminals are compared. At this time, IC3 pin⑦ changes from the high level to the low level. IC4 is an alarm delay circuit, formed by R14 and C6. Its continuous time is about 1 minute.When IC3 pin⑦ becomes low level, C6 discharges through VD2, IC4 pin② becomes low level,  which is compared with IC4 pin③ reference voltage. When it is lower than its reference voltage, IC4 pin① changes to high level, VT2 is turned on, and the buzzer BL is powered on and emits an alarm sound. After the infrared signal of the humans disappears, IC3 pin⑦ outputs to high level, and VD2 is cut off at this time. Since the voltage at both ends of C6 cannot change suddenly, charge C6 slowly through R14. When the voltage at both ends of C6 is higher than its reference voltages, IC4 pin① becomes low level for about 1 minute. That is, the alarm time lasts for 1 minute.The power-on delay circuit is composed of VT3, R20, and C8. It is mainly to prevent alarming immediately when powering on, so that the user has enough time to leave the monitoring site, and at the same time can prevent a false alarm occurred during a power cut. The device uses 9-12V DC power supply, with T step-down, full-bridge rectification, and C10 filtering. The detection circuit uses IC5 for power supply, and automatic non-stop conversion with AC and DC. 👉 Components SelectionIC1 adopts imported device Q74, the wavelength is 9~10um. IC2 uses op-amp LM358, which has high gain and low power consumption. IC3 and IC4 are dual voltage comparators LM393 with low power consumption and low offset voltage. Among them, C2 and C5 must use tantalum capacitors with small drain electrodes, otherwise the debugging will be affected. R12 is the key element to adjust sensitivity, and linear high-precision sealed type should be selected. Other components can be selected as shown in the circuit diagram. 👉 DIY and AdjustmentWhen making, a Fresnel lens is installed in front of the IC1 sensor. Since the frequency range of the human body is 0.1~10Hz, it is necessary to use the Fresnel lens to multiply the frequency of the human body. After installation finished, connect the power supply for debugging. Let a person walk about 7-10m in front of the detector, adjust R12 in the circuit, and make the buzzer alarm. As long as the other parts are of good quality and welded correctly, they can work normally without debugging. The static working current of this machine is about 10mA. It will enter the waiting state about 1 minute after the power is turned on. As long as someone enters the monitoring area, it will alarm, and stops in 1 minute. In addition, if the buzzer is changed to a relay to drive other devices, it will be used for other controls. Ⅱ Smoke Alarm Circuit DesignThis smoke alarmer can be used in family rooms or various places where smoking is forbidden (such as hospitals, conference rooms, etc.). When someone smokes, the no-smoking warning device will emit a warning sound of "No Smoking!" to remind the smoker to stop smoking consciously.👍 Circuit Working ModelFigure 2. Smoke Alarm CircuitThe no-smoking warning circuit is composed of a smoke detector, a monostable trigger, a voice generator and a power amplifier circuit. The smoke detector consists of potentiometer RP1, resistor R1 and gas sensor. The monostable trigger has time-base integrated circuit IC1, resistor R2, capacitor C1, and potentiometer RP2. The voice generator circuit is composed of voice integrated circuit IC2, resistors R3-R5, capacitor C2 and Zener diode VS. The audio power amplifier circuit includes transistor V, boost power amplifier module IC3, resistors R6 and R7, capacitors C3 and C4, and speaker BL.When the gas sensor doesn’t detect smoke, the resistance value between A and B is relatively large. IC1 pin2 is high level (higher than 2VCC/3), pin3 outputs low level, while voice generator circuit and the audio power amplifier circuit does not work. When someone smokes and the gas sensor detects the smoke, the resistance value between the A and B becomes smaller, causing the voltage of IC1 pin2 to drop. When the voltage of this pin drops to VCC/3, IC1 pin3 changes from low level to high level. Pass through current limiter R3, filter C2 and Zener diode VS, the high level will generate 4.2V DC voltage, which is supplied to voice IC2 and crystal arm. After IC2 energizes and works, it outputs a voice electrical signal. After the signal is amplified by V and IC3, it makes BL to emit a voice warning sound of "No Smoking!" 👉 Components SelectionRl~R7 selects 1/4W carbon film resistor or metal film resistor for use. RP1 and RP2 can choose small linear potentiometer or variable resistor. C1, C2 and C4 all use aluminum electrolytic capacitors with a withstand voltage of 16V; C3 uses monolithic capacitors. VS selects the silicon Zener diode of 1/2W, 4.2V for use. V uses S9013 or C8050 silicon NPN transistors. IC1 uses the NE555 timer IC; IC2 uses the voice integrated circuit; lC3 uses the WVH68 boost power amplifier thick-mode IC. BL selects 8Ω, 1~3W electrodynamic speakers. The gas sensor is MQK-2 type sensor. 👉 DIY and AdjustmentThis no-smoking warning device can be used as a smoke alarm to detect fires or harmful gases, and combustible gases. Adjusting the RP1 resistance can change the heating current of the gas sensor (usually about 130mA). And adjusting the RP2 resistance can change the sensitivity of the monostable trigger circuit. Ⅲ Temperature Controlled Circuit Using NE555This circuit is an automatic temperature controller composed of a 555 timer IC and a few peripheral components. Because the voltage at each point in the circuit comes from the same DC power supply, it does not need a high-performance regulated one. Using the capacitor step-down method can work reliably. The circuit components are low in price, small in size, and easy to self-made under amateur conditions. The automatic temperature controller made by this circuit can be used for electric heating control in industrial production and household use, with good effect.👍 Circuit Working ModelFigure 3. 555 Timer Based Circuit for Temperature ControlWhen the temperature is low, the resistance of the thermistor Rt with a negative temperature coefficient is large, the potential of pin2 of the 555 timer IC is lower than 1/3 of the voltage of Ec (about 4V), and its pin3 output high level. At this time, V conducts, the heater RL is heating, and the timing cycle starts. When the temperature of the thermistor Rt is higher than the set value and the timing cycle has not been completed, the heater RL will cut off after the timing cycle stops. When the Rt temperature drops below the set value, V will conduct again and turn on the heater RL for heating. In this way, automatic temperature control can be achieved. 👉 Components SelectionIn this circuit, the thermistor Rt can be a negative temperature coefficient type MF12 or MF53, or other types of negative temperature coefficient thermistors with different resistance values, as long as Rt＋VR1= 2R4 is satisfied under the temperature condition to be controlled. A larger potentiometer VR1 can have a larger adjustment range, but its sensitivity will decrease. The bidirectional thyristor V can also be selected according to the size of the load current. There are no special requirements for other components. Choose according to the parameters given in the circuit diagram. 👉 DIY and AdjustmentThe whole circuit can be installed on PCB. Generally, debugging is not required. The time interval is 1... .1R2×C3, which should be smaller than the thermal time constant of the heating system, but not too small, otherwise it will cause excessive radio frequency interference due to the thyristor V turns on or off rapidly. After installation and debugging, it can be put into a small plastic box, and the thermistor Rt can be led to the required place. Ⅳ Temperature Sensor Circuit for Temp MeasuringThis circuit is a thermometer made by AD590 special integrated temperature sensor, which has the characteristics of simple structure, reliable use and high precision.👍 Circuit Working ModelFigure 4. Digital Thermometer CircuitAfter the 100V AC voltage passes through the transformer T1, the rectifier bridge stack UR and the capacitor C1, the DC voltage is obtained, and then the adjustable voltage regulator circuit μA723C provides a stable working voltage for the temperature sensor AD590. AD590 is a new type of current output temperature sensor, composed of multiple transistors and resistors with the same parameters. When a specific DC working voltage is applied to both ends of the sensor, if the sensor temperature is 1 degree Celsius, the output current of the sensor changes by 1 μA. The changing current of the sensor is converted into a voltage signal through the resistor R5 and the variable resistor RP2, and then output to the digital meter, which displays the temperature change. 👉 Components SelectionThe IC selects AD590-series temperature sensor. There are no special requirements for other components of this circuit, and can be selected according to the parameters given in the circuit diagram. 👉 DIY and AdjustmentBy adjusting the value of resistor R5 and variable resistor RP2, the sensitivity of the circuit output can be improved. Ⅴ Water Tank Temperature Controlled ProjectAn automatic fish tank water temperature controller uses a negative temperature coefficient thermistor as a temperature sensor to automatically heat the fish tank through heating gas. The transient time of this circuit is small, which is beneficial to the accuracy of temperature control. And it is suitable for various sizes of fish tanks.👍 Circuit Working ModelFigure 5. Automatic Control of Fishbowl Water TemperatureAfter being rectified by diodes VD2~VD5 and filtered by capacitor C2, a voltage of about 12V is provided to the control part of the circuit. 555 timer is connected as a monostable flip-flop, the transient state is 11s. Set the control temperature to 25ºC, adjust the potentiometer RP, to get RP + Rt = 2R1 ( Rt is the thermistor with negative temperature coefficient). When the temperature is lower than 25ºC, the Rt resistance value increases, and the pin2 of the 555 timer is low level, then the pin3 output changes from low level to high level. The relay K is turned on, and its contact is closed. The heating tube starts to heat until the temperature returns to 25ºC, the Rt resistance value becomes smaller, the pin2 of the 555 timer is at high level, and the pin3 outputs low level. The relay K loses power, its contact is open, and the heating stops. 👉 Components SelectionIC uses NE555, NA555, SL555 and other 555 timer ICs; VD1 uses IN4148 silicon switching diodes; LED uses common light-emitting diodes; VD2~VD5 uses IN4001 silicon rectifier diodes; Rt uses 470Ω MF51-type negative temperature coefficient thermistors at room temperature; RP uses WSW organic solid trimming potentiometer; R1and R2 uses RXT-1/8W carbon film resistors; C1 and C3 uses CD11-16V electrolytic capacitors; C2 uses CT1 ceramic dielectric capacitors; K uses 12V JZC-22F electromagnetic relay. 👉 DIY and AdjustmentThe temperature sensor probe connects the thermistor Rt with wires, and then seals the solder joint with epoxy glue, to avoid water erosion. As long as the circuit is correct in the DIY process, this circuit is easy to operate. If the component performance is good, it can be used without debugging after installation. Ⅵ Cyclic Timing Circuit DiagramThe circuit can set the cycle time of the equipment and each time it works, allowing the equipment to work continuously according to the set time. This circuit can be applied to control occasions such as timing pumping, timing ventilation, and timing cut off.👍 Circuit Working ModelFgiure 6. Cycle Timing CircuitAfter the circuit is stepped down through the capacitor C2 and the bleeder resistor R3, and then rectified by the bridge stack IC2, and stabilized by VD2, a DC voltage of about 12V is obtained to supply power to IC1 and other circuits. IC1 is a 14-bit binary counter/frequency divider integrated circuit. A clock oscillator with a certain frequency is formed by the internal circuits of R1, R2, C1 and IC1 to provide clock pulses for timing IC1. When the circuit is powered on, it first enters the working gap waiting time of the device. IC1 internally realizes the delay by counting and dividing the clock pulse.  When the timing is up (according to the parameters in the figure, about 3 hours), the Q14 terminal of IC1 outputs high level, making the transistor V conducts. The relay KA gets to work, and drives the controlled equipment to start working. At this time, IC1 starts to count the working time of the device again. When the timing expires (according to the parameters in the figure, about 20 minutes), the Q14 terminal outputs low level. So that V is cut off and the device stops working. And meanwhile, IC1 automatically resets and starts the next timing. So that the device can perform timing cycle according to requirements. In the figure, VL is a working indicator. 👉 Components SelectionIntegrated circuit IC1 chooses 14-bit binary counter/frequency divider CD4066, or CC4066 or other digital circuit integrated blocks with the same function. IC2 selects a 1A, 50V bridge stack, or can be connected with four 1N4007 diodes. Transistor V uses NPN-type transistor 8050, and other transistors such as 9013 or 3DG12 can also be used. VD1 selects rectifier diode 1N4007; VD1 selects 1W, 12V silicon regulator tube, such as 1N4742; VD3 ~VD5 use switching diodes 1N4148; VL selects ordinary light-emitting diodes. Resistors R1, R2, R4, R6 and R7 use 1/4W metal film resistors; R3 and R5 use 1/2W carbon film resistors. C1 selects polyester or monolithic capacitors; C2 selects polypropylene capacitors with a withstand voltage of 450V and above; C3 selects aluminum electrolytic capacitors with a withstand voltage of 16V. Relay KA chooses a miniature relay with a coil voltage of 12V, and the contacts capacity is determined according to the power of the controlled device. 👉 DIY and AdjustmentAfter the circuit is installed, it can work normally without debugging. When you need to adjust the control time, you can adjust the parameters of R1, and C1. Also you can change the position of the IC1 output control terminal (Q4 ~Q14). Ⅶ Indoor Overvoltage Protection Circuit DesignBecause the instability of the mains, the household appliances often affected, their service life may reduce. In serious cases, it is easy to burn out due to voltage surge. The circuit described in this example can solve this problem well.👍 Circuit Working ModelFigure 7. Overvoltage Protection Circuit for AppliancesThe mains supply provides a stable 12V working voltage for the switch integrated circuit via C1, VD1, and DW1. VD3, R2 and RP1 form a voltage divider sampling circuit. When the mains voltage is normal, DW2 cannot be turned on, the working voltage of TWH8778 pin⑤ is lower than 1.6V. The relay J does not pull in, and the mains supplies the CZ socket through the J-1 normally closed contact. When the mains voltage is high than the normal setting, DW2 breaks down, the potential of TWH8778 pin⑤ rises to 1.6V, causing the IC to flip, pin ③ outputs high level. At this time, the relay is pulled in, and the electrical power supply is immediately cut off, avoiding the overvoltage affects electrical appliances. 👉 Components SelectionC1 uses 0.47µ/400V electrolytic capacitor, relay J uses 6V DC contactor; RP uses ordinary trimming potentiometer, chip IC can be TWH8778-type electronic switch or TWH8752-type electronic switch. 👉 DIY and AdjustmentAfter the device is welded correctly, connect the mains power to the input end of the voltage regulator, cooperate with the voltage regulator and carefully adjust RP1, so that the relay J is closed when the voltage is 250V, and then the circuit is connected to the mains power grid. Ⅷ Temperature Fan Controller DiagramThis is an automatic fan temperature controlled governor, which can automatically adjust the speed according to the temperature change. The circuit can be adjusted, so it can be used for the control of other electrical equipment.👍 Circuit Working ModelFigure 8. Automatic Temperature Control and Speed Regulation in Fan CircuitThe IC in the picture is a 555 timer IC, which forms a multivibrator with components of R2, R3 and C2. It can send out a rectangular wave signal with an adjustable duty cycle. When the temperature changes, the resistance value of the thermistor changes, so the duty cycle of the square wave output by the multivibrator changes. Adjusting the conduction angle of the bidirectional thyristor VT changes the voltage across the fan electrodes, which automatically adjusts the speed of the electric fan. 👉 Components SelectionThe integrated circuit IC selects NE555 timer, and models such as LM555 and TLC555 can also be used. VT is a bidirectional thyristor, its withstand voltage should be above 400V, and the rated current should be reasonably selected according to the capacity of the electric fan to be controlled. Resistor R1～R5 can choose ordinary 1/8 or 1/4W carbon film resistors; Rt is a negative temperature coefficient thermistor, and can choose a thermistor with a resistance of about 10KΩ at room temperature. Capacitor C1 uses ordinary aluminum electrolytic capacitors; Capacitors C2 and C3 are polyester capacitors. VD is a Zener diode with a steady voltage of 9.1V. 👉 DIY and AdjustmentYou can make your own PCB, or use a universal one. After the circuit is installed, the temperature of the thermistor Rt can be artificially changed to observe the speed of the fan motor. If the temperature control effect is not ideal, the resistance value or temperature change range of the thermistor can be adjusted appropriately. Ⅸ Water Boiling Alarm Circuit DesignOnce the water boils in the kitchen, if it is not turned gas off in time, the boiling water will overflow and extinguish the flame. The gas may spill, which is very unsafe. This problem can be solved by using the water alarm.👍 Circuit Working ModelFigure 9. Boiling Water Alarm CircuitThis circuit uses thermistor as the temperature sensing element. When the water temperature rises, the resistance of the thermistor decreases and the potential at point A increases. When the potential at point A is higher than the conversion voltage of the IC-1 inverter, the IC -1 will output low level, IC-2 will output high level. Making the audio oscillator composed of IC-3 and IC-4 work, and the piezoelectric ceramic sheet makes sound. When IC-2 outputs low level, the audio oscillator doesn’t work, and the piezoelectric ceramic chip is silent. 👉 Components SelectionIC uses C066 two input terminal four NAND gate, working voltage 3V~18V, power supply is 3V~6V; RT thermistor selection resistance value is about 1kΩ; piezoelectric ceramic chip diameter is 27mm; resistor selection is ordinary 1/8 or 1/4W metal film resistors. 👉 DIY and AdjustmentFind two starter shells of waste fluorescent lamps, use iron sheet as a clip, close the tops of the two starters, and fasten them with screws. One of the starters can be set on the mouth of the kettle to obtain the temperature of the water. The two pins of the thermistor are welded on the cover of the other starter and put into the shell. Note that the thermistor must be close to the inner shell wall to facilitate heat transfer. Solder the outer lead of the thermistor and the temperature sensor. After all the components are welded and checked, you can turn on the power for debugging. Put the temperature sensor on the mouth of the kettle, and adjust the RP when the water boils to make the piezoelectric ceramic sheet sound. Repeat it several times before this circuit can be used normally. If you want to change the sound frequency, you can change the C2 capacity. If you feel that the sound is light, you can connect an external transistor to the IC-4 output terminal to amplify the sound.  Ⅹ FAQ1. How do you make a security alarm circuit?The cathode of the photodiode is connected to the supply while the anode is connected to a 10KΩ resistor. Another end of the resistor is connected to the ground. The anode terminal of the photodiode is also connected to pin 5 of the LM358 op-amp, which is the non-inverting terminal. 2. What is the technique of alarm circuits?In a closed-circuit system, the electric circuit is closed when the door is shut. This means that as long as the door is closed, electricity can flow from one end of the circuit to the other. But if somebody opens the door, the circuit is opened, and electricity can't flow. This triggers an alarm. 3. What is a security alarm circuit?This circuit will help you to guard your precious documents as well as jewelry from intruders or theft. All you need is just to place this circuit in front of the locker or below the mat so when any unknown person comes and walks over the switch, the circuit will trigger and the sound of an alarm comes. 4. What type of circuits are security alarms made of?The simplest type of contact-operated security circuit consists of an alarm bell (or a buzzer or electronic 'siren sound' generator, etc.), wired in series with a normally-open (n.o.) close-to-operate switch; the combination being wired across a suitable battery supply, as shown in the basic 'door-bell' alarm circuit ... 5. What are the three basic parts of an alarm system?The main components of an alarm system would be a sensor, a camera, a motion detector, a buzzer a flash light and batteries. It is a component that is usually used to detect noise or movement. Sensors are usually connected to the circuit. 

IntroductionIn electronics, what is clipper? A circuit which removes the peak of a waveform is known as a clipper. Clipper circuit is designed to prevent a signal from exceeding a predetermined reference voltage level. The clipper circuit can be designed by utilizing both the linear and nonlinear elements such as resistors, diodes, or transistors. The diode clipper, also known as a diode limiter, is a wave shaping circuit that limits positive or negative amplitude, or both. In electronics, diode clipper circuits are commonly used to process various signals. It is is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. Clipping changes the shape of the waveform and alters its spectral components.Clipper Circuits IntroductionCatalogIntroductionⅠ Clipper Circuit Types1.1 Positive Clipper Circuit1.2 Negative Clipper Circuit1.3 Combinational Limiter CircuitⅡ Clipper Circuits Analysis2.1 Clipper Circuit Structure2.2 Clipper Circuit ProblemsⅢ General Forms of Clipper Circuits3.1 Clipper Circuit Description3.2 Common Clipper Circuit ExamplesⅠ Clipper Circuit TypesDiode clipper is a limiting circuit which limits the output voltage. In electronics, a clipper is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. A basic diode limiter circuit is composed of a diode and a resistor. It is divided into three types: positive clipper circuit, negative clipper circuit and combinational clipper circuit. The positive clipper circuit produces a clipping effect when the input voltage is higher than a certain upper limit value; the negative clipper circuit produces a limit effect when the input voltage is lower than a certain lower limit value; the combinational clipper circuit produces a limit effect when the input voltage is too high or too low. In a positive clipper, the positive half cycles of the input voltage will be removed. During the negative half cycle of the input, the diode is forward biased and so the negative half cycle appears across the output. The clipper circuits are described as following.1.1 Positive Clipper CircuitThe diode in clipper circuit is connected in series to the input signal and that attenuates the positive portions of the waveform. The positive clamping circuit blocks the input signal when the diode is forward biased. During the negative half cycle of an AC signal, the diode is forward biased and allows electric current through it. In following figure, when the input signal voltage is lower than a preset upper limit voltage, the output voltage will change with the input voltage, however, when the input voltage reaches or exceeds the upper limit, the output voltage will remain at a fixed value, so that the signal amplitude is limited at the output.1.2 Negative Clipper CircuitThe diode in clipper circuit is connected in series to the input signal and that attenuates the negative portions of the waveform, is termed as negative series clipper. For the figure below, the diode is series to the input and output. If the diode has ideal switching characteristics, when iu is lower than E, D will not conduct, ou=E; when ui is higher than E, D will conduct, ou=iu. The limiting characteristic of this limiter circuit is shown in the figure.1.3 Combinational Limiter CircuitThis kind of circuit combines the positive and negative limiters together which shows in the following figure. Ⅱ Clipper Circuits Analysis2.1 Clipper Circuit StructureIn the circuit, Al is an integrated circuit (a common component), VT1 and VT2 are transistors, Rl and R2 are resistors, and VDl to VD6 are diodes.Analyzing the effect of VD1 and VD2 in the circuit mainly explains the following points.1) It can be seen from the circuit that the circuit structure of the two groups of diodes are the same. Both play the same role in this circuit, so the working principle of them are the same.2) The pin ① is connected to the base of the transistor VT1 through a resistor Rl. Obviously Rl is a signal transmission resistor. The signal output on the pin ① is added to the base of VT1 through Rl (there is no DC blocking capacitor between pin ① and VT1). From this circuit structure, it can be judged that the pin ① is an output signal pin, and it outputs a composite signal of DC and AC. The purpose of determining that the pin ① is to figure out the specific function of the diode VD1 in the circuit.3) The DC voltage output by pin ① is not high enough to make the external diode in a conducting state. The analysis is: if the DC voltage output by the pin ① is high enough, then VD1, VD2 and VD3 conduct, and the internal resistance becomes small. This will shunt the AC signal output by the pin ① to the ground, so the signal will be attenuated. However, this circuit does not need such attenuation. Therefore, the conclusion drawn from this: VD1, VD2 and VD3 are not turned on by pin ① DC voltage output.4) The output from pin ① is the superimposed signal of DC and AC, which is added to the base of the transistor VT1 through the resistor Rl. VT1 is an NPN transistor. If the amplitude of the positive half-cycle AC signal added to the base of VT1 is very large, which may burn the VT1. When the negative half-cycle signal added to the base of VT1 is large, which has no effect on VT1, because the negative signal on the base of VT1 reduces current.Follow the above circuit analysis, it can be judged that VD1, VD2, and VD3 in the circuit has clipper function, to prevent VT1 from burning out. 2.2 Clipper Circuit ProblemsIn the figure, Ul is the DC voltage in the output of pin ①, U2 is the limiting voltage value.When the AC voltage in the output signal of pin ① is relatively small, the positive half cycle of the AC signal plus the DC output voltage does not make the VD1, VD2 and VD3 conduction. Therefore, all diodes are cut off, which has no effect on the AC signal output by pin ①. Assuming that the positive half-cycle output AC signal by pin ① is very large during a certain period, as shown in the signal waveform, at this time it plus the DC voltage can conduct VD1, VD2 and VD3. If the conduction voltage of each diode is 0.7V, then three diodes is 2.1V. Since the tube voltage drop after conduction is basically the same, that is, the maximum voltage of pin ① is 2.1V. So the excess part of the positive half cycle of the AC signal is limited by the resistor. When the DC and AC output signals at pin ① is less than 2.1V, diodes will not conduct and keep cutoff state, which has no clipping effect on the signal.For the specific details of clipper circuit, there are several explanations as follows.1) The negative half cycle large signal output by the pin ④ will not cause VT1 overcurrent, because it will decrease the base voltage of the NPN transistor and the base current, so there is no need to add the limiter circuit.2) The one-way limiter circuit mentioned above, it can only limit the large signal part of the positive or negative half of the signal, and does not limit the signal in the other half. The other is the combinational limiter circuit, which can limit the positive and negative half-cycle signals at the same time.3) There are many reasons for the abnormal increase of the signal amplitude. For example, the fluctuation of the power supply voltage cause it to increase a lot at a certain moment, and the large-scale interference pulse from the outside into the circuit also causes a certain increase.4) After the three diodes VD1, VD2 and VD3 conduct, the sum of the DC and AC voltages on pin ① is 2.1V. This voltage added to the base of VT1 through resistor Rl is maximum, so as to the current of VT1.5) Since the pin ① is the same as the external circuit of pin ②, the working principle of the limiter circuit is the same. So only one circuit needs to be analyzed when analyzing the circuit.6) According to the characteristics of the series circuit, the current in the series circuit is equal everywhere. It can be known that the three series diodes VD1, VD2 and VD3 are turned on at the same time, or they will be turned off at the same time. Therefore, in the series circuit, a diode is turned on and other diodes are turned on.Ⅲ General Forms of Clipper Circuits3.1 Clipper Circuit DescriptionThere are two types of clippers namely series and parallel. In series clipper, diode is connected in series with the load. In parallel clipper, diode is in parallel to the load.1) Series clippers: if the diode is connected in series with load resistanceUnbiased series clipper: in that case the circuit diode is connected in series with load resistance and no external voltage is applied to the circuit.+ve unbiased series clipper: if the +ve portion of output is clipped its called +ve unbiased series clipper.-ve unbiased series clipper: if the -ve portion of output is clipped its called +ve unbiased series clipper.Biased series clipper: if in the circuit, diode is connected in series with load resistance and external voltage is applied to the circuit+ve biased series clipper: if the +ve portion of output is clipped its called +ve biased series clipper.-ve biased series clipper: if the -ve portion of output is clipped its called +ve biased series clipper.2) Parallel clippers: if the diode is connected in parallel with load resistanceUnbiased parallel clipper: in that case the circuit diode is connected in parallel with load resistance and no external voltage is applied to the circuit.+ve unbiased parallel clipper: if the +ve portion of output is clipped its called +ve unbiased parallel clipper.-ve unbiased parallel clipper: if the -ve portion of output is clipped its called +ve unbiased parallel clipper.Biased parallel clipper: if in the circuit, diode is connected in parallel with load resistance and external voltage is applied to the circuit+ve unbiased parallel clipper: if the +ve portion of output is clipped its called +ve biased series clipper.-ve unbiased parallel clipper: if the -ve portion of output is clipped its called +ve biased series clipper. 3.2 Common Clipper Circuit ExamplesIn general, clippers circuit are classified into two types: Series Clippers, Shunt Clippers, and Dual (Combination) Clippers.Series Clipper: The diode is connected in series with the load resistance. 👇Figure 1. Series Positive ClipperThe positive amplitude waveform is cut, and the negative amplitude waveform is retained, as follows:Figure 2. Series Positive Clipper with Positive BiasThe positive amplitude waveform is cut, and the offset positive voltage is retained on the negative amplitude waveform, as follows:Figure 3. Series Positive Clipper with Negative BiasThe waveform of positive amplitude is cut, and the negative voltage is shifted based on the waveform of negative amplitude, as follows:Figure 4. Series Negative ClipperThe negative amplitude waveform is cut, and the positive amplitude waveform is retained, as follows:Figure 5. Series Negative Clipper with Positive BiasThe negative amplitude waveform is cut, and the positive voltage is offset on the positive amplitude waveform, as follows:Figure 6. Series Negative Clipper with Negative BiasThe negative amplitude waveform is cut, and the negative voltage is offset on the positive amplitude waveform as follows: Shunt Clipper: Diode is in parallel with load resistance in circuit. 👇Figure 7. Shunt Positive ClipperFigure 8. Shunt Positive Clipper with Positive BiasFigure 9. Shunt Positive Clipper with Negative BiasFigure 10. Shunt Negative ClipperFigure 11. Shunt Negative Clipper with Positive BiasFigure 12. Shunt Negative Clipper with Negative Bias Dual (Combination) Clipper: It is desired to remove a small portion of both positive and negative half cycles. 👇Figure 13. Combination ClipperWhen the positive and negative waveforms must be limited, a combinational limiter circuit is required, as follows:Images Reference: Clipper Circuits - Series Clipper, Shunt Clipper, and Dual Clipper Frequently Asked Questions about Diode Limiter and Clipper Circuit1. What is Clipper and clamper?The major difference between clipper and clamper is that clipper is a limiting circuit which limits the output voltage while clamper is a circuit which shifts the DC level of output voltage. ... While clamper is used when we need multiples of the input voltage at the output terminal. 2. What is the function of clipper circuit?In electronics, a clipper is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. A clipper does not distort the remaining part of the applied waveform. 3. What is Clipper circuit and its types?A clipper is a device which limits, remove or prevents some portion of the wave form (input signal voltage) above or below a certain level, in other words, the circuit which limits positive or negative amplitude ,or both is called chipping circuit. The clipper circuits are of the following types. Series positive clipper. 4. What is the difference between a positive clipper and a negative Clipper?Positive Clipper and Negative Clipper. In a positive clipper, the positive half cycles of the input voltage will be removed. ... During the negative half cycle of the input, the diode is forward biased and so the negative half cycle appears across the output. 5. How does diode clipping work?The Diode Clipper, also known as a Diode Limiter, is a wave shaping circuit that takes an input waveform and clips or cuts off its top half, bottom half or both halves together. This clipping of the input signal produces an output waveform that resembles a flattened version of the input. 6. What is the main purpose of a diode limiter?The diode limiter also called Clipper as it is used to limit the input voltage. A basic diode limiter circuit is composed of a diode and a resistor. Depending upon the circuit configuration and bias, the circuit may clip or eliminate all or part of an input waveform. It limits the output voltage to a specific value. 7. What is the purpose of a clamping diode?The clamping circuit fixes the voltage lower limit to zero, that is, the start of the signal is 0 V. The positive clamping circuit blocks the input signal when the diode is forward biased. During the negative half cycle of an AC signal, the diode is forward biased and allows electric current through it. 8. What is a diode clamping circuit?A clamper circuit shifts the DC level or the reference level of the signal to the desired level without changing the shape of the waveform. The clamper circuit can be designed using the diode, resistor, and the capacitor.

IntroductionPCB exists in every electronic device. A fully functional PCB is mainly used to create connections between components, such as resistors, capacitors, inductors, diodes, transistors, integrated chips, etc. It is the carrier of the entire logic circuit. Sound PCB design can save production costs, and achieve good circuit performance and heat dissipation effect. PCB designs vary in complexity according to product needs. This article mainly talks about wiring, one of the basics of PCB design.PCB Design: From Idea to Schematic to PCBCatalogIntroductionⅠ PCB Basics: Wiring RulesⅡ Three PCB Wiring MethodsⅢ PCB Design: Wire InspectionⅣ Complete PCB Design Projects Inspection4.1 General PCB Design Inspection Projects4.2 PCB Electrical Characteristics Checking Projects4.3 PCB Physical Characteristics Checking Projects4.4 PCB Mechanical Design Factors4.5 PCB Installation Requirements4.6 PCB Pull-out Requirements4.7 PCB Mechanical Considerations4.8 PCB Electrical Considerations4.9 Electronics Inspection Before Into A PCBⅤ ConclusionⅠ PCB Basics: Wiring Rules1. The area within 1mm from the edge of the PCB board and within 1mm around the mounting hole will not take wiring.2. The power line width should not be less than 18mil; the signal line width should not be less than 12mil; the cpu input and output lines should not be less than 10mil (or 8mil); the line spacing should not be less than 10mil.3. It is necessary noted that the power line and the ground line should be as radial as possible, and the signal line must not be looped.4. Ground circuit rulesThe loop area formed by the signal line should be as small as possible. The smaller the loop area, the less external radiation and the less interference from the outside. An example is shown in the figure below:5. Crosstalk controlHere crosstalk refers to the mutual interference caused by long parallel wiring between different networks on the PCB, which caused by the distributed capacitance and inductance between the parallel lines. The main measures to overcome it are:a. Increase the spacing of parallel wiring and follow the 3W rule. To ensure that the distance between the lines is large enough, when the distance between the line and the center of the line is not less than 3 times the line width (as shown in the figure below). If the line center distance is not less than 3 times the line width, 70% of the line electric fields will not interfere with each other, which is called 3W rule.b. Insert a grounded isolation wire between the parallel wires. Reduce the distance between the wiring layer and the ground plane.6. The direction control rules of routing:The routing directions of adjacent layers are orthogonal. Different signal lines in the same direction on adjacent layers should be avoided to reduce unnecessary interlayer crosstalk. When the signal rate is high, use a ground plane to isolate each wiring layer, in other words, isolate each signal line with ground line. The neighbouring wires used in the input and output end of the circuit shouldn’t be parallel to prevent the feedback, and it is best to add a ground wire between these wires.7. Open loop inspection rules for wiring:Generally, it is not allowed to have a floating wiring at one end, because of the "antenna effect" and unnecessary interference radiation and reception, which may bring unpredictable results.8. Impedance matching inspection rulesThe wiring width of the same network should be kept the same. Line width variations will bring uneven line characteristic impedance, and reflection will occur when the transmission speed is high. This situation should be avoided in the design. Under certain conditions, such as the lead wires of the connector and the similar structure of the lead wires of the BGA package, the change of the line width may not be avoided, so that the length of the middle inconsistent part should be minimized.9. Wiring closed loop inspection rules:Prevent signal lines from forming self-loops between different layers. Such problems are prone to occur in multilayer board design, and it will cause radiation interference. As shown below:10. The branch length control rule of wiring:Try to control the length of branches, and the general requirement is Tdelay≤Trise/20.11. Resonance rules of wiring:For high-frequency signal design, the wiring length must not be an integer multiple of its wavelength to avoid resonance.12. Line length control rules:In fact, it refers to the short-circuit rule. When designing, you should keep the wiring length as short as possible to reduce interference problems caused by unnecessary lines. Especially for some important signal lines, such as clock lines, be sure to place oscillators close to the device. In the case of driving multiple devices, the network topology should be decided according to the specific situation.13. Parallel input and output wires on the PCB board should be avoided as far as possible to avoid parallel. It is best to place a ground wire between the two wires to avoid circuit feedback coupling.14. Digital ground and analog ground should be separated. For low-frequency circuits, single-point parallel grounding should be used. High-frequency circuits should be grounded in series with multiple points. For digital circuits, the ground wire should be closed into a loop to improve anti-noise capability.15. The wiring and via distribution of the whole circuit board should be uniformity. When the outer signal of the circuit board has a large blank area, auxiliary lines should be added to make the lines distribution on the board basically balanced.16. The low-frequency circuit can be grounded at a single point in parallel, and the actual wiring can be connected in series and then grounded in parallel. The high-frequency circuit can be grounded in series with multiple points. The ground wire should be short and thick. For high-frequency components, a large area ground foil can be used. The ground wire should be as thick as possible. If the ground wire is a very thin, the ground potential will change with the current, which reduces the noise resistance.17. Multilayer boards should be as symmetrical as possible when designing the laminated structure, as well as the wiring density and copper layout of each layer to reduce warpage and reduce EMI during soldering.18. The signal line should not cross the power supply and ground. The signal reference plane should be as complete as possible.19. Impedance controlThe signal lines that need impedance control must be wired in strict accordance with the calculated data, in addition, it is necessary to tell manufacturers it. For signal lines that do not require it, the impedance should be calculated to prevent unnecessary interference.20. Grid copper should be used less in low frequency circuits. Although it can effectively reduce the problem of large area copper skin blistering. When using grid copper, you need to consider the electrical length of the grid line and the working frequency of the circuit board. If using grid copper, the power supply should also be coated with solid copper as much as possible.21. A group of buses with the same attribute should be wired side by side as much as possible, and the length should be as equal as possible. Ⅱ Three PCB Wiring MethodsThe wires should take the shortest route between components according to the specified wiring rules. Limit the coupling between parallel wires as much as possible. Good PCB design requires the minimum number of wiring layers, and also requires fair use of the widest wire and the largest pad size corresponding to packaging density. For example, rounded corners and smooth inner corners design may avoid some electrical and mechanical problems, therefore, sharp corners and sharp corners in the wire should be avoided. Here introduces three main PCB routing methods; right-angle wiring, differential wiring, and serpentine wiring to illustrate PCB layout:A. The influence of right-angle wiring on the signal is mainly reflected in three aspects:1. The corner can be equivalent to the capacitive load on the transmission line to slow down the rise time.2. Discontinuous impedance will cause signal reflection.3. The EMI generated by the right-angle tip reaches the RF field above 10GHz. Such a right-angle is likely to develop into the source of high-speed problems. B. To figure out what is differential wiring, you must first understand what is differential signal. In a word, the driving end sends two equal and inverted signals, and the receiving end judges the logic state "0" or "1" by comparing the difference between the two voltages. The pair of traces carrying differential signals is called differential traces. Compared with ordinary single-ended signal traces, differential signals have the most obvious advantages in the following three aspects:1. Have Strong anti-interference ability. Because the coupling between the two differential traces occurs, when there is noise interference from the outside, they are almost coupled to the two lines at the same time. However, the receiving end only cares about the difference between the two signals. Therefore, the external common mode noise can be completely canceled.2. It can effectively suppress EMI. Due to the opposite polarity of the two signals, the electromagnetic fields radiated by them can cancel each other out. What’s more, the tighter the coupling, the less the electromagnetic energy leaked to the outside world.3. The timing positioning is accurate. Because the switch change of the differential signal is located at the intersection of the two signals. Unlike ordinary single-ended signals, which rely on the high and low threshold voltages to judge. Timing positioning is less affected by the process and temperature, and also more suitable for circuits with low amplitude signals. The current popular LVDS (low voltage differential signaling) refers to this small amplitude differential signaling technology. C. Serpentine line is a type of wiring method often used in PCB layout. Its main purpose is to adjust the delay to meet the system timing design requirements. The two most critical parameters are the parallel coupling length (Lp) and the coupling distance (S). Obviously, when a signal is transmitted on a serpentine trace, the parallel line segments will be coupled in a differential mode. The smaller the S, the greater the Lp, the greater the coupling. It may cause the transmission delay to be reduced, also the signal quality is greatly reduced due to crosstalk. The mechanism can refer to the analysis of common mode and differential mode crosstalk. The following are some suggestions when dealing with serpentine wring:1. Try to increase the distance (S) of parallel lines, at least more than 3H(H refers to the distance from the signal trace to the reference plane). As long as S is large enough, the mutual coupling effect can be almost completely avoided.2. Reduce the coupling length Lp. When the double Lp delay approaches or exceeds the signal rise time, the crosstalk generated will reach saturation.3. The signal transmission delay caused by the strip-line or embedded micro-strip line is less than that of the micro-strip. Theoretically, the strip-line will not affect the transmission rate due to differential mode crosstalk.4. For signal lines with high-speed and strict timing requirements, try not to take serpentine lines, especially in a small area.5. You can often use s-shaped routing at any angle, which can effectively reduce the mutual coupling.6. In high speed, the serpentine line has no ability so-called filtering or anti-interference, and can only reduce the signal quality, so it is better to use for timing matching.7. Sometimes you can consider the spiral routing method for winding. Simulation shows that its effect is better than normal serpentine routing.Ⅲ PCB Design: Wire Inspection1.Wire SpacingThe minimum spacing of wires must be determined to eliminate voltage breakdown or arcing between adjacent wires. The spacing is variable, it mainly depends on the following factors:1) Peak voltage between adjacent wires2) Atmospheric pressure (maximum working altitude)3) Coating layer4) Capacitive coupling parametersComponents with critical impedance or high-frequency components should be placed very close to reduce the critical stage delay. There is something need to pay attention to. Transformers and inductive components should be isolated to prevent coupling. Inductive signal wires should be laid orthogonally at right angles. Components that generate any electrical noise due to magnetic field movement should be isolated or rigidly installed to prevent excessive vibration.2. Whether the wire is short and straight without sacrificing function.3. Whether the restrictions on the wire width are complied with.4. There must be a minimum distance between wires, wires and mounting holes, wires and pads.5. Whether to avoid all the wires (including component leads) closer to parallel wiring.6. Whether sharp corners (≤90℃) are avoided in the wire pattern. Ⅳ Complete PCB Design Projects Inspection4.1 General PCB Design Inspection Projects1) Has the circuit been analyzed? Is the circuit divided into basic units to smooth the signal?2) Does the circuit allow short or isolated key leads?3) Where must be shielded, are they effectively shielded?4) Have you made full use of the basic grid graphics?5) Is the best size of the printed circuit board?6) Do you use the available wire width and spacing as much as possible?7) Has the preferred pad size and hole size been used?8) Are the base plate and the sketch consistent?9) Is less cross-wiring used? Do cross wires pass through components and accessories?10) Are the letters visible after assembly? Are their size and model correct?11) In order to prevent blistering, is there any window on the large area of copper foil?12) Are there tool positioning holes?4.2 PCB Electrical Characteristics Checking Projects1) Have you analyzed the influence of wire resistance, inductance, and capacitance, as well as the critical voltage drop on the ground?2) Does the wire spacing and shape meet the insulation requirements?3) Has the insulation resistance value been controlled and specified in key areas?4) Is the polarity fully recognized?5) According to geometric view, has the effect of wire spacing on leakage resistance and voltage been measured?6) Has the medium for changing the surface coating been identified?4.3 PCB Physical Characteristics Checking Projects1) Are all pads and their positions suitable for final assembly?2) Can the assembled PCB meet the shock and vibration conditions?3) What is the required spacing of standard components?4) Are the components that are not firmly installed or the heavier parts fixed?5) Is the heating element heat dissipation and cooling normally? Or is it isolated from the printed circuit board and other heat-sensitive elements?6) Are the voltage divider and other multi-lead components placed correctly?7) Is the arrangement and orientation of components easy to check?8) Has it eliminated all possible interference on the printed circuit board?9) Is the size of the positioning hole correct?10) Are the tolerances complete and reasonable?11) Have you controlled and signed the physical properties of all coatings?12) Is the ratio of via hole and lead diameter within an acceptable range?4.4 PCB Mechanical Design FactorsThe printed circuit board adopts mechanical methods to support the components, however, it cannot be used as an unique structural part of the entire device. On the edge of the printing plate, at least every 5 inches for a certain support. The factors that must be considered when selecting and designing printed circuit boards are as follows:1) The size and shape of the printed circuit board.2) The type of mechanical accessories and plug (seat) required.3) The environmental adaptability of circuits.4) According to some factors, such as heat and dust, install the printed circuit board vertically or horizontally.5) Some environmental factors that require special attention, such as heat dissipation, ventilation, shock, vibration, and humidity, dust, and radiation, etc.6) Physical support7) Install and fix.8) Disassemble4.5 PCB Installation RequirementsAccording to practical experience, the distance between the supporting points of a printed circuit board with a thickness of 0.031-0.062 inches should be at least 4 inches. For a printed circuit board with a thickness greater than 0.093 inches, the distance between the supporting points should be at least 5 inches. Taking this measure can improve the rigidity of the printed circuit board and avoid possible resonance. The following factors should be considered before deciding which mounting technology they use.1) PCB structure.2) Input and output terminals.3) Available equipment space.4) Convenience of loading and unloading.5) Type of attachments.6) Required heat dissipation.7) Required shieldability.8) The type of circuit and its relationship with other circuits.4.6 PCB Pull-out Requirements1) The influence of plugging tools on the installation distance between two printed circuit boards.2) When the plug-in tool used in the equipment, its size should be considered.3) A plug-in device is required, which is usually fixed to the printed circuit board assembly with rivets.4) As for the mounting frame of the printed circuit board, special design such as load bearing flange is required.5) The adaptability of the plug-in tool used and the size, shape and thickness of the printed circuit board.4.7 PCB Mechanical ConsiderationsThe characteristics of the board substrate that have an important influence on the printed circuit assembly are: water absorption, thermal expansion coefficient, heat resistance, flexural strength, impact strength, tensile strength, shear strength and hardness. All these characteristics affect the function and the production efficiency of the printed circuit board structure. For most applications, the dielectric substrate materials of the printed circuit board are as following:1) Phenolic impregnated paper2) Acrylic-polyester impregnated randomly arranged glass mat3) Epoxy impregnated paper4) Epoxy impregnated glass clothEach substrate can be flame retardant or combustible. The first 3 types mentioned above can be processed. The most common used material for printed circuit boards with metalized holes is epoxy-glass cloth. Its dimensional stability is suitable for high-density circuits and can minimize the occurrence of cracks in the metalized holes. One disadvantage of epoxy-glass cloth laminate is that it is difficult to punch in the usual thickness range of printed circuit boards. For this, all holes are usually drilled and copied and milled to form a print shape of the circuit board.4.8 PCB Electrical ConsiderationsIn DC or low-frequency AC applications, the most important electrical characteristics of insulating substrates are: insulation resistance, anti-isolation, printed wire resistance, and breakdown strength. In high frequency and microwave applications, include: dielectric constant, capacitance, and dissipation factors. In all applications, the current carrying capacity of printed wires is important.4.9 Electronics Inspection Before Into A PCB1) Check the rationality and correctness of the schematic diagram.2) Check the correctness of the component packaging of the schematic.3) The distance between strong and weak current lines, and the distance between isolation areas.4) Check the schematic diagram and PCB diagram to prevent the loss of the network table.5) Whether the package of the component matches the physical object.6) Whether the placement of the components is appropriate.7) Whether the components are easy to install and disassemble.8) Whether the temperature sensitive element is too close to the heating element.9) Whether the distance and direction of the mutual inductance components are appropriate.10) Whether the placement between the connectors is smooth.11) Easy to plug in and plug out12) Input and output13) Strong current and weak current14) digital and analog should be interlaced.15) Arrangement of elements on the upside and downside16) Check whether the directional component has been wrong flipped instead of rotated.17) Check whether the mounting holes of the component pins are suitable and whether it is easy to insert.18) Check whether the empty pin of each component is normal and whether it is a missing line.19) Check whether there are vias between the upper and lower wiring of the same net table. And the pads are connected through the holes, to prevent disconnection and ensure the integrity of the circuit.20) Silk screen printing should be clear, so that the operation of welding or maintenance can be easy.21) The arrangement of power and signal lines in the socket should ensure signal integrity and anti-interference.22) Pay attention to the proper ratio of pads and solder holes.23) Each plug should be placed on the edge of the PCB board as much as possible and easy to operate.24) Whether the size and distribution of the mounting holes on the PCB are appropriate to reduce the PCB bending stress.25) Pay attention to the height distribution of the components on the PCB to ensure easy assembly.Ⅴ ConclusionBased on the above mentioned rules, drawing the PCB schematics you need becomes easier. Decide what PCB you want to and install a PCB design software. PCB software is really helpful and powerful. Also a software can check your design to make sure the design does not contain errors such as traces that incorrectly touch, traces too skinny, or drill holes that are too small. For example, run the Electrical Rules Checker (ERC) to see if you’ve made any typical errors. There is less thing stopping you from making your first PCB, right? Frequently Asked Questions about PCB Design Diagram1. Which side of PCB is correct for soldering?The bottom side of the PCB is usually the side without components and the side that touches the solder wave during assembly. That is why sometimes it is also called SOLDER side. However more often, PCB are populated on both sides and the assembly process does not require wave soldering. 2. Which soldering method is suitable for soldering printed circuit board?Soldering Iron – Used to melt solder and connect component pins to board pads. A cheap soldering pencil may be sufficient, but a temperature-controlled solder station is best for high performance boards. Solder – An alloy of tin and lead with a low melting point. 3. What is PCB diagram?A PCB schematic is a simple two-dimensional circuit design showing the functionality and connectivity between different components. ... Once the blueprint has been completed, the PCB design comes next. The design is the layout, or physical representation of the PCB schematic and includes the copper track and hole layout. 4. Why we use PCB in soldering?PCB soldering is another term for the process of soldering electrical circuit boards. ... As the soldering iron melts this metal, it is then used a bit like glue to stick to pieces together. As the solder metal cools, it will re-harden into one large shape that connects the two parts. 5. How do you read a PCB board?Start with an easy analog circuit, such as a guitar distortion pedal, and work your way up to more complicated versions. Make a drawing of the top of the circuit board. Show the positions of the capacitors, integrated circuits, resistors, transistors and other components. Review it to make sure everything is included.

Ⅰ IntroductionThe vacuum tube was an essential part of early radios, used to create and amplify the electrical signals needed for the radio to work. The vacuum tube radio was a new stuff of the early 20th century, and immediately became the "new favorite" of that era with the launch of the radio show. Due to the continuous development of technology and the emergence of transistors, vacuum tubes were swept away by the powerful transistors in the 1960s and 1970s. With the improvement of people's lives, they have a new understanding of sound quality, and people are once again interested in the beautiful sound of vacuum tube radios.Vacuum Tube Radio RepairCatalogⅠ IntroductionⅡ Vacuum Tube Radio Circuit2.1 Input Circuit2.2 Converter Stage2.3 Detection Stage2.4 Intermediate Amplifier Stage2.5 Audio Voltage Amplifier2.6 Audio Power Amplifier Stage2.7 RectifierⅢ Classification3.1 AM Radio3.2 Heterodyne Radio3.3 FM Radio3.4 Service LifeⅣ Audio Maintenance PrincipleⅤ Specific Troubleshooting5.1 Tube Inspection5.2 Resistor Inspection5.3 Capacitor Inspection5.4 Transformer InspectionⅥ One Question Related to Vacuum Tube Radio and Going FurtherCompared with the semiconductor radio, the biggest advantage of the tube radio is that the sound quality is obviously better than that of the semiconductor radio. The second is that it is stable and elegant, with classical temperament. In addition, the history of tube radios is far greater than that of semiconductor radios, which are more valuable for collection. Ⅱ Vacuum Tube Radio CircuitFigure 1. 12AV6 Vacuum Tube Radio Circuit2.1 Input CircuitThe circuit from the antenna of the radio to the input of the first-stage tube is called the input circuit. It has two tasks to complete: One is to transmit the high-frequency signal voltage induced on the antenna to the grid of the first electron tube (usually the frequency conversion stage). To accomplish this task, there should be a certain coupling between the radio antenna and the input circuit to facilitate signal transmission. Second, because the antenna induces a lot of signals, it is necessary to select the radio broadcast signal you want to listen to  suppress unnecessary signals. To accomplish this task, the input circuit should be composed of a selective resonant circuit, so the input circuit should compose of coupling elements and the resonant circuit.Depending on the coupling form of the antenna and the resonance circuit. The input circuit can be divided into three types: inductive coupling (transformer coupling) circuit, capacitive coupling circuit, and inductive capacitive coupling circuit. Since the voltage transmission coefficient of the inductive coupling circuit is relatively high and uniform, tube radio usually adopts this type. In order to improve the suppressing ability of mid-frequency interference (because the intermediate-frequency detuning is smaller for medium wave, and it is larger for short wave.). An intermediate-frequency trap circuit is also applied in the antenna loop.2.2 Converter StageThe converter stage is located between the input circuit and the intermediate amplifier stage. Its function is to change the high-frequency amplitude modulation signal into a fixed intermediate-frequency amplitude modulation signal. In order to complete the task, the frequency converter should be composed of four parts: oscillator (generating a high frequency constant-amplitude oscillating voltage with an intermediate-frequency different from the frequency of the external radio signal), a high frequency circuit (used to select the radio signal, usually it is the input circuit), non-linear components (usually pentagrid converter, used to change the frequency), the intermediate-frequency loop.The converter stage of a tube radio is generally composed of a pentagrid converter tube. The high-frequency circuit is connected to the third grid (signal grid). The oscillator is composed of the screen grid (oscillation anode), the first grid (oscillation grid) and the cathode. The anode load is an intermediate frequency resonance circuit. Therefore, the main mark that distinguishes the converter stage from the tube amplifier is the pentagrid tube and three resonant circuits. The frequency converter can be divided into single-grid converter and double-grid converter according to the different ways of inputting signal voltage and local oscillation voltage. The single-grid inverter applies the signal voltage and the local oscillation voltage to the same electrode of the inverter tube, so the traction effect is large, and the operation is unstable. The double-gate inverter adds the signal voltage and the local oscillation voltage to the different electrodes of the inverter tube separately, the traction effect is greatly reduced, thus double-bar frequency converters are commonly used in tube radios.The structural feature of pentagrid tubes is that there are two metal sheets on the second grid, called the collection screen. It blocks the electrons moving to the anode. There are two metal rods on the third grid in the gap of the collecting screen, which carry negative potential. When the electrons passing through the second grid hit the negatively charged metal rod while advancing, the electrons flying to the anode is divided into two streams, one flying to the anode, and the other being collected by the collecting screen without returning to the cathode. In this way, when the signal grid voltage changes, it will only affect the distribution of the two currents, and has little effect on the total current. Because the local oscillator adopts the total current feedback, the oscillator is basically not affected, so the oscillation frequency is stable. There are many types of frequency converter circuits with different performances, but their principle difference lies in the way of local oscillation feedback. 2.3 Detection StageThe detection stage is located between the intermediate amplifier stage and the audio voltage amplifier stage. Its task is to transform the intermediate-frequency signal into the original modulated audio signal. To complete the task of frequency conversion, the detector must consist of an intermediate-frequency signal circuit (it is the output circuit of an intermediate-frequency amplifier), a non-linear elements (usually a diode), and a load (resistor). 2.4 Intermediate Amplifier StageThe intermediate amplifier stage is located between the frequency converter stage and the detection stage, and specifically amplifies the 465kHz intermediate-frequency signal. The main feature of the intermediate amplifier stage is: in order to achieve automatic gain control, the intermediate amplifier tube generally uses a remote cut-off tube. The intermediate-frequency transformer is the main component of the intermediate-frequency amplifier, and its quality directly affects the quality of the radio. In addition, a shielding cover is usually used to avoid the parasitic coupling between the intermediate-frequency loop and the eternal to improve the working stability. The shielding cover is made of good conductors such as aluminum and copper, and is attached to the case (ground potential), to isolate the entry of high frequency electromagnetic fields. 2.5 Audio Voltage AmplifierTo make the power amplifier stage output a certain amount of power, its anode current must have a certain amount of AC component, which requires that the grid audio signal voltage used to control the anode current must have a sufficiently large amplitude (voltage). The output voltage of the detector stage is usually very low. Therefore, between the power amplifier stage and the detector stage, there is always one or several audio voltage amplifier stages. Its function is to amplify the audio signal voltage to meet the input signal requirements.The audio voltage amplifier stage can be divided into a resistance-capacitance coupling amplifier and a transformer-coupled amplifier according to the different anode load forms. In the vacuum tube radio, the resistance-capacitance coupling amplifier is used mostly. The audio voltage amplifier stage and the detection stage usually share an electron tube. The input signal is generally controlled by a volume control potentiometer to adapt to different broadcasts and listening situations. Some radios have a tone control circuit connected to the output end of the audio voltage amplifier stage to flexibly change the frequency characteristics of the amplifier to make the sound pleasant. Due to the different forms of volume and tone control circuits. There are many types of audio voltage amplifier stages. 2.6 Audio Power Amplifier StageThe audio power amplifier stage is the last stage of the tube radio, and its function is to output a certain amount of audio power to make the speaker work normally. Someone may wonder, can a voltage amplifier be used instead of a power amplifier? This will not work. Although there is no difference between the basic circuits of a power amplifier and a voltage amplifier, due to the different tasks of the two, there are significant differences in the selection of electron tubes, the circuit components, and the nature of the load. It should be pointed out that the so-called power amplifier does not amplify the input power itself, but uses the control function of the electron tube grid voltage to convert the power supplied by the anode circuit DC power supply into the required audio power. From the viewpoint of energy conversion, the power amplifier is an energy converter. 2.7 RectifierThe rectifier stage of the tube radio is composed of three parts: power transformer, rectifier tube and filter. There are many forms of rectifier circuits, and the most common is a full-wave rectifier circuit.Ⅲ Classification3.1 AM RadioIn the era when tube radios were popular. AM radios were the mainstream products. Amplitude modulation is to modulate the high frequency carrier with audio signal. Its waveform is symmetrical up and down, and the amplitude is the same as the modulated signal. After detection, the highfrequency component is filtered out to obtain the audio signal. The frequency of the carrier signal (the frequency of the broadcasting station) is the carrier frequency.AM radios can receive medium wave and short wave broadcasts, and some can receive long wave broadcasts. Since the mid-band frequency interval has been unified to 9KHz, its highest audio frequency is only 4KHz. The sound quality is affected, and electromagnetic interference is relatively large.There are two main types of AM radios: direct-amplifier type and heterodyne type.1)Direct-amplified radio, also known as high-amplification radio, its typical circuit structure is such as: High-amplification→Detection→Low-amplification→Power amplifierA circuit that uses a grid detector circuit and a high-frequency positive feedback, called a regenerative radio, can achieve better sensitivity and selectivity. It can receive AM telegraph signals with high-amplifier and short-wave. Old Japanese-made radios mostly have this circuit. High-frequency signals of direct-amp radios are prone to self-excitation, and the high-end and low-end gains are uneven, and there is no high-amplifier regeneration. Widespread use of reed speakers with poor sound quality made it obsolete. Out of nostalgia, some enthusiasts are still keen on getting recycled radios. The regenerative circuit can not only be applied to direct-amplified radios, but also in simple heterodyne radios, because proper positive feedback can also be used to improve sensitivity.Simple regenerative radios often use reed speakers, which have high impedance (about 10K) and high sensitivity, and can be directly used as the load of the power amplifier tube. Its frequency range is only 350~3000Hz, so the sound quality is poor. Later regenerative radios used moving coil speakers, and the sound quality was better. However, due to the low impedance, an output transformer is needed, and its primary impedance must match the load impedance of the power amplifier tube. Moving coil speakers are divided into permanent magnet, constant magnet and excitation type. In addition, excitation horns are used in AC tube radios, and their excitation coils can also be used as filter chokes. 3.2 Heterodyne RadioThe heterodyne radio uses a frequency conversion circuit. The signal generated by the high-frequency oscillation circuit is different from the input signal at a certain frequency. After the two are combined, a fixed intermediate frequency signal (455~465KHz) is generated. The oscillation circuit needs independent vacuum tube as a part before the emergence of the dedicated frequency conversion tube. Some people call the oscillation frequency higher than the signal frequency by a heterodyne type.Heterodyne plus intermediate-frequency amplifier circuit is called superheterodyne. This type of circuit requires a single electron tube to oscillate. Later a multi-pole or composite tube dedicated to frequency conversion appears, such as 1A2, 6A2, 6SA7GT, 6U1, 6K8, etc. The superheterodyne type is the most common circuit of commercial radios. It has an automatic volume control circuit and can add tuning instructions. The superheterodyne radio can obtain more stable and higher gain due to the fixed frequency amplified. The disadvantage is that there is image frequency interference.The circuit structure of a typical superheterodyne radio is as follows:Frequency conversion→Middle amplifier→Detection→Low amplifier→Power amplifier 3.3 FM RadioFM is to use audio signal to modulate the frequency of high-frequency carrier. Its advantages are strong anti-interference ability, high signal-to-noise ratio, good frequency bandwidth and sound quality, and the audio frequency can reach 20~15000Hz. Because the FM audio work in the ultra-high frequency band, it can accommodate many radio stations. Because of its linear propagation characteristics, the same frequency can be reused at a distance of hundreds of kilometers, which can effectively solve the problem of congestion of medium and short-wave radio stations.Modern FM broadcasting is compatible with stereo and mono (in the early days of stereo broadcasting, two frequencies were used and received by two radios). Amateurs like to use a simple super-regenerative circuit to receive FM broadcasts. Because it works in a self-oscillation state, it is unstable and has strong super noise. 3.4 Service LifeThe general design life of the valves is 2000 hours (special tube has 5000~10000 hours), but in reality, many electron tubes break after using 2000 hours, for example, there is no sound. Its performance is not up to the design standard. When there is not any sound from the actual tube, it may have reached 3000 hours or more. The actual service life of the amplifier tube of the front stage is longer. To cite the simplest example: the old picture tube (picture tube is also a kind of vacuum tube) of a TV set, the actual life span usually excesses 10 years.If use it for 5 hours a day, you need to change the tube once a year to meet the actual design performance, and the replaced tube can also be used for other purposes.Ⅳ Audio Maintenance PrincipleHow to repair the failure of the vacuum tube radio depends on the difficulty of the failure. Under normal circumstances, the following steps are used.First point is to seek clues. What is the difference in the use of the radio before and after the failure, thinking about whether it has been repaired, or what components have been replaced, etc.Second point is the fault display. For faults such as flashover, smoking, burning, etc. Turn off the power immediately and find the factor to avoid damage to the audio. According to the displayed failure phenomenon, rotate audio button to compress the failure to clarify where the failure may occur, and to provide necessary information for analysis and judgment.Third point is analysis and judgment. Make comprehensive analysis and judgment based on the information obtained by self-examination inference and fault display. List all possible direct causes of the failure, and develop a scientific inspection procedure. This not only prevents blind movement, but also accumulates maintenance experience and improves efficiency.Fourth point is troubleshooting. Gradually narrow the scope of the fault, and accurately detect the fault point. Sometimes it refers to (such as electron tubes, capacitors, resistors, coils, transformers, etc.) connecting wires, welding points of a certain component. Determine where the failure occurred, which is important for fault repair. Tube radios are usually divided into high-frequency part, intermediate frequency part, audio part, power supply part and auxiliary circuit according to their working frequency and circuit function. The fault should be compressed to a specific circuit, such as DC circuit, AC circuit, or the anode circuit, the screen grid circuit, grid circuit, cathode circuit, etc. Since each loop in the electronic tube circuit affects each other, a failure of a component may affect several loops at the same time. Therefore, in the inspection process, comprehensive analysis should be performed, that is, each circuit should not be isolated.Fifth point is repairing practice. The repair test can be performed after determining the cause of the failure.Sixth point is repair inspection. In the actual maintenance process, if a failure point is detected, it must be immediately eliminated and repaired. After all the faults are investigated, the radio should be inspected as necessary to ensure the quality of the repair. The specific content of the inspection depends on the specific fault and the type and quantity of the instrument. The simplest one should also be auditioned and take general technical observations.Ⅴ Specific TroubleshootingA radio is composed of many components, and component damage is the main cause of radio failure. When the fault location is gradually reduced, the quality of the components must be checked to determine the fault. Therefore, inspecting components is one of the main methods to find the cause of failure.5.1 Tube InspectionThe common faults of electronic tubes are mostly filament broken, poor contact of the electric board, broken pole, pole touching, leakage, breakdown between the cathode and the filament, aging, air leakage, and micro-sound effects. When the radio is turned on, if the filament of a certain tube does not light up, the filament may be broken or a serious leak. The tube shell is cold when the filament is broken, and the tube shell is often warm when the gas leaks. Unplug the tube for further inspection. Use a multimeter to measure the filament resistance at the "R×1"gear. If the meter indicates infinite, the filament is disconnected. If the indicator of the needle is zero, it means that the tube is short-circuit. When the indicator of the needle indicates a constant value, it means that there is leakage between the electrodes. The smaller the resistance, the more serious the leakage. At this time, the top of the tube is usually milky white.The electron tube electrode is in poor contact, intermittently electrode touching (some are hot electrode touching), and the radio will sometimes have no sound or noise. This type of failure is characterized by being greatly affected by vibration. Therefore, you can tap the tube shell lightly. If there is no sound or noisy sound (sometimes there may be no sound or normal sound after tapping), it means that the tube electrode is in poor contact or intermittently electrode touching. When the fault is serious, the electrode is completely disconnected, which means a broken pole. The tube does not work, and the radio is silent.When the electron tube ages, the positive current and the amplification will decrease. If it was frequency conversion tube, the local oscillator will oscillate abnormally, resulting in the radio cannot receive the radio signal, low sound, or the high frequency end of the band can receive one or two radio stations, and the low-frequency end cannot receive the radio signal. The micro-phonic effect of the vacuum tube is often caused by improperly fixing the electrode, and it can be judged by tapping the tube case lightly. Sometimes it is difficult to determine whether the valve is normal or not. The easiest way is to replace it with the same type of electron tube. If the failure disappears, it means that there is a problem with the vacuum tube. 5.2 Resistor InspectionThere are two types of resistors used in radios: fixed resistors and variable resistors (potentiometers). They are not easy to damage. Possible damages include: resistor burnout, resistor body broken or lead broken, internal open circuit, or poor lead contact, etc. Some of failure can be observed. For example, the increase of fault current in a certain part of the circuit, which means the resistor is burned out. At this time, the paint layer on the outside of the resistor is burnt and hot. If the resistor is internally disconnected or the resistance value changes, it can be checked by measuring the ohm gear of a multimeter. If the meter indicates infinity, it means that the resistor is internally open; if the measurement result is too far from the nominal value (the error exceeds 20%), it means that the resistance has deteriorated.The lead of the resistor body is in poor contact and will be broken unbroken, which will cause noise or sound from the radio. This kind of failure is very susceptible to vibration and produces vibration noise. Therefore, you can gently shake the resistor body to see if the sound changes. It can also be measured with a multimeter. When measuring, shake the resistor body. If the pointer is unstable, it means that the contact is bad.The potentiometer that controls the volume of the radio usually has a power switch. The common faults of the potentiometer are: dirty carbon film, wear of the carbon film, poor contact of the sliding contact, loose lead-out piece, burnt of the carbon film, broken bakelite frame of the sliding contact, leakage, and damage to the power switch. When the potentiometer is normal, the radio can only hear a very light sound after power on. If the potentiometer is closed, the broadcast voice should not be heard. After turning off the power, there is no sound. If you cannot control the power on and off, it indicates that the power switch is partially damaged; if the noise is very loud, especially when the volume is adjusted, the loudspeaker has a large sound or interrupted sound, it means that the potentiometer is in poor contact. 5.3 Capacitor InspectionThere are two types of capacitors used in radios: fixed capacitors and variable (semi-variable) capacitors. The faults of fixed capacitors are usually leakage, breakdown, internal open circuit, poor internal contact, broken lead, or capacity failure, etc. The common faults of variable capacitors are bump, short circuit, leakage and so on. 5.4 Transformer InspectionCommon faults in transformers are coil mold breakage, a partial short circuit, leakage and other faults. A multimeter can also check out the coil mold. When high-frequency coils and intermediate-frequency transformers are locally short-circuited, it is not easy to measure. The substitution method can be employed to test or adjust the loop frequency to figure problems out.Ⅵ One Question Related to Vacuum Tube Radio and Going Further6.1 QuestionWhy do vacuum tubes sound better?6.2 AnswerTubes sound better because their distortion products are more musical. Those are the fundamental reasons why tubes simply sound better. Vacuum tubes are the more linear and require less feedback. Tubes are voltage amplifiers as opposed to transistors which are current amplification devices. Frequently Asked Questions about Vacuum Tube Radio1. What is a vacuum tube radio?VACUUM TUBE RADIO. Vacuum Tube Radio. By the late 1920s, vacuum tube radio equipment replaced the primitive spark-gap systems on most merchant ships. This new equipment could send and receive signals virtually worldwide, by using high frequency or "short-wave" bands. 2. How do radio vacuum tubes work?The basic working principle of a vacuum tube is a phenomenon called thermionic emission. It works like this: you heat up a metal, and the thermal energy knocks some electrons loose. ... When the cathode is heated, and a positive voltage is applied to the anode, electrons can flow from the cathode to the anode. 3. Why are vacuum tubes better for audio?Tube amplifiers sound better because of the euphonic distortions they add to the music, as well as plenty of other reasons I'll cover below. ... We use tubes simply because they make the music we create sound better: smoother, warmer and cleaner. Ditto for guitar amplifiers used in creating music. 4. How do you know if a vacuum tube is bad?When a vacuum tube develops an air leak (a small crack or bad seal by a pin for example) this getter color will change to pure white. If you see this you know with 100% certainty that the tube is bad. Third, look for a purple glow that is very focused around specific elements inside the tube.