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 IntroductionPower systems are more complex than we see. In reality, we cannot see components of electricity, but we can inject how it works (or does not work). A current transformer is one of many elements that come together like a puzzle to form electrical power. A CT is made up of a laminated steel core, a secondary winding around the core, and insulating material surrounding the windings in its most basic form.Current transformers can be used in a variety of metering applications and use, including Wattmeters, power factor meters, watt-hour meters, protective relays, and as trip coils in magnetic circuit breakers, or MCBs.  CatalogIntroductionⅠ What is a Current TransformerⅡ Classification and Types of Current TransformerⅢ The function of Current TransformerⅣ Application of  Current TransformerⅤ Current Transformer Ratio and Polarity    5.1 Current Transformer Ratio  5.2 Current Transformer Polarity    5.3 Electrical Drawing Conventions for CT PolarityⅥ  How to Test CT PolarityⅦ  How to Choose The Right Current Transformer7.1 Genres of System7.2 Requirement of PrecisionⅧ Frequently Asked Questions about Current  Transformer  Ⅰ What is a Current Transformer A current transformer is a device that generates an alternating current in its secondary that is proportional to the alternating current in its primary. When a current or voltage is too high to measure directly, this method is applied. The induced secondary current is then appropriate for measuring instruments or processing in electronic equipment that requires isolation between the primary and secondary circuits.Because high-voltage currents are reduced, a standard ammeter can be used to safely monitor the actual electrical current flowing in an AC transmission line.Figure1: current transformers An electrical CT differs from a voltage or power transformer in that its primary winding has only one or a few turns. It also differs from a voltage transformer in that the prime current is not controlled by the secondary load current but rather by an external load. The CT ratio is the number of secondary turns multiplied by the number of primary turns. This ratio is calculated based on the primary conductor passing through the transformer window once. Ⅱ Classification and Types of Current Transformer There are two categories in the current transformer. The first, a measuring current transformer, is applied to conjunct with measuring devices for current magnitude, energy, and power. The other, a protective current transformer, is used in conjunction with protective equipment such as trip coils, relays, and the like.Current transformers are classified into three basic types: wound, toroidal, and bar.  1. Wound Current Transformer–The primary winding of the transformer is physically connected in series with the conductor carrying the measured current flowing in the circuit. The magnitude of the secondary current is determined by the transformer's turns ratio.  2. Toroidal Current Transformer -There is no primary winding in these. Instead, the line carrying the network's current is threaded through a window or hole in the toroidal transformer. Some current transformers have a "split core," allowing them to be opened, installed, and closed without disconnecting the circuit to which they are connected.  3. Bar-type Current Transformer-The primary winding of this type of current transformer is the actual cable or bus-bar of the main circuit, which is equivalent to a single turn. They are fully insulated from the system's high operating voltage and are typically bolted to the current-carrying device. Bar-type Current Transformer.Figure2: the typical current transformer  Ⅲ The function of Current Transformer One of the functions of the current transformer is to be used for measurement, and it is often used for billing or measuring the current of the equipment in operation. When measuring large alternating currents, to facilitate meter measurement and reduce the risk of direct measurement of high-voltage electricity, it is often necessary to use current transformers to convert them into a more uniform current. Thus, current transformers are considered as the role of current conversion and electrical isolation.Another function is protection : It is frequently used in tandem with a relay device. When a short circuit or overload occurs in the line, the current transformer sends a signal to the relay device to cut off the fault circuit, thereby protecting the power supply system's safety. The current transformer used for protection is not the same as the current transformer used for measurement. It can only operate effectively when the current is tens of times greater than the normal current, and it requires reliable insulation as well as a sufficiently great accurate limit. The coefficient has adequate thermal and dynamic stability.  Ⅳ Application of  Current Transformer Current transformers are widely used for measuring current and monitoring power grid operation. Revenue-grade CTs, along with voltage leads, power the electrical utility's watt-hour meter on many larger commercial and industrial supplies.To isolate high-voltage current transformers from the ground, they are mounted on porcelain or polymer insulators. Some CT configurations wrap around the bushing of a high-voltage transformer or circuit breaker, allowing the conductor to be automatically centered inside the CT window.Current transformers can be installed on a power transformer's low or high-voltage leads. A section of a bus bar can sometimes be removed to replace a current transformer.High-voltage current transformers are mounted on porcelain or polymer insulators to isolate them from the ground. Some CT configurations wrap around the bushing of a high-voltage transformer or circuit breaker, allowing the conductor to be centered inside the CT window automatically.  Ⅴ Current Transformer Ratio and Polarity5.1 Current Transformer RatioAt full load, the CT ratio is the ratio of primary current input to secondary current output. A CT with a ratio of 300:5 is rated for 300 primary amps at full load and will generate 5 amps of secondary current when 300 amps pass through the primary.If the primary current changes, so will the secondary current output. For example, if 150 amps flow through a primary rated at 300 amps, the secondary current is 2.5 amps. Figure3: A current transformer's ratio is equivalent to a potential transformer's voltage ratio.  At full load, the CT ratio is the ratio of primary current input to secondary current output. A CT with a ratio of 300:5 is rated for 300 primary amps at full load and will generate 5 amps of secondary current when 300 amps pass through the primary.If the primary current changes, so will the secondary current output. For example, if 150 amps flow through a primary rated at 300 amps, the secondary current is 2.5 amps.   5.2 Current Transformer PolarityThe polarity of a current transformer is determined by the direction in which the coils are wound around the CT's core (clockwise or counterclockwise), as well as the manner in which the secondary leads are brought out of the transformer case.To ensure an appropriate installation, all current transformers are subtractive polarity and will have the following designations: H1 - Primary current, oriented in the direction of the lineH2 - Primary current in the load-facing directionX1 denotes secondary current (multi ratio CTs have additional secondary terminals) Figure4:  Split-Core CT with a 200A rating. Take note of the polarity marking in the center of the core, which indicates the direction of the source. (Split-Core CT with a 200A rating.) Take note of the polarity marking in the center of the core, which indicates the source's direction. (Photo courtesy of Continental Control Systems, LLC.)The H1 primary lead and the X1 secondary lead are on the same side of a subtractive polarity transformer. When the polarity of a CT is indicated by an arrow, it should be installed with the arrow pointing in the direction of the current flow.When installing and connecting current transformers to power metering and protective relays, it is critical to maintain proper polarity.   5.3 Electrical Drawing Conventions for CT PolarityFor current transformers, polarity markings on electrical drawings and diagrams can be made in a variety of ways. Dots, squares, and slashes are the three most common schematic conventions. On electrical drawings, polarity markings represent H1, which should be facing the source.Figure5: Electrical Drawing Conventions for CT Polarity   Ⅵ  How to Test CT PolarityMaterials need:an analog voltmeter9-volt batteryThe factory has occasionally misapplied markings on current transformers. The following test procedure can verify the polarity of a CT in the field with a 9V battery: Step1: Cut the Power SupplyBefore testing, turn off all power and connect an analog voltmeter to the secondary terminal of the CT to be tested. The meter's positive terminal is connected to CT terminal X1, while the negative terminal is connected to X2.  Step2: Connect the 9-volt BatteryConnect the positive end of the 9-volt battery to the H1 side (sometimes marked with a dot) and the negative end to the H2 side with a piece of wire run through the high side of the CT window. It is critical to avoid continuous contact, which will result in a short circuit of the battery.  Step3: Check the PolarityIf the polarity is correct, the momentary contact causes a tiny positive deflection in the analog meter. If the deflection is negative, the current transformer's polarity is reversed. The terminals X1 and X2 have to be switched before the test.Figure6:The factory has occasionally misapplied markings on current transformers. A 9-volt battery can be used to test the polarity of a CT in the field.   Ⅶ  How to Choose The Right Current TransformerWhen selecting a current transformer for any application, there are numerous factors to consider. As this can be confusing, and there is a lot of inaccurate information out there, it can lead to installing the wrong current transformer and having to replace equipment.To avoid this, the first step should be to contact the current transformer manufacturer if you have any questions or concerns about compatibility. Midwest Current Transformer's team is available to answer your questions and ensure that you are using the correct product. Speaking with our team before ordering current transformers ensures that you have the right equipment for the job, avoiding any last-minute decisions and potential confusion. 7.1 Genres of SystemWhen using any genre of the meter or power system, it is critical to use a current transformer that is specifically designed for that system. It is especially important with meters because they are not all uniformly designed. Another way to put it is that the system's metering or protection is matched with the type of current transformer.It is also critical to understand the primary range of the current transformer and ensure that it is compatible with the application. This type of compatibility is provided by the various configurations of the primary and secondary windings.  7.2 Requirement of PrecisionThe degree of accuracy is critical for current transformers used for measurement. Not all current transformers provide high accuracy, and the more specific the requirement, the more important the quality of data measurement provided by the CT.This accuracy rating is classified according to class, with the current having an effect on the accuracy provided by the current transformer. The ability of the current transformer to perform to the required levels is always a factor in making the right choice for protective transformers..The degree of accuracy is critical for current transformers used for measurement. Not all current transformers provide high accuracy, and the more specific the requirement, the more important the quality of data measurement provided by the CT.This accuracy rating is classified according to class, with the current having an effect on the accuracy provided by the current transformer. The ability of the current transformer to perform to the required levels is always a factor in making the right choice for protective transformers. Ⅷ Frequently Asked Questions about Current Transformer 1.What is the use of current transformer?A Current Transformer (CT) is used to measure the current of another circuit. CTs are used worldwide to monitor high-voltage lines across national power grids. A CT is designed to produce an alternating current in its secondary winding that is proportional to the current that it is measuring in its primary. 2.What is the use of CT and PT?CT is used to measure current while PT is used to measure voltage. CT is connected in series while PT is connected in parallel. CT ratio range is from 1 to 5A while the PT range is from 110V. We connect the output parameter from CT to the ampere meter while we connect the PT output to the voltmeter. 3.What do you mean by a current transformer?A current transformer is a device used to produce an alternating current in its secondary, which is proportional to the AC current in its primary. This is primarily used when a current or voltage is too high to measure directly. ... This ratio is based on the primary conductor passing once through the transformer window. 4.How is CT ratio calculated?When analog ammeters are installed, we can easily determine the CT ratio by observing the meter full scale value and then divide that value by 5. Figure 3. Ammeter with a full scale of 150 amps. The meter in Figure 3 has a full scale of 150 amps. 5 Why CT is connected in series?A CT may be considered as a series transformer. The primary current in a C.T is independent of the secondary circuit conditions (burden/load). The primary winding of the CT is connected in series with the line carrying the current to be measured. Hence it carries of the full line current.   

IntroductionThe potentiometer is a three-terminal resistive element whose resistances can be adjusted according to a certain change rule. According to it, it is used in a large variety of electrical and electronic circuits, such as voltage dividers, variable resistor, and current controllers. The potentiometer is usually composed of a resistor body and a movable brush. When the brush moves along the resistor body, the resistance value or voltage will be changed at the output end. Due to its special structure and function, it is necessary to pay attention to its damage and take regular maintenance during operation.Potentiometers - Basic IntroductionCatalogIntroductionⅠ Potentiometer Using TipsⅡ How to Clean Potentiometer?Ⅲ How to Test Potentiometer?3.1 General Methods3.2 Variable Potentiometer TestⅤ Replacing Potentiometer with 4 StepsⅠ Potentiometer Using Tips1) The resistor body of the potentiometer is mostly made of polycarbonate synthetic resin. Avoid contact with the following items: ammonia, other amines, aqueous alkali solutions, aromatic hydrocarbons, ketones, lipid hydrocarbons, and strong chemicals (excessive acid-base value), etc. Because chemical reaction with those will affect their performance.2) The terminal of the potentiometer should avoid using water-soluble flux when soldering, which will cause metal oxidation and mold material. In addition, avoid using inferior flux, and poor soldering may cause difficulty in soldering, resulting in poor contact or open circuit.3) If the soldering temperature is too high or the soldering time is too long, it may cause damage to the potentiometer terminals. The pin terminal should be soldered at 235℃±5℃ within 3 seconds, and the soldering space should be more than 1.5mm away from the potentiometer body. Do not use solder to hit through the circuit board when soldering, and wire terminal soldering should be soldered at 350℃±10℃ within 3 seconds. Except that, the terminal should avoid heavy pressure, otherwise it is easy to cause poor contact.4) During soldering, the height of the rosin (flux) entering the printing machine board should be adjusted properly, and the flux should be prevented from entering the potentiometer, otherwise it will cause poor contact between the brush and the resistor, resulting in INT, noise and other undesirable phenomena.Potentiometer Structure5) The potentiometer is best used in the voltage adjustment, and the connection method should choose "①" pin grounding. The current adjustment structure should be avoided, because the contact resistance between the resistor and the contact piece will stop the passage of large currents.6) Avoid condensation or water droplets on the surface of the potentiometer, and avoid using it in a humid place to prevent insulation deterioration or short circuit.7) When installing the rotary potentiometer, the strength should not be too tight to avoid damage to the screw teeth or poor rotation. When install the sliding type potentiometer, avoid using too long screws, otherwise it may affects the movement of the sliding handle, and even directly damages the potentiometer body.8) In the process of putting the potentiometer on the knob, the pushing force used should not be too large (not exceeding the parameter index of the pushing and pulling force of the shaft in the specification note), otherwise it may cause damage to the potentiometer.9) The operating force (rotation or sliding) of the potentiometer will become faster as the temperature rises, and slower as the temperature drops. If the potentiometer is used in a low temperature environment, it needs a kind of special low temperature resistant grease.10) The shaft or sliding handle of the potentiometer should be as short as possible when designing it. The shorter the shaft or sliding handle, the better and stable the hand feel. On the contrary, the longer the shaking, the greater the shaking, and the feel is easy to change.11) The power of the carbon film of the potentiometer can withstand the ambient temperature of 70°C, and its function may be lost when the temperature is higher than it.12) The resistor body of the sealed potentiometer is mostly made of polycarbonate synthetic resin. Avoid mixing with ammonia, aromatic hydrocarbons, lipid hydrocarbons, ketones, and strong chemicals (excessive pH), other amines, alkaline aqueous solution, etc, because they will affect its performance.Potentiometer TypesⅡ How to Clean Potentiometer?The potentiometer is to wrap the carbon sheet with POM, PC, ABS and other plastic materials. After assembly, the carbon sheet will not be exposed to the outside, it is not easy to oxidize, and dust is not easy to enter, which protects the potentiometer body.Cleaning Steps of Potentiometer1) Use a screwdriver to carefully open the sealing cover fixing card of the sealing potentiometer, and remove the protective cover.2) Remove the fixed spring card of the rotating shaft and pull out the rotating shaft.3) If some sealed potentiometers cannot take out the shaft, you can directly wipe the carbon film and the metal contacts on the shaft with a cotton ball dipped in pure alcohol.4) Adjust the position and angle of the metal contacts, changing the contact position with the carbon film and increasing the pressure.5) Apply some lubricating oil or special grease on the carbon film to delay the service life.6) Reinstall and fix the metal cover to complete the entire cleaning process. Ⅲ How to Test Potentiometer?3.1 General Methods1) Before detecting the potentiometer by the method of appearance and manual adjustment, firstly observe its appearance. Rotate the knob to check whether the rotation is smooth, whether the switch is flexible, whether the "click" sound is crisp when the switch is turned on and off, and listen to the sound of friction between the internal contact points of the potentiometer and the resistor body, if there is a loud noises indicate that the quality is not good. Normally, the handle should be slightly damped when turning.2) Using the multimeter to measure the potentiometer, you should first select the appropriate ohm gear of the multimeter according to the nominal resistance of the measured potentiometer and then do the measurement. When measuring, touch the red and black test leads of the multimeter to the pins of the fixed pins on both sides, and the multimeter reading should be the nominal resistance of the potentiometer. If the multimeter reading is much different from the nominal resistance value, it indicates that the potentiometer has been damaged.When the nominal resistance of the potentiometer is normal, then measure its changing resistance and whether the movable contact is in good contact with the resistor (fixed contact). At this time, one test lead of a multimeter is connected to the moving contact pin (usually the middle pin), and the other test lead is connected to a certain contact pin (pins on both sides).After connecting the test leads, the multimeter should display zero or the nominal resistance value, and then rotate the multimeter's shaft from one extreme position to the other extreme position, and the resistance value should continuously change from zero (or nominal resistance) to the nominal resistance value (or zero). During the rotation or sliding of the shaft of the potentiometer, if the pointer of the multimeter moves steadily or the displayed indication changes uniformly, it means that the measured potentiometer is in good condition. If the resistance reading of the multimeter fluctuates when the shaft is rotated, it means the movable contact has a fault with poor contact.3.2 Variable Potentiometer Test1) Measure the total resistance at both ends to see if it matches the nominal value.2) Measuring the resistance between a fixed end and the sliding end: rotary the potentiometer to see if the resistance change is continuous. Then measuring the resistances between the other fixed end and the sliding end, if the measured intermediate resistance value changes discontinuously, it indicates that there is a poor contact in the sliding process.PotentiometersⅣ Replacing Potentiometer with 4 StepsThere are many types of potentiometers, and most models cannot be used interchangeably, otherwise the control effect will not be very good. When replacing it, the nominal resistance value should be the same as the damaged variable resistance value or the close to. At the same time, its packages must be considered, otherwise the installation will be difficult. Therefore, we must distinguish between linear potentiometers, exponential potentiometers and logarithmic potentiometers before use. In addition, please note that the precision resistor can only be replaced with a same one when it is damaged, and cannot be replaced with an ordinary variable resistor, otherwise its adjustment accuracy will also be affected.The potentiometer has multiple pins. In order to prevent the wrong pins from being connected during replacement, the following specific operation steps and methods can be used:Step 1: Remove the set screw of the original potentiometer, but do not take off the leads on the potentiometer.Step 2: Install the new potentiometer and fix it.Step 3: Solder a lead on the original potentiometer pin slice, solder it on the corresponding pin slice of the new potentiometer, and the welding method is the same as the old one.Step 4: In the same way, solder each pin wire. Pay attention, welding the next one and then the other one can avoid the wrong position of the leads being welded to each other. Frequently Asked Questions about Potentiometer Uses and Its Replacement1. What is the use of potentiometer?The measuring instrument called a potentiometer is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. 2. What causes a potentiometer to fail?An electrical short or open will cause the indication to fail at one extreme or the other. If an increase or decrease in the potentiometer resistance occurs, erratic indicated valve position occurs. 3. What does a potentiometer measure?A potentiometer is an instrument which is used for measurement of potential difference across a known resistance or between two terminals of a circuit or network of known characteristics. A potentiometer is also used for comparing the emf of two cells. 4. How do you troubleshoot a potentiometer?Set your ohmmeter to a setting higher than the total resistance of the potentiometer. For example, if your potentiometer is rated at 1,000 ohms, set your ohmmeter to 10,000 ohms. Look at your potentiometer. There should be three tabs sticking out of it. 5. Does a potentiometer need to be grounded?This configuration also acts as a voltage divider and can be used in a number of ways to control a signal. Like any resistor, potentiometers per se do not need to be connected to the ground plane of the circuit, but in the majority of configurations/uses, they will be.

CatalogIntroductionⅠWhat is a MAP Sensor ?1.1 The Definition of a MAP Sensor1.2 Abbreviations for MAP sensorsⅡ How does a MAP Sensor Works？Ⅲ  The Application of a MAP Sensor on Vehicles3.1 The Problem Caused of a Faulty MAP Sensor3.2 The Factors of Causing This Fault3.3 How to RepairⅣ 7 Symptoms of a Faulty MAP SensorⅤ Common MAP Sensor Fault CodesⅥ The Difference Between MAP and MAF sensorsⅦ Frequently Asked Questions about MAP SensorsIntroductionFirstly, We need to have a general definition of a sensor. A sensor, in the broadest sense, is a device, module, machine, or subsystem whose purpose is to detect events or changes in its environment and transmit the information to other electronics, most commonly a computer processor. A sensor is always used in conjunction with other electronics.Figure1：The function of  a MAP sensorⅠWhat is a MAP Sensor ?1.1 The Definition of a MAP SensorThe manifold absolute pressure sensor (MAP sensor) is one of the sensors used in the electronic control system of an internal combustion engine.MAP sensors are frequently used in engines that inject fuel. The manifold pressure sensor transmits real-time manifold pressure data to the engine's electronic control unit (ECU). The function of data is to calculate the air density and determine the engine's air mass flow rate, determining the fuel metering required for optimal combustion and influencing the ignition timing advance or retardation. In order to detect intake airflow, fuel-injected engines may use a mass airflow sensor (MAF sensor). Aspirated engines typically use one or the other, whereas forced induction engines typically use both at the same time. The MAF sensor on the intake pipe is connected to the throttle body, and the MAP sensor on the intake port is connected to the pre-turbine.The second variable from IAT (intake air temperature sensor) can be applied to convert MAP sensor data to air quality data. It is referred to as the speed-density method. The engine speed (RPM) is also used to determine the position on the lookup table, which determines the amount of fuel to be added, and thus the speed density (engine speed/air density). The MAP sensor can also be used in OBD II (on-board diagnostics) applications to test the function of the EGR (exhaust gas recirculation) valve, which is a common application in OBD II-equipped general automobile engines.1.2 Abbreviations for MAP sensorsAbbreviations often used are:MAPThere are some other common names of MAP sensors：Manifold Absolute Pressure SensorEngine Load SensorPressure SensorBoost Sensor Ⅱ How does a MAP Sensor Works？ Its operation is based on supplying 5 volts of DC power to the sensor from the PCM (Power System Control Module). Inside the MAP sensor is a resistor that moves in response to the intake manifold pressure. The resistor alters the voltage between 1V and 4.5V (depending on engine load), and the voltage signal returns to the PCM to indicate manifold pressure (vacuum). This signal is required by the PCM to determine fuel delivery and is occasionally used to determine whether the EGR valve is functioning properly. The Manifold Pressure Sensor is useful for diagnostics because it measures throttle performance, turbo performance, and leaks in the inlet manifold. Due to its position, it should always read negative pressure unless the turbocharger is boosting pressure. This is depicted in the diagram below. Ⅲ The Application of a MAP Sensor on vehiclesA computer and a series of sensors in modern vehicles control the engine's fuel consumption and other operations. While you may never have to work on any of these sensors, one, in particular, is critical to the smooth operation of an engine — the MAP (manifold absolute pressure) sensor. What exactly is a MAP sensor and what does it do? When your engine runs strangely, it could be due to a MAP sensor failure, so let's take a look at what the MAP sensor does.Figure2: the application on vehicles  3.1 The Problem Caused of a Faulty MAP SensorA faulty MAP sensor can cause a variety of performance issues in your vehicle. If the sensor is faulty, reading too high, the fuel management system may use more fuel than necessary, reducing fuel economy. If the MAP sensor reads too low, the onboard computer will reduce the amount of fuel it believes is required and starve the engine, causing it to run erratically and produce less power. In either case, if the sensor is not properly reading, your vehicle will fail emissions testing. When you connect a diagnostic code reader, you may discover trouble codes P0068, P0069, P1106, or P1107. 3.2 The Factors of Causing This FaultA MAP sensor failure can be caused by several factors. The sensor's operation is dependent on both electronic and mechanical components. A vacuum chamber within the sensor allows the sensor to detect changes in manifold pressure. A leak in the vacuum chamber can develop over time, rendering the sensor unable to read correctly. Years of extreme temperature fluctuations and vibration can also wreak havoc on the internal circuitry due to the sensor's location in the harsh engine compartment environment. Another source of failure is dirt or other contamination that prevents the sensor from physically accessing the intake manifold air flow. 3.3 How to RepairThe difficulty of replacing a bad MAP sensor varies depending on the vehicle. It is typically bolted or screwed to the outside of the intake manifold or throttle body. Unplug the sensor wire, then unscrew the screws and carefully remove the faulty sensor. Simply reinstall the screws and plug the wire back in to get your new one up and running. Depending on the vehicle and whether or not a trouble code was set, resetting the check engine light may necessitate the use of a diagnostic tool.Many people are perplexed when they learn that they have a faulty sensor and wonder, "What is a MAP sensor?" While its function is straightforward, it has been critical to obtaining good fuel economy and performance from your vehicle's engine for many years. If you suspect a MAP sensor failure, your neighborhood NAPA Auto Care center can handle the problem and get you back on the road. Ⅳ 7 Symptoms of a Faulty MAP Sensor 1. Poor Fuel Economy.If the ECM detects low or no vacuum, it assumes the engine is under load and dumps more fuel, and advances the spark timing. This results in excessive fuel consumption, poor fuel economy, and, in extreme cases, detonation. 2. Lack of Power.When the ECM perceives a high vacuum, it assumes that the engine load is low and reduces fuel injection, and retards spark timing. On the one hand, fuel consumption will be cut down, which appears to be a good thing. However, if not enough fuel is consumed, the engine may lack acceleration and passing power. 3.Failed Emissions InspectionWhen the ECM perceives a high vacuum, it assumes that the engine load is low and reduces fuel injection, and retards spark timing. On the one hand, fuel consumption will be cut down, which appears to be a good thing. However, if not enough fuel is consumed, the engine may lack acceleration and passing power. 4. Rough Idle.Inadequate fuel injection deprives the engine of fuel, resulting in rough idling and possibly random cylinder misfiring. 5. Hard Starting.Similarly, an excessively rich or lean mixture makes it difficult to start the engine. You most likely have a MAP sensor problem if you can only start the engine when your foot is on the accelerator. 6. Hesitation or Stalling.Stepping on the gas may not be fun when starting from a stop or attempting a passing maneuver, especially if the ECM is displaying a lean mixture based on faulty MAP sensor readings. 7. Check Engine Light.MAP sensor diagnostic trouble codes (DTC) can range from a simple circuit or sensor faults to correlation or range faults, depending on the age of your vehicle. A dead MAP sensor will not read anything, whereas a failing MAP sensor may send data to the ECM that is illogical, such as low engine vacuum when the throttle position sensor (TPS) and crankshaft position sensor (CKP) both show the engine at idle.Figure3: check dash board light Ⅴ Common MAP Sensor Fault CodesThe following codes are associated with the MAP sensor and should be looked for if your check engine light has illuminated:  P0068: MAP/MAF - Throttle Position CorrelationP0069: Manifold Absolute Pressure - Barometric Pressure CorrelationP0105: MAP Circuit MalfunctionP0106: MAP/Barometric Pressure Circuit Range/Performance ProblemP0107: Manifold Absolute Pressure Figure4: one of the faulty code  Ⅵ The Difference Between MAP and MAF sensorsThe intake manifold pressure sensor is the full name of the map manifold absolute pressure sensor, and the computer uses the speed increase pressure change to adjust the speed. The following conclusions are for reference only.MAF is an air flow sensor with the full name Mass air flow meter. Figure5: the MAF sensor  The first thing I mentioned was the MAP formula, which is MAP+Manifold vacuum = Barometric Sensor. The function of the Barometric Sensor.It indicates the height of the car's altitude, allowing the length of the fuel injection to be determined when the car is cold.In general, there are two variables: the manifold vacuum and the barometric. The manifold vacuum changes with speed, while the barometric is almost constant, unless you're in the sky. 1, Manifold vacuum Full throttle (WOT) = 0 hgidle 18-22 hg2, MAp should be equal to baro in the case of KOEO (manifold vacuum is 0 hg)3, KOEO 3v-4vKOER will drop to about 1v as the vacuum increases4, 5v reference nap throttleFigure6: 5v reference nap throttle  5, KOEO 150 hz KOER will be lower than this in the future6, Reference value sunnyvale 150hz/ 30HG denver 123 hz7, if egr is stuck slightly open, map will also report an error8, The duty cycle and counts of iac will also decrease,9, stft -9% at idle accelerating jumps to lean change map. There is no absolute value, and the calibration of each car manufacturer is not the same MAF-air flow sensor, simple and rude, directly tells the computer how much flow.1, idle 0.5-1v2, egr&tps follow3, If there is another baro (calculate or extra), the method is the same as map, 30 hg4, maf is dirty, will undereportting, cause too much air to enter, fuel trim is too thin5, down side: If there is turbulence in one of the intake and exhaust, the problem cannot be determined6, maf gs/s = liter (known Toyota, Ford.)7, baro relearn( 80% tps with low rpm)Figure7: baro relearn Ⅶ Frequently Asked Questions about MAP Sensors1. Can I drive my car with a bad MAP sensor?It is not advisable to drive your vehicle with the MAP (manifold absolute pressure) sensor disconnected. ... With the MAP sensor disconnected, the fuel delivery will be excessive and could cause harm to the engine and exhaust system (catalytic converters). 2. Will a MAP sensor cause a misfire?Your engine misfires and shakes: If a MAP sensor reports a false high pressure reading, the engine's computer will signal for more fuel. This results in a rich mixture, which can foul the spark plugs and cause a cylinder not to fire. A misfiring engine will shake and transmit that motion into the cabin of the vehicle. 3. Can you clean a MAP sensor?Use an electric parts cleaner on a soft rag or paper towel to clean the outside of the MAP sensor. ... Shake out the excess and let the MAP sensor dry. Check the MAP sensor vacuum hose or intake manifold port for additional contamination. Clean these with electric parts cleaner and a brush if necessary. 4. How much is a MAP sensor?The MAP sensor usually sits in an easy to reach area, on or near the intake manifold. The sensor itself will cost you anywhere from $30 to $200, depending on your vehicle and if you use OEM or aftermarket parts. 5. Can I use alcohol to clean MAP sensor?Clean the outer surface of the MAP sensor using electric parts cleaner. ... Spray the alcohol liberally over the MAF sensor. Be sure to cover the MAF sensor's wires, intake and all its crevasses to thoroughly clean the part. Do not touch or scrub the MAF sensor's wires because they are very delicate and could break. 

What is Breadboard?When learning how to build a circuit, the breadboard is one of the most basic parts. There are many small jacks on the breadboard, which are specially designed and manufactured for solderless experiments of electronic circuits. A breadboard consists of plastic block holding a matrix of electrical sockets of a size suitable for gripping thin connecting wire, component wires or the pins of transistors and integrated circuits (ICs). The sockets are connected inside the board, usually in rows of five sockets. Since various electronic components can be inserted or pulled out at will according to needs, welding is eliminated, circuit assembly time is saved, and components can be reused, so it is very suitable for the assembly, debugging and training of electronic circuits.What is Breadboard?Topics Covered in this GuideWhat is Breadboard?Why are breadboards called breadboards?How Breadboard Looks like?IC & DIPHow to Use Breadboards?Types of BreadboardsBasic Principles of Breadboard WiringBreadboard Using Tips for BeginnersMaintenance of the BreadboardsWhich Breadboard is Best?What are the Holes in the Breadboard Called?Is a Breadboard Necessary?How much Voltage can a Breadboard Handle?How Does Current Flow in a Breadboard?How Many Amps Can a Breadboard Take?Why are breadboards called breadboards?The name of the breadboard can be traced back to the era of vacuum tube circuits. At that time, most of the circuit components were large in size. People usually fixed them on a wooden board for cutting bread with screws and nails for connection. Later, the circuit components became more and more smaller, but the name of the breadboard is still used. The breadboard most commonly used today is usually made of white plastic and is a pluggable (solderless) breadboard. It was designed by Ronald J. Portugal in 1971.It is a process of verifying ideas by creating an initial model. If you are not sure how a circuit will react normally under a given parameter setting, it is best to build a prototype to test it. For those who are new to electronic circuits, the breadboard is a good start. The advantage of a breadboard is that it can hold the simplest and most complex circuits at the same time. If your circuit cannot be accommodated by the current breadboard, you can splice other boards to adapt to all circuits of different sizes and complexity. Such as integrated circuits (ICs). When you try to master how a module works and need to rewire multiple times, you certainly don't want to solder the circuit interface every time. Once you find a problem, you can disassemble each part to prepare for some troubleshooting. How Breadboard Looks like?The shape of the breadboard is mostly cuboid, with different sizes. The breadboard generally has two layers, the top is a grid shape with double-sided tape adhering to it( you can tore it to fix the breadboard in a certain position). The upper layer of the breadboard is composed of a grid of rows and columns, and there is no conduction between rows.The whole board is made of thermosetting phenolic resin, and there are metal strips at the bottom of the board. Holes are punched at the corresponding positions on the board so that the components can be in contact with the metal strips when inserted into the board, so as to achieve the purpose of conducting electricity. Generally, every 5 orifice plates are connected by a metal strip. There are two rows of vertical jacks on both sides of the board, also a group of 5. These two sets of jacks are used to provide power to the components on the board.Breadboard Layout ExampleSome breadboards have two columns on the left and right sides. These two columns are customarily used as the positive and negative poles of the power supply (This is not necessarily true, depending on your own usage habits and circuit needs). Each of the five grids in the same column of the two columns is a group, which is conductive. But there is no conduction between columns. Then in the middle part, every five columns of grids form a group, and the five grids in this group are conductive. There is generally a groove in the center of the board, which is designed for the needs of integrated circuit (IC) and chip testing, and is used to separate the left and right parts of a board. Some breadboards do not have two columns on the left and right sides due to the size, but the other structures are the same.The motherboard uses a glass fiber board with a conductive layer of copper foil, which is used to fix the solderless breadboard and lead out the power terminal.There may be slight differences in the structure between different breadboards, but they are basically the same. IC & DIPAn unique feature of the breadboard is: Integrated Circuit (IC) and Dual in-line Package (DIP)Dual in-line Package (DIP) Chip：MA2053Do you see the small gap in the middle of the breadboard? There is a reason for this gap, the use of integrated circuits. There are ICs in almost every electronic device. They run motors, regulate voltage, act as timers, perform logic tasks, and perform almost everything you need to perform.ICs can have different numbers of pins, sizes and functions. However, many ICs are suitable for a standard called dual in-line packaging (DIP), which means they all share a set width. As you guessed, the width fits the gap in the middle of the breadboard. This makes it easier to use the IC without having to worry about connecting the wrong pins together. the holes of the breadboard are spaced 0.1” (2.54mm) apart in both the X and Y direction which is the spacing used for adjacent DIP IC leads as well as many other components such as headers.IC & DIP Example on Breadboard How to Use Breadboards?You can use breadboard to make quick electrical connections between components- like resistors, LEDs, capacitors, etc, so that you can test your circuit before permanently soldering it together. Without welding and manual wiring, the circuit and components can be tested by inserting the component into the hole, which is convenient to use. Before use, determine which component's pins should be connected together, and then insert them into the same group of 5 small holes.How to Use a Breadboard?Example: LED Lighting1) MaterialsOne breadboard, several connecting wires (the connecting wires should use needle-shaped wires at both ends), one led light, and one 3V button battery.2) First, put the battery into the battery holder (this can be bought online), and plug it into the breadboard. Then, insert the battery holder into the left and right parts of the breadboard. Parts are separated by grooves to avoid short circuit between the positive and negative poles of the power supply).3) Lead two wires from the positive and negative poles of the battery, and then plug the LED into any two grids that are not conductive on the breadboard (the long pin of the led is positive and the short pin is negative), and finally connect the wires from the positive and negative poles of the battery to the two LED segments.Types of Breadboards1) Solderless BreadboardA solderless breadboard is a motherboard that does not serve as a base, and does not have a soldering power socket to draw out but can expand a single breadboard. Connect the two poles of the power supply to the sockets on both sides of the breadboard, and then you can plug in the components for experiment (the power supply should be disconnected during the process of inserting the components). When more than 5 components or a set of jacks cannot be inserted, you need to connect multiple sets of jacks with a breadboard cable.The advantages of solderless breadboards are small size and easy to carry, but the disadvantages are relatively simple, inconvenient power connection, and small area. It is not suitable for large-scale circuit experiments. If you want to use it for large-scale circuit experiments, you need to fix multiple breadboards on a large wooden board with screws, and then connect them with wires.2) Single BreadboardA single breadboard is a part with a motherboard as a base and a dedicated terminal for power access, and even some breadboards that can perform high-voltage experiments include ground terminals. This kind of board is more convenient to use, that is, directly connect the power supply to the terminal, and then insert the components for experiment (the power supply should be disconnected during the process of inserting the components) when more than 5 components or a set of jacks cannot be inserted, you need to use breadboard cables to connect multiple sets of jacks.The advantage of a single breadboard is that it is small in size, easy to carry, and can easily switch on and off the power supply, but it has a small area and is not suitable for large-scale circuit experiments.3) Composite breadboardComposite breadboard is a board composed of many solderless breadboards. Generally, 2-4 solderless breadboards are fixed on the motherboard, and then the power cords of each board are connected together with the copper foil in the motherboard. The kind of breadboards is also specially designed for different circuit units to control the power supply, so that each board can carry different voltages according to the needs. The use of the composite breadboard is the same as the single breadboard.The advantage of the composite breadboard is that it can conveniently switch on and off the power supply, has a large area to carry out large-scale experiments, and is highly mobile, and has a wide range of uses. However, it is large and heavy for carrying, so it is suitable for laboratories and electronic hobbyists use. Basic Principles of Breadboard WiringComplete the circuit overlap on the breadboard, different people have different styles. However, no matter what style or habit, the following basic principles must be paid attention to when completing the circuit overlap:1. The fewer connection points, the better.Each additional connection point actually increases the probability of failure artificially. There are common faults such as impassability in the breadboard hole, loose wire, and broken wire inside.2. Try to avoid overpasses.The so-called "overpass" means that components or wires ride on other components or wires. Beginner is easy to make such mistakes. It will bring trouble to the replacement of components in the later stage. On the other hand, in the event of a failure, the messy wires can easily make people lose confidence.3. Try to be as reliable as possible.There are two phenomena that need attention:① Breadboard integrated circuits are easy to loosen. Therefore, for integrated circuits such as operational amplifiers, it is necessary to press down forcefully. Once it is not reliable, the position needs to be changed.② The pins of some components on the breadboard are too thin, so please be careful to move them slightly. If you find that they are not secure, you need to change the position.Electronic BreadboardBreadboard Using Tips for Beginners1. When installing discrete components, it should be easy to see their polarity and signs. After placing the component pins, bend them where needed. In order to prevent the exposed leads from short-circuiting, a wire with a sleeve must be used, and the component pins are generally not cut to facilitate repeated use. Generally, do not insert components with a pin diameter> 0.8mm, so as not to damage the elasticity of the contact piece inside the socket.2. The pins of integrated circuits that have been used many times must be repaired neatly, the pins cannot be bent, and all the pins should be slightly skewed outward, so that the lead angles and the jacks can be reliably contacted. The arrangement of the components on the breadboard should be determined according to the circuit diagram in order to facilitate the wiring. In order to be able to correctly route and facilitate wire checking, the insertion direction of all ICs must be kept the same, and which cannot be inserted upside down for the convenience of temporary wiring or to shorten the length of the wire.3. According to the sequence of the signal flow, the method of installation and debugging is adopted. After the components are installed, first connect the power cord and the ground wire. In order to check the line conveniently, try to use different colors for the line. For example, the positive power supply generally uses a red wire, the negative power supply uses the blue, the ground wire uses the black, and the signal wire uses the yellow. Other colors can also be selected according to the real conditions.4. The breadboard should use a single-strand wire with a diameter of about 0.6mm. Cut the wire according to the distance of the wire and the length of the jack. The wire end is required to be cut into a 45º, and the stripped length of the wire end is about 6mm. All the wires are required to be inserted into the bottom plate to ensure good contact. In addition, bare wires should not be exposed to prevent disconnection with other wires.5. The connection is required to be tightly attached to the breadboard to avoid collision and ejection of the breadboard, resulting in poor contact. The wiring must pass around the integrated circuit, and it is not allowed to cross the integrated circuit, and the wires must not be overlapped with each other, try to be horizontal and vertical. This is conducive to line wiring and checking, and components replacement.6. It is best to connect a capacitor with a capacity of tens of microfarads in parallel between the input terminal of each power supply and the ground, so as to reduce the impact of current during transients. In order to suppress the high-frequency components in the power supply, a high-frequency decoupling capacitor should be connected in parallel at both ends of the capacitor, generally 0.01~0.047Uf.7. During the wiring process, it is required to place the various components on the corresponding position on the breadboard and mark the pin numbers used on the circuit diagram to ensure the smooth progress of debugging and troubleshooting.8. All ground wires must be connected together to form a common reference point. Maintenance of the BreadboardsUsing a breadboard is more convenient than using a soldering method, easy to replace wires and components, and can be used multiple times. However, the breadboard should be maintained during daily use. In the multiple use of the breadboard, the spring sheet will become loose and the elasticity will become poor, which is easy to cause poor contact and virtual welding. They are difficult to find out.The breadboard that has been used many times should be uncovered from the back, and the spring sheet with poor elasticity should be taken out, repaired and then inserted into the original position. This can enhance the elasticity and increase the reliability and service life of the breadboard. In addition, pay attention to where the breadboard is used. Large-volume, high-quality or high-power components cannot be plugged into the breadboard because the breadboard jacks are small and the leads of such large components are relatively thick. At this time, the components can only be placed outside the board. Use a single strand of hard wire to solder to the lead, and then insert it into the breadboard.Breadboards are not suitable for high-frequency circuits, because the lead inductance and distributed capacitance of the breadboard are relatively large, which has a great impact on the performance of high-frequency circuits. Breadboard is suitable for integrated circuits, especially for digital integrated circuits, because digital integrated circuits usually have low operating frequency and low power, and they use fewer RC components. It is more difficult for discrete component circuits to use breadboards, especially for circuits with high frequency and high power. Which Breadboard is Best?Best Breadboard Kit ReviewsELEGOO Upgraded Electronics Fun KitREXQualis Electronics Component Fun KitElegoo EL-CP-003 3 MB-102 830-pin solderless PCB board kitFreenove Solderless Breadboard Ultimate Starter KitKeywishbot Electronic Component BreadboardREXQualis Solderless BreadboardKuman GPIO expansion kit for Raspberry PieBoot 3 400-point solderless circuit breadboardPaxcoo 4 breadboard kits with 120 jumper wires for ArduinoSmraza Basic Starter KitSunFounder breadboard kit RAB holderTEKTRUM Solderless plug-in breadboard kitMicrotivity IB401 400-point experiment breadboardElenco 9440 breadboard with 350 jumper wire set kitMakeronics Breadboard + Electronics Fun Kit What are the Holes in the Breadboard Called?Breadboards are designed to work with through-hole electronic components. They have many tiny sockets (called 'holes') arranged on a 0.1" grid. The leads of most components can be pushed straight into the holes. ICs are inserted across the central gap with their notch or dot to the left.The holes in the top-most rail are highlighted in orange and the holes in the bottom-most one are highlighted in green. In the central area of the board are vertical lines of five holes that are electrically connected. These lines of five holes are known as nodes. Is a Breadboard Necessary?Although a breadboard is essential to prototype circuits without having to solder them together and when you have verified that the circuits works you can solder it onto a perfboard. But note that breadboards are never necessary. A properly-milled and constructed panel should generally stay flat under normal conditions, so the only time I add a breadboard end is if I think the design benefits from it visually.In addition, high frequency (above 10MHz) Where the additional breadboard capacitance would present problems (oscillators, etc) Where glitches due to poor wire connections would result in poor operation. Where most of the parts are not through hole 0.1" (2.54mm) centers. How much Voltage can a Breadboard Handle?Breadboards are mostly used for low voltage and current applications, however, breadboards can handle 12 volts. Breadboards are made by different manufacturers, so the voltages they can handle depends on how they are constructed. How Does Current Flow in a Breadboard?The vertical columns of the breadboard are called terminals, while the horizontal long rows are called power rails because they are mostly used to connect the power supply to the breadboard. The positive rails are indicated by red lines, while the negative rails are indicated by black ones. That means our electric current, which is made up of moving charges, flows out of the positive side of the battery, through the wire and into the breadboard power bus. It then flows out of the black wire and into the second power bus, through the power bus and back to the negative side of the battery. How Many Amps Can a Breadboard Take?Due to the temporary nature of the contacts, most breadboard has a current limit of one amp or less. Breadboard generally cannot handle frequencies greater than ten megahertz because of the nature of the contacts, which create a stray capacitance of around two to twenty picofarads (pFs) for every connection.

What is a Laser Diode?A laser diode (injection laser diode, or diode laser) is a semiconductor device that can generate laser light, emitting a narrow light containing a single color, which is similar to a light-emitting diode (LED). The three conditions for generating laser light are: achieving particle number inversion, meeting threshold conditions and resonance conditions. Since laser diodes are extremely electrostatic sensitive, they should be used with care to prevent static electricity. They can be divided into homojunction laser, single heterojunction (SH) laser, double heterojunction (DH) laser and quantum well (QW) laser according to the different PN junction materials.Topics Covered in this GuideLaser Diode Tech Guide in 2021What is a Laser Diode?Laser Diode SpecificationsLaser Diode CharacteristicsLaser Diode ApplicationsHow Does a Laser Diode Work?What is the Laser Diode Symbol?What are the types of Laser Diode?Laser Diode Using TipsHow to Test a Laser Diode?How to Make a Laser Diode?How to Power a Laser Diode?How to Build a Laser Diode Driver Circuit?How to Wire a Laser Diode?How to Select the Right Laser Diode?How to Drive Pulse Laser Diode?What is Power Source of 532 Laser Diode?What is the Difference between Laser Diode(LD) and LED?What is the Wavelength Range of a Laser Diode?Is Diode Laser Permanent?Is LED a Laser Light?How Long do Diode Lasers Last?Can an LED be Used as a Laser?What are the Advantages of Using Laser Diode Instead of an LED?What is the Disadvantage of Laser?FAQsLaser Diode Specifications(1) Wavelength– It is the laser tube working wavelength, including 635nm, 650nm, 670nm, 690nm, 780nm, 810nm, 860nm, 980nm, etc, used for photoelectric switch laser.(2) Threshold Current– The current at which the laser tube starts to generate laser oscillation. For general low-power laser tubes, the value is about tens of mA, and the threshold current of laser tubes with multi-quantum well structure can be as low as 10mA or less.(3) Operating Current– It is the drive current that laser tube to achieve the rated output power, which is more important for the design and commissioning of the laser drive circuit.(4) Vertical Divergence Angle– It is the open angle that the laser diode's light-emitting band in the direction of the vertical PN junction, generally in the 15˚ ~ 40˚ or so.(5) Horizontal Divergence Angle– It is open angle that the laser diode's light-emitting band in the parallel direction with the PN junction, generally in 6˚ ~ 10˚ or so.(6) Monitoring Current– It is the current flowing on the PIN tube when the laser tube is at rated output power. Laser Diode CharacteristicsThe basic structure of the semiconductor laser diode is shown in the figure. A pair of parallel planes perpendicular to the PN junction surface form the Fabry-Perot resonant cavity, they can be the solution surface of the semiconductor crystal, but also can be polished plane. The remaining two sides are relatively rough to eliminate the laser action in other directions than the main direction. In addition, lasers consist of three main components: a lasing medium (solid, liquid or gas), a stimulating energy source (pump) and an optical resonator.Figure 1. Semiconductor Laser Diode StructureOne of the characteristics of laser diodes is the ability to modulate the intensity of their output light directly from current. Because the relationship between output optical power and input current is mostly linear, laser diodes can use analog or digital current to directly modulate the output light intensity, no need for expensive modulators, which makes the diode more economical to use.The most important characteristic of a diode is its unidirectional conductivity, and laser diodes, as one of the diode types, have the same features. In a circuit, current can only flow in from the positive terminal of the diode and out from the negative terminal. The following are specific descriptions.1) Forward FeatureIn electronic circuits, the diode conducts when the positive terminal of the diode is connected to the high potential terminal and the negative terminal to the low potential terminal. In terms of this connection, it called forward bias. In addition, when the forward voltage applied to both ends of the diode is very small, the diode still cannot conduct and the forward current flowing through is very small. Only when the forward voltage reaches a certain value (this value is called the "threshold voltage", about 0.2V for germanium tubes and 0.6V for silicon tubes), the diode can conduct. After it, the voltage across the diode remains basically unchanged (about 0.3V for germanium and 0.7V for silicon diode), which is called the "forward voltage drop".2) Reverse FeatureIn electronic circuits, the positive terminal of the diode is connected to the low potential terminal, and the negative terminal is connected to the high potential terminal. When there is almost no current flowing through the tube, the diode is in the cutoff state. This connection called reverse bias. Diode in reverse bias, there will still be a weak reverse current flow through, called leakage current. When the reverse voltage across the diode increases to a certain value, the reverse current will increase sharply, the diode will lose its unidirectional conductive characteristics, this state is called diode breakdown. Laser diode injection current must be greater than the critical current density, which is related to the temperature of the contact surface and indirectly affects the tube performance, to meet the residence reversal conditions and emit laser. When operating at high temperatures, the critical current increases, reducing efficiency and even damaging the component. Laser Diode ApplicationsAs the most common type of laser products, laser diodes have the advantages of high efficiency, small size and long life, but their low output power (generally less than 2mW), poor linearity and monochromaticity are not good for cable TV system applications, because they cannot transmit multi-channel and high-performance analog signals. Based on the advantages of laser diodes, they play a important role in many applications areas. For example, in the return module of bi-directional optical receivers, uplink transmission generally uses quantum well laser diodes as the light source. Also it is widely used in the computer on the CD-ROM drive, laser printer in the print head, bar code scanner, laser ranging, laser medical, optical communications, laser indication and other small power optoelectronic equipment. The lighting, laser surgery, laser welding and laser weapons and other high-power equipment have laser diodes too.Compared with LEDs, With different light source, lasers are more powerful and operate at faster speeds than LEDs, and they can also transmit light farther with fewer errors. They are also much more expensive than LEDs.Figure 2. Laser DiodeHow Does a Laser Diode Work?Light Emitting PrincipleLight emission in semiconductors is usually caused by carrier complexation. When a positive voltage is applied to the PN junction, it will weaken the PN junction barrier, forcing electrons to be injected into the P region from the N region, and holes to be injected into the N region from the P region. These non-equilibrium electrons and holes injected near the PN junction will be compounded, thus emitting photons of wavelength λ with the following equation.λ=hc/EgWhere: h - Planck's constant, c - speed of light, Eg - band gap width of the semiconductor.The above luminescence phenomenon due to the spontaneous compounding of electrons and holes is called spontaneous radiation. When the spontaneous radiation generated by the photon through the semiconductor, once the electron-hole pair has been emitted near, it can excite the two composite to generate new photons. This photon has been induced to excite the carrier compound and issued a new photon known as excited radiation.If the injection current is large enough, a carrier distribution opposite to the thermal equilibrium state will be formed, that is, the particle number reversal. When the carrier within the active layer in the case of a large number of inversion, a small amount of spontaneous radiation generated by the photons due to the resonant cavity two end reflect and then have induction radiation, resulting in frequency-selective resonance positive feedback, or a gain for a frequency. When the gain is greater than the absorption loss, a coherent light with good spectral lines can be issued from the PN junction, that is, the laser.How Laser Diodes Work?As for Laser diode light-emitting principle, the P-N junction in a laser diode is formed by two doped GaAs layers. It has two flat-ended structures, parallel to a end (highly reflective surface) and a partial reflection. Laser diodes emit coherent light in which all the waves are at the same frequency and phase. The wavelength of the light to be emitted is exactly related to the length of the junction. When the P-N junction is forward biased by an external voltage, the electrons move through the junction and recombine as in a normal diode. When the electrons are compounded with holes, photons are released. These photons hit the atoms, causing more photons to be released. As the forward bias current increases, more electrons enter the depletion region and cause more photons to be emitted. Eventually, some of the photons randomly drifting in the depletion region strike the reflecting surface vertically, thus reflecting back along their original path. The reflected photons are again reflected back from the other end of the junction. This movement of photons from one end to the other is continuous several times. During the photon motion, more atoms release more photons due to the avalanche effect. This process of reflection and production of more and more photons produces a very intense laser beam.Each photon produced in the emission process explained above is identical to the other photons in terms of energy level, phase relationship and frequency. Thus, the emission process gives a laser beam of a single wavelength. To produce a laser beam, the current in the laser diode must be made to exceed a certain threshold level. Currents below the threshold level force the diode to behave as an LED, emitting incoherent light. What is the Laser Diode Symbol?The laser diode symbol used is often the same one used for light emitting diodes in circuit diagrams. It uses the basic semiconductor diode symbol with arrows indicating the generation and emanation of light.Figure 3. Laser Diode Symbol What are the types of Laser Diode?There are several types of laser diodes:✔️Quantum well lasers✔️Quantum cascade lasers✔️External-cavity diode lasers✔️Interband cascade lasers✔️Separate confinement heterostructure lasers✔️DHL (double heterostructure lasers)✔️DFB-LD (distributed feedback laser diode)✔️DBR-LD (distributed bragg reflector laser)✔️FBG (FBG laser diodes laser diodes)✔️VCSEL ( vertical-cavity surface-emitting laser)✔️VECSEL(vertical-external-cavity surface-emitting-laser)✔️MOEMS-LD (micro-opto-electro-mechanical systems laser diode) Laser Diode Using Tips1) laser diode emitted laser light may cause harm to the human eyes. When using, don’t directly watch the light source. It requires warning signs.2) The device needs a suitable drive power supply, the instantaneous reverse current should not exceed 2uA, and the reverse voltage should not exceed 3V. In the power supply on and off, to prevent inrush current. When testing the drive circuit with an oscilloscope, disconnect the power supply and then connect the oscilloscope probe, if the probe is tested under power on, the inrush current may damage the device.3) The device should be stored or worked in a clean environment.4) Working at higher temperatures will increase the threshold current, lower conversion frequency and accelerate the aging of the device. When adjusting the amount of light input, use the optical power meter to detect to prevent exceeding the large rated output.5) The output power works higher than the specified parameters, which will accelerate the aging of the components.The following measures can be taken to slow down device aging.    a. Driving the laser diode with a DC constant current source.    b. Connect a current limiting resistor in series with a bypass capacitor to the laser diode circuit.    c. Since an increase in the temperature of the laser diode will increase the current flowing through it, the heat dissipation measures must be applied to ensure that the device operates within a certain temperature range.(4) To avoid the laser diode breakdown due to withstand excessive reverse voltage, it can be connected in reverse parallel on both ends of the fast silicon diode.(6) The machine needs to be fully dissipated or used under cooling conditions to prevent high temperature use. The output wavelength of the laser is affected by the operating current and heat dissipation, to maintain good heat dissipation conditions and reduce the temperature of the tube core when working.7) Diodes are electrostatic sensitive devices, to take appropriate anti-static measures.Figure 4. Injection Laser DiodeHow to Test a Laser Diode?a. Resistance measurement methodRemove the laser diode, use a multimeter R × 1k or R × 10k file to measure its positive and negative resistances. If normal, the forward resistance value is between 20~40kΩ, and the reverse resistance value is ∞ (infinity). If the measured forward resistance value has exceeded 50kΩ, it means that the performance of the laser diode has declined. If the measured forward resistance value is greater than 90kΩ, it means that the diode has been seriously aged, can no longer be used.b. Current measurement methodUse a multimeter to measure the voltage drop across the load resistor in the laser diode drive circuit, and then estimate the current value flowing through the tube according to Ohm's law. When the current exceeds 100mA, if the laser power potentiometer is adjusted, and no significant change in current, the laser diode can be judged to be seriously aged. If the current increases sharply and out of control, it means that the optical resonant cavity of the laser diode has been damaged.c. Pins DetectionThe laser diode has three pins: LD transmitter, PD receiver, LD-N common1) To distinguish between LD and PD. Use R × 1k block to measure the resistances of laser diode three pins. If a resistance value between the two pins reaches a few thousand ohms, at this time, the black pen is connected to the end of the PD anode, the red pen is connected to the pin for the common terminal, the remaining pin for the LD cathode, so as to distinguish the PD part (bc part of the figure) and LD part ( This distinguishes the PD part (bc part of the figure) and the LD part (ab part of the figure).2) Detect the PD part. PD part of the laser diode is essentially a photosensitive diode, using a multimeter test method is as follows: R × 1k block to measure its resistance, if the forward resistance of a few thousand ohms, the reverse resistance is infinite, it initially indicates that the PD part is good. If the forward resistance is 0 or infinity, it shows that the PD part has been bad. If the reverse resistance is not infinity, it means that the PD part has reverse leakage and the tube quality has become poor.3) Detect the LD part. Use the multimeter R × 1k block to measure the forward resistance of the LD part, that is, the black pen connected to the common terminal b, red pen connected to the a, the forward resistance should be between 10kΩ ~ 30kΩ, the reverse resistance should be infinity. If the measured forward resistance value is greater than 55kΩ, the reverse resistance value of 100kΩ or less, indicating that the LD part has been seriously aging, so the use of the effect will become worse. How to Make a Laser Diode?Step 1: Before made a laser diode, you should clear somethings firstly, including safety equipment, procedures, training in place, as well as disposal etc. Step 2: Build a working laser yourself you start with buying the diode. then you need a lens , and a heat sink , and a powersupply that won't blow it (they're very sensitive) .... all these components are on online, and that's quiet a tricky job ...much easier and cheaper to buy an assembled laser.Step 3: Spend a couple of pounds to purchase a laser pointer, and pull the diode & circuit out of that.Step 4: Don't power it up when it's direction is not firmly fixed away from your eyes, from anyone's eyes , and there might be reflective surfaces on the beam path nearby. Pay attention, do it legally where you are. How to Power a Laser Diode?Laser diodes are operated in forward conduction mode within a specified current range that is optimal for lasing operation, because they are current-driven devices. Laser diode power supplies can operate in one of two modes, constant current (CC) and automatic power control (APC). Most, but certainly not all, smaller laser diodes (5.6- and 9-mm packages) are operated in APC mode. For APC operation, the power supply must have a photodiode mounted inside the laser diode package. How to Build a Laser Diode Driver Circuit?Firstly, you should know that a laser diode driver circuit is a circuit which is used to limit the current and then supplies to the laser diode, and then follow the below steps:Step 1: Have a project with laser diode.Step 2: Find out all the useful parts and their parameters from your project.Step 3. Build the circuits according to the related project schematic.Step 4. Connect the Laser Diode and test it. How to Wire a Laser Diode?According to unidirectional conductivity, laser diodes only allow current to flow in one direction, and they're always polarized. First look at the positive and negative poles of the diode, and then the positive potential is connected to the anode of the diode, and the negative potential is connected to the cathode of the diode. How to Select the Right Laser Diode?Choose a laser diode for your application according to the following steps:Step 1: Turn application requirements into laser parametersStep 2: Selecting the laser typeStep 3: Selecting the laser materialStep 4: Make your final chart and go searching How to Drive Pulse Laser Diode?Laser Diode Driver is to provide current to the laser diode. With the amount of current controlled by the user or some automatic apparatus, you can drive a pulse laser diode. In addition, a laser driver can only regulate the current as long as the laser voltage stays within certain limits, so you should have a check the circuit parameters to select a proper diode driver. What is Power Source of 532 Laser Diode?Check the following table to find out the power source of 532 laser diode:532nm Green Laser DiodePowerPackageDescription0.004WTO-Can- Integrated Photodiode- Compact Size0.005WTurn-Key Module- Compact Size- Long Lifetime0.01WTurn-Key Module- Fiber-Coupled Output- Integrated Photodiode0.1WTO-Can- Integrated Photodiode- Compact Size0.2WTO-Can- Integrated Photodiode- Mode-Hop Supression0.4WButterfly- Integrated Photodiode- Integrated Heater0.5WButterfly- Internal Heater- Integrated PhotodiodeWhat is the Difference between Laser Diode(LD) and LED?LDs and LEDs both emit photons to produce light, but both of them have many differences according to the following table:ParametersLDLEDWorking PrincipleStimulated emissionSpontaneous emissionOmnidirectional emissionFull FormLight Amplification by Stimulated Emission of RadiationLight Emitting DiodeResponseFast response in comparison to LEDSlow responseDriving CurrentRanges from 5 to 40mARanges from 50 to 100mANature of Emitted LightCoherent and MonochromaticIncoherent and consists of various colors.Junction Area during ManufacturingNarrow and small JunctionWide Junction AreaBandwidth RangeRanges from 1MHz to 2MHZRange from10 to 50THzPower to light Conversion EfficiencyApprox 70 %Approx 30%Numerical Aperture of the obtained Light BeamExtremely low as compared to LEDs.Higher in LEDsCostHigh cost and thus used in the specific application.Low cost and thus economicalWhat is the Wavelength Range of a Laser Diode?Diode lasers deliver wavelengths ranging from 810 to 1064 nm. Diode lasers are compact and portable solid-state units. They are used strictly for soft tissue procedures and penetrate 2 to 3 mm or more into soft tissue, depending on the wavelength and tissue biotype. Is Diode Laser Permanent?Diode lasers use a single wavelength of light that has a high abruption rate in melanin. As the melanin heats up it destroys the root and blood flow to the follicle disabling the hair growth permanently. ... Diode lasers deliver high frequency, low fluence pulses and can be safely used on all skin types. Is LED a Laser Light?LEDs typically last longer than lasers, while lasers are faster. ... LEDs have a higher output with wider bandwidths, meaning that they can produce a broad range of less-concentrated light. Lasers have a lesser output and a small bandwidth, produced with a tiny pinpoint of light. How Long do Diode Lasers Last?Typical lifetime of laser diode modules are 25,000 to 50,000 hours. If the laser diode temperature continues to rise exceeding the maximum operating temperature, the diode can be catastrophically damaged or the long term performance may degrade significantly. Can an LED be Used as a Laser?The LED and laser emit light in a relatively narrow range of wavelengths. However, lasers put all their energy in a single wavelength, which emits from a tiny spot. LEDs spread the energy over more wavelengths and send that light from a larger spot into wide cone. What are the Advantages of Using Laser Diode Instead of an LED?It produces a very intense beam of light or infrared radiation which is having following properties. Laser diode used in optical fiber systems are made of gallium arsenide phosphide. The laser having size of grain of sand can produce power output of about 10 mWatt. ON/OFF switching speed of laser is faster than LED. What is the Disadvantage of Laser?Following are the drawbacks or disadvantages of Laser:It is expensive and hence more expenditure to the patients requiring laser based treatments.It is costly to maintain and hence more cost to doctors and hospital management. Increases complexity and duration of the treatment based on laser devices or equipments. FAQs1. Why do we prefer GaAs for laser diode?GaAs advantagesGaAs devices are relatively insensitive to overheating, owing to their wider energy band gap, and they also tend to create less noise (disturbance in an electrical signal) in electronic circuits than silicon devices, especially at high frequencies. 2. What is the advantage of laser over LED?The output power of a 1 watt LED can be < 100 milliwatts. Besides dramatic differences in total output, the laser also offers a significant advantage in terms of how usable that power is to the optical system. Specifically, the laser is a point source of coherent light that produces a well-behaved beam. 3. Why is laser light monochromatic?Monochromatic Laser LightThe light from a laser typically comes from one atomic transition with a single precise wavelength. So the laser light has a single spectral color and is almost the purest monochromatic light available. 4. What happens if the laser diode is forward biased?Forward bias injects charges into the junction, causing spontaneous emission of photons. When the diode is forward-biased, charges are injected into the active area of the junction, while electrons and holes recombine in the junction, creating spontaneous emission of photons. 5. Is a laser diode an LED?Light-emitting diodes (LEDs), like laser diodes, generate radiation via electrical current injection into a junction. LED light comes from spontaneous emission, whereas laser diode light arises from stimulated emission. Thus, LEDs generally have lower output powers and omnidirectional emission.

IntroductionAs one type of relays, reed relays use an electromagnetic coil to control one or more flexible ferromagnetic metal reed switches directly. It is composed only by the contacts themselves that triggers the conduction in the secondary circuit. Reed relay switches can be used as magnetic proximity switches or relays, which are smaller in size, higher in speed and longer in working life than general mechanical switches. Here, let's explore this special relay.What is a Reed Relay? Characteristics IntroductionCatalogIntroductionⅠ A Special Relay: Reed RelayⅡ Structure Comparison: Relay vs Reed RelayⅢ Reed Relay CharacteristicsⅣ What is a Reed Relay Used For?Ⅰ A Special Relay: Reed RelayIn electronic circuits, relays are the switches which close and open the circuits contacts electronically as well as electromechanically. When the relay coil is energized or de-energized, it plays the role of automatic regulation, safety protection and circuit conversion. Relays are available with two main types. As everyone knows, relays are divided into mechanical relays and semiconductor relays.Figure 1. Mechanical Relay vs Semiconductor RelayOn the insulation detection circuit of BMS, we often use a device called PhotoMOS, which is used to switch the Wheatstone bridge. Actually, it is a semiconductor relay.Figure 2. PhotoMOS AQV258For example, AQV258 is a model we often choose.PhotoMOS is a semiconductor relay with LED as input and MOSFET as output, but we are not mainly discussing PhotoMOS today.In recent years, another device has appeared on the insulation detection circuit, which is called Reed Relay Switch, Reed Switch, Reed Relays, etc. It is also used for the switch of the Wheatstone bridge arm. Ⅱ Structure Comparison: Relay vs Reed RelayReed relay is a kind of mechanical relays, but its structure is different from the traditional electromagnetic relay. The traditional electromagnetic relay is an electrical relay that uses the suction force generated by the circuit in the input circuit between the electromagnet core and the armature to work. This kind of relay is large in size, slow in action, and limited in life, but it is reliable. With the development of electronic appliances in the direction of miniaturization, new requirements have been put forward for relays. In this case, reed relays can meet the needs of this development in many aspects.Figure 3. Electromagnetic Relay StructureThe reed relay is composed of two parts: a reed switch and a coil. Compared with other types of relays, it is more compact and has higher energy efficiency. The following describes its structure and principle in detail.As shown in the figure below, the magnetic reed switch consists of two magnetic reeds, which are sealed inside a glass tube. The two magnetic reeds have a contact overlap area at the middle end of the glass tube, and has a small gap. The inside of the glass tube is filled with inert gas, such as nitrogen, to prevent oxidation. In order to improve the strength of electrical breakdown, the inside of the glass tube can also be evacuated.Figure 4. Reed Relay StructureThe magnetic reed body is made of nickel-iron alloy, and the surface of the contact overlap area of the two magnetic reeds is plated with hard metals such as rhodium or ruthenium to play a role in wear resistance. Placing the magnetic reed switch in a magnetic field, when the two magnetic reeds are magnetized into opposite polarities, they generate attractive force, and the contact overcomes the elastic force to connect. Similarly, when the magnetic field disappears, the contact is pulled away without magnetic force.In order to allow the reed switch to be closed or opened by human control, the coil is wound on the surface of the glass tube, and the coil is energized, thus forming an electromagnet, which generates a magnetic field for the reed switch to act.Figure 5. Relay CoilTherefore, as a circuit switch device controlled by a magnetic field signal, the reed switch can be used as a sensor for counting and limiting (in the security system, it is mainly used for the production of door and window magnets). It is widely used in various communication devices. In practical applications, permanent magnets are usually used to control whether the two metal pieces are connected or not, so they are also called magnetic relay.What’s more, the more turns the coil has, the less current reed relay switch needs to work. The relationship between the number of turns and the working voltage is restricted by the following factors: the wire diameter of the coil, the number of turns, the resistivity of the conductor, and the size of the reed contact.In theory, the working principle of the reed relay is like a switch: when the permanent magnet is close to the reed switch or the magnetic field formed by the coil winding on the reed switch magnetizes the reed, the contact part of the reed will be attracted by the magnetic force. When the attractive force is greater than the elastic force of the reed, the normally open contact will attract and close; when the magnetic force is reduced to a certain extent, the contact is opened by the elastic force of the reed.Figure 6. Reed Relay Magnetic FieldThe lifespan of reed switches is shorter than that of semiconductor switches, but much longer than general electromagnetic relays. The following figure shows the operating parameters of a certain type of reed switch, which can be switched on and off millions of times.Figure 7. Life Test DataThe reason for using the reed relay in the bridge method is that it has higher insulation and withstand voltage regardless of the load end or input/output. Ⅲ Reed Relay Characteristics1) High reliabilityThe failure rate of general relays is set at 50ppm, so in order to meet this requirement, the quality level of reed switches is much higher than this standard. So far, there has not been any electromechanical device that can achieve this level of quality.2) High securityReed relay switch has excellent insulation properties. Its insulation resistance can reach up to 1015Ω, that is, its leakage current only has 10-15A. Such extremely low leakage levels are widely used in medical electronic equipment, such as probes inserted into the human body or cardiac pacemakers, because these equipment require no leakage current close to the heart, even if the current is microampere or submicroampere, which will change the electrical properties of key parts of the heart.3) High adaptabilityThe reed sensor is sealed. Because the switch components is airtightly sealed in an inert gas, it will not contact the external environment, so it can work in almost any environment without being sensitive to humidity and not affected by the outside world. At the same time, the reed switch has no special requirements for the ambient temperature and has a wide temperature adaptability. The typical working temperature range can be from -50℃ to +150℃, and no special additional conditions, restrictions or costs are required.4) Long lifespanBecause the reed switch is a wear-free component and does not use a sliding component, there will be no worn metals, ensuring practically unlimited mechanical service life. At the same time, because the contact made of inert precious metal rhodium has a high melting point, it can reduce the loss of arc power generation on the contact surface, so it is more resistant to wear and can maintain a longer working life. General reed switches can work up to a million times under low-level loads (less than 5V and lower at 10mA).5) Small sizeThe reed relay switch can be installed in a limited space and is very suitable for miniaturized equipment.6) Superior electrical performanceReed relay switches have a series of excellent electrical properties. For example, their contacts have extremely low on-resistance when they are turned on, typically as low as 50mΩ. In addition, their direct switching signals can range from a few nanovolts to thousands of volts, and the current ranges from micro An to An, etc.7) High speed operationSince each movable component has only a very small weight, the operating speed is very high, making the reed switch a part that can be used in transistor circuits or integrated circuits.Ⅳ What is a Reed Relay Used For?Reed relay switches have been widely used in many fields of automatic control systems, such as machinery, automobiles, electronics, electric power, petroleum, chemical industry, office automation, communications and other engineering. For example, in the military field, high-voltage reed relays are related to national defense components for modern weapons and equipment. Frequently Asked Questions about Reed Relay Basics and Uses1. What is a reed relay used for?Reed Relays are ideally used for switching applications requiring low and stable contact resistance, low capacitance, high insulation resistance, long life and small size. 2. What is the difference between relay and reed relay?A relay switch is composed of an electromagnet that actuates a high power switch made of two metallic contacts. ... A reed switch is composed only by the contacts themselves that triggers the conduction in the secondary circuit. 3. Why is reed relay used in a switching circuit?The reed relay consists of a switch with magnetic contacts that move under the influence of an external magnetic or the induced field from its solenoid. They have faster switching speed compared to the electromechanical ones but their switching current and voltage is lower mainly because of its contacts thickness. 4. What is required to operate a reed relay in a switching circuit?The coil surrounds the reed switch and generates the axial magnetic field needed to close the reed contacts. 5. Where is a reed switch used?Reed switches are used in fluid level sensors for brake fluid reservoirs and to monitor motor oil levels. They are also used in speed sensors for engine control and power steering. Automatic door locks, air bags, parking brakes, seat, door, and hood proximity sensors also utilize reed switches.