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Ⅰ Introduction   One type of primary capacitor is the variable capacitor. Capacitors are classified into two types based on their capacitance. These are known as 'Fixed Capacitors' and 'Variable Capacitors.' Capacitors with a fixed capacitance value are referred to as 'Fixed Capacitors.' Similarly, capacitors with varying capacitance are referred to as Variable Capacitors.   What is a variable capacitor diode – how does it work? | Intermediate Electronics     This type of capacitor has the competence to change the capacitance values "Electrically" or "Mechanically." Variable Capacitors, unlike Fixed Capacitors, provide specific ranges of values rather than deciding the values during manufacturing. These capacitors are chosen based on the required values. This type of capacitor is preferred in the majority of Tuning Circuits.     Catalog Ⅰ Introduction Ⅱ What is a Variable Capacitor? Ⅲ Construction of Variable Capacitor 3.1 Summery Ⅳ Types  of Variable Capacitors 4.1 Tuning Capacitors 4.2 Common problems in turning circuits 4.3 Trimmer Capacitors 4.4 Mechanical Capacitors 4.5 Electronic Capacitors Ⅴ Working principle of Variable Capacitors 5.1 Turning types 5.2 Ceramic trimmers 5.3 Plastic foil types Ⅵ Variable Capacitor Applications Ⅶ FAQ     Ⅱ What is a Variable Capacitor?   Figure1:Variable Capacitor Symbol       Ⅲ Construction of Variable Capacitor   The variable capacitor's construction is shown below. As their simple construction, these capacitors are commonly used in a variety of applications. These capacitors are typically constructed with two sets of hemispherical metal plates separated by air gaps. One set of metal plates is fixed, while the other is connected to a shaft, allowing the user to turn the assembly and change the capacitance as needed. As a result, the construction of each type of capacitor differs.   Figure2: construction-of-variable-capacitor     The working principle of a basic capacitor can be applied to design this capacitor. The conductive plates of this capacitor are arranged in parallel and separated by dielectric coatings made of various materials such as reinforced paper, mica, or certain types of ceramics. These capacitors, unlike traditional fixed capacitors, are designed to change capacitance levels. In most cases, we can gain variable capacitance by varying the distance between parallel plates within a capacitor.     3.1 Summery This capacitor is built by inserting metal plates into it.Some of them are 'Fixed Plates,' while the rest are 'Movable Plates.'The area between the Fixed and the movable plates changes as a consequence of the rotation of the movable plates.Each type of capacitor in this category is built uniquely.     Ⅳ Types  of Variable Capacitors   In the market, there are two types of variable capacitors, which are as follows. The capacitance of the following capacitors can be changed manually with screwdrivers; otherwise, any device can be used.   Tuning CapacitorsTrimmer CapacitorsMechanical CapacitorsElectronic Capacitors     4.1 Tuning Capacitors   Tuning capacitors can be designed with the help of a frame. This frame has both a stator and a rotor. The frame of the capacitor can support both the mica material and the stator. When the stator is turned off, the rotors begin to rotate with the assistance of a shaft. When the movable rotor plates enter the immobile stator, the capacitance value is maximum; otherwise, it is minimum. These capacitors can provide capacitance values ranging from picofarads to tens of picofarads. Figure3:Tuning Capacitors     These capacitors are used in radio receivers with LC circuits. Tuning condensers is another name for these capacitors.       4.2 Common problems in turning circuits Variable capacitors used in tuning circuits can cause several issues. The main issue with the older types is a bend in the plates, which causes the component to short and thus become inoperative. As shown in Figure 1, this short can be detected.   Figure 4 - Testing a variable capacitor with a multimeter.     There must be no indication of low resistances around the entire turn of the variable capacitor. In good condition, the meter's needle should remain on infinite to a variable. If a short is discovered between the plates, the first step should be to attempt to correct the alignment of these plates using the screw that exists in the mobile variable axis. It is possible to adjust the plates if they are bent by pressing and releasing this screw. If the plates are bent, the technician can attempt to correct the defect very carefully, always performing a continuity test to detect the moment when the component is recovered. The insulating sheets inside them may have a small variable short problem. By carefully dismantling the component, you can obtain the defective sheets and attempt to correct the defect, or with insulating use of other variables abandoned by the same problem, or even with the improvisation of insulating sheets. Figure 5 depicts how the metal plates are arranged, with an insulating foil sandwiched between them to prevent contact between the mobile and fixed assemblies.     Figure 5 - Construction of a variable with plastic insulation.     After reassembly, an isolation test should be carried out to ensure that the short between the plates was indeed removed. If the problem is moisture or dirt, the variable can be disassembled for cleaning, but be careful not to bend plates and remember to reassemble any insulating sheet.       4.3 Trimmer Capacitors   Trimmer capacitors are used to provide basic calibration of equipment during manufacturing or servicing. These capacitors are frequently arranged on the printed circuit board in such a way that the user does not have access to change them. As a result, these capacitors are inexpensive. These capacitors are used in circuits to set the oscillator frequency, rise, latencies, and fall times. These capacitors enable servicemen to adjust devices as needed. These capacitors are classified into two types: air trimmer and ceramic trimmer.   There are three leads in this capacitor. The first lead is connected to the immobile part, the second to the rotary, and the third to the common. The purpose of a semi-circle-shaped movable disc is to observe the movement of this capacitor. This capacitor has two plates that are separated by a dielectric material and are arranged in parallel to each other.     Figure6:Trimmer Capacitors     These capacitors can be classified based on the dielectric material used, such as air trimmer or ceramic trimmer.     4.4 Mechanical Capacitors These capacitors are made up of a series of curved plates that are connected to a knob. The main advantage of this is that the capacitance of the capacitor can be easily changed if necessary. Mechanically, these are dependable because they are not overly complicated.     4.5 Electronic Capacitors By applying a DC voltage to these capacitors, you can change their capacitance. These capacitors' main applications are multimeters, resistance, and amperage. The DC (direct current) here refers to the type of current supplied by a battery.       Ⅴ Working principle of Variable Capacitors   The capacitance can be varied between a minimum and a maximum value using an electrode system composed of one fixed and one movable part – stator and rotor. The temperature coefficient (TC) for the various dielectrics has a great difference from the corresponding values for fixed capacitors. Except for the best precision components, the variations are significantly larger, which has to do with the mechanical conditions as well as the entire construction. Trimmer capacitors are primarily used on printed circuit boards (PCBs), but surface mount designs are becoming increasingly popular. Trimmers frequently have friction, which increases the turning moment and, as a result, locks the capacitor in its adjusted position.     5.1 Turning types   Air dielectric As shown in Figure 7, the classic variable capacitor is be composed of semicircular electrodes that can be turned into each other. The styles are designed for either PCB or panel mounting. They are mainly used for tuning resonance circuits.   Figure7: A variable air-insulated capacitor schematic and an example of Tronser's design.     Mechanical precision is required due to the air-insulated electrodes. The plate distance is usually between 0.2 and 1 mm. The cost is fairly high.     5.2 Ceramic trimmers We can make a ceramic trimmer capacitor by reducing the plates in Figure 7 to just one silver-plated ceramic rotor that is turned in over the stator electrode. Figure C5-2 depicts an example of this design. There are also multilayer designs. The capacitors are available in both hole mount and surface mount configurations.Because Type 1 ceramics are used, losses will be minimal.     Figure 8: Explanatory sketch of a cross-cut using a ceramic trimmer.       5.3 Plastic foil types If we replace the air insulation in Figure 7 with some plastic foil, the electrode distance can be reduced while the r – and thus the capacitance – increases, albeit at the expense of a slightly lower Q value. Low loss plastics such as Teflon (PTFE), polypropylene (PP), and polycarbonate (PC) are common, but polyester (PETP) is also available.       Ⅵ Variable Capacitor Applications         Ⅶ FAQ   1). What is the main function of the variable capacitor? It is used to fix the resonant frequency in the LC circuit.   2). How these capacitors are made? These are made with two sets of curved metal plates and they are divided by air gaps   3). What is a ganged capacitor? The combination of two capacitors that are connected together is known as a ganged capacitor.   4). What are the two types of variable capacitors? They are tuning capacitors and trimming capacitors.   5). What is the capacitance values of a variable capacitor? Typically ranges from 100pF to 500pF   Thus, this is all about variable capacitors and the characteristics of the variable capacitor mainly include accuracy, tolerance, polarity, voltage rating, and capacitance range. Here is a question for you, what are the advantages of a variable capacitor?

Introduction A resistor is a passive two-terminal electrical component. After it is connected to the circuit, the resistance is fixed, which can limit the current through the branch connected to it. On one hand, the resistance that cannot be changed is called a fixed resistor, on the other hand, the resistances of potentiometers or variable resistors are changeable. The main physical characteristic of a resistor is to transform electrical energy into thermal energy. It can also be said that it is an energy-consuming element, because internal energy is generated when current passes through it. Figure 1. Use Resistor in Circuit Catalog Introduction Ⅰ Functions of Resistor Ⅱ Three Basic Principles for Resistor Selection Ⅲ The Role of Resistors in Transistor Circuits 3.1 Why Should a Resistor Be Added to the Base of the Transistor? 3.2 Pull-down Resistor in Transistor Circuits Ⅳ FAQ Ⅰ Functions of Resistor In short, the function of resistance is to limit current, divide current, divide voltage, and convert electric energy into internal energy (heating) in the circuit. According to Ohm's law, through calculations, resistors in parallel and series connections can be used to achieve the desired current and voltage. Also there are different resistors and switches combined to produce voice-activated switches, photosensitive switches, infrared switches and so on. How to Use Resistors in circuits? 1) Limit CurrentIn order to prevent the components connected in series from being burnt out by the excessive current and to ensure the normal operation of the electrical appliances, a variable resistor can usually be connected in series in the circuit.2) Current DiversionThe resistor is connected in parallel to the component or circuit that needs to be shunted, and the voltage does not change. The function of this resistor is to divide current.3) Voltage DiversionGenerally, electrical appliances are marked with a rated voltage value. If the power supply is higher than it, the electrical appliance cannot be directly connected to the power supply for a normal operation. In this case, a resistor with suitable resistance can be connected in series in the circuit to share a part of the voltage, therefore the electrical appliance can work at the rated voltage. At this time, the role of the resistor is to divide the voltage.4) Provide Bias VoltageIn the transistor circuit, the resistor is connected between the base of it and the working voltage. At this time, the power supply provides a bias voltage to the base through the resistor, and the resistance can determine the bias voltage. The role of the resistor in the circuit at this time is to provide a bias voltage.5) Negative FeedbackUsed in the resistance between the base and collector of the transistor, then the feedback branch of the negative feedback circuit is formed in the circuit. At this time, the resistor plays a negative feedback role in the circuit.6) OscillationResistor and capacitor form an RC circuit, which can be combined in parallel and in series.7) Damping EffectConnecting a resistor in parallel in the LC resonant circuit can reduce the Q value, at this time, resistor plays a damping effect.8) DecouplingThe use of resistors in multi-stage amplifier circuits can prevent harmful low-frequency interference, which play a decoupling effect.9) Convert Electrical Energy into Internal Energy (Heating)When the current passes through the resistor, it will convert all (or part) of the electrical energy into internal energy, which will generate heat. This principle is often used in electric stoves and heaters in our lives.10) Convert Current into VoltageWhen current flows through the resistor, a voltage will be generated across the resistor. As shown in the figure below, the collector load resistor R2 plays this role, converting the current flowing through the resistor R2 into a voltage and outputting it from U0. Figure 2. Resistor Circuit   Ⅱ Three Basic Principles for Resistor Selection 1) Choose resistors that are manufactured by a certification body that implement high-level standards.2) Choose resistors produced by manufacturers with functional advantages, quality advantages, efficiency advantages, price advantages, and service advantages.3) Choose a manufacturer that can meet the above-mentioned requirements in the model catalog.   Ⅲ The Role of Resistors in Transistor Circuits 3.1 Why Should a Resistor Be Added to the Base of the Transistor? First of all, we must understand the basic principle of the transistor. It is a current-controlled element, which is different from the MOFET, a voltage-controlled element. The transistor has three working areas: cut-off area, amplification area and saturation area. Take NPN transistor as an example, the voltage difference（UBE）of BE is about 0.6V (the actual size depends on the model of the component). When UBE＜0.6V , the transistor is off; when UBE=0.6V, the transistor is in the amplification or saturation region. Figure 3. Schematic Diagram of the NPN Transistor Current When the transistor is in the amplification area, the added resistance between the base and VCC is a bias resistance. The following explains why the base should be added when the transistor is used as a switch. What is the difference between transistor and MOSFET circuits when adding a resistor.The following figure is the most commonly used circuit diagram of NPN transistors. The common input terminal is the I/O port of the microprocessor (microcontroller, DSP, ARM, etc.). Figure 4.  NPN Transistor Take the microcontroller I/O port with 0/5V input as an example. Why must a resistor be connected in series with the base? Can it work without a resistor? Here the resistor is a current control element. When the transistor is in an amplified or saturated state, the voltage of the UBE is 0.6V, and the base current can be calculated according to the input voltage U. The calculation formula is Ib=(U-0.6 )/R1. It can also be seen from the formula that if the current limiting resistor R1 is not connected, when the input voltage is greater than 0.6V, the base current will be very large to burn the tube.Moreover, the resistor cannot be used casually. It needs to be calculated according to the input voltage and the characteristics of the tube. For example, the amplification factor β of the transistor is 50, the maximum current of the collector is 500mA, and the input voltage is 5V. If the design requires the transistor to be in a saturated state, then Ic=500mA, Ib=Ic/β=10M=mA, where the current-limiting resistance R1=(5V-0.6V)/Ib=430Ω. If it is required to input 5V, the collector current is about 200mA, then Ib=Ic/β=200mA/50=4mA can be calculated, finally the current-limiting resistance R1=(5V-0.6V)/Ib=1075Ω (1K can be selected Standard resistance). Note: The above figure is used to explain the example, but it is not very reliable. A more reliable connection method should be to connect a large resistor (such as 10K, or 20K) between the base and the ground. When there is no input, pull the base down quickly to ensure that the tube is in a stable cut-off state.If the NPN transistor in the figure above is replaced with an N-channel MOS tube, the principle is the same. When a high level is input, the tube is turned on, and when a low level is input, the tube is turned off. Figure 5. MOSFET Circuit Since the MOSFET is a voltage-controlled device, the current of the gate (G) is very small and can be ignored, so it can work normally without connecting the resistor R1.The figure after remove the resistor is shown in the below: Figure 6. MOSFET Circuit without Resistor Note: In actual applications, a resistor is generally connected in series to improve reliability. The product reliability is very important. Without current-limiting resistor, when the MOS is   damaged by voltage breakdown, the components on the control terminal will be affected easily, especially the processor, is easily damaged by high current. 3.2 Pull-down Resistor in Transistor Circuits 🔺For TransistorsThe transistor is a current-type driving component, so a current-limiting resistor is connected to the base, generally less than 10K, and the typical values are 3.3K, 4.7K, 5.1K, 6.8K, etc. What is the function of this pull-down resistor?The following figure shows the transistor 8050 switching circuit. The transistor will be turned on when the I/O port outputs a high level, and the transistor will not be turned on. If the I/O port does not output a high level, the base will always be pulled low without a 68K pull-down resistor, that is to say it is in the cut-off state. The circuit may be in an unstable state, especially when it is initialized at the moment of power-on. It is easy to generate noise and easily cause the transistor to malfunction, especially for some general input/output ports. Therefore, this resistor is actually a bias resistor, which makes the base to be pulled down when there is no driving signal, making the circuit more reliable. Figure 7.  Pull-down Resistor in Transistor Circuit Although the pull-down resistor can make the circuit more reliable, tit cannot be too large or too small. If the resistance too large, the base current will not be enough to drive the transistor. On the contrary, if it is too small, the bias voltage will be less than the transistor conduction voltage. In general, this resistance is not more than 100K.Sometimes we see that a capacitor is connected in parallel with this resistor. In fact, this is generally designed in high-speed signal switching circuits. Adding a capacitor can improve performance, as shown below: Figure 8.  RC Circuit 🔺For MOSFETUnlike transistors, MOS transistors are voltage-controlled components, which are driven by voltage. We all know that there is parasitic capacitance between the two pins of MOS transistors. In fact, the key of MOS transistors’ conduction is the charging and discharging of capacitors. Therefore, for the N-type MOS, it will be turned on when Vgs is greater than a certain value, but for the P-type MOS, it will be turned on when the value of Vgs is less than a certain value.Therefore, due to the capacitive effect between the three pins, when the MOS is constantly turned off, the parasitic capacitance voltage can be properly discharged, which is similar to the role of a bleeder resistor and is a kind of protection for the MOS. Figure 9.  MOSFET Circuit Ⅳ FAQ 1. What is the function of the resistor?A resistor has the ability to reduce voltage and current when used in a circuit. The main function of a resistor is to limit current flow. Ohm's law tells us that an increase in a resistors value will see a decrease in current.   2. How do resistors work?A conductor has low resistance, while an insulator has much higher resistance. Devices called resistors let us introduce precisely controlled amounts of resistance into electrical circuits. ... A resistor works by converting electrical energy into heat, which is dissipated into the air.   3. Why do you need resistors?A resistor controls the flow of the electrical current within a circuit. ... Resistors are essential to many electoral circuits, and they can be applied to a myriad of different applications. Protect against voltage spikes. Resistors also protect components against voltage spikes.   4. What role do resistors play in electronic devices?A resistor is a passive two-terminal electrical device that resists the flow of current. It is probably the simplest element in an electronic circuit. It is also one of the most common components as resistance is an inherent element of nearly all electronic circuits. They are usually color-coded.   5. What is a good example of a resistor?A few examples include limiting electric current, voltage division, heat generation, matching and loading circuits, gain control, and setting time constants. They are commercially available with resistance values over a range of more than nine orders of magnitude.   6. What happens if I use a higher ohm resistor?The cases where using a higher value resistor will damage a circuit exist, but are a bit less usual than the cases where it may simply produce a weaker result than desired, or a different frequency response than desired.   7. What is a resistor simple explanation?A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor. ... The most common type in electronic devices and systems is the carbon-composition resistor.   8. What happens when a resistor blows?Blowing Up a Resistor. By applying too high a voltage to a resistor, the resistor will draw too much current. This causes excessive power to be dissipated in the resistor which makes it go up in flames and a cloud of smoke as this video shows.   9. How is a resistor connected in a circuit?Resistors are said to be connected in “Series”, when they are daisy chained together in a single line. Since all the current flowing through the first resistor has no other way to go it must also pass through the second resistor and the third and so on.   10. Do resistors change voltage?The larger the resistor, the more energy used by that resistor, and the bigger the voltage drop across that resistor. Ohm's Law can be used to verify voltage drop. In a DC circuit, voltage equals current multiplied by resistance. V = I R.

Introduction A Capacitor is a component that can store and release electricity, and it is also one of the most commonly used electronic components. Its distinguishing feature is the "Pass Alternating Current (AC), Stop Direct Current(DC)". In a DC circuit, a capacitor is equivalent to an open circuit. Based on this, we will have this question: What the differences betwen ac and dc capacitors? or Are ac and dc capacitors interchangeable? What's the difference between batteries and capacitors? or Why can't we use capacitors instead of batteries? As for capacitor calculations, what the time constant for discharging a capacitor? Here you will get the answers. Figure 1. Capacitor Symbol Catalog Introduction Ⅰ Why Can the Battery (DC) Charge the Capacitors? Ⅱ DC Capacitors vs AC Capacitors Ⅲ Battery or Capacitor? Ⅳ Calculate the Time Constant for the Discharge of the Capacitors? Ⅴ FAQ Ⅰ Why Can the Battery (DC) Charge the Capacitors? In circuit analysis, there are two types of circuit responses: zero-input response and zero-state response. The so-called zero input response means that the input signal is zero; the so-called zero-state response means that the states of all energy storage components and various power supplies in the circuit are zero.When analyzing the zero-state response, short-circuit the voltage source and open the current source. For the capacitor, at the moment of energization in the zero state response, it can be considered as a voltage source with zero voltage, so it is equivalent to a short circuit. Analyze the following figures: Figure one is the circuit structure: power supply E, internal resistance r, switch QF, capacitor C and resistance R. When the switch QF is turned on, let's take a look at the current Ic and voltage Uc flowing through the capacitor: Figure 2. Zero-input Response and Zero-state Response Curve We see that at the moment t=0, the current flowing through the capacitor is the largest. The capacitor at this time is equivalent to a voltage source with zero voltage, and the power source E must be charged to it through the internal resistance r. Therefore, we can understand that it is actually a short circuit, so the maximum charging current, that is, the charging current Icmax at t=0 is: . In the figure, we can see that after 5τ, the current has been zero and the voltage has been charged to almost E. After that, the current flowing through the capacitor will not change any more, and the capacitor at this time plays a role in isolating the direct current. As can be seen in the figure, the charging process of the capacitor is divided into two parts, one is the transient transition process, and the other is the steady state process.Next, analyze the transition process carefully. Let us first look at the opportunity RC of the resistance r and the capacitance C. Resistance is equal to voltage divided by current, and capacitance is equal to electricity divided by voltage, and electricity is equal to current divided by time, so there is: , here T is called the time constant, generally represented by τ.The current thus flowing through the capacitor is: The exponential function here, its exponent is equal to the ratio of time to the time constant, so it is a pure number. When the time is equal to 0, Ic=Icmax; when the time is equal to 5τ, the value of the exponential function is 6.738×10-3. After substituting the above formula, get the current at this time is: At this time, the expression of the capacitor voltage Uc is: Note: Theoretically, the voltage on the capacitor should be charged to ER/(R+r), but because in the steady state, the impedance of the capacitor is infinite, so its voltage can be charged to E.From here we can see that the so-called capacitor blocking DC actually refers to its steady-state characteristics. In the steady state, the equivalent impedance of the capacitor is infinite, and the DC current cannot pass through it, so the current is zero, and there is a very small leakage current at most. In the transient state, the capacitor can flow current, and in the initial stage since the current is similar to a voltage source due to the capacitance, its characteristic is almost a short circuit, so the initial value of the current is the maximum. If our power source is not a battery, but a square wave pulser, what is the voltage of the resistor R after the capacitor? Figure 3. Square Wave Pulser The Figure 3. is a case where the time constant is small, which reflects the impulse response of the capacitor; and the picture below is a case where the time constant is large, which reflects these two effects have a large number of applications. If our power supply is AC, what is the voltage on the resistor R after the capacitor?When discussing the response of the capacitor to the AC current range, we need to temporarily look back at the first picture. From the figure, we can see that when the current takes the maximum value, the voltage is the minimum value, however, when the current takes the minimum value, the voltage is the maximum value. Why is that?The capacitance is equal to the ratio of the electric quantity to the voltage, that is, C=Q/U=It/U, from which the current is obtained: I=CU/t. And the voltage Uc on the capacitor is actually constantly changing. It is a function of time, so the above formula can be written as: This formula is very important, it is the key to unlock the capacitor under the action of AC power.The AC voltage can be expressed as, put it into the expression of the capacitor current , and get: We can see that when the voltage is zero, the current has reached its maximum value. In other words, for an AC power supply, the current I flowing through the capacitor leads the voltage by 90 degrees. It reveals the expression form of capacitance under AC voltage.Capacitors are used to block direct current, but they only have this performance in steady state. When the DC power supply changes rapidly, that is, the power supply continuously changes from zero to the maximum value, and becomes zero again. In this cycle, we can see that the capacitor not only does not block the DC, but becomes a component with almost zero impedance.In fact, it can be known from the capacitive reactance () that when the frequency of the power supply increases, the capacitive reactance of the capacitor decreases linearly with the increase in frequency. When we charge the capacitor with a DC power supply enough, the charging voltage of the capacitor can reach the same level as the electromotive force of the power supply. Here the key is that the capacitor is an energy storage element. Figure 4. Various Capacitors Ⅱ DC Capacitors vs AC Capacitors 1) Whether DC capacitors and AC capacitors are polarized: AC capacitors are also called non-polarized capacitors. As can be seen from the literal meaning, it can be polarity-independent. So it can be used in AC and DC circuits. The DC current uses a polarized capacitor, which has a high capacity, and a relatively small withstand voltage. In addition, both of them will be lost over time.2) The mobility of DC capacitors and AC capacitors are different: the voltage at one end of the DC capacitor is always high, and the current will always be the same and flow in one direction. While the two lines from the AC capacitor power supply, their voltage level is changing, so that the current can flow from A to B, or from B to A, and make certain adjustments and changes over time.3) Direct current and alternating current are different in direction conversion: alternating current can be regarded as two groups of direct current in turn to exert an effect on the load, which can be understood as the vector sum of the two groups of direct current in different time periods. The alternating current can be understood as a group of direct current in one direction in a short enough time. Figure 5. Ceramic Capacitors Ⅲ Battery or Capacitor? Capacitors and batteries are both electrical components, and both are energy storage components. But battery and capacitor are two completely different concepts. The difference between them is:1) Chemical Energy vs Electrical EnergyThe battery stores chemical energy, and then converts it into electrical energy to output. Capacitors store electrical energy, which depends on the two plates to determine the capacity. The former is a chemical change, the latter is a physical change. The main physical feature of a capacitor is to store electric charge, which can be charged and discharged like a battery, but does not undergo a chemical reaction.2) CapacityBatteries store a lot of electrical energy, but capacitors store less.3) Charge and Discharge Figure 6. Charge and Discharge Curve The charging and discharging speed and the number of times are different. Generally, it only takes a few seconds or minutes to charge a capacitor, while a battery usually takes several hours. The number of charging and discharging of the capacitor is at least tens of hundreds to thousands of millions of times, and the battery is generally only a few hundred to a thousand times.4) FunctionsThe purpose of the two is different. Capacitors can be used for coupling, blocking, filtering, phase shifting, RC, LC resonance and as energy storage components for instantaneous large current discharge. The battery is only used as a power source. Replacing Bike Battery with Capacitor Ⅳ Calculate the Time Constant for the Discharge of the Capacitors? Let’s review the calculation formula for the charge and discharge time of the capacitor. Suppose there is a power supply that charges the capacitor C through the resistor R, V0 is the initial voltage value on the capacitor, Vu is the voltage value after the capacitor is fully charged, and Vt is the voltage value at any time t On the capacitor, then the following calculation formula can be obtained:Vt = V0 + (Vu – V0) * [1 – exp( -t/RC)]If the initial voltage on the capacitor is 0, the formula can be simplified to:Vt = Vu * [1 – exp( -t/RC)]...Charging formulaIt can be seen from the above formula that because the index value can only be infinitely close to 0, but it will never be equal to 0, it takes infinite time for the capacitor to be fully charged.🔺When t = RC, Vt = 0.63Vu🔺When t = 2RC, Vt = 0.86Vu🔺When t = 3RC, Vt = 0.95Vu🔺When t = 4RC, Vt = 0.98Vu🔺When t = 5RC, Vt = 0.99VuIt can be seen that after 3~5 RCs, the charging process is basically over. When the capacitor is fully charged, the power supply is short-circuited, and the capacitor C will be discharged through R. At any time t, the voltage on the capacitor is:Vt = Vu * exp( -t/RC)...Discharging formula   Ⅴ FAQ 1. Can you use a capacitor as a battery?A voltage applied across the conductors creates an electrical field in the capacitor, which stores energy. A capacitor operates like a battery in that, if a potential difference is applied across it that can cause a charge greater than its "present" charge, it will be charged up.   2. Why can't we use capacitors instead of batteries?Capacitors don't provide large amount of energy because they have less energy density than batteries. Capacitors are useful to provide short duration power requirements because they can be charged or discharged at a higher rate than the batteries.   3. What is the difference between a battery and supercapacitor?Differences Between Capacitor and BatteryBatteries excel at storing energy, while supercapacitors rate better for power. In practical terms, this means that supercapacitors are better at discharging their stored energy quickly, while batteries save more energy in the same amount of material.   4. Which is better battery or capacitor?A capacitor is able to discharge and charge faster than a battery because of this energy storage method also. ... However, in general batteries provide higher energy density for storage, while capacitors have more rapid charge and discharge capabilities (greater Power density).   5. What is discharging of capacitor?Discharging a capacitor means releasing the charge stored within the capacitor. ... Hence the capacitor current exponentially reaches zero from its initial value, and the capacitor voltage reaches exponentially to zero from its initial value during discharging.   6. Is it safe to discharge a capacitor with a screwdriver?It's often safe to discharge a capacitor using a common insulated screwdriver; however, it is usually a good idea to put together a capacitor discharge tool and use that for electronics with larger capacitors such as household appliances.   7. Can you discharge a capacitor with a multimeter?The multimeter isn't used directly to discharge the stored energy of a capacitor. Instead, people use it to measure the voltage and power of the capacitor to know whether it is fully released or not. You can use different tools such as a light bulb or a DIY discharge tool for the process.   8. Why do we need to discharge a capacitor?You must discharge the capacitors before working on power supply circuits so you won't get shocked. ... Using a screwdriver to discharge the capacitor is not recommended because you can generate a spark and damage the printed circuit board or circuitry of the power supply. You can even blow the power section.   9. What is discharging time of capacitor?RC Discharging Table. Note that as the decaying curve for a RC discharging circuit is exponential, for all practical purposes, after five time constants the voltage across the capacitor's plates is much less than 1% of its inital starting value, so the capacitor is considered to be fully discharged.   10. What is the time constant of a capacitor?The time constant of a series RC (resis-tor/capacitor) circuit is a time interval that equals the product of the resistance in ohms and the capacitance in farad and is symbolized by the greek letter tau (τ). The time in the formula is that required to charge to 63% of the voltage of the source.   11. Is the time constant the same for charging and discharging the capacitor?The time constant of a resistor-capacitor series combination is defined as the time it takes for the capacitor to deplete 36.8% (for a discharging circuit) of its charge or the time it takes to reach 63.2% (for a charging circuit) of its maximum charge capacity given that it has no initial charge.   12. What is the formula of discharging of capacitor?q=ϵC(1−eCR−t) where q is the charge on the capacitor at time t,CR is called the time constant, ϵ is the emf of the battery. Discharging: If the plates of a charged capacitor are connected through a conducting wire, the capacitor gets discharged.   13. What is energy stored in capacitor?Electrical potential energyEnergy stored in a capacitor is electrical potential energy, and it is thus related to the charge Q and voltage V on the capacitor. We must be careful when applying the equation for electrical potential energy ΔPE = qΔV to a capacitor. Remember that ΔPE is the potential energy of a charge q going through a voltage ΔV.   14. Where is energy stored in capacitor?A charged capacitor stores energy in the electrical field between its plates. As the capacitor is being charged, the electrical field builds up. When a charged capacitor is disconnected from a battery, its energy remains in the field in the space between its plates.   15. Which type of current is blocked by a capacitor?Alternating current doesn't really "flow", it just oscillates back and forth. A capacitor acts like an elastic membrane, it allows the oscillation but blocs the flow of DC current.

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.

CatalogⅠ What is a Ballast Resistor ?Ⅱ Types of Ballast Resistors2.1 Fixed Resistors2.2 Self-Variable ResistorsⅢ The Working Principle of  Ballast ResistorsⅣ Ballast Resistor – Uses and Applications4.1 Ballast Resistor in Fluorescent Lamps4.2 Ballast Resistor for Automotive Applications4.3 Ballast Resistor in a LED CircuitⅤ Symptons of Failture Ballast-ResistorⅥ Frequently Asked Questions about Ballast resistors Introduction  “Ballast” is generally considered as “something that provides stability in English dictionary.  ” Thus, when we refer to an electrical ballast, we are referring to an electrical device that is important in maintaining the stability of the electrical circuit. However, you might be wondering how it provides stability. Depending on the circuit in which they are used, some electric ballasts limit current while others limit voltage. By doing so, they reduce the risk of overvoltage or overcurrent in the circuit, thereby improving system stability. The complexity of electric ballast varies greatly. It can be as simple as a resistor, capacitor, inductor, or a combination of these, or as complex as the electronic ballast found in fluorescent lamps.  Ⅰ What is a Ballast Resistor ? A ballast resistor is an electronic component that is usually used to regulate the current in a circuit. Some devices, such as fluorescent lamps, can exhibit negative resistance characteristics, and an increase in current will result in a decrease in voltage. Negative resistance can cause damage to the power supply or equipment. Ballast resistors are usually connected in series with the negative load, taking advantage of the fact that all components in the series circuit receive the same current. Some ballasts are just series resistors, while others use capacitors and more complex components. Figure1: complex components Ⅱ Types of Ballast ResistorsA resistor is a current-limiting electronic component that can reduce circuit voltage and current. Ballast resistors are classified into three types: fixed, variable, and reactive.2.1 Fixed ResistorsThis genre of ballast resistors have a fixed resistance. A high resistance value is primarily taken considered for most applications. This genre of ballast resistor is commonly used in simple circuits with low-powered loads such as neon or LED lamps. This fixed resistor is also applied to control the ventilation fan speed. It employs a fixed ballast resistor with two center taps. The fan speed selector switch detours portions of the ballast. Therefore, the entire ballast resistor is suitable for full speed, while no section of the ballast resistor is suitable for the low speed.2.2 Self-Variable ResistorsThese ballast resistors have the property of resistance in response to changes in current, such as an increase in current increasing resistance and a decrease in current decreasing resistance. Incandescent lamps frequently use these ballast resistors. As the current through the lamp increases, the ballast resistor heats up, and the resistance rises with the temperature, as does the voltage drop across the resistor. When the current is down, the temperature of the ballast resistor decreases as well, as does its resistance and thus the voltage drop. The benefits of using this type of ballast resistor are that it provides more precise current control than a suitable fixed resistor. Another benefit is that the power lost in the resistive ballast is decreased because a smaller section of the overall power is lost in the ballast when compared to a fixed resistor. Ⅲ The Working Principle of  Ballast Resistors When 220V 50HZ AC power is applied to the switch closed circuit, the current flows through the ballast, and the lamp filament starter heats the filament（The starter was turned off in the beginning. The gas arc discharge in the jumping bubble in the starter caused the bimetallic sheet to heat and deform due to the application of an AC voltage greater than 190V, and the two electrodes were close together to form the filament heated by the passage.) Because there is no arc discharge when the two electrodes of the starter are close together, the bimetal cools and the two poles separate. As the ballast is inductive, when the circuit is suddenly interrupted, 600V is generated at both ends of the lamp for about 1ms. The pulse voltage is -1500V; the exact voltage value depends on the type of lamp. When the lamp discharges, the voltage at both ends drops immediately. At this point, the ballast limits the lamp current on the one hand while also supplying power on the other. There is a phase difference of 55° to 65° between the voltage and the working current of the lamp in order to keep the secondary starting voltage of the lamp stable.Figure2:  the working principle of  a ballast resistor Due to its simple structure, inductive ballast, as the first type of ballast to work with fluorescent lamps, has a relatively large market share. However, on account of its low power factor, poor low-voltage startup performance, heavy energy consumption, stroboscopic and many other shortcomings , its market is gradually being replaced by electronic ballasts. The energy consumption of inductive ballasts: 40W (lamp tube power) + 10W (inductive ballast self-heating consumption) is equal to the total power 50W consumption of the whole set of lamps and lanterns. An electronic ballast is a converter that converts low frequency alternating current power to high frequency alternating current power. Its basic operation is as follows: after passing through a radio frequency interference (RFI) filter, full-wave rectification, and a passive (or active) power factor corrector (PPFC or APFC), the industrial frequency power supply becomes a DC power supply. The output of high-frequency AC power of 20K-100KHZ is added to the LC series resonant circuit connected to the lamp via the DC/AC converter to heat the filament, but the lamp is "discharged" into the "on" state and then enters the light-emitting state. At this point, the high-frequency inductor limits the current increase, ensuring that the lamp tube receives the voltage and current required for normal operation. Various protection circuits, such as abnormal protection, surge voltage, and current protection, temperature protection, and so on, are frequently constructed to improve reliability. Ⅳ Ballast Resistor – Uses and Applications Ballast resistors are most commonly used to adjust the current to a negative resistance load. They can also be applied in other contexts. Fixed ballast resistors are common in low-power devices like light-emitting diodes (LEDs) and neon lights. LEDs are a positive resistive load that can benefit from ballast resistors. 4.1 Ballast Resistor in Fluorescent Lamps Fluorescent lighting, as we all know, is a popular and efficient lighting system. However, there is a disadvantage to using this type of lighting system. When directly connected to a voltage source, it heats up very quickly. This situation is due to the lamp's uncontrollable current draw as soon as its operation. A ballast resistor, connected in series with the lamp, is applied to the circuit to prevent overheating caused by excessive current draw. Therefore, the function of ballast resistor is to regulates the current and reduces the voltage. However,  for the lamp to light up, an arc has to be formed between its two electrodes. This necessitates a high starting voltage that is nearly equal to the supply voltage. The ballast resistor provides the required voltage during startup, and then immediately after an arc is established, it reduces the voltage while also regulating the current flow. Figure3: application in fluorescent lamp 4.2 Ballast Resistor for Automotive Applications Ballast resistors are generally included in the ignition kits of automotive machines such as automobile engines. Such devices are often called Ignition Ballast Resistors because of their application. The application of this device reduces the possibility of coil failure. It is connected between the ignition coil's primary voltage source and the coil stud. This connection helps to reduce the coil voltage and coil current, so the coil does not get as hot as it would without it, extending the coil's life. However, a high voltage equal to the primary voltage source is required to start the ignition engine. As a result, a jumper wire is frequently connected to the ballast resistor. This jumper wire provides the voltage required to start the engine.  Figure4: application in automotives 4.3 Ballast Resistor in a LED Circuit If the source voltage in an LED circuit is greater than the rated voltage of an LED lamp, the LED may be damaged. It is strongly advised to connect a ballast resistor in series with the lamp to avoid this case. By connecting the ballast resistor in this manner, the voltage across the LED is down to a tolerable level. The circuit diagram for the same is shown in the figure below.  Figure5: application in leds  The following formula is the value of resistance of the ballast :R = (E – Vf)/IFWhere: R= resistance of the ballast resistorE = voltage sourceVf = forward voltage of the LEDIF =Forward current of the LED. So, let's say you have an LED with a voltage rating of 4 volts, a forward current of 10 mA, and a voltage source of 6 volts. This means that the voltage across the LED should be 4 or less than 4 volts. As a result, the resistance of the ballast resistor should be R= (6-4)/0.010 = 200 or greater. Now that we've covered the applications briefly, let's look at the different types of ballast resistors on the market. Ⅴ Symptons of Failture Ballast-Resistor A ballast resistor is a device in your car that limits the amount of current flowing through an electric circuit. Because they did not have the benefit of circuit boards like most modern vehicles, ballast resistors are commonly found in older vehicles. Normal wear and tear can damage the ballast resistor over time, so there are a few things to look for if you suspect a bad or failing ballast resistor needs servicing. 1. Vehicle starts, then immediately goes out The most obvious symptom is that the vehicle starts but then dies as soon as you remove the key. If this occurs, Your Mechanic's experts will be able to measure the voltage coming from the ballast resistor and determine if it needs to be replaced. They will inform you of the condition of your ballast resistor once they have read the voltage. 2. Not starting at all The vehicle will not start if the ballast resistor is not functioning properly. Because it is an electrical system, it is best left to the professionals. The only way to get the vehicle running again is to replace the ballast resistor. 3.  Don’t jump the resistor Some people attempt to jump the resistor, which means that the ballast resistor is ignored and the extra current is routed to the points. The points are not designed to withstand the additional voltage, causing them to wear out and fail prematurely. This will result in a much more extensive repair than if the ballast resistor was replaced at the start. Furthermore, because you are tampering with electricity, it can be dangerous, especially if you don't know what you're doing. 4.  Let the vehicle beIf your ballast resistor is out of work, your vehicle will not start and you will need to have it towed to a mechanic's shop. Because the professionals at Your Mechanic make house calls, you will be able to save money on towing. Furthermore, because the vehicle will not start, it is not a dangerous situation as long as you leave it alone. Do not attempt to bypass the ballast resistor and do not continue to try to start the engine. Allow the professionals to repair it so you can get back on your way. Ⅵ Frequently Asked Questions about Ballast resistors 1. Is a ballast resistor necessary?　If the coil required a ballast resistor when it was used with points, then you must still use the resistor. If it didn't, then no resistor is necessary. The ballast resistor keeps the engine running by preventing the engine from receiving full amperage from the ignition once started.　 2. Why do ignition coils need ballast resistor?　In simple terms, the ballast resistor in a Mopar limits the amperage, or current flow, through the coil while the engine is running, thereby extending the life of the coil and breaker points of the distributor. 3. How do you know if a ballast resistor is bad?To test your ballast resistor you need an ohm meter or multimeter set to ohms. Remove the connectors from both sides of the resistor. The ohms should read between 1.8 and 5 ohms. You should be getting 9 volts to the positive side of the coil. 4. What causes a ballast resistor to fail?The resistance through the ballast resistor varies with current flow which varies with engine rpm. This naturally causes the resistor to expand and contract from heat. That's why they eventually fail. 5. Can a resistor wire go bad?　　The only way the wire will "go bad" is if it gets a break in it so it has infinite resistance (an open circuit). 6. Which circuit the ballast resistor is used?　　Ballasts can also be used simply to limit the current in an ordinary, positive-resistance circuit. Prior to the advent of solid-state ignition, automobile ignition systems commonly included a ballast resistor to regulate the voltage applied to the ignition system. 7. What is inside of a ballast?　A magnetic ballast (also called a choke) contains a coil of copper wire. The magnetic field produced by the wire traps most of the current so only the right amount gets through to the fluorescent light. That amount can fluctuate depending on the thickness and length of the copper wire. 8. What's the difference between a ballast and non ballast coil? Basically, a non-ballast coil is designed to produce full spark output with 12 volts on the input (+ terminal). A ballast coil is designed to produce the same spark output, but with only 6 to 9 volts on the input. 

IntroductionInductor is a passive component that used extensively with capacitors and resistors to create filters for analog circuits and in signal processing. Also it is an energy storage device in many switched-mode power supplies. As a major value of inductor, inductance is the ratio of wire current and the magnetic flux which is created by the flow of electrical current in the magnetic field. When a DC current passes through the inductor, there are only fixed magnetic lines around it, which do not change with time. However, when an alternating current is passed through the coil, the magnetic lines around inductor that will change with time.Inductors and Inductance DefinitionCatalogIntroductionⅠ Inductor Working PrincipleⅡ What Does Inductor Do?Ⅲ Inductor Main ParametersⅣ Inductor ClassificationⅤ Chip Inductor5.1 Purpose of a Chip Inductor5.2 Chip Inductor Classification5.3 Three Methods for Reading Chip InductorsⅠ Inductor Working PrincipleWhen ac current is applied to an inductor coil, its own current changes, making its own magnetic flux to change, and then causing induced electromotive force. This phenomenon is called self-inductance. The direction of self-induced current always be affected. When the alternating current increases, the direction of self-inductance current is opposite to that of AC current. When the AC current is weaken, the direction of self-inductance current is the same as that of alternating current, which has blocking effect.1) Self-inductionWhen current flows through the coil, a magnetic field is generated around the coil. When the current in the coil changes, the surrounding magnetic field also changes accordingly. This changing magnetic field can cause the coil itself to generate induced electromotive force (EMF is used to represent the terminal voltage of the ideal power supply for active components).2) Mutual InductanceWhen two inductor coils are close to each other, the change of the magnetic field of one coil will affect the other one, and this effect is mutual inductance. The magnitude of the it depends on the degree of coupling between the self-inductance and the two coils. The components made by this principle are called mutual inductors.Ⅱ What Does Inductor Do?The inductor mainly plays the role of filtering, oscillating, delaying, tuning and frequency selection in the circuit, as well as filtering signal, filtering noise, stabilizing current and suppressing electromagnetic wave interference. The most common role of inductance in a circuit is to form an LC filter circuit together with a capacitor. Capacitors have the characteristic of "block DC and pass AC", while inductors have the function of "pass DC and block AC". It can be made into low-frequency and high-frequency choke coils by making use of its properties. Common filter inductors are for this purpose.➡️Pass DC: It means that in a direct current circuit, the inductor acts as a wire and has no effect.➡️Block AC: In an AC circuit, the inductor will have impedance, that is, XL. The current in the entire circuit will become smaller, which has a certain blocking effect on AC. The self-induced electromotive force is always opposed to the current change in the coil. Mainly can be divided into high-frequency choke coil and low-frequency choke coil.➡️Inductor has the function of generating self-induced EMF, which is also called energy storage function. Like a capacitor, it is also an important energy storage component, which is widely used in switching power supplies. In addition, the phase relationship between the voltage across the inductor and the current: the voltage leads the current by 90 degrees, which is just the opposite of the capacitor. Using this characteristic, inductors and capacitors form LC series and parallel circuits, which can be used for frequency selection. In reality, they have been widely used in circuits, especially in radio circuits.If the direct current accompanied by many interference signals is passed through the LC filter circuit, then the AC interference signal will be consumed by the inductance into heat. When the pure DC current passes through the inductor, the AC interference signal in it will also become magnetic induction and heat energy, the higher frequency is most likely to be blocked by the inductor, which used to suppress the higher frequency interference signal.➡️Tuning and Frequency SelectionThe inductance coil and the capacitor are connected in parallel to form an LC tuning circuit. That is, the natural oscillation frequency f0 of the circuit is equal to the frequency f of the non-AC signal, and the inductance and capacitive reactance of the loop are also equal, so the electromagnetic energy oscillates between the inductor and the capacitor. This is the resonance phenomenon of the LC loop. During resonance, since the inductance and capacitive reactance of the circuit are equal and opposite, the inductance of the total current of the loop is the smallest and the current is the largest (referring to the AC signal of f=f0), so the LC resonance circuit has the function of selecting the frequency, therefore an AC signal of a certain frequency is selected.➡️ChokeIt is used to block low-frequency alternating current, and pulsating direct current flows to pure direct-current in circuits. Go further, it is commonly used in the middle of two filter capacitors at the output of a rectifier circuit. The choke and capacitor form a filter circuit. In the high-frequency circuit: to prevent the high-frequency current from flowing to the low-frequency end, which is commonly as the high-frequency choke of old regenerative radio.➡️FilterIt also prevents the rectified pulsating DC current from flowing to the pure DC circuit. The choke (to simplify the circuit and reduce the cost, replace the choke with a pure resistance) and two capacitors (electrolytic capacitors) form a filter circuit. The use of capacitor charging and discharging and AC choke coil to block the alternating current to smooth direct current and obtain the pure direct current.➡️OscillationWe often say that rectification is to transform AC into DC, so oscillation is the reverse process of it. We call the circuit that completes this process an "oscillator." Oscillator waveform: there are sine wave, sawtooth wave, trapezoidal wave, square wave, rectangular wave, spike wave. The frequency ranges from a few Hz to tens of GHz. It is widely used in the field of wired power and radio.Ⅲ Inductor Main ParametersThe main parameters of inductor include inductance, allowable deviation, quality factor, distributed capacitance and rated current.1) InductanceInductance is also called self-inductance, which is a physical quantity that represents the self-inductance of an inductor. The size of the inductance mainly depends on the number of turns  of the coil, the winding method, the core and its material, etc. Generally, the more coil turns and the denser the coils, the greater the inductance. A coil with a magnetic core has a larger inductance than a coil without a magnetic core. What’s more, a coil with a larger magnetic core has a larger inductance.The basic unit of inductance is Henry, represented by the letter "H". Commonly used units are millihenry (mH) and microhenry (μH). The relationship between them is:1H=1000mH1mH=1000μH2) Allowable DeviationThe allowable deviation refers to the allowable error value between the nominal inductance and the actual inductance.Generally, inductors used in circuits such as oscillation or filtering require high accuracy, with an allowable deviation of ±0.2%~±0.5%; while the accuracy requirements of coils used for coupling and high-frequency blocking are not high; the allowable deviation is ±10 %~15%.3) Quality FactorQuality factor, also called Q value, is the main parameter to measure the quality of an inductor. It refers to the ratio of the inductance presented by the inductor to its equivalent loss resistance when it works under a certain frequency of AC voltage. The higher the Q value of an inductor, the smaller its loss and the higher its efficiency.The Q factor is related to the DC resistance of the coil wire, the dielectric loss of the coil frame, and the loss caused by the core and shield.4) Distributed CapacitanceDistributed capacitance refers to the capacitance that exists between the turns of the coil, the coil and the magnetic core, the coil and the ground, and the coil and the metal. The smaller the distributed capacitance of the inductor, the better its stability. Distributed capacitance can make the equivalent energy dissipation resistance larger. To reduce it, silk-covered wire or multi-strand enameled wire is commonly used, and sometimes honeycomb winding method is also used.5) Rated Current The rated current refers to the maximum current value that the inductor can withstand under the allowable working environment. If the operating current exceeds the rated current, the inductor will change its performance parameters due to heat, and even burn out due to overcurrent.Ⅳ Inductor ClassificationAccording to the form of inductor: fixed inductance, variable inductance.According to the nature of the magnetic conductor: air core coil, ferrite coil, iron core coil, copper core coil.According to work nature: antenna coil, oscillating coil, choke coil, trap coil, deflection coil.According to winding structure: single-layer coil, multi-layer coil, honeycomb coil.According to working frequency: high frequency coil, low frequency coil.According to structural characteristics: magnetic core coil, variable inductance coil, color code inductor coil, non-magnetic core coil, etc. Ⅴ Chip Inductor5.1 Purpose of a Chip InductorChip inductors are electromagnetic induction components wound with insulated wires. It is a commonly used electronic component. The function of the chip inductor: it is simple to say that it can isolate and filter the AC signal or form a resonant circuit with capacitors, resistors, etc. The inductor coil and capacitor in parallel can form an LC tuning circuit. Any current flowing through the chip inductor will generate a magnetic field, and its magnetic flux will act on the circuit.When the current passing through the chip inductor changes, the DC voltage potential generated in the chip inductor will prevent the current from changing. When the current passing through the inductor coil increases, and the current passing through the inductor coil decreases, the self-induced electromotive force is in the same direction as the current, which prevent the current from decreasing and release the stored energy at the same time. The direction of flow is opposite to prevent the increase of current, and at the same time, part of the electric energy is converted into magnetic field and stored in the inductor. Therefore, with inductor filtering, not only the pulsation of load current and voltage is reduced, the waveform becomes smooth, and the rectifier diode is turned on.The role of shielded chip inductors is different from that of the general one. The general chip inductors are not shielded in the circuit to achieve the desired effect. The shielded current instability of this kind inductor in some circuits plays a good blocking role. A metal shield surrounds the positively charged conductor, and the inside of the shield will induce the same amount of negative charge as the charged conductor. A positive charge equal to that of a charged conductor appears on the outside. If the metal shield is grounded, the positive charge on the outside will flow into the ground, and there will be no electric field on the outside, that is, the electric field of the positive conductor is shielded.The shielding inductance also plays a role of coupling in the circuit. In order to reduce the coupling interference voltage of the alternating electric field to the sensitive circuit, the inductance can be set with a metal shield with good conductivity between the interference source and the sensitive circuit, in addition, the metal shield is grounded. The coupling interference voltage to the sensitive circuit depends on the product of the alternating electric field voltage, the coupling capacitance and the ground resistance of the metal shield. As long as the metal shield is well grounded, the coupling interference voltage can be reduced. The electric field shielding is mainly based on reflection, so the thickness of the shielding body does not need to be too large, and the structural strength is the main consideration.5.2 Chip Inductor Classification1) Winding TypeIt is characterized by a wide range of inductance (mH～H), high inductance accuracy, low loss (that is, large Q), large allowable current, strong manufacturing process inheritance, simplicity, and low cost, and the shortcoming is size. For example, the ceramic core winding type chip inductor can maintain a stable inductance and a fairly high Q value at such a high frequency, so it occupies a place in the high-frequency circuit.NL series inductors are wire-wound type, 0.01~100uH, accuracy 5%, high Q value, which can meet general needs. NLC type is suitable for power circuit, rated current up to 300mA.NLV type is high Q value, environmentally friendly (reconstituted plastic), and can be interchanged with NL.NLFC has a magnetic screen and is suitable for power cords.2) Layer TypeIt has good magnetic shielding, high sintering density and good mechanical strength. The disadvantages of it are low pass rate, high cost, small inductance, and low Q value.Compared with wire wound chip inductors, it has many advantages: Small size is helpful to the miniaturization of the circuit.Closed magnetic circuit will not interfere with surrounding components, and will not be interfered by neighboring components, which is beneficial to high-density installation.Integrated structure, high reliability; good heat resistance and solderability.Regular shape is suitable for automatic surface mounting production.MLK type inductor has the characteristics of small size, good solderability, magnetic screen, high-density design, monolithic structure, and high reliability.MLG type has a small inductance and uses high-frequency ceramics, which is suitable for high-frequency circuits.MLK type working frequency is 12GHz, with high Q and low inductance (1n~22nH).3) Film TypeIt has the characteristics of maintaining high Q, high precision, high stability and small size in the microwave frequency band. The internal electrodes are concentrated on the same layer, and the magnetic field distribution is concentrated, which can ensure that the device parameters after mounting do not change much, and show good frequency characteristics above 100MHz.4) Weaving TypeIts characteristic is that the inductance per unit volume at 1MHz is larger than other chip inductors, small in size, and easy to install on the substrate. It is usually used as a miniature magnetic component for power processing.In actual applications, the inductor should be selected according to the situation, circuit requirement, and the material cost.5.3 Three Methods for Reading Chip Inductors1) Digital Position Identification (generally rectangular chip resistors use this nominal method)This method is to use three digits on the resistor to indicate its resistance. Its first and second digits are significant digits, and the third digit represents the number of "0"s added after the significant digits, no letters will appear in this place.For example: "472'" means "4720Ω"; "151" means "1510Ω". If it is a decimal, use "R" to mean "decimal point". It occupies one significant digit, and the remaining two are significant digits.For example: "2R4" means "2.4Ω"; "R15" means "0.15Ω".2) Resistor Color Code (generally cylindrical fixed resistors use this nominal method)Chip resistors are the same as general resistors. Most of them use four rings (sometimes three rings) to indicate their resistance. The first ring and the second ring are significant numbers, and the third ring is the magnification. For example: "brown, green and black" means "15Ω"; "blue, gray, orange and silver" means "68kΩ", the error is ±10%.3) E96 Number Mixes with LetterThis method also uses three digits to indicate the resistance value, that is, "two digits plus one letter". Two digits represent the E96 series resistance. Its third digit is the magnification expressed by the letter code. For example: "51D" means "332×103; 332kΩ"; "249Y" means "249×10-2; 2.49". Frequently Asked Questions about Inductor Uses1. What is inductor and its function?An inductor is arguably the simplest of all electronic components. It's a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. Typically, an inductor will consist of an insulated wire that's wound into a coil, much like a resistor. 2. What is the basic principle of inductor?An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy. Basically, it uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction. 3. What is the function of inductor in AC circuit?Inductors store their energy in the form of a magnetic field that is created when a voltage is applied across the terminals of an inductor. The growth of the current flowing through the inductor is not instant but is determined by the inductors own self-induced or back emf value. 4. Does an inductor block AC?We know that inductor has inductive reactance property by which it opposes the flow of current through it. The equation of inductive reactance is, ... For this reason, an inductor can totally block the very high-frequency AC. 5. Why AC is blocked by inductor?Since inductor behaves like a resistor, DC flows through an inductor. The AC flowing through L produces timevarying magnetic field which in turn induces self- induced emf (back emf). ... For an ideal inductor of zero ohmic resistance, the back emf is equal and opposite to the applied emf.