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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.

Introduction As a passive device, Capacitors have unique functions in electronic circuits such as tuning, bypassing, coupling, and filtering. For example, it is used in the tuning circuit of the transistor radio, and also used in the coupling circuit and bypass circuit of the color TV. With the rapid development of electronic information technology, the update speed of digital electronic products is getting faster and faster. Capacitors play an important role in consumer electronic products such as flat-panel TVs (LCD and PDP), notebook computers, digital cameras and other products. Therefore, it is very important to ensure the capacitances and test its quality. Here this article will talk about how to test/check a capacitor in detail. 3 Ways to Check Capacitors in Circuit with Meters & Testers Catalog Introduction Ⅰ Test a Capacitor Using Multimeter 1.1 Digital Multimeter Use 1.2 Capacitor Measurements Matter 1.3 Test Non-polar Capacitors 1.4 Test Polar Capacitors 1.5 Test Chip Capacitors 1.6 Test Solid State Capacitors 1.7 Test Electrolytic Capacitors 1.8 Test Variable Capacitors 1.9 Capacitor Polarity Distinction Ⅱ Test a Capacitor Using Bridge Ⅲ Test a Capacitor Using Professional Equipment Ⅳ FAQ Ⅰ Test a Capacitor Using Multimeter 1.1 Digital Multimeter Use 1.1.1 Using Capacitance GearSome digital multimeters have the function of measuring capacitance, and their ranges include five ranges: 2000p, 20n, 200n, 2μ and 20μ. During test, the two pins of the discharged capacitor can be directly inserted into the Cx jack on the meter board, and the display data can be read after selecting the appropriate range.🔺2000p range is suitable for measuring capacitances less than 2000pF.🔺20n range is suitable for measuring capacitances between 2000pF and 20nF.🔺200n range is suitable for measuring capacitances between 20nF and 200nF.🔺2μ range is suitable for measuring capacitances between 200nF and 2μF.🔺20μ gear is suitable for measuring the capacitance between 2μF and 20μF. Experiments have proved that some types of digital multimeters have large errors when measuring small capacitors below 50pF, and there is almost no reference value for measuring capacitors below 20pF. At this time, the series method can be used to measure small-value capacitors. For example: measure a capacitor of about 220pF. Test its actual capacity C1 with a digital multimeter, and then connect the small capacitor in parallel to measure its total capacity C2, then the difference between the two (C1-C2) is the capacity of the small capacitor. It is very accurate to use this method to measure small capacitance of 1-20pF. 1.1.2 Using Resistance GearIn practice, it has proved that the charging process of the capacitor can also be observed with a digital multimeter, which is actually a discrete digital quantity that reflects the change of the charging voltage. Assuming that the measurement rate of the digital multimeter is n times/second, in the process of observing the charging of the capacitor, n independent and successively increasing readings can be seen every second. According to this display values, the quality of the capacitor can be detected and the size of the capacitance can be estimated. This method is suitable for measuring large-capacity capacitors from 0.1μF to several thousand microfarads. 1.1.3 Using Voltage GearUsing a digital multimeter to detect capacitors with DC voltage is actually an indirect method. This method can measure small-capacity capacitors from 220pF to 1μF, and can accurately measure the size of the capacitor's leakage current. 1.1.4 Using BuzzerUsing the buzzer of the digital multimeter, you can quickly check the quality of the electrolytic capacitor. For example, set the digital multimeter to the buzzer position, and use two test leads to contact the two pins of the capacitor Cx to be tested. A short buzzer should be heard, then the sound stops, and the overflow symbol "1" is displayed at the same time. Then, exchange the two test leads for another measurement, the buzzer should sound again, and finally the overflow symbol "1" is displayed. This situation indicates that the measured electrolytic capacitor is basically normal. At this point, you can dial to 20MΩ or 200MΩ to measure the leakage resistance of the capacitor to judge whether it is good or bad. Figure 1. Various Capacitor Stuff 1.2 Capacitor Measurements Matter (1) Before the measurement, the two pins of the capacitor should be short-circuited and discharged, otherwise the reading process may not be observed.(2) Do not touch the capacitor electrode with two hands during the measurement process, so as to prevent the meter from jumping.(3) During the measurement process, the value of Vin(t) changes exponentially, and it drops quickly at the beginning. As time goes by, the speed of decline will become slower and slower. When the capacity of the capacitor Cx under test is less than several thousand picofarads, and the measurement rate of the meter is low, it is too late to reflect the initial voltage value, so the initial display value of the meter is lower than the battery voltage at very first.(4) When the measured capacitance value is greater than 1μF, in order to shorten the test time, the resistance gear can be used. In addition, when the capacity of the capacitor under test is less than 200pF, it is difficult to observe the charging process because the change in readings is very short.Be sure to cut off the power and discharge capacitor before measuring. The method of discharging is to find a metal object such as a screwdriver, hold the exposed part of the metal on the insulating handle with the two pins, and measure the capacitance with a digital multimeter. Locate the capacitor block and then plug the two pins into the socket for capacitance measurement, and wait for the changing reading on the meter screen to stabilize. The actual value is the capacitance of the capacitor on the side. If has leakage, an analog multimeter can be used. When measuring, the small-capacity capacitor multimeter can be placed in RX1K or RX100. The two test leads are connected to the capacitor, the pointer deflects clockwise, and then as the capacitor is fully charged, there is no current flows, finally the watch hand will reappear counterclockwise and return to infinity. The larger the angle of the watch hand, the greater the capacity. During the deflection process, the pointer must swing at a constant speed so that it can return to infinity, which preliminarily shows that the capacitor has no leakage.If the needle suddenly slows down or does not return at a certain position on the dial, it means that the capacitor is leaking in a certain period. If it is displayed as infinity at the end, it shows that there is no leakage, but this can only be a rough judgment. If you want to find an accurate value, you have to use a capacitance meter. And the observation characteristic on the capacitance leakage tester or oscilloscope, this is impossible for ordinary people to have. There are also capacitors that have withstand voltage, which is generally written on their body. However, some ceramic capacitors are not marked on it, be careful when selecting them. Figure 2. Film Capacitor (cbb21) 1.3 Test Non-polar CapacitorsIf it is a non-polar capacitor, the multimeter can be adjusted to the "diode" gear to measure the on-off state. If the multimeter displays "1", it is normal; if displays "0" or other numbers, it means the capacitor is damaged. 1.4 Test Polar CapacitorsElectrolytic capacitors with polarities have "bulging", "deformation" or "leakage" in the shell, which show they are damaged. The capacitance block of a digital multimeter can also be used to measure the quality of the capacitor:(1) According to the rated capacitance marked by the capacitor, set the multimeter to the appropriate block.(2) Insert the capacitor into the hole of the multimeter to measure the capacity.If the capacitance is within the rated value range, it means the capacitor is intact, otherwise the capacitor is damaged. 1.5 Test Chip Capacitors1) Adjust the multimeter to the appropriate ohm gear. The principle of gear selection is: 1μF capacitor uses 20K gear, 1~100μF capacitor uses 2K gear, and larger than 100μF uses 200 gear.2) Determine the polarity. First adjust the multimeter to 100 or 1K ohms. Assuming that one pole is positive, connect the black test lead to it, and the red test lead to the other pole. Note the resistance value, and then discharge the capacitor. Then change the test lead to measure the resistance. The black test lead with a large resistance value is connected to the positive electrode of the capacitor.3) Then connect the red pen of the multimeter to the positive electrode of the capacitor, and the black pen to the negative electrode of the capacitor. If the display gradually increases from 0, and the overflow symbol 1 is displayed at the end, which shows the capacitor is normal. If it is always displayed as 0, the capacitor is short-circuited. If 1 is displayed, the internal circuit of the capacitor is open. Figure 3. Chip Capacitors 1.6 Test Solid State Capacitors✔️Capacitance Greater than 20μFWith a common digital multimeter, the maximum measured value of the capacitance block is 20μF, which sometimes cannot meet the test requirements. To this end, the following simple method can be used to measure capacitance greater than 20μF, and also the maximum capacitance of several thousand microfarads can be measured. When using this method to measure large-capacity capacitors, there is no need to make any changes to the original circuit of the digital multimeter.The measurement principle of this method is based on the formula C = C1C2/(C1+C2) in series with two capacitors. Since two capacitors with different capacities are connected in series, the total capacity after series connection is smaller than the smaller capacitor. Therefore, if the capacity of the capacitor under test exceeds 20μF, only one capacitor with a capacity less than 20μF should be used. In series with it, it can be directly measured on the digital multimeter. According to the formula above mentioned, it is easy to deduce C1=C2C/(C2-C), using this formula can calculate the capacitance value of the capacitor under test. ✔️Capacitance Less than 10μFBecause the capacity of a fixed capacitor below 10pF is too small, it can only be roughly checked for leakage, internal short circuit or voltage breakdown with a multimeter. When measuring, you can choose the R×10k block, and use two test pens to connect the two pins of the capacitor arbitrarily, and the resistance should be infinite. If the measured resistance value (the pointer swings to the right) is zero, it means that the capacitor is damaged by leakage or has internal breakdown. ✔️Capacitance between 10PF and 0.01μFDetect whether the capacitor is charging, and then judge whether it is good or bad. The multimeter selects the R×1k block. The β value of the two transistors is above 100, and the penetration current should be small. A composite tube can be used consist of silicon transistors. The red and black test leads of the multimeter are respectively connected to the emitter e and collector c of the composite tube. Due to the amplification effect of the composite triode, the charge and discharge process of the capacitor under test is amplified, and the amplitude of the pointer of the multimeter is enlarged, which is convenient for observation. It should be noted that during the test operation, especially when measuring small-capacity capacitors, it is necessary to repeatedly exchange the contact points A and B of the tested capacitor pin to clearly see the swing of the meter pointer. ✔️Fixed Capacitance of 0.01μFFor a fixed capacitance above 0.01μF, the R×10k block of a multimeter can be used to directly test whether the capacitor has the charging process and internal short circuit or leakage, in addition, the capacitance of the capacitor can be estimated according to the magnitude of the pointer swing to the right. Figure 4. Electrolytic Capacitors 1.7 Test Electrolytic Capacitors1) Because the capacity of electrolytic capacitors is much larger than that of general fixed capacitors, ranges should be selected for different capacities when measuring. According to experience, in general, the capacitance between 1 and 47μF can be measured with the R×1k block, and the capacitance larger than 47μF can be measured with the R×100 block.2) Connect the red test lead of the multimeter to the negative pole and the black test lead to the positive pole. At the moment of contact, the pointer of the multimeter will deflect to the right by a greater degree (for the same electrical barrier, the greater the capacity, the greater the swing), and then gradually turn to the left Turn around until it stops at a certain position. The resistance value at this time is the forward leakage resistance of the electrolytic capacitor, which is slightly larger than the reverse leakage resistance. Practical experience shows that the leakage resistance of electrolytic capacitors should generally be more than several hundred kΩ, otherwise, it will not work normally. In the test, if there is no charging phenomenon in the forward and reverse directions, that is, the hand does not move, it means that the capacity has disappeared or the internal circuit is broken; if the measured resistance value is very small or zero, it means that the capacitor has a large leakage or has been broken down.3) For electrolytic capacitors with unknown positive and negative signs, the above method of measuring leakage resistance can be used to distinguish. That is to measure the leakage resistance arbitrarily, remember its size, and then exchange the test leads to measure a resistance value. The larger resistance of the two measurements is the positive connection, that is, the black test lead is connected to the positive electrode, and the red test lead is connected to the negative electrode. Use a multimeter to block electricity and charge the electrolytic capacitor. According to the magnitude of the pointer swing to the right, the capacity of the electrolytic capacitor can be estimated.When measuring electrolytic capacitors, if the measured value does not change significantly, the corresponding pins of the probe should be exchanged for multiple measurements. 1.8 Test Variable Capacitors1) Rotate the shaft gently and smoothly. When pushing the load shaft in full directions, there should be no looseness of it.2) Rotate the shaft with one hand and gently touch the outer edge of the film set with the other hand. You should not feel any looseness. The variable capacitor with poor contact between the rotating shaft and the moving plate can no longer be used.3) Place the multimeter in the R×10k gear, connect the two test leads to the moving piece and the lead end of the fixed piece of the variable capacitor with one hand, and slowly rotate the shaft several times back and forth with the other hand. The pointers of the multimeter should not move at infinity. In the process of rotating the shaft, if the pointer sometimes points to zero, it indicates that there is a short-circuit point between the moving piece and the fixed piece. If it encounters a certain angle, the multimeter reading is not infinity but a certain resistance value, indicating that the variable capacitor has a leakage phenomenon between the film and the stator. 1.9 Capacitor Polarity DistinctionThe black part with a mark on the capacitor is negative. There are two semicircles on the position of the capacitor on the PCB, and the pin corresponding to the colored semicircle is the negative electrode. The length of the pins is also useful to distinguish the polarity: the long pin is anode and the short pin is cathode.When we don't know the positive and negative poles of the capacitor, we can use a multimeter to figure them out. The medium between the two poles of the capacitor is not an absolute insulator, and its resistance is not infinite, but a finite value, generally above 1000 megohms. The resistance between the two poles of a capacitor is called insulation resistance or leakage resistance. Only when the positive electrode of the electrolytic capacitor is connected to the positive power supply (the black test lead), and the negative terminal is connected to the negative power supply (the red test lead), the leakage current is small (the leakage resistance is large), on the contrary, the leakage current increases (the leakage resistance decreases).Without knowing it, you can first assume the “+” pole of a certain pole. Using R*100 or R*1K of the multimeter, connect the test leads, and record the scale of the stop of the test needle (the resistance value of the test needle to the left is large), and the reading can be read directly for a digital multimeter. Then discharge the capacitor, then exchange the two test leads, and perform the measurement again. In the two measurements, the black test lead is connected to the positive electrode of the electrolytic capacitor when the last position of the needle is to the left (or the end with large resistance).When measuring large capacity capacitors, if you need to measure the positive and negative back and forth, discharge it to avoid damage to the multimeter. In addition, in high-frequency circuits, switching power supply circuits have many small capacitors, which ordinary multimeters cannot correctly judge whether they are good or bad. In terms of this case, it is recommended to use a dedicated digital capacitance meter to measure. Figure 5. SMD Capacitor Ⅱ Test a Capacitor Using BridgeThe data measured with a multimeter is not too accurate, and it can only measure the deviation of the capacity. For a little professional, you can use a bridge. When testing a capacitor with a digital bridge, you can clamp the lead of the capacitor to test its capacity, which can also show the loss of the capacitor, especially through the loss, it is easier to distinguish the quality of the capacitor.   Ⅲ Test a Capacitor Using Professional EquipmentIn general, capacitors have special test equipment for each performance, such as capacitor durability test, destructive test, loss angle test, inter-electrode withstand voltage test, self-healing test, charge and discharge test, pulse voltage test, spontaneous combustion test, ripple current durability test, etc., but for most users, these devices are more expensive and difficult to operate. If you really want these data, you can entrust a third party to test or ask the manufacturer for relevant information.   Ⅳ FAQ1. How do you check if a capacitor is bad?Use the multimeter and read the voltage on the capacitor leads. The voltage should read near 9 volts. The voltage will discharge rapidly to 0V because the capacitor is discharging through the multimeter. If the capacitor will not retain that voltage, it is defective and should be replaced.   2. How do you tell if a capacitor is bad with a multimeter?If the capacitance value is within the measurement range, the multimeter will display the capacitor's value. It will display OL if a) the capacitance value is higher than the measurement range or b) the capacitor is faulty.   3. What are the symptoms of a bad start capacitor?Start Capacitor FailureMotor run capacitor failure symptoms include warm air flowing from the vents inside the home, the air conditioner taking more time than usual to kick on or it turns off before it is programmed to, or there is a constant low hum emitting from the machine that isn't typical.   4. Can a capacitor test good and still be bad?It can, and most often does, although it is probably lower in capacitance than it originally was, but still usually within tolerance. There isn't likely to be a problem with leakage. There are two ways to test an ESR meter, a circuit unpowered or an oscilloscope.   5. How long can a capacitor last?Age. Like all things, capacitors have a limited life span. Most are designed to last approximately 20 years, but a number of factors can cause them to wear out more quickly.   6. How do you identify a capacitor?Ceramic types of capacitors generally have a 3-digit code printed onto their body to identify their capacitance value in pico-farads. Generally the first two digits indicate the capacitors value and the third digit indicates the number of zero's to be added.   7. Will a capacitor discharge on its own?Will a Capacitor Discharge On Its Own? In theory, a capacitor will gradually lose its charge. A fully charged capacitor in an ideal condition, when disconnected, discharges to 63% of its voltage after a single time constant. Thus, this capacitor will discharge up to near 0% after 5 time constants.   8. How do I know if my AC capacitor is bad?The most common signs and symptoms of a bad AC capacitor include:AC not blowing cold air.AC takes a while to start once you turn it on.Humming sound coming from your air conditioner.AC shuts off on its own.AC won't turn on.   9. What side of capacitor is positive?To tell which side is which, look for a large stripe or a minus sign (or both) on one side of the capacitor. The lead closest to that stripe or minus sign is the negative lead, and the other lead (which is unlabeled) is the positive lead.   10. Can I use a multimeter to discharge a capacitor?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.   11. How fast can a capacitor discharge?A fully charged capacitor discharges to 63% of its voltage after one time period. After 5 time periods, a capacitor discharges up to near 0% of all the voltage that it once had.   12. Can a bad capacitor ruin a compressor?Using the wrong capacitor rating or a poor quality capacitor can adversely affect the operation of the motor, the compressor or an entire HVAC system. ... Depending on the motor load, this may result in a reduction in the motor's overall speed.   13. Can I replace a start capacitor with a run capacitor?Run Capacitors. Start capacitors give a large capacitance value necessary for motor starting for a very short period of time (usually seconds long). ... A start capacitor can never be used as a run capacitor, because it cannot not handle current continuously.   14. How do you check a capacitor without a multimeter?Just connect those two ends of the capacitor to a single phase supply and switch it ON for a few seconds. Then take that two terminal and short it, you will get a spark. And so you can somewhat assume that your capacitor is in good condition.   15. What if a capacitor reads high?The high resistance across the capacitor is a sign that the capacitor is faulty. It is reading as if there is an open circuit.   16. How many ohms should a capacitor have?Make sure the capacitor is fully discharged. Set the meter on the Ohmic range (Set it at least on 1000 Ohm = 1kΩ). Connect the multimeter probes to the capacitor terminals (Negative to Negative and Positive to Positive).   17. What if a capacitor reads low?If it reads lower than nominal value, you may want to replace it. Non-polar capacitors lower than 1μF should not alter that much with aging. Capacitors in frequency sensitive circuits such as filters, time delays, should have a tighter tolerance.   18. What happens when capacitor goes bad?A bad capacitor prevents the exterior unit from properly functioning, which hinders the cooling process as a whole. Second, improper voltage delivery to exterior unit components forces the system to work harder as it attempts to perform its job. Additional components often sustain damage due to a faulty capacitor.   19. How can you tell if a capacitor is bad?Symptoms of defective capacitors may include:Excessive noise in audio or video, including 60hz audio hum or rolling bars in video.Scratchy, distorted, or missing audio.Low contrast, blurry, or distorted LCD displays.Intermittent or outright failure.   20. What does a damaged capacitor look like?A busted capacitor can be obviously broken (leaking brownish fluid, corroded, or with the leads severed), but sometimes it's subtle. The top of a blown capacitor will be slightly bent outwards in a convex shape, rather than flat or slightly indented inwards like a working capacitor.

Ⅰ IntroductionWhen connected to a voltage source, capacitors are basic passive devices that can store an electrical charge on their plates. The capacitor, like a miniature rechargeable battery, has the ability or "capacity" to store energy in the form of an electrical charge, producing a potential difference (Static Voltage) across its plates. Capacitors come in a variety of sizes and shapes, ranging from tiny capacitor beads used in resonance circuits to enormous power factor correction capacitors, but they always store charge. this video shows how capacitors work CatalogⅠ IntroductionⅡ Types of Capacitor2.1 Dielectric Capacitor2.2 Variable Capacitor Symbol2.3 Film Capacitor Type2.4 Axial Lead Type2.5 Ceramic Capacitors2.6 Electrolytic Capacitors2.7 Aluminium Electrolytic Capacitors2.8 Tantalum Electrolytic Capacitors2.9 Frequently Asked Questions About Different Types Of CapacitorⅢ The Capacitance of a Capacitor3.1 SI Unit of Capacitance3.2 μF vs. nF vs. pF3.3 Frequently Asked Questions about the Capacitance of a CapacitorⅣ Capacitor Conversion: µF-nF-pF 4.1 Capacitor Conversion Chart4.2 Popular Capacitor Conversions4.3 Frequently Asked Questions about Capacitor ConversionⅤ Capacitor Color Code5.1 Capacitor Colour Code Tables5.2 Color Codes of Different Capacitors5.3 Frequently Asked Questions about Capacitor Color CodeⅥ Capacitor Code6.1 Types of Capacitor Code6.2 Frequently Asked Questions about Capacitor CodeⅦ Capacitor Code Calculator7.1 Capacitor Safety Discharge Calculator Tool7.2 Series and Parallel Capacitance Calculator Ⅱ Types of CapacitorFrom very small delicate trimming capacitors used in oscillator or radio circuits to enormous power metal-can type capacitors used in high voltage power correction and smoothing circuits, capacitors are available. The dielectric used between the plates is commonly used to make comparisons between different types of capacitors. There are variable varieties of capacitors, just like resistors, that allow us to adjust their capacitance value for use in radio or "frequency tuning" circuits. Metallic foil is interwoven with thin sheets of either paraffin-impregnated paper or Mylar as the dielectric material in commercial capacitors. Because the metal foil plates are rolled up into a cylinder to produce a compact box with the insulating dielectric material sandwiched in between, some capacitors resemble tubes. Ceramic materials are frequently used to make small capacitors, which are subsequently sealed with epoxy resin. Capacitors play a crucial role in electronic circuits in any case, therefore here are a few of the most "common" capacitor types available. 2.1 Dielectric CapacitorWhen a constant variation in capacitance is necessary for tuning transmitters, receivers, and transistor radios, dielectric capacitors are normally of the variable variety. Multi-plate air-spaced variable dielectric capacitors have a set of fixed plates (the stator vanes) and a set of movable plates (the rotor vanes) that move in between the fixed plates. The overall capacitance value is determined by the position of the moving plates concerning the fixed plates. When the two sets of plates have entirely meshed together, the capacitance is usually at its highest. With breakdown voltages in the thousands of volts, high voltage tuning capacitors have relatively large spacings or air gaps between the plates. 2.2 Variable Capacitor SymbolTrimmers are pre-set type variable capacitors that are available in addition to continuously variable varieties. These are typically small devices that may be modified or "pre-set" to a specific capacitance value with a small screwdriver, and are available in very low capacitances of 500pF or less, and are non-polarized. variable capacitor symbol 2.4 Axial Lead TypeLong thin strips of thin metal foil with the dielectric material sandwiched between them are twisted into a tight roll and then sealed in paper or metal tubes for film and foil capacitors. To lessen the possibility of tears or punctures in the film, these film types require a significantly thicker dielectric film and are thus better suited to lower capacitance values and bigger case sizes. axial-lead-type Metalized foil capacitors have the conductive film metalized sprayed directly onto each side of the dielectric, giving the capacitor self-healing capabilities and allowing thinner dielectric films to be used. For a given capacitance, this enables for larger capacitance values and smaller case sizes. Film and foil capacitors are typically employed in situations that require more power and precision. 2.5 Ceramic CapacitorsCeramic capacitors, also known as Disc capacitors, are created by coating two sides of tiny porcelain or ceramic disc with silver and stacking them together to form a capacitor. A single ceramic disc of roughly 3-6mm is utilized for very low capacitance values. Ceramic capacitors have a high dielectric constant (High-K) and are available in tiny physical sizes, allowing for relatively high capacitances. ceramic capacitor Because they are non-polarized and exhibit huge non-linear changes in capacitance with temperature, they are employed as de-coupling or by-pass capacitors. Ceramic capacitors range in size from a few picofarads to one or two microfarads, but their voltage ratings are often modest. A three-digit code is usually inscribed on the body of ceramic capacitors to identify their capacitance value in pico-farads. The first two digits usually represent the capacitor's value, while the third digit represents the number of zeros to be added. A ceramic disc capacitor marked 103, for example, would indicate 10 and 3 zeros in pico-farads, which is equal to 10,000 pF or 10nF. The numerals 104, for example, represent 10 and 4 zeros in pico-farads, which is comparable to 100,000 pF or 100nF, and so on. The digits 154 on the ceramic capacitor image above represent 15 and 4 zeros in pico-farads, which is comparable to 150,000 pF, 150nF, or 0.15F. To signify their tolerance value, letter codes are occasionally employed, such as J = 5%, K = 10%, M = 20%, and so on. 2.6 Electrolytic CapacitorsWhen very large capacitance values are required, electrolytic capacitors are typically utilized. Instead of employing a very thin metallic film layer for one of the electrodes, a semi-liquid electrolyte solution in the form of jelly or paste is employed (usually the cathode). The dielectric is a very thin layer of oxide that is produced electrochemically in the manufacturing process and has a thickness of fewer than ten microns. Because the insulating layer is so thin, capacitors with a big capacitance value can be made in a small physical size because the distance between the plates, d, is so short. electrolytic capacitor The majority of electrolytic capacitors are polarized, which means that the DC voltage applied to the capacitor terminals must be of the correct polarity, i.e. positive to the positive terminal and negative to the negative terminal, or the insulating oxide layer will be broken down and permanent damage may result. The polarity of all polarized electrolytic capacitors is indicated with a negative sign to signify the negative terminal, which must be followed. Due to their huge capacitance and small size, electrolytic capacitors are commonly employed in DC power supply circuits to help reduce ripple voltage or for coupling and decoupling applications. Electrolytic capacitors have a low voltage rating, which means that they can't be utilized on AC supply because of their polarization. Aluminium Electrolytic Capacitors and Tantalum Electrolytic Capacitors are the two most common types of electrolytes. 2.7 Aluminium Electrolytic CapacitorsThe plain foil type and the etched foil type are the two varieties of Aluminum Electrolytic capacitors. These capacitors have extremely high capacitance values for their size due to the thickness of the aluminum oxide coating and the high breakdown voltage.aluminium electrolytic capacitor A DC current is used to anodize the capacitor's foil plates. The polarity of the plate material is established during the anodizing process, which defines which side of the plate is positive and which side is negative. The aluminum oxide on the anode and cathode foils has been chemically etched to increase surface area and permittivity, which makes the etched foil type different from the plain foil type. This results in a smaller capacitor than a normal foil type of comparable value, but it has the disadvantage of not being able to handle strong DC currents. Their tolerance range is also fairly high, reaching up to 20%. Capacitance values for aluminum electrolytic capacitors typically range from 1uF to 47,000uF. Plain foil electrolytes are better suited as smoothing capacitors in power supply, while etched foil electrolytes are best employed in the coupling, DC blocking, and by-pass circuits. However, because aluminum electrolytes are “polarized” devices, inverting the applied voltage on the leads will damage the insulating layer within the capacitor, as well as the capacitor itself. The capacitor's electrolyte, on the other hand, aids in the healing of a damaged plate if the damage is minor. The electrolyte has the power to re-anodize the foil plate since it can self-heal a damaged plate. The electrolyte can remove the oxide layer from the foil if the anodizing process is reversed, as it would if the capacitor was connected with reverse polarity. Because the electrolyte can conduct electricity, if the aluminum oxide layer is removed or destroyed, current can flow from one plate to the other, causing the capacitor to fail, "so be alert." 2.8 Tantalum Electrolytic CapacitorsTantalum Electrolytic Capacitors and Tantalum Beads come in both wet (foil) and dry (solid) electrolytic varieties, with dry tantalum being the most prevalent. Solid tantalum capacitors have a second terminal of manganese dioxide and are physically smaller than analogous aluminum capacitors. Tantalum oxide's dielectric characteristics are superior to those of aluminum oxide, resulting in reduced leakage currents and greater capacitance stability, making it ideal for blocking, by-passing, decoupling, filtering, and timing applications. Tantalum capacitors, although being polarized, can withstand being linked to a reverse voltage considerably better than aluminum capacitors, but they are rated at much lower operating voltages. Solid tantalum capacitors are commonly employed in circuits with low AC voltages compared to DC voltages. Some tantalum capacitors, on the other hand, comprise two capacitors in one, connected negative-to-negative to make a “non-polarized” capacitor for use in low voltage AC circuits. The positive lead of a tantalum bead capacitor is usually identifiable by a polarity mark on the capacitor body, which has an oval geometrical shape. Capacitance values typically vary from 47nF to 470F. 2.9 Frequently Asked Questions About Different Types Of Capacitor1. Which type of capacitor is best?Class 1 ceramic capacitors offer the highest stability and lowest losses. They have high tolerance and accuracy and are more stable with changes in voltage and temperature. Class 1 capacitors are suitable for use as oscillators, filters, and demanding audio applications. 2. Does the type of capacitor matter?Yes, the type of capacitor can matter. Different types of capacitor have different properties. Some of the properties that vary between capacitor types: polarized vs unpolarized. 3. Are all capacitors the same?Not all capacitors are created equal. Each capacitor is built to have a specific amount of capacitance. The capacitance of a capacitor tells you how much charge it can store, more capacitance means more capacity to store charge. 4. Which type of capacitor is known as Polarised capacitor?Electrolytic Capacitors. The Electrolytic Capacitors are the capacitors which indicate by the name that some electrolyte is used in it. They are polarized capacitors which have anode + and cathode − with particular polarities. A metal on which insulating oxide layer forms by anodizing is called as an Anode. 5.Which capacitors are not polarized?Ceramic, mica and some electrolytic capacitors are non-polarized. You'll also sometimes hear people call them "bipolar" capacitors. A polarized ("polar") capacitor is a type of capacitor that have implicit polarity -- it can only be connected one way in a circuit. Ⅲ The Capacitance of a CapacitorThe Farad (abbreviated to F) is the unit of capacitance and is named after the British physicist Michael Faraday. Capacitance is the electrical property of a capacitor and is the measure of a capacitor's ability to store an electrical charge onto its two plates. When a charge of One Coulomb is stored on the plates by a voltage of One volt, a capacitor has a capacitance of One Farad. It's worth noting that capacitance, or C, is always positive and has no negative units. However, because the Farad is a relatively big unit of measurement on its own, sub-multiples such as micro-farads, nano-farads, and pico-farads are commonly used. 3.1 SI Unit of CapacitanceCapacitors are a common type of electrical component, and their values are usually stated in microfarads, F (or uF if a micro character is not available), nanofarads, nF, or picofarads, pF. Microfarad (μF)  1μF = 1/1,000,000 = 0.000001 = 10-6 FNanofarad (nF)  1nF = 1/1,000,000,000 = 0.000000001 = 10-9 FPicofarad (pF) 1pF=1/1,000,000,000,000 = 0.000000000001 = 10-12 F 3.2 μF vs. nF vs. pFAlthough most current circuits and component descriptions use the nomenclature F, nF, and pF to specify capacitor values, older circuit designs, circuit descriptions, and even the components themselves may employ a variety of non-standard acronyms that aren't always evident. The following are the main changes for the various capacitance sub-multiples: Micro-Farad, µF: Larger value capacitors, such as electrolytic capacitors, tantalum capacitors, and even some paper capacitors measured in micro-Farads, may have been labeled with uF, mfd, MFD, MF, or UF. All of these terms refer to the value in µF. Electrolytic and tantalum capacitors are commonly connected with this nomenclature. Nano-Farad, nF: Because nF or nano-Farads nomenclature was not frequently used prior to terminology standardization, this submultiple lacked a variety of abbreviations. The term nanofarad has gained in popularity in recent years, while it is still not widely used in some countries, with values given in huge numbers of picofarads, such as 1000pF for 1 nF, or fractions of a microfarad, such as 0.001 µF for a nanofarad. Ceramic capacitors, metalized film capacitors, including surface mount multilayer ceramic capacitors, and even some modern silver mica capacitors all use this terminology. Pico-Farad, pF: The value in picoFarads, pF, was again indicated using a variety of acronyms.  MicroromicroFarads, mmfd, MMFD, uff, µµFwere among the terms used. All of these numbers are in pF. Picofarad capacitor values are commonly employed in radio frequency, RF circuits, and equipment. As a result, this nomenclature is most commonly associated with ceramic capacitors, however, it is also applied to silver mica capacitors and some film capacitors. The conversion of values from one submultiple to the next has been aided by the standardization of terminology. It has resulted in a significant reduction in the potential for misunderstanding. Converting from µF to nF and pF is simpler. This is important when a capacitor value is listed in one way on a circuit diagram and another way on a list of electronic components distributors. Because different electrical component manufacturers label components differently, the capacitance conversion table is highly useful. For example, some manufacturers label their equivalent capacitors as a fraction of a microfarad, while others label them as a fraction of a nanofarad, and so on. Electrical component wholesalers and retailers will prefer to adopt the manufacturer's nomenclature. Similarly, circuit diagrams may use different symbols to represent components to maintain commonality, etc. As a result, being able to convert between picofarads, nanofarads, and microfarads, as well as vice versa, is beneficial. When the bill of materials or parts list for the circuit has values expressed in microfarads, µF, and picofarads, pF, this can aid identify components labeled in nanofarad values. It is generally useful to be able to utilize a capacitance conversion calculator like the one above, but it is also important to be familiar with the conversions and popular equivalents, such as 1000pF = nanofarad and 100nF = 0.1µF. These conversions become second nature while working with electrical components and designing electronic circuits, but the capacitance conversion tables and calculators can still be quite useful. Capacitors, as well as other electronic components like inductors, benefit from these conversions. 3.3 Frequently Asked Questions about the Capacitance of a Capacitor1. What is capacitance in simple terms?Capacitance is the ability of a system of electrical conductors and insulators to store electric charge when a potential difference exists between the conductors. Capacitance is expressed as a ratio of the electrical charge stored to the voltage across the conductors. 2.What is C in capacitance?The capacitance C is the ratio of the amount of charge q on either conductor to the potential difference V between the conductors, or simply C = q/V. 3.What is difference between capacitor and capacitance?Capacitance is nothing but the ability of a capacitor to store the energy in form of electric charge. In other words, the capacitance is the storing ability of a capacitor. It is measured in farads. 4.What is the formula of capacitor?The governing equation for capacitor design is: C = εA/d, In this equation, C is capacitance; ε is permittivity, a term for how well dielectric material stores an electric field; A is the parallel plate area; and d is the distance between the two conductive plates. 5.What four factors affect capacitance?The capacitance of a capacitor is affected by the area of the plates, the distance between the plates, and the ability of the dielectric to support electrostatic forces. Ⅳ Capacitor Conversion: µF-nF-pF  The use of the nanofarad (nF) is less common in some fields, with values stated in fractions of a µF and huge multiples of picofarads (pF). When components marked in nanofarad are available, it may be necessary to convert to nanofards, nF in these circumstances. When a circuit diagram or electronic components list mentions the value in picofarads, for example, and listings for an electronic component distributor or electronic components store state it in another way, it can be confusing. Capacitor values can be in the 109 range or even higher, thanks to the introduction of supercapacitors. The common prefixes pico (10-12), nano (10-9), and micro (10-6) are often used to avoid misunderstanding with high numbers of zeros connected to the values of different capacitors. When converting between them, a capacitor conversion chart or capacitor conversion table for the various capacitor values can be useful. Another requirement for capacitance conversion is that the actual capacitance value is reported in picofarads in some capacitor marking systems, therefore the value must be converted to the more common nanofarads or microfarads. 4.1 Capacitor Conversion ChartMicrofarads ( µF)Nanofarads(nF)Picofarads(pF)0.0000010.00110.000010.01100.00010.11000.001110000.0110100000.11001000001100010000001010000100000001001000001000000004.2 Popular Capacitor ConversionsCapacitor values can be written in a few different ways. A ceramic capacitor, for example, is frequently assigned a value of 100nF. It is often interesting to realize that this is 0.1µF when utilized in circuits with electrolytic capacitors. These handy conversions can aid in the design, construction, and maintenance of circuits. When building circuits or employing capacitors in any fashion, keeping these capacitor conversions in mind when values migrate from picofarads to nanofarads and then nanofarads to microfarads is typically beneficial. A more comprehensive table of conversion factors to convert between the different values, nF to pF, µF to nF etc is given below.Table of Conversion Factors to Convert between µF,nF and pF convertmultiply by:pF     to     nF1 x 10-3pF     to     µF1 x 10-6nF     to     pF1 x 103nF     to     µF1 x 10-3µF     to     pF1 x 106µF     to     nF1 x 103 4.3 Frequently Asked Questions about Capacitor Conversion1. Can I replace a capacitor with a higher uF?An electric motor start capacitors can be replaced with a micro-farad or UF equal to or up to 20% higher UF than the original capacitor serving the motor. 2.What happens if I use a higher uF capacitor?The higher the number of micro-farads, the more energy the capacitor can hold. In theory, if a device has a high uF, it will last longer in a power outage.3.What happens if you use the wrong size capacitor?If the wrong run capacitor is installed, the motor will not have an even magnetic field. This will cause the rotor to hesitate at those spots that are uneven. This hesitation will cause the motor to become noisy, increase energy consumption, cause performance to drop, and cause the motor to overheat. 4.Can I replace a capacitor with a lower capacitance?Yes, it's possible given the necessary skills and tools. Yes, it's safe. The only rating that matters for safety is the rated voltage: if you put a higher voltage than the maximum you might see your cap explode. 5.Can I use a run capacitor in place of a start capacitor?The capacitance and voltage ratings would have to match the original start capacitor specification. A start capacitor can never be used as a run capacitor, because it cannot not handle current continuously. Ⅴ Capacitor Color Code5.1 Capacitor Colour Code TablesWhen the capacitance value is a decimal value, problems with the marking of the "Decimal Point" arise since it is easily overlooked, leading to a misunderstanding of the real capacitance value. Instead of the decimal point, letters like p (pico) or n (nano) are used to indicate the position and weight of the number. A capacitor might be labeled as n47 = 0.47nF, 4n7 = 4.7nF, or 47n = 47nF, for example. Also, capacitors are occasionally labeled with the capital letter K to indicate a value of one thousand pico-Farads, thus a capacitor marked 100K would be 100 x 1000pF or 100nF. An International color-coding scheme was devised many years ago as a simple manner of identifying capacitor values and tolerances to reduce the confusion regarding letters, numbers, and decimal points. The Capacitor Colour Code system, which consists of colored bands (in spectral order) and whose meanings are given below, is a system that consists of colored bands (in spectral order). Band ColourDigit ADigit BMultiplier DTolerance (T) > 10pfTolerance (T) < 10pfTemperature Coefficient (TC)Black00x1± 20%± 2.0pF Brown11x10± 1%± 0.1pF-33×10-6Red22x100± 2%± 0.25pF-75×10-6Orange33x1,000± 3% -150×10-6Yellow44x10,000± 4% -220×10-6Green55x100,000± 5%± 0.5pF-330×10-6Blue66x1,000,000  -470×10-6Violet77   -750×10-6Grey88x0.01+80%,-20%  White99x0.1± 10%± 1.0pF Gold  x0.1± 5%  Silver  x0.01± 10%  Capacitor Colour Code Table Band ColourVoltage Rating (V) Type JType KType LType MType NBlack4100 1010Brown62001001.6 Red10300250435Orange15400 40 Yellow205004006.36Green25600 1615Blue35700630 20Violet50800   Grey 900 2525White31000 2.53Gold 2000   Silver     Capacitor Voltage Colour Code Table Capacitor Voltage ReferenceType J–  Dipped Tantalum Capacitors.Type K–  Mica Capacitors.Type L–  Polyester/Polystyrene Capacitors.Type M–  Electrolytic 4 Band Capacitors.Type N–  Electrolytic 3 Band Capacitors. 5.2 Color Codes of Different Capacitors 1.Metalised Polyester Capacitor  2. Disc & Ceramic Capacitor  For many years, unpolarized polyester and mica molded capacitors were coded using the Capacitor Colour Code system. Although this color coding method is no longer in use, many “old” capacitors can still be found. Small capacitors, such as film or disk kinds, now comply with the BS1852 Standard and its new replacement, BS EN 60062, which replaces the colors with a letter or number coding system. 5.3 Frequently Asked Questions about Capacitor Color Code1. What do capacitor colors mean?All the color bands painted on the capacitors body are used to indicate the capacitance value and capacitance tolerance. The color codes used to represent the capacitance values and capacitance tolerance is similar to that used to represent resistance values and resistance tolerance. 2.How do you read a capacitor code?If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero. 3.Which type of capacitor is available in color code?A color code was used on polyester capacitors for many years. It is now obsolete, but of course there are many still around. The colors should be read like the resistor code, the top three color bands giving the value in pF. Ignore the 4th band (tolerance) and 5th band (voltage rating). 4.Are capacitors color coded?The capacitors use a capacitor color code similar to the resistors color code (3, 4 or 5 bands). The first two colors indicate significant digits of the value of the capacity (in pF), the next colour is the corresponding power of 10, the other two colors are optional and indicate tolerance and maximum voltage. Ⅵ Capacitor Code6.1 Types of Capacitor CodeFor example, a capacitor labeled 474J should be read as 47 times the value listed in Table 1 corresponding to the third number, in this case, 10000: 47 * 10000 = 470000 pF = 470 nF = 0.47µF, with the J indicating a 5% tolerance. If a temperature coefficient is present, the second letter will be it. You'll rapidly learn to tell whether a capacitor's value is expressed in pF, nF, or µF based on its size and kind. The capacitance of a capacitor designated 2A474J is encoded as mentioned above; the two initial signs are the voltage rating, which can be decoded from table 2 below. According to the EIA standard, 2A is a 100V DC rating. Some capacitors are only marked 0.1 or 0.01, mostly in these cases the values are given in µF. Some small capacitance capacitors contain an R between the numbers, such as 3R9, which indicates that the value is less than 10pF and has nothing to do with resistance. 3R9 has a 3.9pF value. Table 1 – Capacitor codes with letters and tolerances3rd numberMultiply withLetterTolerance01D0.5pF110F1%2100G2%31,000H3%410,000J5%5100,000K10%61,000,000M20%7Not usedM20%80.01P+100%/-0%90.1Z+80%/-20% Table 2A – Electronic Industries Alliance (EIA) – DC voltage code table0E = 2.5 VDC2A = 100 VDC3A = 1 kVDC0G = 4.0 VDC2Q = 110 VDC3L = 1.2 kVDC0L = 5.5 VDC2B = 125 VDC3B = 1.25 kVDC0J = 6.3 VDC2C = 160 VDC3N = 1.5 kVDC1A = 10 VDC2Z = 180 VDC3C = 1.6 kVDC1C = 16 VDC2D = 200 VDC3D = 2 kVDC1D = 20 VDC2P = 220 VDC3E = 2.5 kVDC1E = 25 VDC2E = 250 VDC3F = 3 kVDC1V = 35 VDC2F = 315 VDC3G = 4 kVDC1G = 40 VDC2V = 350 VDC3H = 5 kVDC1H = 50 VDC2G = 400 VDC3I = 6 kVDC1J = 63 VDC2W = 450 VDC3J = 6.3 kVDC1M = 70 VDC2J = 630 VDC3U = 7.5 kVDC1U = 75 VDC2I = 650 VDC3K = 8 kVDC1K = 80 VDC2K = 800 VDC  Table 2B – Electronic Industries Alliance (EIA) – AC voltage code table2Q = 125 VAC2T = 250 VAC2S = 275 VAC2X = 280 VAC2F = 300 VACI0 = 305 VACL0 = 350 VAC2Y = 400 VACP0 = 440 VACQ0 = 450 VACV0 = 630 VAC  Table 3 – Capacitor code tablepico-farad (pF)nano-farad (nF)micro-farad (µF) Capacitor Code1 pF capacitor code0.001 nF capacitor code0.000001 µF capacitor code101.5 pF capacitor code0.0015 nF capacitor code0.0000015 µF capacitor code1R52.2 pF capacitor code0.0022 nF capacitor code0.0000022 µF capacitor code2R23.3 pF capacitor code0.0033 nF capacitor code0.0000033 µF capacitor code3R33.4 pF capacitor code0.0039 nF capacitor code0.0000039 µF capacitor code3R93.5 pF capacitor code0.0047 nF capacitor code0.0000047 µF capacitor code4R75.6 pF capacitor code0.0056 nF capacitor code0.0000056 µF capacitor code5R66.8 pF capacitor code0.0068 nF capacitor code0.0000068 µF capacitor code6R88.2 pF capacitor code0.0082 nF capacitor code0.0000082 µF capacitor code8R210 pF capacitor code0.01 nF capacitor code0.00001 µF capacitor code10015 pF capacitor code0.015 nF capacitor code0.000015 µF capacitor code15022 pF capacitor code0.022 nF capacitor code0.000022 µF capacitor code22033 pF capacitor code0.033 nF capacitor code0.000033 µF capacitor code33047 pF capacitor code0.047 nF capacitor code0.000047µF capacitor code47056 pF capacitor code0.056 nF capacitor code0.000056 µF capacitor code56068 pF capacitor code0.068 nF capacitor code0.000068 µF capacitor code68082 pF capacitor code0.082 nF capacitor code0.000082 µF capacitor code820100 pF capacitor code0.1 nF capacitor code0.0001 µF capacitor code101120 pF capacitor code0.12 nF capacitor code0.00012 µF capacitor code121130 pF capacitor code0.13 nF capacitor code0.00013µF capacitor code131150 pF capacitor code0.15 nF capacitor code0.00015 µF capacitor code151180 pF capacitor code0.18 nF capacitor code0.00018 µF capacitor code181220 pF capacitor code0.22 nF capacitor code0.00022 µF capacitor code221330 pF capacitor code0.33 nF capacitor code0.00033 µF capacitor code331470 pF capacitor code0.47 nF capacitor code0.00047 µF capacitor code471560 pF capacitor code0.56 nF capacitor code0.00056 µF capacitor code561680 pF capacitor code0.68 nF capacitor code0.00068 µF capacitor code681750 pF capacitor code0.75 nF capacitor code0.00075 µF capacitor code751820 pF capacitor code0.82 nF capacitor code0.00082 µF capacitor code8211000 pF capacitor code1 / 1n / 1 nF capacitor code0.001 µF capacitor code1021500 pF capacitor code1.5 / 1n5 / 1.5 nF capacitor code0.0015 µF capacitor code1522000 pF capacitor code2 / 2n / 2 nF capacitor code0.002 µF capacitor code2022200 pF capacitor code2.2 / 2n2 / 2.2 nF capacitor code0.0022 µF capacitor code2223300 pF capacitor code3.3 / 3n3 / 3.3 nF capacitor code0.0033 µF capacitor code3324700 pF capacitor code4.7 / 4n7 / 4.7 nF capacitor code0.0047 µF capacitor code4725000 pF capacitor code5 / 5n / 5 nF capacitor code0.005 µF capacitor code5025600 pF capacitor code5.6 / 5n6 / 5.6 nF capacitor code0.0056 µF capacitor code5626800 pF capacitor code6.8 / 6n8 / 6.8 nF capacitor code0.0068 µF capacitor code68210000 pF capacitor code10 / 10n / 10 nF capacitor code0.01 µF capacitor code10315000 pF capacitor code15 / 15n / 15 nF capacitor code0.015 µF capacitor code15322000 pF capacitor code22 / 22n / 22 nF capacitor code0.022 µF capacitor code22333000 pF capacitor code33 / 33n / 33 nF capacitor code0.033 µF capacitor code33347000 pF capacitor code47 / 47n / 47 nF capacitor code0.047 µF capacitor code47368000 pF capacitor code68 / 68n / 68 nF capacitor code0.068 µF capacitor code683100000 pF capacitor code100 / 100n / 100 nF capacitor code0.1 µF capacitor code104150000 pF capacitor code150 / 150n / 150 nF capacitor code0.15 µF capacitor code154200000 pF capacitor code200 / 200n / 200 nF capacitor code0.20 µF capacitor code204220000 pF capacitor code220 / 220n / 220 nF capacitor code0.22 µF capacitor code224330000 pF capacitor code330 / 330n / 330nF capacitor code0.33 µF capacitor code334470000 pF capacitor code470 / 470n / 470nF capacitor code0.47 µF capacitor code474680000 pF capacitor code680 nF capacitor code0.68 µF capacitor code6841000000 pF capacitor code1000 nF capacitor code1.0 µF capacitor code1051500000 pF capacitor code1500 nF capacitor code1.5 µF capacitor code1552000000 pF capacitor code2000 nF capacitor code2.0 µF capacitor code2052200000 pF capacitor code2200 nF capacitor code2.2 µF capacitor code2253300000 pF capacitor code3300 nF capacitor code3.3 µF capacitor code3354700000 pF capacitor code4700 nF capacitor code4.7 µF capacitor code4756800000 pF capacitor code6800 nF capacitor code6.8 µF capacitor code68510000000 pF capacitor code10000 nF capacitor code10 µF capacitor code10615000000 pF capacitor code15000 nF capacitor code15 µF capacitor code15620000000 pF capacitor code20000 nF capacitor code20 µF capacitor code20622000000 pF capacitor code22000 nF capacitor code22 µF capacitor code22633000000 pF capacitor code33000 nF capacitor code33 µF capacitor code33647000000 pF capacitor code47000 nF capacitor code47 µF capacitor code47668000000 pF capacitor code68000 nF capacitor code68 µF capacitor code686100000000 pF capacitor code100000 nF capacitor code100 µF capacitor code107330000000 pF capacitor code330000 nF capacitor code330 µF capacitor code337470000000 pF capacitor code470000 nF capacitor code470 µF capacitor code477680000000 pF capacitor code680000 nF capacitor code680 µF capacitor code6871000000000 pF capacitor code1000000 nF capacitor code1000 µF capacitor code1086.2 Frequently Asked Questions about Capacitor Code1. What is the code of a capacitor?Generally, the actual values of Capacitance, Voltage or Tolerance are marked onto the body of the capacitors in the form of alphanumeric characters. For example, a capacitor can be labeled as, n47 = 0.47nF, 4n7 = 4.7nF or 47n = 47nF and so on. 2.What does the numbers on a capacitor mean?The first two numbers represent the value in picofarads, while the third number is the number of zeroes to be added to the first two. For example, a 4.7 μF capacitor with a voltage rating of 25 volts would bear the marking E476. 3.What is the value of a capacitor?Capacitor values can be of over 109 range, and even more as super capacitors are now being used. To prevent confusion with large numbers of zeros attached to the values of the different capacitors the common prefixes pico (10 -12 ), nano (10 -9) and micro (10 -6) are widely used. 4.How can you determine the value of a capacitor?The value of capacitors can be determined by several ways depending up on the type of capacitor like electrolytic, disc, film capacitors, etc. These methods include value or number printed on the body of the capacitor or color coding of the capacitor. 5.How can I determine the capacitance of an unknown capacitor?To determine an unknown capacitance using an oscilloscope , a dc power source such as a 9-V battery, a known resistance, a switch and the capacitor are all connected in series. An oscilloscope probe tip and ground lead are connected across the capacitor. Additionally, you need a short wire jumper to shunt across the capacitor. Ⅶ Capacitor Code Calculator7.1 Capacitor Safety Discharge Calculator ToolThis Capacitor Safety Discharge Calculator helps to determine the discharge rate of a capacitor at known capacitance and charge through a fixed-value resistor. Enter the initial voltage, time, resistance, and capacitance into the calculator. The calculator will display the total voltage discharged and remaining. Many factors need to be considered when choosing a discharge resistor. Safety standards require the voltage across a capacitor to reach a safe voltage before a person is able to touch it. In the USA, standards such as UL, OSHA, NTA, ETL, MET, etc. will have the requirements available for the needs of your product.Capacitor Safety Discharge Calculator Tool 7.2 Series and Parallel Capacitance CalculatorThis tool calculates the overall capacitance value for multiple capacitors connected either in series or in parallel.Series and Parallel Capacitance Calculator 

IntroductionIn 2025, while surface mount technology (SMT) dominates mass production, the ability to read resistor color codes remains a fundamental skill for electronics prototyping, repairs, and education. Color bands are used to identify leaded resistors, typically with a power rating of up to one watt. The international standard IEC 60062 specifies this coding system, which applies to both resistors and capacitors.This system allows engineers and hobbyists to quickly identify resistance values without a multimeter. While digital marking codes are common on SMD resistors, the color band system remains the global standard for through-hole components.Figure: A guide to the resistor color code standard. Several bands provide the complete data for the component. They indicate the resistance value, tolerance, and sometimes the failure rate (reliability). Resistors typically have between three and six bands. The first two (or three) bands represent the significant digits of the resistance value, followed by a multiplier band. Resistance levels are standardized into specific series (E-series) of preferred values.Video: Visual guide to understanding resistor color codes.Ⅰ 1 Ohm Resistor Color Code1.1 Color Code Of 1 Ohm 4-Band ResistorThe resistor color code table is used to determine the value. Below is the breakdown for a 1 Ohm, 4-band resistor:Figure: Color code of 1Ω 4-band resistor.BandColorValue1st BandBrown 12nd BandBlack 03rd Band (Multiplier)Gold x 0.14th Band (Tolerance)Gold ±5%Calculation1st digit: 12nd digit: 0Multiplier: 0.11 OhmTolerance: ±5% Calculation logic:1st-band = Brown = 1 (1st digit)2nd-band = Black = 0 (2nd digit)3rd-band = Gold = 0.1 (Multiplier)4th-band = Gold = ±5% (Tolerance) Formula: $10 \times 0.1 = 1 \Omega$.Tolerance range: 5% of 1Ω is 0.05Ω. Theoretically, the actual resistance of a 1Ω resistor lies between 0.95Ω and 1.05Ω. Note on Low Values: For low-value resistors (under 10 Ohms), the multiplier band is often Gold (x0.1) or Silver (x0.01). In modern IEC 60062 standards, a Pink band is sometimes used for x0.001 multipliers in high-precision shunts. In 4- and 5-band resistors, the last band indicates tolerance. Gold indicates ±5%, Silver ±10%, Brown ±1%, and Red ±2%. If the fourth band is missing, the tolerance is standardized at ±20% (rare in 2025). 1.2 Color Code Of 1 Ohm 5-Band ResistorThe 1 Ohm 5-band resistor color code is Brown, Black, Black, Silver, Black:Figure: Color code of 1Ω 5-band resistor.1st-band = Brown = 1 (1st Digit)2nd-band = Black = 0 (2nd Digit)3rd-band = Black = 0 (3rd Digit)4th-band = Silver = x 0.01 (Multiplier)5th-band = Black = ±1% (Tolerance) For a 1 Ohm 5-band precision resistor, the calculation is $100 \times 0.01 = 1 \Omega$. The tighter tolerance (Black band = 1%) makes these ideal for current sensing applications. 1.3 Frequently Asked Questions about 1 Ohm Resistor1. What does a 1 ohm resistor do?A 1 Ohm resistor is often used as a current sense resistor (shunt) to measure current flow or to simulate a specific load. In power supplies, it can also act to simulate the ESR (Equivalent Series Resistance) of a large capacitor. 2. What is the definition of 1 ohm?The Ohm is the SI unit of electrical resistance. 1 Ohm is defined as the resistance between two points of a conductor when a constant potential difference of 1 volt applied between these points produces a current of 1 ampere. 3. Is 1 ohm a lot of resistance?No, 1 Ω is a very small amount of resistance. It is close to a short circuit. Resistances in electronic circuits usually range from hundreds (Ohms) to millions (Megaohms). 4. What is the formula for resistance?Rearranging Ohm's Law ($V = I \times R$) gives $R = V / I$. Therefore, 1 Ohm = 1 Volt per Ampere. Ⅱ 10 Ohm Resistor Color Code2.1 Color Code of 10 Ohm 4-Band ResistorThe 4-band 10 Ohm resistor color code is shown below:Figure: Color code of 10Ω 4-band resistor. BandColorValue1st BandBrown 12nd BandBlack 03rd Band (Multiplier)Black x 1 ($10^0$)4th Band (Tolerance)Gold ±5% Calculation:1st band = Brown = 12nd band = Black = 03rd band = Black = Multiplier $10^0$ = 1Result: $10 \times 1 = 10 \Omega$.With ±5% tolerance (0.5Ω), the actual value lies between 9.5Ω and 10.5Ω. Pro Tip: Be careful not to confuse Brown (1st band) and Red bands under poor lighting, as a "Red-Black-Black" sequence would read 20 Ohms. 2.2 Frequently Asked Questions about 10 Ohm Resistor1. What is the power consumed by a 10 ohm resistor with no current?If no current flows (open circuit), the power consumed is zero. 2. What is the current through a 10 ohm resistor in a circuit?Current depends on voltage. For example, if a 10 Ohm resistor is connected to a 6V source with some internal resistance (total circuit resistance 10.8Ω), the current is $I = V/R = 6 / 10.8 \approx 0.55$ Amps. 3. What is the voltage across the 10 ohm resistor?Ohm's Law states $V = I \times R$. If 1.2 Amps flows through a 10 Ohm resistor, the voltage drop is $1.2 \times 10 = 12$ Volts. 4. How much power is dissipated by a 10 ohm resistor?Power is calculated as $P = I^2R$ or $P = V^2/R$.Example: If 12 Volts is applied directly across a 10 Ohm resistor, the current is 1.2A. The power is $P = 1.2^2 \times 10 = 14.4$ Watts. Warning: A standard 1/4 Watt resistor would burn instantly in this scenario. You would need a high-power ceramic resistor. 5. What is a 10 ohm resistor used for?Low-value resistors like 10 Ohms are often used as current limiters in power circuits, in voltage dividers, or as part of RC filters (snubbers) to suppress voltage spikes. Ⅲ 100 Ohm Resistor Color Code3.1 Color Code of 100 Ohm 4-Band ResistorFor a 100 Ohm resistor, the bands are Brown, Black, Brown, Gold.Figure: Color code of 100Ω 4-band resistor. BandColorValue1st BandBrown12nd BandBlack03rd Band (Multiplier)Brownx 10 ($10^1$)4th Band (Tolerance)Gold±5% Calculation:1st digit (Brown) = 12nd digit (Black) = 0Multiplier (Brown) = 10Result: $10 \times 10 = 100 \Omega$.With ±5% tolerance, the resistance ranges from 95Ω to 105Ω. 3.2 Color Code of 100 Ohm 5-Band ResistorA 5-band 100 Ohm resistor allows for higher precision. The sequence is Brown, Black, Black, Black, Gold (or Brown/Red for tolerance).Figure: Color code of 100Ω 5-band resistor.1st-band = Brown = 12nd-band = Black = 03rd-band = Black = 04th-band (Multiplier) = Black = x 1 ($10^0$)5th-band (Tolerance) = Gold (±5%)Calculation: $100 \times 1 = 100 \Omega$. 3.3 Frequently Asked Questions about 100 Ohm Resistor1. What is a 100 ohm resistor used for?It is commonly used for LED protection, gate drive resistance in MOSFET circuits, and signal termination. It fits perfectly into breadboards for prototyping. 2. How can you tell if a resistor is 100 ohm?Look for the color bands: Brown-Black-Brown (4-band) or Brown-Black-Black-Black (5-band). 3. What is the value of 100 ohm in Megaohms?100 Ohms is $0.0001 M\Omega$ ($100 \times 10^{-6}$). 4. What is the actual range of a 100 ohm resistor?With standard ±5% tolerance, it measures between 95Ω and 105Ω. An older ±20% resistor (rare today) would measure between 80Ω and 120Ω. Ⅳ 120 Ohm Resistor Color Code4.1 Color Code of 120 Ohm 4-Band ResistorThe 120 Ohm resistor is famously used in CAN Bus termination. The color code is Brown, Red, Brown, Gold.Figure: Color code of 120Ω 4-band resistor. BandColorValue1st BandBrown12nd BandRed23rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 1, 2Multiplier: x 10Result: $12 \times 10 = 120 \Omega$.Tolerance range (±5%): 114Ω to 126Ω. 4.2 Frequently Asked Questions about 120 Ohm Resistor1. Why is 120 Ohm the standard for CAN Bus?The characteristic impedance of twisted pair cables used in automotive CAN networks is approximately 120 Ohms. Placing a 120Ω resistor at each end of the bus prevents signal reflections (ringing), ensuring data integrity. 2. Where do you place the 120 Ohm resistor?It is placed between CAN High (pin 7) and CAN Low (pin 2) at the two physical ends of the bus network. 3. Can I measure 120 Ohms on a live CAN bus?If the system is powered down, measuring resistance between CAN High and CAN Low should yield 60 Ohms. This is because there are two 120Ω terminating resistors in parallel ($120 / 2 = 60$). Ⅴ 150 Ohm Resistor Color Code5.1 Color Code of 150 Ohm 4-Band ResistorThe sequence for 150 Ohms is Brown, Green, Brown, Gold.Figure: Color code of 150Ω 4-band resistor. BandColorValue1st BandBrown12nd BandGreen53rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 1, 5Multiplier: x 10Result: $15 \times 10 = 150 \Omega$.Tolerance range: 142.5Ω to 157.5Ω. 5.2 Frequently Asked Questions about 150 Ohm Resistor1. How do I identify a 150 ohm resistor?Look for the Green band in the second position (representing 5) and the Brown band in the third position (representing x10 multiplier). Ⅵ 220 Ohm Resistor Color Code6.1 220 Ohm Resistor Color Code (5% Tolerance)This is extremely common for driving LEDs from 5V logic.Figure: 220 ohm resistor color code (Red-Red-Brown-Gold). BandColorValue1st BandRed22nd BandRed23rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 2, 2Multiplier: x 10Result: $22 \times 10 = 220 \Omega$. 6.2 220 Ohm Resistor Color Code (10% Tolerance)If the last band is Silver, the tolerance is ±10%. This means the resistor could be anywhere between 198Ω and 242Ω. 6.3 Frequently Asked Questions about 220 Ohm Resistor1. What does a 220 ohm resistor do?It resists current flow. In 2025, it is the standard "go-to" resistor for limiting current to standard LEDs when powered by USB (5V) or microcontrollers like Arduino or ESP32. 2. Will a 5 volt LED with a 220 ohm resistor run safely?Yes. If a red LED drops 2.0V, the resistor drops the remaining 3.0V. Using Ohm's Law ($I = V/R$), $3.0V / 220\Omega \approx 13.6 mA$, which is a safe and bright current for most indicator LEDs. Power dissipation is minimal ($0.04W$), so a 1/8W or 1/4W resistor is perfect. Ⅶ 330 Ohm Resistor Color Code7.1 Color Code of 330 Ohm 4-Band ResistorSequence: Orange, Orange, Brown, Gold.Figure: Color code of 330Ω 4-band resistor. BandColorValue1st BandOrange32nd BandOrange33rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 3, 3Multiplier: x 10Result: $33 \times 10 = 330 \Omega$. 7.2 Frequently Asked Questions about 330 Ohm Resistor1. Why use a 330 ohm resistor for an LED?If you need slightly less brightness or are using a 3.3V power supply (common in modern electronics like Raspberry Pi), a 330Ω resistor offers a good balance of brightness and protection. 2. What is the real value of a 330 ohm resistor?With 5% tolerance, it falls between 313.5Ω and 346.5Ω. Ⅷ 470 Ohm Resistor Color Code8.1 Color Code of 470 Ohm 4-Band ResistorSequence: Yellow, Violet, Brown, Gold.Figure: Color code of 470Ω 4-band resistor. BandColorValue1st BandYellow42nd BandViolet73rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 4, 7Multiplier: x 10Result: $47 \times 10 = 470 \Omega$. 8.2 Frequently Asked Questions about 470 Ohm Resistor1. What is a 470 ohm resistor used for?It is often used to drive blue or white LEDs (which have higher forward voltages) from higher voltage sources like 9V batteries or 12V automotive systems. 2. How do I know if I have a 470 ohm resistor?Look for the distinct Yellow (4) and Violet (7) starting bands. Ⅸ 500 (510) Ohm Resistor Color Code9.1 Color Code of 510 Ohm 4-Band ResistorNote: 500 Ohms is not a standard "E24 series" value. The closest standard value is 510 Ohms. In 99% of circuits, a 510Ω resistor is a perfect substitute for a 500Ω requirement.Figure: Color code of 510Ω 4-band resistor (Green-Brown-Brown-Gold). BandColorValue1st BandGreen52nd BandBrown13rd Band (Multiplier)Brownx 104th Band (Tolerance)Gold±5% Calculation:Digits: 5, 1Multiplier: x 10Result: $51 \times 10 = 510 \Omega$. 9.2 Frequently Asked Questions about 510 Ohm Resistor1. Can you substitute 500 ohm for 510 ohm?Yes. The error is only 2%. Given that standard resistors have a 5% tolerance, 510 Ohms is well within the acceptable range for a "500 Ohm" design. Alternatively, you can place two 1kΩ resistors in parallel to get exactly 500Ω. Ⅹ 1k Ohm Resistor Color Code10.1 Color Code of 1k Ohm 4-Band ResistorThe 1kΩ (1000 Ohm) resistor is arguably the most common resistor in electronics, used extensively for pull-up and pull-down logic circuits.Figure: Color code of 1kΩ 4-band resistor (Brown-Black-Red-Gold). BandColorValue1st BandBrown12nd BandBlack03rd Band (Multiplier)Redx 100 ($10^2$)4th Band (Tolerance)Gold±5% Calculation:Digits: 1, 0Multiplier: Red = x 100Result: $10 \times 100 = 1000 \Omega = 1 k\Omega$. 10.2 Frequently Asked Questions about 1k Ohm Resistor1. What is a 1k ohm resistor used for?It is the industry standard for pull-up resistors on microcontroller pins (like Arduino inputs) to prevent floating signals. 2. What is 1k ohm?"k" stands for Kilo (1000). Thus, 1k Ohm is 1000 Ohms. Ⅺ 2k Ohm Resistor Color Code11.1 Color Code of 2k Ohm 4-Band ResistorSequence: Red, Black, Red, Gold.Figure: Color code of 2kΩ 4-band resistor. BandColorValue1st BandRed22nd BandBlack03rd Band (Multiplier)Redx 1004th Band (Tolerance)Gold±5% Calculation:Digits: 2, 0Multiplier: Red = x 100Result: $20 \times 100 = 2000 \Omega = 2 k\Omega$. Ⅻ 2.2k Ohm Resistor Color Code12.1 Color Code of 2.2k Ohm 4-Band ResistorFamous for the "Three Reds" pattern.Figure: Color code of 2.2kΩ 4-band resistor (Red-Red-Red-Gold). BandColorValue1st BandRed22nd BandRed23rd Band (Multiplier)Redx 100 ($10^2$)4th Band (Tolerance)Gold±5% Calculation:Digits: 2, 2Multiplier: Red = x 100Result: $22 \times 100 = 2200 \Omega = 2.2 k\Omega$. 12.2 Frequently Asked Questions about 2.2k Ohm Resistor1. What does a 2.2k resistor do?It is commonly used in voltage dividers, particularly with LDRs (Light Dependent Resistors) to read ambient light levels with a microcontroller. 2. Calculating Current for a 1/2 Watt 2.2k ResistorIf you have a 1/2 Watt (0.5W) resistor, the maximum current it can handle is calculated using the power formula $P = I^2 \times R$.Rearranging for current ($I$):$I = \sqrt{P / R}$$I = \sqrt{0.5 / 2200}$$I \approx 0.015$ AmperesConclusion: A 2.2kΩ 1/2W resistor can safely handle approximately 15 milliamperes (mA). XIII Resistor Color Code Calculator13.1 4 Band Resistor Color Code CalculatorNeed to double-check your work? Use this tool to instantly decode 4-band axial lead resistors. Open 4 Band Resistor Color Code Calculator13.2 5 Band Resistor Color Code CalculatorFor high-precision 5-band resistors, use the calculator below: Open 5 Band Resistor Color Code Calculator 13.3 6 Band Resistor Color Code CalculatorIncludes the 6th band for Temperature Coefficient (PPM). Open 6 Band Resistor Color Code Calculator

The heart of this circuit is the LM3914 from national semiconductors. The LM3914 can sense voltage levels and can drive a display of 10 LEDs in dot mode or bar mode. The bar mode and dot mode can be externally set and more than one ICs can be cascaded together to gat an extended display. The IC can operate from a wide supply voltage (3V to 25V DC). The brightness of the LEDs can be programmed using an external resistor. The LED outputs of LM3914 are TTL and CMOS compatible.In the circuit diagram LEDs D1 toD10 displays the level of the battery in either dot or bargraph mode. Resistor R4 connected between pins 6,7 and ground controls the brightness of the LEDs. Resistors R1 and POT R2 forms a voltage divider network and the POT R2 can be used for calibration.The circuit shown here is designed in order to monitor between 10.5V to 15V DC. The calibration of the circuit can be done as follows. After setting up the circuit connect a 12V DC source to the input. Now adjust the 10K POT to get the LED10 glow (in dot mode) or LEDs up to 10 glow (in bar mode). Now decrease the voltage in steps and at 10.5 volts only LED1 will glow. Switch S1 can be used to select between dot mode and bar graph mode. When S1 is closed, pin9 of the IC gets connected to the positive supply and bar graph mode gets enabled. When switch S1 is open pin9 of the IC gets disconnected to the positive supply and the display goes to the dot mode.With little modification the circuit can be used to monitor other voltage ranges. For this just remove the resistor R3 and connect the upper level voltage to the input. Now adjust the POT R2 until LED 10 glows (in dot mode). Remove the upper voltage level and connect the lower level to the input. Now connect a high value POT (say 500K) in the place of R3 and adjust it until LED1 alone glows. Now remove the POT, measure the current resistance across it and connect a resistor of the same value in the place of R3. The level monitor is ready.Circuit diagram of battery level indicator using LM3914.Cascading two LM3914.Two or more LM3914 ICs can be cascaded together to get an extended display. The schematic of two LM3914 ICs cacaded together to get a 20 LED voltage level indicator is shown belowFew other battery level related circuits that you may like.1.Simple battery level indicator : This circuit can be used for monitoring the level of 3V batteries. The circuit is based on MN13811G from Panasonic. MN13811G is a CMOS  voltage detector IC that can be used a variety of voltage monitoring applications. In the circuit LED D1 will flash when ever the battery voltage drops below 2.4 volts.2.3 LED battery level indicator : A 3 LED battery level indicator that can be used for monitoring the voltage level of 12V automobile battery is shown here. Three states of the battery ie; below 11.5V, between 11.5 and 13.5 and above 13.5 are shown by the glowing of LEDs.3. Flashing battery monitor : This circuit can be used for monitoring the voltage level of 6 to 12V batteries. The circuit is based on transistors and the voltage level at which the LED starts flashing can be adjusted by using a potentiometer.

Inside a secretive AI nonprofit backed by Elon Musk and other Silicon Valley figures, a handful of robots designed to help out in warehouses are gradually learning how to do useful household chores.OpenAI, which was created to do basic AI research, is reprogramming robots developed by Fetch Robotics, a company that supplies warehouse automation hardware. Researchers at OpenAI are equipping the robots with software that lets them train themselves through trial and error. The effort reflects a bet that innovations in software and machine learning, rather than breakthroughs in hardware, are the way to give robotics remarkable new capabilities. Fetch makes a range of robots for warehouses, including systems that follow workers around a building, carrying items dropped into a basket. OpenAI is using a system that features a mobile base but also 3-D depth sensors, a 2-D laser scanner, and a robotic arm with seven degrees of freedom. In April, OpenAI recruited Pieter Abbeel, a professor at the University of California, Berkeley, and a leading expert on robot learning. Abbeel has shown how robots can use a machine-learning approach called deep reinforcement learning to acquire completely new skills that would be hard to program by hand, such as folding towels or retrieving items from a refrigerator. Google DeepMind, an AI subsidiary based in the U.K., uses this technique to get computers to play computer games at a superhuman level.Abbeel’s robots learn tasks from scratch, using a neural network that receives sensor input and controls physical movement. The network adjusts its parameters automatically as it inches closer to its goal. A robot might try thousands of grips, for instance, in the process of learning how to hold a certain object. “If this goal can be achieved, then there will be economic and industrial benefits,” says Marc Deisenroth, an expert on reinforcement learning at Imperial College London. “Imagine a Roomba not only cleaning your floor but also doing the dishes, ironing the shirts, cleaning the windows, preparing breakfast.”Deisenroth says using off-the-shelf robots could drive costs down. “Currently, the software seems to be the bottleneck,” he adds. “However, independent of this, better hardware could also lead to substantial improvements.” Soft manipulators and elastic feet similar to a monkey’s feet are concepts that researchers have started working on, he says.Some manufacturers, including the Japanese company Fanuc, are testing reinforcement learning as a way to train industrial robots quickly in new tasks such as learning to grasp unfamiliar objects. When many robots work in parallel, the training time required is reduced accordingly . Robot researchers at Google are testing similar learning techniques.“Moving away from having to program robots by hand by endowing robots to learn autonomously is a key element for the future of robotics,” says Jens Kober, an expert on robot learning at Delft University of Technology in the Netherlands. Kober says having robots share the information they have learned will be crucial.While robots such as those made by Fetch are finding their way into many factories and warehouses, domestic robot helpers remain the stuff of science fiction. Performing seemingly simple tasks like washing dishes or folding laundry in a messy home setting is incredibly hard for a machine. A robot programmed the conventional way can easily be thrown off by an unfamiliar object or a slight variation in lighting.OpenAI confirmed that it is working with the robots from Fetch, but it declined to comment further. Melonee Wise, the company’s founder, couldn’t be reached for comment.OpenAI was created by Musk and a handful of well-known (and well-heeled) Silicon Valley entrepreneurs, including investor Peter Thiel, Y Combinator president Sam Altman, and the incubator’s cofounder Jessica Livingston. The nonprofit’s backers have committed $1 billion in funding to the project, and it is being led by Ilya Sutskever, a prominent AI researcher who left Google to join the project, and Greg Brockman, an early employee at the high-profile digital payment company Stripe.While OpenAI has committed to making the technology it develops publicly available, it could certainly benefit companies backed by Musk and Thiel, as well as those emerging from Y Combinator.Produced by Will Knight