The Kynix Blog

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 Everyone is familiar with Cameras. Owning a mobile phone is equivalent to owning a smart camera device that is very portable. So what does the camera use to image? And how do you get a clear picture of the object? Here we take you to understand the secrets hidden in the camera. Figure 1. Camera Image Processing Catalog Introduction Ⅰ Photomultiplier Tube (PMT) Ⅱ Charge-coupled Device (CCD) 2.1 CCD Terminology 2.2 CCD Chips 2.3 CCD Types Ⅲ Complementary Metal Oxide Semiconductor (CMOS) 3.1 CMOS Invention 3.2 CCD vs CMOS Ⅳ Imaging System 4.1 Key Elements 4.2 Calculation of Image/Video Data Volume 4.3 Storage Space Calculation 4.4 Camera Composition and Principle 4.5 Intelligent Camera Image Processing Hardware Ⅴ Smart Camera Interfaces and Communication Protocols Ⅵ Image Signal Processor (ISP) Ⅶ FAQ Ⅰ Photomultiplier Tube (PMT) PMT is the earliest image sensor, which is very mature, and it is the sensor with the best performance at present. A photomultiplier tube, useful for light detection of very weak signals, is a photoemissive device in which the absorption of a photon results in the emission of an electron. Because it has multiple electrodes built-in to convert incoming light signals into electrical signals, and even very weak light can be accurately captured. Its highest dynamic range can reach 4.2, compared with other types of sensors that can only reach 3.2~3.6. And it can operate for more than 100,000 hours. However, due to its high cost, it can only be used in professional printing, publishing industry scanners and engineering analysis. Figure 2. Photomultiplier Tube (PMT) Ⅱ Charge-coupled Device (CCD) 2.1 CCD Terminology CCD was invented by Bell Labs in the United States in 1969. It is similar to computer chip CMOS  and can also be used for computer memory and logic operation chips. CCD is a special semiconductor material composed of a large number of independent photodiodes, which are generally arranged in a matrix form (except Fuji's Super CCD). The photosensitive ability of CCD is lower than that of PMT, but in recent years, CCD technology has made great progress, and because of its small size and low cost, it is widely used in scanners, digital cameras and digital video cameras. The image sensors used in most digital cameras today are CCDs.Early CCDs were interlaced (Interline Transfer), which increased the shutter speed, but the image accuracy was greatly reduced. New CCDs are generally progressive scan (FullFrame Transfer). Figure 3. Charge-coupled Device Semiconductor 2.2 CCD Chips It integrates a light-sensitive device on a single piece of semiconductor: a photodiode and some circuits. Each unit is arranged in a neat matrix, CCD pixel = number of rows multiplied by the number of columns. About 30% of each pixel cell is used to make photodiodes, and in the remaining available area, a transfer register is placed. After receiving a command, the light intensity sensed by the photodiode is placed in this transfer register and temporarily stored here, which is an analog signal. The next step is to convert the light intensity value in each pixel into a digital signal, which is then combined into a digital image by the processor in the camera.Since in each pixel unit, only about 30% of the area is actually used for light-sensing, its light-sensing efficiency is relatively low. So in the real finished product, a small optical lens will be placed on top of each pixel unit, which we call "microlens". In terms of structure, it is directly placed above the photodiode, and its area is relatively large, so that more incident light can be concentrated on the photodiode. Therefore, the equivalent photosensitive area reaches about 70% of the pixel area. 2.3 CCD Types Primary color CCD and complementary color CCD: In fact, the CCD itself cannot distinguish colors. Therefore, color filters are required in practical applications. Generally, the filter layer of the CCD device is coated with different colors. The different color blocks on the filter are arranged like a mosaic in the order of G-R-G-B (green-red-green-blue), so that the pixels under each mosaic can sense different colors. Figure 4. Color Filter Array Sensor For example, a 1.3-megapixel CCD has 325,000 pixels sense red, 325,000 pixels sense blue, and 650,000 pixels sense green. In a digital camera with a resolution of 1280x1024 using this CCD, there are 640x512 red pixels, 640x512 blue pixels and 640x1024 green pixels, having more green pixels due to the human eye's sensitivity to green and other color is not the same. Finally, when the image is recorded, the true color of each pixel is the average of its blending with the surrounding pixel image. At present, most digital cameras use this kind of CCD.Linear CCD, different from matrix CCD, may be arranged in a linear arrangement of photosensitive elements, so it is a strip, like barcode scanners.   Ⅲ Complementary Metal Oxide Semiconductor (CMOS) 3.1 CMOS Invention CMOS was not used to make image sensors until 1998. The advantage of CMOS is that the structure is simpler than that of CCD, the power consumption is only about 1/3 of that of ordinary CCD, and the manufacturing cost is lower than that of CCD. Since Canon adopted CMOS in the professional digital SLR camera EOS D30, more and more digital SLR cameras have used it, and almost half of the digital SLR cameras now use CMOS as the image sensor. Figure 5. Complementary Metal Oxide Semiconductor (CMOS) 3.2 CCD vs CMOS CCD and CMOS sensors are different in "internal structure" and "external structure". The imaging points of the CCD device are arranged in an XY vertical and horizontal matrix, and each imaging point consists of a photodiode and a charge storage area controlled by it. Where the CCD can only output analog electrical signals, which need to be decoded by subsequent addresses. Further more, it also needs to provide three-phase power supply and synchronous clock control circuit with different voltages.CMOS devices have high integration, small size and light weight. Its biggest advantage is that it has a high degree of system integration. Because of the digital-analog signal mixed design, in theory, all functions required by image sensors, such as vertical displacement, horizontal displacement register, sensor array drive and control system (CDS), analog-to-digital converter (ADC) interface circuit, etc. can be fully integrated to achieve single-chip imaging, avoid the use of external chips and equipment, and greatly reduce the size and weight of the device.The charge information stored by the CCD needs to be read after being transferred bit by bit under the control of the synchronization signal. The charge information transfer and read output need to be coordinated by a clock control circuit and three sets of different power supplies. slower. The CMOS photoelectric sensor directly generates a voltage signal after photoelectric conversion, the signal reading is very simple, and it can also process the image information of each unit at the same time, which is much faster than CCD.From the perspective of power consumption and compatibility, CCD requires external control signals and clock signals to obtain satisfactory charge transfer efficiency, and also requires multiple power supplies and voltage regulators, so the power consumption is large. While CMOS-APS uses a single operating voltage, with low power consumption (only equivalent to 1/10-1/100 of CCD) and good compatibility, can also be compatible with other circuits.CCD sensors require special processes, use special production processes, and have high costs; while CMOS sensors use 90% of the same basic technologies and processes as semiconductor devices, and have high yield and low manufacturing costs. Currently, 500,000-pixel CMOS sensors are used for cameras.CCDs use charge shift registers, and when the register overflows, it leaks charge into adjacent pixels, causing the bright light to spread out and create unwanted streaks in the image. In CMOS-APS, the photodetector and the output amplifier are both part of each pixel. The integrated charge is converted into a voltage signal in the pixel and output through the XY output line. This row-column addressing method makes the window operation possible. You can also perform on-film translation, rotation and zooming, without smear, halo and other false signals, to get high image quality.High speed is an inherent characteristic of CMOS circuits. CMOS image sensors can drive the column bus of the imaging array extremely fast, and the ADC operates at an extremely fast rate on-chip, and has low sensitivity to output signals and external interface interference, which is beneficial to next level processor connection. CMOS image sensors are highly flexible and can perform random access to local pixel images, increasing flexibility. Camera Image Sensors as Fast As Possible   Ⅳ Imaging System 4.1 Key Elements 1) Field of View: The portion of an object that can be seen on a display.2) Depth of Field: The difference between the nearest and farthest distances at which an imaging system can remain in focus.3) Working Distance: When observing an object, the distance from the vertex of the last lens to the observed object.4) Distortion: The optical error caused by the lens makes the magnification of each point on the image surface different.5) Parallax: It is caused by the traditional lens, the change of each point on the object outside the best focus point, the telecentric lens can solve this problem.6) Image Sensor Size: The effective working area of the image sensor (usually CCD or CMOS), generally refers to the horizontal size. This parameter is important in determining the pre-magnification factor (PMAG) for the desired field of view. Most image sensors have a length to width ratio of 4:3.7) Pre-magnification: It refers to the ratio of the field of view to the size of the image sensor, which is done by the lens.8) System Magnification: It refers to the ratio of the image on the display to the actual size of the object, that is, the magnification of the entire system. It can also be written as the product of pre-magnification and electronic magnification, which is the ratio of display size to image sensor size.9) Resolution: The distance between two points on an object that can be minimally distinguished, indicating the ability to distinguish details. 4.2 Calculation of Image/Video Data Volume Definition of picture resolution in different camera pixels (number of photosensitive elements of CCD/CMOS sensor):FCIF (Full Common Intermediate Format) Resolution: 352*288=100,000 pixels DCIF Resolution: 512*384=200,000 pixelsD1(4CIF) Resolution: 704*576=400,000 pixels720P Resolution: 1280*720=1 million pixels1080P Resolution: 1920*1080=2 million pixels Figure 6. Camera Pixel Art The computer's true color pixels are stored according to the RGB three-color principle, and each color of red, green and blue is 256 (2 to the 8th power, one byte length), so a pixel needs 3 bytes and 24 bits. Now that the calculation capacity is large, a 256 grayscale is added on the basis of RGB storage, so 4 bytes are needed, that is, 32 bits. In addition, such pixels are now also called true color.Bit rate refers to the number of bits transmitted per second. The unit is bps (bit Per second). The higher the bit rate, the larger the data transmitted. The bit rate indicates how many bits per second the encoded (compressed) audio and video data needs to be represented, and a bit is the smallest unit in binary, either 0 or The relationship between bit rate and audio and video compression is simply that the higher the bit rate, the better the quality of audio and video, but the larger the encoded file. If the bit rate is lower, the situation is just the opposite.DataRate refers to the data flow used by video files in unit time, also called bit rate, which is the most important part of picture quality control in video coding. Under the same resolution, the larger the code stream of the video file, the smaller the compression ratio and the higher the image quality.1) 720P single image data volume = 1280 × 720 × 24/8/1024 = 2700 KByte.2) The amount of data of the moving image3) H.264 compressed payload data volumeThe biggest advantage of H.264 is that it has a high data compression ratio. Under the same image quality, the compression ratio of H.264 is more than 2 times that of MPEG-2, and 1.5 to 2 times that of MPEG-4. For example, the original file is 88GB, 3.5GB after MPEG-2 compression, the compression ratio is 25:1, and the H.264 compression is 1.1GB, from 88GB to 1.1GB, the compression ratio of H.264 reaches 80:1. For example, in the video conference, the original code stream is encoded and compressed by adopting H.264.4) The amount of transmitted data compressed by H.264Adding network overhead, the amount of data transmitted = the amount of payload data * 1.3At 20%, the amount of data transmitted after compression = 1.6 * 1.3 = 2.08 Mbit/s5) Home monitoring storage capacityBandwidth Calculation:The required bandwidth of the CIF video format: 512Kbps (the bit rate of the video format) × 50 (the total number of cameras at the monitoring point)=25Mbps (downlink bandwidth). That is: the network downlink bandwidth required by the monitoring center using CIF video format is at least 25Mbps.The required bandwidth of the D1 video format: 1.5Mbps (bit rate of the video format) × 50 (the total number of cameras in the monitoring point) = 75Mbps (downlink bandwidth). That is: the network downlink required by the monitoring center using D1 video format bandwidth is at least 75Mbps.The required bandwidth of 720P (1 million pixels) video format: 2Mbps (bit rate of video format) × 50 (the sum of the total number of cameras at the monitoring point) = 100Mbps (downlink bandwidth). That is: adopting 720P video format monitoring, the network downlink bandwidth required by the center is at least 100Mbps.The required bandwidth of the 1080P (2 million pixel) video format: 4Mbps (bit rate of the video format) × 50 (the total number of cameras at the monitoring point) = 200Mbps (downlink bandwidth) That is: adopting 1080P video format monitoring, the network downlink bandwidth required by the center is at least 200Mbps. 4.3 Storage Space Calculation Stream size (unit: KB/s; namely: bit rate ÷ 8) × 3600 (unit: second; seconds in 1 hour) × 24 (unit: hour; length of one day) × 30 (days saved) × 50 (the total number of camera recordings to be saved at the monitoring point) ÷ 0.9 (10% space loss from disk formatting) = the size of the required storage space (Note: unit conversion 1TB=1024GB, 1GB=1024MB, 1MB=1024KB)The required storage space for 50 channels to store 30 days of CIF video format video information is: 64 × 3600 × 24 × 30 × 50 ÷ 0.9=8789.1GB ≈ 9TBThe required storage space for 50 channels to store 30 days of D1 video format video information is: 192 × 3600 × 24 × 30 × 50 ÷ 0.9=26367.2GB ≈ 26TBThe required storage space for 50 channels of 720P (1 million pixels) video format recording information for 30 days is: 256 × 3600 × 24 × 30 × 50 ÷ 0.9=34.33GB ≈ 35TBThe required storage space for 50 channels of 1080P (2 million pixels) video format video recording information that can be stored for 30 days is: 512 × 3600 × 24 × 30 × 50 ÷ 0.9=68.66GB ≈ 69TB 4.4 Camera Composition and Principle The working principle of the camera is to project the optical signal obtained by the optical component onto the image sensor, complete the conversion from the optical signal to the electrical signal, and then convert it into a digital image signal, and finally perform the algorithm processing of the signal. The main components of the camera are optical components lens, CMOS sensor, DSP, module assembly and other components. 4.5 Intelligent Camera Image Processing Hardware Image processing capability: FPGA<DSP<High-end CPUASICs are ideal for performance and power consumption. Develop a dedicated SoC (system on chip) for a given application, implement a custom architecture to accommodate data flow, and optimize power consumption. However, the development cost is high and it is suitable for consumer products (i.e. production volumes of thousands of units). ASIC devices have very little or zero flexibility and programmability due to their specificity.FPGAs are the best choice for low- or medium-volume high-performance applications. They are very flexible and can meet the requirements of almost any application. Due to the ever-increasing number of available logic elements per device in FPGAs, increasing clock frequencies, and the possibility to exploit massive parallelism, it is possible to achieve processing performance close to ASICs, with the advantage of being fully reconfigurable. However, the power consumption of FPGAs is relatively high, and even if design methodologies and development environments exist, FPGA-based solutions require more development time and expertise than CPU-based solutions (DSP, microcontroller, etc.).DSP devices and media processors share many characteristics with embedded general-purpose RISC processors (PowerPC, ARM, etc.) and microcontrollers. All these devices are CPU based, i.e. based on processor cores. Therefore, they all have excellent programmability, using programming tools such as C/C++ and dedicated development environments. NRE (non-recurring engineering) is very low cost and has good flexibility, so it is suitable for most applications.The main difference between CPU-based devices comes at the performance level. A microcontroller can be seen as an enhanced RISC processor by adding CPU core memory (RAM, ROM, Flash), peripherals and I/O interfaces (ADC, DAC, etc.). In addition, the DSP core provides a dedicated architecture and some specific hardware structures to optimize the execution of arithmetic operations, such as MAC (multiply-accumulate) and SIMD units. Finally, media processors are a class of DSP devices dedicated to audio and video processing, suitable for processing data streams. DSPs and media processors may have a VLIW (Very Long Instruction Word) architecture, such as NXP TriMedia processors. Figure 7. Camera Color Coding Ⅴ Smart Camera Interfaces and Communication Protocols Wired Interface and Wireless Interface Table 1. Most Common Wired Communication Protocols Protocol Theoretical Bandwidth in bits per second (bit/s) RS-232 serial link USB 1.x Full-speed USB 2.0 Hi-speed FireWire or IEEE 1394a/b Camera Link Ethernet, Fast Ethernet GigE Vision (Gigabit Ethernet) 19,200 bit/s 12 Mbit/s 480 Mbit/s 400/800 Mbit/s 2.04, 4.08, or 5.44 Gbits 10/100 Mbit/s 1 Gbit/s   Table 2. Most Common Wireless Protocols Protocol Theoretical Bandwidth (bit/s) Wireless Range (m) WiFi IEEE 802.11a WiFi IEEE 802.11b WiFi IEEE 802.11g Bluetooth ZigBee (IEEE 802.15.4) 54 Mbit/s 11 Mbit/s 54 Mbit/s 1 Mbit/s 250 Kbit/s Up to 10m ~50m indoor, ~200m outdoor ~27m indoor, ~75m outdoor ~10-100m ~10-100m indoor, up to 150m outdoor For example, if the camera is equipped with the MT9M413 image sensor from Aptina Imaging (formerly Micron Imaging), capable of delivering images up to 660M pixels/s, a camera interface is required to take full advantage of the sensor (5.44 Gbit/s (680 M Bytes/s in full configuration) ). However, if there are other constraints, the rules of keeping data rates compatible between sensors and communication interfaces may be broken. For example, with a battery-operated smart camera, even real-time video transmission with a bandwidth of 250 Kbit/s makes no sense. There are two workarounds:1) Wireless ZigBee protocol, because its power consumption is very low.2) Another solution to reduce bandwidth requirements is an image compression algorithm. However, compressing and decompressing images places additional processing burden on the camera and host, and can result in loss of picture quality, depending on the desired compression ratio.And bandwidth isn't the only deciding factor. For example, GigE Vision systems are inexpensive to implement, but the end result can hinder application responsiveness and development time. GigE Vision is still in its infancy, while Camera Link and IEEE 1394 have proven. The integrity of the standard must also be considered. GigE Vision and IEEE 1394 cameras are compatible between vendors and are easier to configure than Camera Link.   Ⅵ Image Signal Processor (ISP) It is widely used in mobile phone cameras and car cameras and other fields, and is the core chip of image signal processor.ISP pipeline process: The light passes through the lens, after lens correction and color correction, is projected onto the sensor, photoelectrically converted into an analog electrical signal, and then converted into a digital signal by A/D, and then handed over to the ISP chip for processing. Then, the obtained image of the bayer pattern goes through BLC (black level compensation), lens shading (lens shading correction), BPC (bad pixel correction), CIP (demosaic), DNS (denoise), AWB (automatic white balance), color correction gamma correction, color space conversion (RGB conversion YUV), and then output data in YUV (or RGB) format, and finally transmitted to the CPU for processing through the I/O interface.The functions of each module are briefly described as follows:1) Bayer PatternThe filters that cover the surface of the image sensor are usually called Color Filter Arrays (CFA). At present, the most commonly used filter array is in checkerboard format, and the primary color Bayer Pattern CFA RGB represents the filter array unit of red, green and blue. Since human vision is most sensitive to green, the G component in Bayer CFA is twice that of R and B, and only one color component information can be obtained on each pixel, and then an interpolation algorithm is passed according to the color component information, finally get a full color image.2) Black Level Correction (BLC)Physical devices cannot be ideal. Due to impurities, heat and other reasons, even if no light is irradiated to the pixel, the pixel unit will generate charges, and these charges generate dark current. Moreover, dark current is difficult to distinguish from the charge generated by light. Black Level is used to define the signal level corresponding to 0 for image data. An effective way to reduce the influence of dark current on the image signal is to subtract the reference dark current signal from the obtained image signal. Generally, in the sensor, the first few lines of the pixel area are used as the non-photosensitive area. This part of the area is also used for RGB color filter. The average value is used as the correction value for automatic black level correction, and then the pixels in the following area are subtracted from this. Pay attention to, the brightness of the picture is reduced after black level correction.3) Lens Shading Correction (LSC)Due to the physical properties of the lens itself, the brightness around the image gradually decreases relative to the center brightness. When the image light shines on the pixel through the lens, the focus angle at the corners is greater than the center focus angle, resulting in loss of light at the corners. In order to compensate for the surrounding brightness, Lens Shading correction is necessary. The method is to calculate the brightness correction value corresponding to each pixel according to the algorithm, so as to compensate the brightness of the surrounding attenuation.4) Bad Pixel Correction (BPC)Under normal circumstances, the RGB signal should have a linear response relationship with the brightness of the scene. However, due to the bad pixels of senor, the output signal is abnormal, and there are dead spots: white spots in the output image in a dark environment, and black spots in the output image in a bright environment. There are usually two methods of repairing dead pixels: one is to automatically detect and repair the dead pixels, and the other is to establish a linked list of dead pixels to repair bad pixels at fixed positions. This method is the OTP method. 5) DNSUsing CMOS sensor to acquire images, light level and sensor issues are the main factors that generate a lot of noise in the image. At the same time, when the signal passes through the ADC, some other noise is introduced. These noises will blur the image as a whole and lose a lot of details, so the image needs to be denoised. The traditional methods of spatial denoising include mean filtering, Gaussian filtering and so on. However, the general Gaussian filter mainly considers the spatial distance relationship between pixels when sampling, and does not consider the similarity between pixel values, so the blurring result obtained in this way is usually a blur of the entire picture. Therefore, a nonlinear denoising algorithm, such as bilateral filter, is generally used, which not only considers the relationship between pixels in spatial distance, but also considers the similarity between pixels, so that the general segmentation of the original image can be maintained to keep the edge. In practical applications, wavelet denoising is more suitable, and each segment in the entire pipeline will be more or less applied to DNS, which is particularly important in the entire process of ISP, and exists in almost every part of it.6) Color InterpolationWhen the light passes through the Bayer-type CFA array, the light hits the sensor, and the BGR data is obtained respectively. Here, the data sampling ratio of BGR is 1:2:1, because the human eye is more sensitive to green light (550nm). Among them, G is also called luminance information, and BR is chrominance information. It can be seen that in the above Bayer diagram, each pixel has only one of the BGR data, so it is necessary to use CIP interpolation to supplement the color information of the other two channels to form a normal full-color image.7) Automatic White Balance (AWB) The basic principle of automatic white balance is to restore white objects to white objects in any environment, that is, by finding white blocks in the image, and then adjusting the ratio of R/G/B.The AWB algorithm usually steps as follows:Color temperature statistics, according to the image statistics color temperature.Calculate channel gain: Calculate the gain of R and B channels.Correction of color cast: Calculate the correction of color cast according to the given gain. Grayscale world method and perfect reflection method are more commonly used and effective.8) Gamma CorrectionThe sensitivity value of the human eye to the external light source is not linearly related to the input light intensity, but is exponentially related. Under low illumination, it is easier for the human eye to distinguish the change of brightness. With the increase of illumination, it is difficult for the human eye to distinguish the change of brightness. However, there is a linear relationship between the light sensitivity of the camera and the input light intensity. In order to help the human eye to recognize the image, the image collected by the camera needs to have Gamma correction. It is a nonlinear operation on the gray value of the input image, so that the gray value of the output image has an exponential relationship with the gray value of the input image.9) Color CorrectionDue to the difference between the spectral responsivity of the visible light of the human eye and the spectral responsivity of the semiconductor sensor, as well as the influence of lenses, etc., the color of the obtained RGB value will be biased, so the color must be corrected. The usual method is to pass a 3x3 Color change matrix for color correction.10) RGB Conversion YUV Color Space ConversionYUV is a basic color space, and the human eye is much more sensitive to changes in brightness than changes in color. Therefore, for the human eye, the brightness component Y is much more important than the chrominance components U and V. Therefore, some U and V components can be appropriately discarded to achieve the purpose of compressing data.Laplacian operator: YCbCr is actually a scaled and offset modified version of YUV, Y represents the brightness, Cr and Cb represent the color difference, which are the red and blue components respectively. In the YUV family, YCbCr is the most widely used member in computer systems, and its application fields are very wide. For example, JPEG and MPEG both use this format. Generally speaking, YUV mostly refers to YCbCr.The color space conversion module converts RGB to YUV444, and then performs subsequent color noise removal, edge enhancement, etc. on the YUV color space, which also provides convenience for subsequent output conversion to JPEG images.   Ⅶ FAQ 1. Does photomultiplier tube PMT scan images?Photomultiplier tubes (PMTs), also known as photomultipliers, are remarkable devices. While a PMT was the first device to detect light at the single-photon level, invented more than 80 years ago, they are widely used to this day, particularly in biological and medical applications. 2. Why are photomultiplier tubes so sensitive?Photomultipliers (sometimes called photon multipliers) are a type of photoemissive detectors which have a very high sensitivity due to an avalanche multiplication process, and also exhibit a high detection bandwidth. 3. What does CCD stand for in cameras?CCD stands for "charge coupled device", a semiconductor image sensor used in digital cameras to convert light into electrical signals. In place of the film used in conventional film cameras, digital cameras incorporate an electronic component known as an image sensor. 4. What are CCD sensors used for?CCDs are used in optical microscopes because they can possess over 10 million pixels, which enables many samples to be seen clearly, as well as a low noise ratio, ability to image in color, high sensitivity and a high spatial resolution which all contribute to the high-quality images that are necessary for modern-day. 5. What is good camera pixels?A decent 6-megapixel camera is good enough for most normal camera usage. Go for higher megapixels only if you wish to use your images for canvas-sized prints or large hoardings. If your interest is in night sky photography, then too a higher megapixel camera can be important. 6. What is resolution in camera settings?A picture's resolution describes how many pixels, or dots, are in the image. The more dots, the better the image looks and prints. Megapixel is a measurement of the amount of information stored in an image. 7. What is a good camera resolution?A Camera Resolution Reference Chart Resolution Avg. Quality Best Quality 0.5 megapixels 2x3 in. NA 3 megapixels 5x7 in. 4x6 in. 5 megapixels 6x8 in. 5x7 in. 8 megapixels 8x10 in. 6x8 in. 8. What is H264 format?H. 264 is a well-known video compression standard for high-definition digital video. Also known as MPEG-4 Part 10 or Advanced Video Coding (MPEG-4 AVC), H. 264 is defined as a block-oriented, compensation-based video compression standard that defines multiple profiles (tools) and levels (max bitrates and resolutions). 9. Which is better H 264 or H 265?265 codec compresses information more efficiently than H. 264, resulting in files of comparable video quality that are about half the size. The benefits of this are twofold: H. 265 video files don't take up as much storage space, and they require less bandwidth to stream. 10. What is a camera chip?Able to leap photographic obstacles with a single computer chip. It's a camera. It's a chip. It's a camera-on-a-chip. ... Most of today's digital cameras use charge-coupled device (CCD) sensors rather than the far less expensive complementary metal-oxide semiconductor (CMOS) chips used in most computing technologies. 11. Is CCD better than CMOS?For many years, the charge-coupled device (CCD) has been the best imaging sensor scientists could choose for their microscopes. ... CMOS sensors are faster than their CCD counterparts, which allows for higher video frame rates. CMOS imagers provide higher dynamic range and require less current and voltage to operate. 12. What is camera image sensor?The image sensor of the camera is responsible for converting the light and color spectrum into electrical signals for the camera to convert into zeroes and ones. All commercially available digital cameras (still, movie, or security) use one of two possible technologies for the camera's image sensor: CCD or CMOS. 13. How do photomultiplier tubes detect light?The reflection mode photocathode is mainly used for the side-on photomultiplier tubes which receive light through the side of the glass bulb, while the transmission mode photocathode is used for the head-on photomultiplier tubes which detect the input light through the end of a cylindrical bulb. 14. Which interface is used for camera?The most common USB 3.1 connector used in the machine vision camera industry is the USB 3.1 Micro B connector. Gradually being introduced to the market is USB-C (USB Type C), the connection type designed for the future. 15. Which of the serial communication standard is used in digital camera?Camera LinkCamera Link is a serial communication protocol standard designed for camera interface applications based on the National Semiconductor interface Channel-link. It was designed for the purpose of standardizing scientific and industrial video products including cameras, cables and frame grabbers. 16. What does image signal processor do?As the name implies, the Image Signal Processor (ISP) is used for processing images in embedded vision camera systems. The ISP also performs other operations on the captured image such as demosaicing, denoising, and auto functions that help deliver an enhanced image. 17. What is image and signal processing?The field of signal and image processing encompasses the theory and practice of algorithms and hardware that convert signals produced by artificial or natural means into a form useful for a specific purpose. ... Image processing work is in restoration, compression, quality evaluation, computer vision, and medical imaging. 18. Where are DSP processors used?DSP is used primarily in areas of the audio signal, speech processing, RADAR, seismology, audio, SONAR, voice recognition, and some financial signals. For example, Digital Signal Processing is used for speech compression for mobile phones, as well as speech transmission for mobile phones. 19. What is RGB conversion?RGB to hex conversionConvert the red, green and blue color values from decimal to hex. Concatenate the 3 hex values of the red, green and blue togather: RRGGBB. 20. What is AWB setting?One of the white balance settings, "Auto White Balance" (AWB) automatically adjusts to correct the changes in color under different light sources. The function adjusting the color tone so that white objects look white in the picture is called white balance (WB).

"What Capacitor Types Should I Choose?" - Complete Guide 2025This is a question asked by many beginners and even experienced engineers. I will give you a comprehensive answer to this question, covering all the essential details you need to know. After reading this updated guide, you should be able to confidently select the right capacitor for your project. Understanding why one capacitor type might be better than another is crucial because there are many factors (temperature characteristics, package size, ESR, lifetime, etc.) that can make a specific type of capacitor the optimal choice for your application.2025 Update: This guide has been updated to include the latest capacitor technologies, including advanced ceramic capacitors, solid polymer electrolytes, and new packaging formats that have emerged since 2016.I What is a Capacitor?A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component specifically designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator, and this original name is still widely used in many languages, though not commonly in English.The physical form and construction of practical capacitors vary widely, and many capacitor types are in common use. Most capacitors contain at least two electrical conductors, often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, air, vacuum, and various oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy, though real capacitors have some energy loss.When two conductors experience a potential difference, for example, when a capacitor is attached across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and a net negative charge to collect on the other plate. No current actually flows through the dielectric; however, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. However, if a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.II Capacitor Functions1. Blocking DC (DC Blocking): The function is to prevent the passage of DC current while allowing AC signals to pass through. This is fundamental to AC coupling applications.2. Bypass (Decoupling): Provides a low impedance path for AC signals, effectively bypassing certain components in AC circuits. This is crucial for power supply decoupling and noise reduction.3. Coupling: Acts as a connection between two circuits, allowing AC signals to pass while blocking DC components. This enables signal transmission to the next stage while maintaining DC isolation.The purpose of using a capacitor as a coupling element is to transmit the AC signal from one stage to the next while preventing DC bias voltages from affecting subsequent stages. This makes circuit design simpler and performance more stable.Without coupling capacitors, AC signal amplification would still occur, but the DC operating points of all stages would need to be carefully coordinated. The interaction between stages makes this extremely difficult, especially in multi-stage amplifiers.4. Filtering: This is critically important for circuits, especially those behind CPUs and power supplies. Capacitors filter out unwanted frequency components.The impedance of a capacitor decreases with increasing frequency (Z = 1/(2πfC)). At low frequencies, the capacitor presents high impedance, allowing signals to pass. At high frequencies, the capacitor presents very low impedance, effectively shorting high-frequency noise to ground.5. Temperature Compensation: Improves circuit stability by compensating for temperature-dependent variations in other components.Analysis: Since the timing capacitor's value determines the oscillation frequency, it must remain stable across temperature variations. Capacitors with positive and negative temperature coefficients can be combined for temperature compensation.When operating temperature increases, one capacitor's value increases while another decreases. Since they're connected in parallel, the total capacitance remains relatively stable. Similarly, when temperature decreases, the opposite occurs, maintaining stable oscillation frequency.6. Timing: Used with resistors to determine circuit time constants in RC timing circuits.When a signal transitions from low to high and passes through an RC circuit, the capacitor's charging characteristics prevent the output from changing immediately. Instead, there's a gradual transition, creating a time delay that depends on the RC time constant.7. Tuning: Used in frequency-selective circuits such as those in mobile phones, radios, and televisions for channel selection and filtering.8. Switching/Rectification: Controls the switching of semiconductor components at predetermined times in power conversion circuits.9. Energy Storage: Stores electrical energy for release when needed. Examples include camera flash units, defibrillators, and backup power systems. Modern supercapacitors can store energy approaching the levels of small lithium batteries.III Capacitor TypesThere are several different types of capacitors that vary by polarity, performance, cost, and application. Below are the most common capacitor types: aluminum electrolytic, ceramic, tantalum, film, mica, and polymer capacitors, along with their features, applications, and selection criteria.1. Aluminum Electrolytic CapacitorAluminum electrolytic capacitors use aluminum foil electrodes separated by electrolyte-impregnated paper. The thin aluminum oxide layer acts as the dielectric. Due to the oxide film's unidirectional conduction properties, these capacitors are polarized.Advantages: High capacitance values, can handle large ripple currents, cost-effective for bulk energy storage.Applications: Power supply filtering, energy storage, motor starting, audio coupling.Disadvantages: Large tolerance (typically ±20%), significant leakage current, limited high-frequency performance (typically below 100kHz), temperature sensitivity, finite lifetime due to electrolyte evaporation.2025 Update: Modern aluminum electrolytics now feature improved electrolytes with operating temperatures up to 150°C and lifetimes exceeding 10,000 hours at rated temperature.2. Ceramic CapacitorCeramic capacitors use ceramic materials with high dielectric constants, such as barium titanate, formed into discs, tubes, or chips. Silver electrodes are applied through firing processes.Available in two main classes:Class 1 (C0G/NP0): Temperature-stable, low loss, used in precision timing and filteringClass 2 (X7R, X5R, Y5V): Higher capacitance density but with temperature and voltage dependenceApplications: High-frequency circuits, decoupling, bypass, timing circuits, RF applications.Advantages: Excellent high-frequency characteristics, low ESR, small size, non-polarized, good temperature stability (Class 1).Disadvantages: Voltage and temperature dependence (Class 2), microphonic effects in some types, limited capacitance values in stable types.2025 Update: Multi-layer ceramic capacitors (MLCC) now achieve capacitance values up to 1000µF in small packages, with improved temperature stability and reduced acoustic noise.3. Tantalum CapacitorUses sintered tantalum powder as the anode with tantalum pentoxide as the dielectric and manganese dioxide or conductive polymer as the cathode.Advantages: Excellent temperature and frequency characteristics, low leakage current, stable capacitance, long service life, high capacitance-to-volume ratio, low ESR (polymer types).Applications: Mobile devices, computers, automotive electronics, medical equipment, aerospace applications.Disadvantages: Higher cost, susceptible to voltage transients, can fail catastrophically if overvoltaged.2025 Update: Polymer tantalum capacitors now offer ESR values below 10mΩ and improved surge current handling, making them ideal for high-performance applications.4. Film CapacitorStructure: Film capacitors use plastic films such as polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), or polycarbonate as dielectrics, with metal foil or metallized film electrodes.Common types include:Polyester (PET): General purpose, good stabilityPolypropylene (PP): Low loss, high frequency capabilityPolystyrene (PS): Excellent stability, low temperature coefficientPolycarbonate: Good temperature stability (now less common)Advantages: Non-polarized, high insulation resistance, excellent frequency characteristics, low dielectric loss, self-healing properties (metallized types).Applications: Power electronics, motor drives, lighting ballasts, audio equipment, power factor correction, snubber circuits.2025 Update: New film capacitor technologies include improved polypropylene films for electric vehicle applications and enhanced metallization techniques for better self-healing properties.5. Mica CapacitorStructure: Uses natural mica sheets as the dielectric with silver electrodes, assembled in a stacked configuration and encapsulated in epoxy or molded plastic.Characteristics: Extremely stable, low temperature coefficient, high Q factor, excellent frequency characteristics up to several GHz.Applications: RF circuits, oscillators, filters, precision timing circuits, test equipment, military and aerospace applications.Advantages: Outstanding stability, low loss, predictable temperature coefficient, radiation resistant.Disadvantages: Higher cost, limited availability, larger size compared to ceramic alternatives.6. Polymer CapacitorStructure: Uses conductive polymers as the cathode material, available in both aluminum and tantalum versions. The polymer provides better conductivity than traditional liquid electrolytes.Advantages:Extremely low ESR (as low as a few milliohms)High ripple current capabilityStable capacitance over frequencyNo voltage derating required within ratingsFail-safe behavior (no catastrophic failures)Long operational lifeApplications: CPU power supplies, graphics cards, high-frequency switching converters, automotive electronics, telecommunications equipment.2025 Update: Hybrid polymer capacitors now combine the benefits of wet and polymer electrolytes, offering improved performance across temperature ranges and extended lifetimes.IV Capacitor Value Marking Methods1) Direct Marking MethodUses letters and numbers to directly mark values on the component body. For example, 1µF denotes 1 microfarad. Some capacitors use "R" to denote decimal points, such as R56 for 0.56 microfarads.2) Character-Symbol MethodCombines numbers and characters where symbols represent units: p (pico), n (nano), µ (micro), m (milli), F (farad). Examples:p10 = 0.1 pF1p0 = 1 pF6P8 = 6.8 pF2µ2 = 2.2 µFTolerance markings for values less than 10pF: B=±0.1pF, C=±0.2pF, D=±0.5pF, F=±1pF.3) Color Code MethodSimilar to resistor color codes, uses colored bands or dots to indicate capacitance, tolerance, and voltage rating.4) Numerical Code MethodThree-digit system where the first two digits are significant figures and the third digit is the multiplier (power of 10). Examples:272 = 27 × 10² = 2700 pF473 = 47 × 10³ = 47000 pF105 = 10 × 10⁵ = 1,000,000 pF = 1 µF2025 Update: QR codes are now being used on some capacitors to provide detailed specifications and traceability information accessible via smartphone apps.V Capacitor Characteristics(1) Capacitance and Tolerance: The maximum allowable deviation between actual and nominal capacitance. Standard tolerance grades include:Grade I: ±5%Grade II: ±10%Grade III: ±20%Precision grades: ±1%, ±2%, ±0.5%, ±0.1%(2) Rated Working Voltage: The maximum continuous voltage a capacitor can withstand while maintaining reliable operation. Higher voltage ratings generally require larger physical sizes for the same capacitance.(3) Temperature Coefficient: The relative change in capacitance per degree of temperature change. Smaller temperature coefficients indicate better stability.(4) Insulation Resistance: Indicates leakage current levels. Higher insulation resistance means lower leakage. Typical values range from megohms to teraohms depending on capacitor type and size.(5) Dielectric Loss: Energy dissipated as heat during operation, usually expressed as loss tangent (tan δ) or dissipation factor (DF).(6) Frequency Characteristics: How electrical parameters vary with frequency. Different capacitor types have different frequency limitations:Small mica capacitors: up to 1 GHzCeramic capacitors: up to several GHzFilm capacitors: up to 1 MHz (depending on type)Electrolytic capacitors: typically below 100 kHz2025 Update: New measurement techniques now allow characterization of capacitor behavior up to millimeter-wave frequencies, important for 5G and beyond applications.VI Capacitor Electrical SymbolsHere are the standard schematic symbols for various capacitors:(1) ①: Basic capacitor symbol for non-polarized types (ceramic, film, mica)(2) ②-⑥: Polarized capacitor symbols (electrolytic, tantalum) - curved plate indicates negative terminal(3) ⑦: Variable capacitor symbol(4) ⑧: Adjustable (trimmer) capacitor symbolStandard Capacitor ValuesCapacitors are available in standard values following the E-series. Here are the most commonly found values:Standard Capacitor ValuespFpFpFpFµFµFµFµFµFµFµF1.01010010000.010.11.0101001000100001.51515015000.0150.151.5151501500150002.22222022000.0220.222.2222202200220003.33333033000.0330.333.3333303300330004.74747047000.0470.474.7474704700470006.86868068000.0680.686.868680680068000VII How to Choose Capacitors Correctly?7.1 Selection Requirements1) Application-Based Selection:Power Supply Filtering: Aluminum electrolytic or polymer capacitorsHigh-Frequency Decoupling: Ceramic capacitors (MLCC)Precision Timing: C0G/NP0 ceramic or film capacitorsAudio Coupling: Film or non-polarized electrolytic capacitorsMotor Starting: Film capacitors rated for AC operationEnergy Storage: Supercapacitors or high-capacity electrolytics2) Voltage Rating Selection: Choose capacitors with voltage ratings 1.5-2 times the maximum expected voltage. For pulsed applications, consider peak voltages. In high-temperature environments, derate voltage further.3) Temperature Considerations: Select capacitors rated for the expected operating temperature range. Consider both ambient temperature and self-heating effects.4) Frequency Response: Match the capacitor's frequency characteristics to your application requirements. High-frequency applications require low-ESR types.5) Lifetime Requirements: Consider operational lifetime, especially for electrolytics. Calculate expected life based on temperature and ripple current.6) Environmental Factors: Consider humidity, vibration, shock, and chemical exposure in the operating environment.7.2 Advanced Selection Criteria1) Frequency-Based Selection:DC to 1 kHz: Aluminum electrolytic, tantalum1 kHz to 1 MHz: Film capacitors, low-ESR electrolytics1 MHz to 100 MHz: Ceramic capacitors (X7R, X5R)Above 100 MHz: C0G/NP0 ceramic capacitors2) Temperature Stability Ranking:C0G ceramic ≥ Film ≥ Solid tantalum ≥ Mica ≥ X7R ceramic ≥ Aluminum electrolytic3) ESR Performance Ranking:Ceramic ≥ Film ≥ Polymer ≥ Solid tantalum ≥ Wet tantalum ≥ Aluminum electrolytic4) Ripple Current Capability:Film ≥ Polymer ≥ Aluminum electrolytic ≥ Ceramic ≥ Tantalum2025 Update: New selection tools include AI-powered capacitor selection software that considers multiple parameters simultaneously and suggests optimal components based on application requirements.7.3 Common Selection Mistakes to Avoid1. Voltage Derating: Always provide adequate voltage margin. A 10V capacitor should not be used in a 10V circuit.2. Temperature Effects: Consider both ambient temperature and self-heating. Electrolytic capacitors lose significant capacitance at low temperatures.3. Frequency Mismatch: Using electrolytics in high-frequency applications or ceramics in precision low-frequency circuits.4. Ignoring ESR: High ESR can cause excessive heating and poor performance in switching applications.5. Lifetime Calculations: Not considering the impact of temperature and ripple current on electrolytic capacitor lifetime.6. Mechanical Stress: Ignoring thermal expansion, vibration, and mechanical mounting stress.2025 Update: Modern design software now includes comprehensive capacitor models that account for parasitic effects, aging, and environmental factors, helping prevent common selection errors.VIII Emerging Capacitor Technologies (2025)1. Supercapacitors (EDLC/Ultracapacitors)Supercapacitors bridge the gap between traditional capacitors and batteries, offering:Capacitance values from 0.1F to over 3000FHigh power densityLong cycle life (>1 million cycles)Fast charging/dischargingWide temperature range operationApplications: Energy harvesting, backup power, automotive start-stop systems, renewable energy storage, IoT devices.2. Solid-State CapacitorsNew solid-state electrolyte technologies offer:Improved safety (no liquid electrolyte)Extended temperature rangeBetter reliabilityReduced size3. Graphene-Enhanced CapacitorsGraphene electrodes provide:Ultra-low ESRHigh frequency capabilityImproved thermal managementEnhanced durabilityIX ConclusionCapacitor technology continues to evolve rapidly, with improvements in materials science, manufacturing processes, and design techniques leading to better performance and lower costs. Whether you're beginning a new design or updating an existing one, it's essential to stay current with the latest capacitor technologies and selection criteria.The key to successful capacitor selection lies in understanding your application requirements and matching them to the appropriate capacitor characteristics. Consider not just the basic electrical parameters, but also environmental factors, lifetime requirements, and cost constraints.Modern design tools and simulation software can help optimize capacitor selection, but fundamental understanding of capacitor behavior remains crucial for successful circuit design.Frequently Asked Questions (FAQ)1. What is a capacitor used for?A capacitor is a passive electronic component used to store electrical energy in an electric field. Common applications include power supply filtering, signal coupling, timing circuits, energy storage, and frequency tuning.2. What is the difference between polarized and non-polarized capacitors?Polarized capacitors (like electrolytics and tantalums) have positive and negative terminals and must be connected correctly. Non-polarized capacitors (like ceramics and films) can be connected either way.3. How do I choose the right voltage rating?Select a voltage rating at least 1.5-2 times higher than the maximum voltage in your circuit. For critical applications or harsh environments, use even higher derating factors.4. What's the difference between ESR and ESL?ESR (Equivalent Series Resistance) represents resistive losses, while ESL (Equivalent Series Inductance) represents inductive effects. Both affect high-frequency performance.5. Can I replace an electrolytic capacitor with a ceramic one?It depends on the application. Ceramics offer better high-frequency performance but may not provide sufficient capacitance for power supply filtering. Consider the specific requirements of your circuit.6. How long do capacitors last?Lifetime varies by type: ceramic and film capacitors can last decades, while electrolytic capacitors typically last 2,000-10,000 hours at rated temperature. Actual lifetime depends on operating conditions.7. What causes capacitor failure?Common failure modes include overvoltage, overtemperature, aging (especially in electrolytics), mechanical stress, and manufacturing defects. Proper selection and derating minimize failure risk.8. Are supercapacitors better than regular capacitors?Supercapacitors excel in energy storage applications but have lower voltage ratings and higher cost per farad. They're complementary technologies rather than direct replacements.9. How do I measure capacitor performance?Key parameters include capacitance, ESR, leakage current, and temperature coefficient. Specialized LCR meters and impedance analyzers provide accurate measurements.10. What's the impact of temperature on capacitor performance?Temperature affects capacitance value, ESR, leakage current, and lifetime. Different capacitor types have varying temperature sensitivities, with C0G ceramics being most stable.2025 Update InformationLast Updated: November 2025

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.

ⅠIntroduction This project mainly introduces how to DIY a Simple Audio Player with  Amplifier LM386 . But before this project, it is very essential to know some basics of LM386. Therefore, the first of this article is about LM386 audio amplifiers and the second part we will have a look at the practical appliance of Simple Audio Player with Amplifier LM386. Catalog ⅠIntroduction Ⅱ Amplifier LM386 Related Video: Ⅲ LM386 Basics 3.1 LM386 Datasheet 3.2 LM386 Pinout 3.3 LM386 Features Ⅳ  Project Introduction 4.1 Hardware Required 4.2 Getting Ready with Your WAV Audio Files: 4.3 Circuit 4.4 Code 4.5 Working of this Arduino Music Player: Ⅴ FAQ How to make an LM386 audio amplifier circuit Amplifier LM386 Video Description: In this Video, We will explore how to use the popular LM386 class AB audio amplifier IC to build a simple mono 1 watt audio amplifier.  Ⅲ LM386 Basics Despite the fact that LM386 audio amplifiers are quite old. They do, however, have a lot of useful information. Assume your audio player has poor sound quality. You want to boost the volume. They are a good option. Because of the low voltage supply and the fact that it works well with a battery.   3.1 LM386 Datasheet You completed an audio circuit  . However, the sound is too faint. Many people use the LM386 to boost the sound to a speaker. The LM386 is a low-power audio amplifier. Also, you should be able to work with a battery,  It has a similar shape to  IC-741  and DIP-8. So, small and simple. Even if it's small, it makes a big sound. But...better. it's If you have previously read the LM386 Datasheet.   3.2 LM386 Pinout Figure1:pinout In DIP-8, we frequently use the LM386. There are only a few pin connections. Other packets are also the same. For example, SOP-8, TSSOP-8, and so on.   3.3 LM386 Features   Ⅳ  Project Introduction Including sounds or music in our project will always make it look and sound much more appealing. If you're working with an  Arduino  and have a lot of free spins, you can easily add sound effects to your project by purchasing an extra SD card module and a standard speaker. In this article, I'll show you how to play music and add sound effects with your  Arduino board, as well as introduce the IC LM386 Amplifier  , which we'll use in this process. We will play the.wav music files stored on an SD card in this project. The Arduino will be programmed to read these.wav files and play the audio on a speak through an LM386 Audio amplifier.   Figure2: Project     4.1 Hardware Required Arduino Due Board8-ohm speaker or headphonesArduino shield with an SD card with cs CS 4 (like the Ethernet shield)Components to build an external audio amplifierLM386 (low power audio amplifier)10 kohm potentiometer10 ohm resistor2 x 10 µF capacitor0.05 µF (or 0.1 µF) capacitor250 µF capacitor   4.2 Getting Ready with Your WAV Audio Files: The audio file to be stored on the SD card must be in.wav format and have 44100 Hz, 16-bit stereo quality. We need audio files in.wav format to play sounds from an SD card using Arduino because the Arduino Board can only play audio files in a specific format, which is wav format. There are many mp3 shields available for use with Arduino to create an Arduino mp3 player. Alternatively, to play mp3 files in Arduino, there are websites that will convert any audio file on your computer into that specific WAV file.   4.3 Circuit The shield is placed on top of the Due, and a micro-SD card is inserted into the slot. The card's root directory contains a.wav file called "test.wav." For a quick test, connect a pair of headphones to the ground and DAC0 while keeping the polarity in mind. To add a speaker to the board, connect an amplification circuit between the DAC0 pin and the speaker. The amplification circuit will boost the speaker's volume,  There are numerous audio amplifiers available, with the LM386 being one of the most common. The following scheme demonstrates how to construct the circuit using the LM386 and a variety of components. You can power the LM386 by connecting the Vs pin to various voltage sources, such as the +5 V on the Arduino Due's 5V pin or an external 9V  battery,  The capacitor is connected to pins 1 and 8 of the LM386 provides the amplifier's gain. The gain is set to 200 with the 10 F capacitor, and 50 without the capacitor. The volume of the amplifier can be adjusted using the potentiometer. Caution: Do not connect the speaker directly to the Arduino Due's pins.   Figure3 : Circuit   Figure4: LM386 mounting on breadboard   4.4 Code   4.5 Working of this Arduino Music Player: Simply press the button connected to pin 2 after programming your Arduino, and your Arduino will play the first song (saved as 1.wav) for you. You can now press the button again to change your track to the next song, 2.wav. Similarly, you can listen to all four songs. You can also play/pause the song by pressing the pin 3 button. Press it once to pause the song and once more to resume it from where it left off. Watch the video below to see the entire process in action (or maybe to relax with some songs). I hope you had a good time with the project. It is now up to your imagination to incorporate them into your projects. You can create a speaking clock, voice assistant, talking robot, voice alert security system, and many other things.   Ⅴ FAQ 1. How many watts is LM386? 700mW, mono, 5- to 18-V, analog input Class-AB audio amplifier. 2. How do you calculate LM386 gain? Voltage Gain Analysis: Without any external components, it has a gain of Gv = 2x15K/(150+1350) = 20 (26 dB). With a capacitor (or shortcutting) between pins 1 and 8 , it has a gain of Gv = 2x15K/150 =200 (46dB). 3. Is LM386 any good? The LM386 is a well-designed, basic workhorse that does a decent job when its hooves are kept clean and it's well-fed. Aside from having a slow op-amp stage by today's standards, it has decent performance. It can also sound horrible if you neglect it. 4. What is an audio amplifier circuit? The circuit of the audio amplifier consists of a transistor a device to apply the input signals and a speaker at the output. The transistors are connected based on the necessity. The important factors that need to be considered while designing a audio amplifier is gain,noise, frequency response and distortion. 5. Which amplifier can be used for audio amplifier? An audio power amplifier (or power amp) is an electronic amplifier that amplifies low-power electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is high enough for driving loudspeakers or headphones. 6. What is the need of power amplifier? The function of a power amplifier is to raise the power level of input signal. It is required to deliver a large amount of power and has to handle large current. The characteristics of a power amplifier are as follows − The base of transistor is made thicken to handle large currents.

DescriptionFor everyone,electrical energy is essential. We always trying to get unlimited electrical energy without spending money. Now kynix share a simple design proposed as small wind turbine for home use or low power usage,it requires low initial cost and gives best return in terms of electrical energy. Use the following small wind turbine circuit and setup to charge laptop,to charge electronic gadgets or to electronic appliances in home and outstations.  NoteBefore we start,we should emphasis that we should note:* High voltage caution! This Circuit Involves in operating High voltage handle with extreme care.* Handle the Wind Turbine Generator and Rotor blade as per the Instructions given by manufacturer.  Windmill Generator DesignSmall 12V wind turbine generator is capable of producing alternate energy through wind, the Bridge rectifier and controller rectifies the energy came from wind turbine generator and regulator-battery charger circuit helps 12V/4.5Ah SLA battery to get charging, then Step-up inverter circuit produce high voltage AC enough to operate home appliances.  Schematic of Wind Turbine Generator is as following.  WorkingThere are five stages:  1. 12V Wind turbine generator/Bridge Rectifier Circuit  2. Regulator / Battery charger circuit  3. Inverter circuit using CD4047  4. mosFET Drivers  5. Output Stage 12V Wind Turbine Generator12 Volt wind turbine or windmill available with different watts range, choose depends on your requirement. Bridge RectifierWe know the bridge rectifier converts AC supply into DC and here we used 1N4007 diode as a bridge rectifier element, it converts the energy from wind turbine into Direct Current (DC) supply. Regulator / Battery ChargerThe LM317 adjustable three terminal Positive voltage Regulator used here and it can give output voltage range from 1.25 V to 37 V with more than 1.5A current rating. final output from the regulator is given to 12/4.5Ah SLA Battery, this Battery provides DC bias to the inverter circuit. Regulator LM317 output voltage Vout can be obtained asVout = 1.25V *(R2/R1+1) R2 => R2+VR1 for given inverter circuit.Inverter Circuit using IC CD4047 (Switching Pulse Oscillator) Monostable / Astable multivibrator  CD4047 used here to produce switching pulse, This IC works in low power and available in 14 pin Dual in line package. It provides full Oscillation output F at Pin 13, 1/2 of oscillation at Pin 10 as Q and Pin 11 as Q’. each output pin gives 50% duty cycle.f = 1/8.8RCHere R => R4+VR2 and C=> C3. by using this formula we can obtain frequency output at pin 13. For pin 10 and 11 the formula changes as f=1/4.4RC. MosFET driversIRF540 N Channel power mosfet from vishay siliconix used as a switching drivers for this inverter circuit. It gives fast switching, and have high operating temperature characteristics (175ºC). Output StageMain part of wind turbine generator is output stage, here transformer X1 is used in reverse with specifications as 230V primary, 9V-0-9V / 1.5A secondary winding center tapped transformer. MOV (Metal oxide Varistor) protects electronic device connected at output. Wind turbine generator output voltage is directly fed into LM317 positive Regulator circuit and it is adjusted to give 12 volt output and Battery connected to this bias through (3A, 50V) Schottky diode. The CD4047 IC is connected and configured as Astable multivibrator, When we turn ON SPST switch this circuit starts oscillation. Output Q and Q’ are directly fed into switching power mosfet IRF540 & drives X1 transformer secondary winding, here the current flow occurs particular duration and not for particular duration. So varying electromagnet induced and primary winding coil produce EMF, hence we get Alternating current output. Depends on the count of winding and switching frequency output Voltage/Frequency get varied.