![]() The ground level of a 5 V source and a 220 VAC source can be quite different the ground voltages observed by the 5 V source do not need to be same as that of the 220 VAC. Although the term “ground level” voltage sounds like it is always 0 V, this is not necessarily the case. The circuits at the side where the optocoupler’s Input/Output (I/O) are located are meant to be protected from possible risks on either side. Why aren’t ground levels on an optocoupler’s input and output side connected? Optocouplers are not directly soldered on the circuit instead they are placed in an Integrated Chip (IC) socket so they can always be replaced easily if burned.įor a detailed explanation of the internal workings of an optocoupler and how to build your own using an LED and photodiode, see an earlier post called Protecting an MCU: Build your Own Optocoupler. ![]() In case of a malfunction, the optocoupler burns and rest of the circuit is not affected. However, optocouplers can be used for securing expensive components. Replacing burned components on a Printed Circuit Board (PCB) can be highly inconvenient. Some commercial-scale optocouplers can withstand up to 10 KV of Input-output isolation voltage which are used for protection against lightning strikes. Most electronic components operate below 10 V, and if a lighting surge enters the system, it can induce voltages up to 10 KV – which is enough to fry electronic components at once. Optocouplers are also called photodiodes, optoisolators, photocouplers, and optical isolators.Ī standard optocoupler such as PC817 supports up to 5 kV of input-output isolation voltage. In case the high voltage circuit induces an electrical surge, the surge remains only on the output side of the optocoupler, and the circuit at input side remains safe and unaffected, as both sides are electrically isolated. Optocouplers create a safe connection between high voltage equipment and microcontrollers with a means of complete electrical insulation. Optocouplers are often used to reject back EMF, noise, and electrical surges from entering an MCU circuit. How to protect sensitive circuits from high voltages Optocouplers are extensively used in electronics, electrical, and communications systems. Optocouplers also make it convenient to control the connection between two circuits by connecting and disconnecting them via an optocoupler. However, optocouplers are more sophisticated than fuses. Optocouplers can avoid a great deal of cost in replacing components by protecting them. Signal transmission between circuits of different potentials and impedances.Įl817 ic, el817 photocoupler, el817 datasheet, el817 optocoupler, el817 pinout, el817 price, el817 optocoupler circuit, el817 circuit, el817 series, 4 pin phototransistor, el817 4 pin phototransistor.Optocouplers not only protect sensitive circuits but enable an engineer to design a variety of hardware applications.Home appliances, such as fan heaters, etc.System appliances, measuring instruments.High isolation voltage between input and output (Viso = 5000 V rms ).Īpplications of EL817 Phototransistor Photocoupler:.Current transfer ratio ( CTR : 50 ~ 600% at IF = 5mA, VCE = 5V).Images/Pinout of EL817 Phototransistor Photocoupler Features of EL817 Phototransistor Photocoupler: It transforms useful input signal into light, sends it across the dielectric channel, captures light on the output side and transforms it back into electric signal. Opto - isolators are usually used for transmission of digital (on / off) signals, but some techniques allow use with analog (proportional) signals.Īn opto-isolator connects input and output sides with a beam of light modulated by input current. ![]() ![]() This common type opto - isolator consists of an LED and a phototransistor in the same package. Commercially available opto - isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 10 kV/us. Opto - isolators prevent high voltages from affecting the system receiving the signal. A photocoupler, or optical isolator or an opto - isolator is a component that transfers electrical signals between two isolated circuits by using light. They are packaged in a 4-pin DIP package and available in wide - lead spacing and SMD option.ĮL817 series of devices are Photo transistor based photo coupler. The EL817 Phototransistor Photocoupler series of devices each consist of an infrared emitting diodes, optically coupled to a phototransistor detector. ![]()
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