![]() Photodiode Optocouplers are better than phototransistor optocouplers in a linear relationship between the current and the light. Photodiode vs Phototransistor optocouplers This can be used in a switched-mode power supply (SMPS) or controlling different circuitry where error detection at the output is required. The illumination of LED is varied or controlled with a sample of voltage or signal, then the phototransistor also provides variable conduction to the output. ![]() In this mode, LED will get a pulse of signal with a variation. The motor will be ON or OFF completely in this mode. ![]() For example in a motor drive using a microcontroller, the motor needs high current and high voltage. This mode is used where needs to protect the microcontroller pins from the high voltage of the output circuit. In saturation mode LED will be ON or OFF so, the output transistor is fully off or fully ON, which means conducting or non-conducting mode. Saturation and linear Mode operation of the optocoupler Saturation mode In SMPS or any power supply circuit optocoupler may use to detect the varying DC sample voltage of output and give feedback to input to control the power supply with maintaining the complete electrical isolation between the input and output circuit. Microcontroller output is directly connected with the input of LED of the optocoupler, and the Phototransistor is connected with the output component like Relay or Triac for 220v Ac connection with the Motor. In this case, we cannot directly connect both. If we need to connect a 220v AC Motor that is controlled by a microcontroller or Arduino etc. Here computer system circuit and Motor controlling device is fully electrically isolated, and there is no interference of electrical signal. The optocoupler is commonly used where A computer system or any digital system needs to control or drive a motor or control the high voltage devices. Optoucpler IC uses an LED optically coupled to a phototransistor, photodiode, or Photo TRIAC in a single package Opto-Triac (photo-Triac) is also used at the place of the Photo-transistor in the optocoupler for direct AC supply control at the output. The electrical isolation is very high generally 10KV or higher. There is non-conductive material and space is transparent between LED and Photo-transistor. Both input and output circuit is fully Electrically isolated. Here the input circuit is connected only with the LED pins of the optocoupler, Output circuit is connected to the phototransistor. When the power is given to led, the led emits the light and that light falls on the BASE of the phototransistor, After falling light on the base of the phototransistor this will activate and the output circuit connected with the transistor can be controlled. And the right side is a phototransistor, this phototransistor is sensitive to light. The left side is a led connected through pin 1 and pin 2. This is the internal circuit mechanism of an optocoupler. in this system, the Input Light is proportional to the current at the output. ![]() when light is emitted by an LED and that light hits on the photosensor (Photodiode, Phototransistor, PhotoTriac) then the photosensor starts to flow the current. This is also used to eliminate unwanted noises.Īn optocoupler consists a Transmitter as IR LED and a Receiver as a photosensitive component. ![]() Optocoupler is mainly used to prevent an electrical collision by the isolate the circuit. Opto-coupler is also called photocoupler, optoisolator or optical isolator. Here both circuit is electrically isolated from each other. In other words, an optocoupler is used to transfer electrical signals between two circuits optically. Opto-coupler is an electronic component that is used to conduct the electrical signals from one circuit to another circuit without directly being connected between them.
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