The PC817X family of optocoupler ICs consists of an IRED (infrared emitting diode, or IR LED) and a phototransistor that is optically coupled to it. Its role is to turn on when an internal phototransistor receives the light emitted by an infrared LED. There are no hard electrical connections in these two parts; As a result, it provides convenient optical noise isolation compared to the use of resistors and capacitors. pc817Simple but useful, trustworthy when transferring signals from one part of a circuit to another in low-voltage DC devices and MCUs.
IR LED input
Pin-1: Anode (+pin inputs the logic signal to the internal IR
pin-2: cathode (-pin with circuit and power supply connected to a common ground.
Phototransistor output
Pin 3: The emitter pin is similar to the cathode pin. It provides a ground connection.
PIN-4: The collector pin transmits a logical output when receiving an IR signal.
Optocoupler electronic symbol
OptocouplersAllows you to send signals to a circuit that is completely isolated from the electronic world. Think of an optocoupler as a transistor, except that it sends light while a phototransistor from another circuit receives the signal and turns the circuit on or off. From an electrical point of view, complete isolation is achieved.
High VCEO (collector-emitter voltage): 80V MAX4pin DIP package and SMT package Input and output internal protection CTR (current transfer ratio) Available in multiple levels Fall Time: 18 s Rise Time: 18 s Maximum collector current: 50mA Maximum power consumption: 200mW High isolation voltage between input and output: 50kV cut-off frequency: 80kHzAs an optocoupler, the PC817 IC is beneficial for reducing noise between the input signal and the electrical circuit, typical applications include:
The IO of the microcontroller isolates, the basic noise-coupled circuits in the switching circuits of conventional galvanic isolation, the switching circuit, the Internet of Things device signal transmission
The upper circuit uses a phototransistor-based optocoupler circuit. Its function is similar to that of a standard DC transistor switch. The PC817, a low-cost phototransistor-based optocoupler, is used in the schematic. The S1 switch will control the IR LED. When the switch is turned on, the 9V battery source will supply current to the LED through a 10K current-limiting resistor. R1 resistor controls the intensity. If we change that value and reduce the resistance, the intensity of the LED will be high, resulting in a high transistor gain.
Transistors, on the other hand, are phototransistors that are controlled by internal infrared LEDs; When the LED emits infrared light, the phototransistor comes into contact and VOUT becomes zero, shutting down the load that spans it. It is important to remember that according to the datasheet, the collector current of the transistor is 50mA. vout 5v is provided by r2. The R2 resistor is a pull-up resistor.
PC817 Application Note
Optocouplers have a lower output current. For example, the maximum output current of the PC817 is 50mA. As a result, high-current components (e.g., motors, etc.) cannot be directly connected to the optocoupler output. In this case, a transistor must be used to provide the current.
The above is based on PC817 optocouplerArduino UNO boardwith2n2222Example of Arduino interface circuit wiring for a transistor.
The first 220 resistors are connected between pin 9 on the Arduino board and the positive pole of the optocoupler drawn from the chip; This resistor reduces the voltage on the board so that it does not overdrive the LEDs and burn them out. If you are using a different optocoupler than the Sharp PC817, you may need to adjust that resistor to compensate; The maximum LED input voltage of the PC817 is 14 volts, the resistor lowers the 5 volts of the Arduino to 125 volts.
The second 220 resistor limits the current flowing through the phototransistor in the chip, the Sharp PC817 will handle 50 volts at 35mA, but in these conditions it will get very hot and it won't last long, so you can put a current limiting resistor in the circuit to keep it in those conditions and that's it.
tlp521、hcnr201moc3021、mocn136
1. What is the forward voltage of PC817?
The input voltage (forward) of the PC817 is 125v。
2.How does an optocoupler work?
An optocoupler consists of a transmitter (IR LED) and a receiver (photosensitive element). When LEDs emit light and shine on a photoelectric sensor (photodiode, phototransistor, phototriac switch), the photoelectric sensor begins to generate an electric current. In this system, the input light is proportional to the output current.
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