Driving relay directly from optocoupler, what is best. Typical relay current driver circuit use an optocoupler connected to a transistor which then drives the relay. Im wanting to control two 12v relays by means of an npn transistor, and will. Yes, you understood how the optocoupler works, and yes, the phototransistor should close the relay circuit when voltage is applied to the led.
Circuit options explore issues, solutions for relay drivers. The transistor is typically and solely employed for operating the relay in response to the commands received from the preceding control stage. What you need to test photocoupler optocoupler pc817 optocoupler resistors 1k. Driving an electromechanical relay from a lowvoltage digital io line is a common situation, but there are. Here is a simple microcontrollerrelay interface circuit with perfect galvanic. Review ac relay circuits optocouplers triacs duration. For demonstrating the working of this relay module, we have used.
Pc817 datasheet, pc817 high density optocoupler technical data, buy pc817. Referring to the above circuit diagram we see that the configuration only. The simple one contains one led and one phototransistor which we have used in the circuit, other types contains many leds and phototransistors. The wellestablished relay driving circuit uses an optocoupler to isolate the grounds and noise coupling between the lowvoltage digitalcontrol signal circuit left and the relay as load right. How to connect a relay through an optocoupler homemade. The wellestablished relaydriving circuit uses an optocoupler to isolate the grounds and noise coupling between the lowvoltage digitalcontrol signal circuit. How to make an 8 channel relay driver board optically isolated. The phototransistor can be used to switch current in the output circuit. Figure 14 shows how to interface two ttl circuits, using an optocoupler circuit that provides a noninverting action. Please be aware that all data in the graph are just for reference and not for guarantee. The following post describes how to drive a relay by using an isolated method, or through an optocoupler device. Relay coil and sensitive logic circuits optimized to switch relays of 12 v rail capable of driving relay coils rated up to 6. Optocoupler tutorial about how optocouplers and optoisolators use light to.
Here, the optocoupler led and currentlimiting resistor r1 are connected between the 5v positive supply rail and the outputdriving terminal of the ttl device rather than between the ttl output and ground, because ttl outputs. Both the circuits are very simple and using very few components which are a pc817 optocoupler, one transistor, one relay and two resistors. Pc817 datasheet, pc817 high density opto coupler technical data, buy pc817. A relay driver circuit is a circuit which can drive, or operate, a relay so that it can function appropriately in a circuit. The question was asked by one of the interested members of this blog, miss. These simple optocoupler relay driver circuits can be used in variety of electronic projects. A relay driver is nothing but an additional transistor stage attached with the relay which needs to be operated. Optocouplers and optoisolators can be used on their own, or to switch a range of other larger electronic devices such as transistors and triacs providing the required electrical isolation between a lower voltage control signal, for example one from an arduino or microcontroller, and a much higher voltage or mains current output signal. As shown in the following circuit diagram, the relay driver may consist a npn transistor or a pnp transistor. In this 4channel relay driver circuit we have used an optocoupler whic his triggered by active low signal, to trigger the npn transistor which further drives the relay. How to test photocoupler pc817optocoupler pc817 youtube.