Opto isolated dual relay module (Arduino)

Opto isolated 2 relay module components

This is a dual relay module using the usual Songle SRD-05VDC-SL-C relays.

The module has two spdt relays which can switch:
10A 250V AC
10A 30V DC
Although this would be less for inductive loads.

The module is an active low device, which means that the input must be low to switch the relay on.

The module also contains 817c optocouplers and the input circuit can be isolated from the relay circuit by removing the JD-VCC jumper and providing a separate power supply for the relay.

Arduino 2 Relay Module

Opto isolated 2 relay module connections

The following circuit diagram shows the relay module with the input isolated from the relay.

Arduino 2 Relay Module Isolated// Opto-isolated relay blink sketch

The following photo shows the Arduino Uno running the sketch listed above with the relay wired to two led strips and a 12v battery.

2 relay module arduino led strip


Keyes SR1y Relay module circuit

How does an Electric Relay work?

4 thoughts on “Opto isolated dual relay module (Arduino)

  1. himo

    Is it possible to post the values of R1 and R2? Also the type of transistor Q1? Also, why is there a optocoupler at all? in what situations is it needed? Thre relay is already separated from the mains voltage.

    1. Solarman

      If your logic board is 3.3v and can not power the magnet of the relay. You dont want to risk sending more voltage into say an 8266 than you need or risk burning it out.


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