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2-Channel 5v Relay Module

I have several dozen relay boards all of which require a LOW(grd) signal on the input to operate the relay.
So, what do your relay boards require on the input to operate the relay ?


2 Answers


Usually the best way to control a relay is to use a low on one pin of the coil with the other end connected to the + side of the power supply. Almost always, a micro-controller has more sink current available than source current. Don’t for get to check if your circuit includes a “snubber” diode across the coil, or you run the risk of the reverse EMF from the coil ruining the output pin of the micro-controller.


I just verified that the 2-Channel 5V Relay Module (and the 4 and 8 channel variations) work as such: Connect GND to ground, VCC to 5V, and IN1 to INx (where x is the last input 2, 4, 8 etc…).

The device is active low which means that connecting the inputs to ground activates the relays. And don’t worry you are protected from syncing very much power because the board has built in EMF diodes and transistors. I hope that helps to answer your question. On an Arduino or Versalino you should be able to connect power and ground and simply drive a LOW through digitalWrite(yourpin, LOW); to the appropriate input to turn it on, and a digitalWrite(yourpin, HIGH); to turn it off.

Joseph Dattilo
Founder Virtuabotix LLC

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