5V reley module with triger power supply

Hi! I wonder if I could power 5V relay module with triger input, with 12V power supply, and triger 3V ?

Is it inside module 5V zener diode ?

Link to reley module on ebay

Thankyou !


It is quite likely that the 12V version of that module will trigger on 3V but unfortunately there’s not enough information on that listing page to tell us that.

Don’t attempt to power the 5V version with 12V. That will burn out the relays and set fire to your workbench.

Which relay module do you have. Is it a active high or active low signal to trigger the relay. the 12V relay module that I have, is an active low. And 3.3V will not energized the relay. 5V will. But it does not have the magnetic holding force that I would like. However a 5V relay module will work on 3.3V without a problem.

in order to make a 3.3V trigger to work on a 12V relay module, you would need to change the current limit resistor for the LED.

I recommend using an active high relay module for 3.3V applications. On these modules, the + power for the LEDs is derived directly from the Arduino, or whatever processor you're using. it is set up for 5V, But will work on 3.3V as well. The power for the relays will not interfere with the operation of the processor.

Hope this helps.

Never connect a 5V relais to 12V directly

You need a resistor in series connected between your relais and V+.

There are no zener diodes in a relais. If you are lucky you have an integrated flyback diode. Let us assume that you have a low power relais requiring 20mA at 5V. So you need a resistor where the voltage drop is 7V (12V-5V). At 20mA you need a 350 Ohms resistor. A 330 Ohms resistor will also work.

The relais still expects a trigger voltage of 5V and will not work at 3V.