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3.3V microcontroller vs 5V relay

Lucky-Luka

Member
Hi all
I was looking for a relay board to be used with my 3.3V Arduino board.
Relay module
I know this isn't a proper relay to drive inductive load at 220V.
I have read that it can be controlled with 3.3V GPIO pins.
I will try to do a test but before that I would like to hear your opinion.
This should be the schematic of the module:
Schematic
Just in case I cannot drive this relay using my 3.3V GPIO pin, what can I do to be able to use this module?
Thanks
 

danadak

Active Member
Quick way of telling is look up the Relay coil current requirements, then look at
the Opto coupler and its CTR to find out how much current out of micro is needed.

Unfortunately the link to the page, browser will not translate the entire page to get at the specs.


Regards, Dana.
 

sagor1

Active Member
You remove the JD-VCC to VCC jumper on the relay board and put +5VDC on the JD-VCC pin for 5V relays. Your relay board VCC then goes to 3.3V VCC of your micro. If your 3.3V I/O can triggger the relay via the opto on the board, fine.
If however, the 3.3V I/O does not trigger reliably, you can just jumper the indicator LED on that board to boost the current through the opto.
Putting +5V on the JD-Vcc ensures the relays pull in properly, even though they may trigger at 3.3V. A lower relay voltage may cause the relay to pull in slowly (too slow)
 

Lucky-Luka

Member
The relay module (powered at 5V both the optocoupler and the coil) is triggered even with 3.3V signal of the GPIO pin.
 

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