Circuit assistance: Relay board hookup

Hi again, I am messing with some generic relays that I need to hookup with mBuino and other boards.

Here is the relay [url]2 DPDT Signal Relay Module Board DC 12v Version for Arduino Raspberry-pi 8051 for sale online | eBay scroll down for schematics.

I have attached GND from my power supply to GND on the module, and 12V power to VDD on module and nothing happens. Might be ok.

Then I short the 3V from my power supply to IN_A on the module - expecting one of the relays to click - but nothing happens.

Suspecting the module to be broken?

Anyway, can you confirm that attaching this to mBuino would be just directly connecting on output pin to on mBuino to IN_A on this module?

GND to GND :slight_smile: That’s the only other thing an mBuino or similar should need.

It’s possible the GNDs on your power supply are isolated from each other, so 3v may still be only 2v when referenced to the other GND. If you connect both GNDs on your power supply and then use the 3v to trigger it, it should operate.

@ Brett - Hey man, you save my butt too often buddy.

No reactions, tried turning polarity and blew the BC517, arghh

bugger !

This is the opto-isolated relay modules I bought and have used on a Pi2 and with netmf [url][/url]. Nice and simple since I don’t need different voltages to run the relay than I operate my device at (mine work fine on 3v3).

@ njbuch - The markings on the relay suggest that the relay needs 24 VDC on the coil to operate so likely need to supply that voltage to Vdd.


The RY12 njbuch has is 12V. There is also a 24V version.

Niels, as a test, power with the 12V and use the same 12V to see if the relay switches on. It should according to the spec.

Powering from the same supply kind of defeats the idea of having optical isolation. :think:

Agreed, although I haven’t RE’d the circuit to see what the opto is really doing . My actual desire was for 3v3 relay operation so I didn’t need to worry about multiple power supply issues (in fact, I was most worried about ground reference issues in my scenario because I didn’t have control of one side of the device) and the opto wasn’t a feature I cared about.

It’s really only doing the same as the BC517 in the circuit that njbuch is using except in this case you are lighting an LED to switch the transistor. Because the GROUND and the VCC are common, it serves no isolation purpose whatsoever.

In fact, with use of dual supplies, the opto-isolator is a good idea as then you don’t need to have a common ground. You can keep them completely isolated and it will work fine.

@ Dave McLaughlin - The one picture I looked at showed the side of the relay which shows 24 VDC and RY-24, just my luck it seems to pick the odd device out.


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