Relay power issue

Hello everyone, :o

I am making a small home automation project which consists of a nano based setup which monitors room usign pir sensor for motion and turns off light fan once it detects people are not there in the room.

So anyways the issue is pretty isolated. I have 2 relays - 2 channel 5v low relay. When I test then with my uno separately connecting it to uno 5v supply I get both channel relays getting power. (In1 and in2) but when i connect it my nano which already has other stuff loaded on it... I get only one channel getting power... Mind that one single connection powers both channels on these relays.

My relay is exactly this one

https://cdn.ampproject.org/ii/w1200/s/cdn.instructables.com/F3X/6HP4/IBRRT6RC/F3X6HP4IBRRT6RC.MEDIUM.jpg

Could it be a power inadequacy ?

Most of the 5 v. relays I have have about 20 ma. current draw to the coil. So if you are feeding two coils from one connection, you're pushing your luck. Why don't you use two digital pins simultaneously (in parallel) to activate the relay? That would bring the current per pin down to about 20 ma.

By the way, don't forget the surge protection diode across the relay coil.

Looks I was able to get to the root using a multimeter. The pin which set for output to the relay pins was not working. - made in China stuff!?

Thanks anyways for the help !!

If you missed to add clamping diodes over the relays, you most probably killed the pin (and possibly more) yourself.

OP is using a 2-relay module. That module draws 2mA from the output pin for the opto LED.
Unlikely that that has killed the pin. Maybe the code (not posted) is wrong.

That module draws 75-80mA per relay from the 5volt pin.
Just ok for the Uno when powered with <=9volt regulated through the DC jack, or powered through USB.

The 5volt regulator on the Nano is smaller than that Uno, and has a smaller heatsink.

How do you power the Nano.
Leo…

DrDiettrich: If you missed to add clamping diodes over the relays, you most probably killed the pin (and possibly more) yourself.

OK what does that mean ?? I thought a relay comes with everything on board. Why would you add diode again ?

I was not sure whether you meant bare relays or relay modules.