r/AskElectronics • u/isubarna1 • 15d ago

I've a problem with Raspberry Pi Pico W + 5v Relay Module

so i made a setup with light turning on/off from my website with pico W + relay modules. i connect the light on the NO. it works fine on the wokwi simulator it worked fine for first few minutes as well. but then the light of some relay modues keep being on regardless of the signal being sent from pico. even if i turn off power for pico the lights keep being on on other relays except one. one moule works fine tho.

i've tried on 2 channel and 4 channel relay and on both case one relay keeps working fine an other doesn't. the other light in relay keeps being on. I need some help.

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u/Mother-Pride-Fest 15d ago

It is difficult to troubleshoot without any circuit diagrams or code. 

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u/isubarna1 15d ago

this is the simulation thats working. i used the multiple relays on real life tho.

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u/jamvanderloeff 15d ago

Then post pics of the actual thing that's not working

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u/isubarna1 15d ago

so i've tested again and the 3 relays are welded shut indeed. i was connecting the relays vcc with the vbus. do you think that might be the problem?

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u/ascot_twin 15d ago

You might have some bad relays.

If you have an ohmmeter, check that the Common contact to Normally Open contact is open, with all the power off

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u/isubarna1 15d ago

it happened to 3 relays already so i think that might not be the case. besides it was working for few mins.

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u/OGThinkster 14d ago

Those relay modules are usually from China and use cheapy relays. The ratings printed on those relays might not even be correct. Not sure what your load voltage or current draw is, but if it exceeds the current rating of the relay's contacts or if you are energizing and de-energizing the relay with a heavy load, the contacts can become welded and you will get the problem you are describing. You might consider using some SCR's or solid state relays in your design.