Switching a 4v AC Bell with an eBay "optoisolated" relay board

Has, over a period of about six months, welded the relay contacts open…
I guess I’m lucky it welded the contacts open rather than closed. Because we wouldn’t have been popular with the neighbours if they’d got stuck with us on holiday…
It’s connected to the doorbell.
I guess I’m now wondering, if I replace the relay board with another one…to avoid the same thing happening again…should I introduce an RC snubber to protect the relay contacts? I’ve read sometimes using them can make a problem worse but I don’t understand if this fits my situation.


@daneboomer, did you mean 24VAC instead of 4VAC? I find it odd that even 24VAC would weld the contacts but some old doorbells are just basic electro-magnets that can draw a lot of startup current. As such, a snubber is a good idea. You could also use a suitably rated SSR with a built-in snubber like an SSR-10A or SSR-25A. I personally have never used one of these for a doorbell but they can do the job.


Here’s a link with a few relay protection circuits:


The snubber you posted looks like it implements both RC and MOV methods.

1 Like