Doorbell Relay to Contact Sensor

Looking for a sanity check here. After lots of reading here and elsewhere, I’m hoping to wire a relay to my old doorbell, using that to trigger two contact sensors. Because I want to retain separate triggers for separate doorbell buttons or separate doors, I’m not using the vibration or reed switch mechanisms. I’m hoping this community can double check my parts list or steer me away from this design. This might also serve as a more specific forum post than I’ve been able to find, helping future seekers of ideas.
So, in a resting state, my transformers output screws measure 13.7 volts AC. I’ve read this can fluctuate when the button is pressed. Can anyone confirm? Either way, how’s the Functional Devices RIBU1C? I believe I would wire two of them with the 10-30 vac/dc coil wire to the hot wire from each button and the common coil wire to neutral in the chime box. I’d cap and tape the 120vac coil wire.
On the contact side, I’d wire the N/O pairs to the screw terminals in Ecolink Contact Sensors. Cap and tape the N/C wires.
The sensor will be set to trigger when “closed.” Or reverse if that’s how they work.
For what it’s worth, I’ve attached a shot of the chime box (yeah, I have a very old house).

So, make sense? I’ll post more details and pictures for future reference as I proceed.


I’ll leave it to others to comment on your specific approach, but if you’d like to see what other people have done, some with very specific project reports, check the quick browse lists in the community – created wiki, go down to the bottom of that page for the project report section, and then choose the list for “doorbell” projects. :sunglasses:

what you describe should work. The RIBs are low power I think about 1VA so unlikely to be a problem for the existing transformer.

That is some hairy wire! See if it’s asbestos The conductors look good shape - maybe they are rubber?


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Thanks for the input! I’ll order some parts and report back what works or doesn’t.

Also thanks for the question on the wire. It is really dusty on the cloth in that picture (didn’t dust off as easily as the rest). The insulator directly on the wire is still pretty pliable and firm to my fingernail. Upon research, I also don’t think the cloth is asbestos. Either way, I’ll probably leave it alone. I’m taken to understand undisturbed asbestos is generally not a concern.