Adding a contact sensor to a doorbell

I’ve done a lot of searching on leaving relays energized constantly and never seen any downside. This is how I run my alarm system, 12vdc relay that that’s energized when the system is armed. No issues. Lots of relays in cars that are energized the whole time the car is running, it can’t be bad for them to do that.

Thanks for details guys. I measured red wire coming from switch on bell to white wire bundle.

Is there a specific relay or name of a relay I should buy? I don’t know much about these devices yet. I am more of a programmer.

Can you post a pic & model number for your doorbell? Sounds like a non-standard setup to me. I’m really curious why you are seeing the voltage drop out, that shouldn’t be happening with a typical coil/plunger doorbell I think…

Sorry for the delay. I have a Broan Model C100 doorbell and it says 16 VAC so I may have mistakenly quoted 12VAC above. Below is a picture. The Transformer is in the crawl space below first floor and wires come to door bell. I measured power from top right screw to the white wire bundle and it was positive and when the doorbell is pressed this measurement goes to 0.

Interesting, there’s a lot more wires there than I’ve seen before. Do you have multiple doorbell buttons? I’m also interested in the BATT REAR designation, no idea what that’s for.

I do have 2 doorbells though the rear one is hardly ever used. I would like to put a contact sensor on the front which is the top right wire. This doorbell appears to be setup for battery operated as you will see slots for 4 C batteries above and below the wires.

If you put the reed switch where those screws are it should work.

I just swapped out the reed switch for a multi sensor. Reed switch missed one of the three doorbell rings we got yesterday. I just tested them both side by side and I was able to ring the bell fast enough that the reed switch didn’t register, but the accel sensor still did.

I like the reed switch setup. I will report back and let everybody know how it goes!

Hoping someone can help me with my doirbell that I’m trying to connect to an Ecolink sensor. I’ve got the transformer visible as shown below - do I wire it to that? I’ve seen some pictures here that show three wires and I’ve only got two. Thanks.

Do you have a reed switch?

I need a reed switch and contact sensor?

There’s a lot of people performing a setup with a wired connection, but depending on your doorbell and the casing, this can be done using a simple ST Multipurpose sensor without the need for a dry contact or Reed switch, etc…

Looking at your 2nd screenshot, your doorbell enclosure is is similar to mine. There are two ways to do this:

  1. Keeping the Device listed as an Open / Close Sensor (my setup) which means to have it show closed, you use the magnet with it. I will show screenshots below:

  2. You can modify the device to act as a garage door which means it will only need the main unit (no magnet) and it will act as an Acceleration / Vibration sensor (however the icon of the device in Things will show as a garage door picture).

Anyway, even using it with 1 above, the magnet only serves the purpose to keep the device as always showing Closed, but I have setup a notification with Big Talker to send me a TTS via LANNouncer that someone rang the doorbell. I also have a Piston setup that turns a light on if it’s after Sunset and vibration is sensed.

Your screenshot is similar to my doorbell. You can see in this first screenshot that I have the main unit of the sensor sitting right above the the doorbell plate:

The second screenshot is with the cover on and the magnet mounted to the top to close the circuit:

Just another option to consider. No wiring or multiple devices necessary.

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Yes. You can’t wire 24 V to the terminals on the contact sensor.

Where is your multisensor located?

Ok so how would the wiring go with this setup? Contact sensor to reed switch and then where?

Then reed switch where the red wiring is next to the coil.

Contact to reed, reed to red wire, other end of red wire to reed, then back to contact?

No the reed just rests next to the coil. When the coil is energized it creates a small magnetic field that moves the reed switch.

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