SmartThings Community

ADT Door Sensor Repurposing


New house, new to SmartThings, first post… be easy on me. :grin: Hopefully someone didn’t already post a similar project… I did a quick search but wasn’t able to find anything.

Bought a house and decided to get the ADT hub when it went on sale to have the option of monitoring should I ever feel I needed it. Turns out that had the added advantage of the related sensors occasionally going on sale rather cheap ($5), which makes good project fodder.

This one started when the battery backup sump system I bought had a set of dry contacts (open/closed, no voltage) that closed when the backup pump ran. Did some research on how the door sensors worked, and the magnet closes a reed switch, so in essence the door and window sensor is a simple open/closed sensor when it comes down to it. So I decided to dig in and see what I could do…

Cracked open the case by twisting a screwdriver in the slot:

This is the reed switch:

Bent back the tabs holding the board to the case:

Found the reed switch solder pads:

Removed the reed switch (sorry for shaky pic):

Soldered in some wires and cut the case to clear:

Connected the sensor and wired it up to the contacts:

Modded a second one and attached to a relay to notify me if the power goes out on an outlet:

Hope this helps someone out there… I have much to learn from the site, so I thought I’d give a little back for all my lurking. Enjoy! :+1:

(Eric) #2

good pics.

What is the part# of the ADT Door sensor? Maybe F-ADT-DW-1 , takes battery CR2450 .

I’ve been looking for a ready-to-go zigbee HA1.2 dry-contact for smartthings, but your hack seems to be the easiest way to get it.


Here are the devices which already include dry contact options:

I have some concerns about the potential fire safety of the project shown in this thread, so if it was me, I would probably pay a little more and choose one of the devices which already offer these connections.

But I appreciate the detail that went into the report, as well as the excellent photographs. :sunglasses:

(Mavrrick) #4

The interesting aspect to this though is the ability to integrate into an alarm to ADT.


Good point. Of course the flipside is that you will only be able to use this method with this device if you have the SmartThings ADT hub model. Other model hubs will not be able to receive the radio message from this device.


Just noticed you said zigbee. Somebody told me the MCT 340 that works with smartthings has dry contacts, but I haven’t been able to confirm that.


Model is F-ADT-DW-1 with a CR2450 battery. Correct that it only works with the ADT-branded hub.

JDRoberts - where do you see a fire hazard? The sensor is all low voltage, but I have been questioning the relay part. Checking today it’s cool to the touch but I’m wondering about the duty cycle, etc.


Unless I am misunderstanding the pictures, which is always possible, I’m seeing exposed connections which could get dust on them. And wires exposed to the inevitable rodent problems.

Power supply enclosure?

That’s what project boxes are for. :wink:

Also you’ve got a battery operated sensor sitting right on top of your battery backup. I’d like to see more distance between the two of those.


Good point on the exposed connections… I’ll find a project box for the relay setup.

As for the backup, it’s actually mounted under the controller, about 3’ from the actual battery. I think that one is fine, but will put it in a box to tidy it up if the price is right.

Thanks for the clarification!