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:


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:

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

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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.

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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!

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These are great hacks! I happened to purchase a bunch of extras at BB @ $5. Now I have a total of 19 of these and would probably just use half and just put wooden dowels and security locks on some windows which would be unlikely used as emergency exits.

So on the BU sump pump where the dry contact is normally open, this means your sensor is normally open. Do you bypass this sensor so you can arm your system? Or this there a way to reverse the function of these sensors? To alarm when closed instead of when open.

I already have a great use for your power detector. I have a freezer in the garage that’s on a GFCI circuit (No other place to plug it into) that occasionally trips. I currently have an always on “nightlight” plugged in to the same outlet as a power indicator. Can you please tell me the components/part numbers if available you used? And if you have an inexpensive source. I’m assuming a low capacity (what amp?) 120V NO SPST relay and a socket?

The other hack that I saw on YTube is using one of these as a tilt sensor on a hinge on a garage door. Then using a wifi relay as a remote switch for the garage door for full automation. :slightly_smiling_face:

Keep em coming!

Yes, for the sump I have the sensor bypassed to allow the system to arm. I have it bypassed in ST so I don’t have to manually bypass each time.

The power detector is used exactly like you are thinking about using it - a freezer with hundreds of dollars of meat on a garage GFCI that I wouldn’t have clue if it tripped. I ordered this relay, but have begun to wonder if there is a lower power draw option.

Interesting hack to use them as a tilt sensor. I currently have one rigged up with a large rare earth magnet on the side of the door, but that just gives me opened/closed status. Can you elaborate on the wifi relay setup?

Nice relay with socket/terminal block. What do you mean lower power draw, as in power consumption?

Check out TaylorTech I think he’s a member here too. That’s how he used a hinge mechanism. He was also using the Sonoff for his wifi switch shown on his other video. Hey that big earth magnet is a good idea too, that would cover the extra distance to the sensor. I have old sub magnets lying around, I’ll give that a try. The problem with the tilt hinge is that it might not swing the magnet far enough if the door was just opened a little bit. I was also thinking of using a pin switch pushing against the floor (like those for auto aftermarket alarms) in place of the reed switch that would be activated even if the door was opened just a little bit.

edit: those retrofit alarm pin switches are NC so a NO (door) switch is needed instead.

Yes, as in power consumption. Keeping the coil energized has to take energy, right?

Slick garage door solution… good to have another option should my install fail. For now, here’s a pic of what I have.

I was going to use an old hard drive magnet :slight_smile:

Yes, that seems to be a very popular spot to put the sensor. I weather sealed mine with a bead of silicone since that side of the house gets beat up by the wind the whole year round and really bad in a storm I figured it would at least keep the dust and rain out of the sensor. How long do these batteries last anyway?

Since these sensors are cheap I’m going to put another one as a way to confirm that the door is open/closed right by where the quick disconnect arm that pulls on the garage door stops on the t-rail. The sensor will be away from the weather but will be subject to vibration so lets see how long that will last.

I will be using the sonoff with the eWelink app but I won’t be flashing it for now.

As for the relay for the other project I found this
but since you were looking for a lower power consumption relay, looks like they are about the same around 1Watt. Your other lower power option would be going with a 12/24V DC relay if you already have a wall wart nearby like for your sprinkler system (I believe these are AC out so you’ll need a simple rectifier circuit to convert to DC) because if you need a dedicated wall wart for this then you’ll probably use up more power and another component that could go bad.

we actually need to find a low power continuous duty relay since this relay will be energized for not only days at a time but months/years. Though you should actually test it monthly to make sure the contacts are not stuck together.

I have a guestion. I use the same sensor on my basement door. It’s a long ways from my hub to the sensor. It does keep a connection but the distance kills the battery in the sensor. Is there an antenna in the sensor I can solder a wire to? Maybe to extend my antenna range?

Unfortunately, no. :disappointed_relieved: Changing the antenna length changes the frequency so the sensor and the hub will no longer be able to communicate.

Thank you, thanks for your time

You could add a switch as an extender half way between the hub and the sensor.

Unfortunately, not for the dual logo SmartThings/ADT devices, which is what this thread is about.

Those use a different frequency, neither zwave nor zigbee, and are not a mesh network. So they don’t use repeaters. Instead each of those devices has a single hop communication directly to the dual logo hub.

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