Hardwired Alarm Sensors & Arduino

@cooperglee mine drop the voltage. Using a relay is so elegant. I love it. I was going down a rabbit hole of trying to monitor voltage on the analog input of my MIMOlite, but instead I’ll pick up a relay that trips around 12V in the next few days and wire it in. Flawless.

@mweston my terminals meter 6.8 and 13.5 like yours. I’ll post back here with a parts list and wiring diagram etc. when I have a working setup.


@NorCalLights Did you ever get this setup? I’d like to try it myself but am not familiar with relays or which one I would need :-\

Finding the right relay could be hard due to the operating voltage and low coil resistance added to the alarm contact sensing board. Just a guess here but the 6.8 and 13 volts probably the voltage of the board that monitors the contact. Adding a bunch of relays to the alarm power supply might not be a good idea. An opto coupler would be best for this application.

What about adding a resistor right before the Schlage contact sensor or Arduino? So it would limit the current going into the sensor, say up to 7 volts and anything over 7 volts would trip the sensor as being open.

Sounds like the most simple option but would that not work?

1 Like

You mentioned one side of your window contact going to Z1. How about the other wire? Does it connect to COM or POS? The current draws is base on the relay you are using. How about put your meter on Z1 and POS? I am just thinking maybe your contact is normally open or your alarm is waiting for a high when you open the window.

Got it working! I noticed that the COM wires already had some wires with resistors on them right before the alarm panel so I wired one schlage wire to the resistor and another to the zone port on the alarm panel.

It works perfectly now. I’m not sure what resistor was used but can post a picture of it if anyone is interested.

I’ve got one open/closed contact device setup for the whole zone. It looks like I could also wire it for each individual door/window but would need either a lot of schlage sensors or an arduino. That may be a project for the future.

Anyone know of a device type that will change the open/close tile into a zone tile?

@mweston I haven’t had time to get a relay… real work got busy leading up to the holiday. Can you take a picture of how you have it wired up?

It is really just an Icon and a color - if the default scalage type doesn’t allow you to change the icon (or if you want the labels to change - i.e. zone safe / zone active / etc ? simple couple of mods to the device type and you should be good - happy to help if you need

Did you have any luck measuring the analog input on the mimolite? From the documentation it seems supported:

@jr0 I have abandoned that path and I haven’t done any more research. You’re right that the analog input seems like it should be supported, but as far as I can tell, no one has really tried to integrate it.

Any idea what that commerical product was called Terry? Do you have a link?

I can’t believe I actually found my reference to it … I guess my huge archive of bookmarks has a purpose.

I actually mis-remembered: It is not a Z-Wave device, but rather a ZigBee device. Arbitrary ZigBee devices can be harder to integrate with SmartThings since there are multiple incompatible protocols.

…CP / Terry.

1 Like

i recently replaced my whole alarm system with a DSC pc1864 and eyez-on evl-3. diysecurityforum is a great start, and i’d suggest doing that, because you can get monitoring for 8.95 a month via eyez-on and have connectivity for all your sensors to smartthings via dsc alarmserver found on these forums.

i find the benefits of buying true home alarm senors like motion and open/close more valuable than the “cheapo” smartthings or z-wave sensors that only interface with their automation sensors.

i purchased 5x dsc wireless door sensors on ebay for 16.50 each. i’m going to attach them on my interior doors and exterior fence gates. that gives me more options with my alarm system AND smartthings than just buying something specifically for ST.

1 Like

That integration also involves keeping a computer hooked up to the alarm panel to run as a server correct?

yes, but if you’re talking about adding components to your alarm system anyway, you could run a linux or windows server or something like raspberry pi easier.

i hope eventually we get a ST app that interfaces directly with the EVL-3 and we can ignore all this.

1 Like

@mweston any chance you could post a picture of your wiring setup? I’m still not able to get this working. I must be missing something simple. Thanks!


Paul pointed me to this topic, thanks! Trying to replace my existing adt alarm panel with something that will connect to my ST Hub. From what I read, I have a lot of sensors so looks like Arduino. I tried to upload a picture of the panel but new users cant do that. I count 12 “single” wires going into screws, 6 “wires with a white plastic piece attached to what looks like small colored filter into screws and roughly 5” two wire bundles" going into screws.

Has anyone created a document that details whats needed and steps to accomplish? It seems like everything is in the post but I dont want to miss anything. Does this require a computer full time? My panel is in a closet and my ST Hub, Modem and router are central at my kitchen desk 40’ away. Is that a problem? I can probably run an Ethernet between the two if I absolutely have to.

Also, I’m a hobbyist. Can I handle Arduino? I don’t have soldering skill or equipment.

In addition to wanting this for my house, I think this is an important “piece of the home automation puzzle” and would be interested in working with whomever to develop something that can be brought to market.

Thanks in advance and looking forward to this community.


todd, lots of us have dsc panels that are working with ST. you need an envisalink3 and a computer that can act as a server for events. check out the dsc threads, a lot cheaper to use your existing than replace, and the dsc is the best home alarm out there.

Thanks Jeremy. My problem is that my existing panel is an savs20adt-1 so it sounds like I need to replace it with a DSC and add an envislink3?

I replaced my old system with a dsc 1864 and it cost me 100 for the system and 100 for the evl3. You can only get an insurance discount with a monitored system and the evl3 gives you the option of 8.50 a month monitoring.

Dsc or Honeywell and you’ll be ok. I bought a raspberry pi for 35 to use as an always on server for ST among other things.