Lots of dry contact monitoring with ZWave/SmartThings?

I have a house that I recently purchased, when it was built it was pre-wired for an alarm system (never installed, so no panel or anything - just wiring). Meaning every door and window has a pair of wires running back to a central location (where the alarm panel would have gone) – so ~40 different pairs/~40 different monitoring points.

What I would like to do is have some sort of Zwave interface to monitor all of those dry-contact pairs. I realize that I wont be able to ‘control’ those points, but it would be really nice to monitor when/if a door or window opens - and use that for part of my automation schemes.

I already have 20-30 ZWave devices in my network that I use to control things like lights, curtains, Sonos, etc. with full Echo integration. So I am good with all the ZWave/HA stuff. I run a SmartThings 2 (and I’m playing with HomeSeer)

Anyone know of a device that could take ~40 different dry contacts and turn their connection states into ZWave events? Don’t mind if I need to bring them all into a big A/D converter, then ship it out serial to something that then speaks ZWave (kinda similar to the ADIO-100 in the HomeSeer land - which is way too small for this and I want to stay with SmartThings). But I can’t be the only person who has ever run into this and I really don’t want to create something new if it has already been solved.

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I would go with the d/a converter.

This would give you the best resolution with the fewest components.

The multi IO interface I could find had a 0-24V input and single relay output. If you wanted item resolution, you would need 10 pairs (4 Data lines into each D/A with a 0-24V output would give you better than 1v resolution.)

Nothing that fits your description exactly, but there are some possibilities. Take a look at the projects on the quick browse list for security in the community – created wiki and you’ll see several where people were taking existing hardwired sensors and integrating them with SmartThings.


That’s the Mimolite. It’s on the official “works with SmartThings” list. It’s a popular device in the community, but it’s limited to one input and one output. The Mimo from the same company allows for four. I definitely wouldn’t buy it off of eBay, though – – most Z wave device manufacturers will not honor warranties for devices bought off of eBay and some of them are counterfeit or even the wrong one in the box. And even so, it’s probably more money than you do want to spend on this kind of project.


For home automation systems it’s generally better to buy from reputable dealers who will take defective devices back. (It happens.) Some of them will also offer a volume discount if you ask.

But again, for this particular project I think most people have gone in a somewhat different direction for the integration. If you check the projects list you’ll see quite a few different approaches. :sunglasses:

It sounds like the inputs on the MIMO and MIMOLite are digital with a variable threshold (Not a true analog interface). So I don’t think the D/A will do any good for resolution. (Sorry about the e-bay link, I thought it was google.)

I only see 2 inputs and 2 relay outputs. what am I missing?

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I have read through the other threads where people are looking for similar solutions. Didn’t really see a solved problem in there. Lots of people asking - not a lot of people posting a solution.

I have a MIMO for some other things, I really dont want to have have a bank of 10 of them just to monitor doors and windows. :wink: Aesthetically that would be most unpleasing.

Thank you all for the help so far. Holding out for someone to say “Oh… here is product X”. Its probably not going to happen - but I can dream. :wink:

If I have to I will do a GPIO board connected to an Arduino or Pi and write code… But that just seems like a lot of work for something that should be already solved. :wink:


My bad, 2 in, 2 out. Thanks for the correction. :sunglasses:

What’s your budget? I’m think Elk might have something, but it might be $400 or more. ( their market tends to be more industrial and RV, so they have a lot of equipment that other people don’t, but it tends to be heavy duty and expensive.)

Well if I have to cobble something together it would probably take $6-700 of my time, and ~$100 of parts. So anything cheaper than that is a win.

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Looks like you could do it directly with 2 RPi 0 boards (26 GPIO on each one)

Here is a crazy looking thing. I have no experience with it and have no idea what it would take to get it to work with ST (or if it’s even possible), but $166 for 32 channels isn’t too bad.

One thing to remember is that you can get some mileage by hooking up your various sensors in series. By grouping things by room you could reduce your 40 contacts to a more manageable number. You wouldn’t be able to tell which door/window was open, but might make the project less scary.

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Arduino Mega Has 54 I/O"s. You could use it with ST_Anything or write your own custom code.

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I’m tired today, and I can’t really read the product page. @johnr might be able to say if this is something that might be integrated directly. :sunglasses:

This one looks like the best solution. it has 32 banks of 8, you can multiplex and get up to 256 sensors. It looks like it will need some programming or a computer in the circuit to work correctly though.

I thought about that, but the thingshield is sold out again. :disappointed_relieved:

Yea, I agree that it looks like it might need a computer or something. Certainly something an RPi could do. It looks to me like they are using Zigbee radios, but might not be implementing the full protocol. I know the Digi modules in the pictures have a “pass through” mode where they just act as a wireless serial link.

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Does your house also have sensors? Or literally just wires?

I ask, because many alarm panel sensors aren’t simple dry contacts. The sensors send one voltage for “open” and a different voltage for “closed”. This lets the panel monitor for tampering (i.e. if the wires are cut or shorted, the voltage will measure zero).

If it’s just wires, you can add your own reed switches, etc. If the sensors are hardwired in (and they are the voltage change kind), you’ll have to get fancy with your monitoring.

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Just reed/magnetic switches at the end. I pulled one out just to be safe. Simple contacts.

Earlier this spring, I was short on time (pending lengthy business trip), so I did this :smile: I had to combine several reed sensors into “zones” since I only had eleven Ecolink open/close sensors. Works great for now …