Monitor a contact? (2015)

Is there something that would allow me to monitor a contact on a relay? Say I have a relay that is triggered by some action. I want to be able to monitor the contact on the relay whether it is open or closed.

If I understand what you’re asking, the usual way would be to replace that relay with a networked relay that would report its own open/close status.

If it’s not possible to replace that relay, you may be able to put a networked relay upstream from the relay being monitored.

It’s just going to depend on the exact details of the set up.

What I’m really trying to understand is how much flexibility I have with monitoring non-networked devices. The relay may have not been the best example.

Let me try a different example. If I put a current switch on the line voltage of my condensing unit for my AC unit and adjusted it to trip at a specific amperage would I be able to monitor the contact of the current switch which would tell me if my compressor is running. I’m thinking of some kind of board that is networked z-wave or something that can monitor switches. If that makes sense.

I am a controls engineer for commercial building automation systems. Mostly in complex HVAC systems and industrial systems. I have a lot of ideas I would like to accomplish with smartthings but my ideas are limited by what kind of hardware is available. The equipment and controllers I use on a hospital for example is way overkill for my house and I think I can potentially do some cool stuff with smartthings that wouldn’t break the bank.

Isn’t coming from the controls world to this event based programming difficult? I’m so used to having mostly loop based controls and also event based logic execution.

There are several ways to monitor current draw, that might give you what you want. Of course it helps if the devices you want to monitor are on their own circuit, otherwise you’ve got to do some calculations for increase/decrease.

There are community members doing some really cool things with GroveStreams. You might take a look at that topic and see if any of it fits in with what you have in mind:

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Well, I just ordered my first hub and have yet to do any automation on my own house so we’ll see. I think the programming may be different for me. Most control systems I’m used to programming are block based Boolean logic with the exception of Allen Bradley with can be text code, block or ladder logic.

I really think my biggest source of frustration coming into this is being limited to certain hardware. That’s why I was thinking it’d be cool if there were some board out there that had some digital inputs and outputs that I can program for anything I want. Or even some analog inputs that can monitor a 0-10VDC voltage. Looking at some of the projects I’ve seen people working on I see so much easier ways to do these things with some sensors, relays and a logic board and a little bit of programming.

Coming from my world and looking into home automation I’m finding out that HA is still in its early stages of development. There’s still a lot of room to grow. However, at the same time with the second gen smartthings hub I think it’s finally at that stage where I’m ready to jump in. I just hope it doesn’t take the 1-4 months Amazon showed on my order.

If you want a fun, low cost method to write some custom code and integrate with ST, why not grab an Arduino UNO + a ST ThingShield? This gives you the ability to create your own Smart Devices.

Take a look at the project my son and I created to help make using the ST ThingShield easier to use…

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@ogiewon that is awesome. I think that is a solution to what I’m looking for. I don’t even necessarily have a project in mind yet as I don’t have my smartthings hub yet but I’m pretty sure I’ll be visiting your github once I get to that point.

Unfortunately for me, my wife and I just sold our house and we haven’t found a new home yet. So I’ll be homeless for a little while. I’m not sure the temporary apartment we might move into will appreciate me automating their unit. So it may be a few months before I fully jump into this.

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Haha me too. So there’s two things you can get to act like relays, there’s the fortrezz mimo lite, or arduino which will require even further programming learning / knowledge.

There’s also some 3rd party rule builders out there such as @obycode’s SmartRules on iOS and @JoeC’s which are like ladder logic. Good luck, ask away here at the community, we tend to help more than complain here, at least I like to think so.

Most door and window sensors have a terminal block with a no NC and common under the hood. Plug your relays dry contact’s into it to monitor status. Edited for phone auto correct fail.

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Why not have a vibration monitor at the compressor instead? Unless it’s exposed to the outside environment. A multi sensor from ST is good for the job.
A couple of members did some mod to a contact sensor for monitoring doorbell, flood sensor and smoke detector. You could go that route as well.


That could work for the compressor. Although it is outside. Good suggestion.

I think I like ogiewon’s solution with the arduino. That could pretty much do anything I can think of. The example of the compressor was just something I made up on the top of my head to try to understand what I could use to monitor just any type of contact. Like in my old house I already have magnets and sensors installed in my windows that all go back to panel in my closet. I think I could use the arduino to pick up all the contacts.

Cheaper to do with a less than 5 dollar relay and a 30 dollar door window sensors imo. But you can definatly do more with the arduino solution.

Check out my ST_Anything_Doors example in my github repository. It monitors 6 traditional magnetic door sensors, controls 2 garage doors, and monitors motion, temperature and humidity. All of this with one Arduino and a ThingShield.


Not really sure how you tie a $5 relay into ST though.

A relay offers dry contact ouputs, most window/ door sensors have dry contact inputs under the cover. So if you wire the normally open relay output to the normally open input of your battery powered door/window sensors it will notify ST when the relay is open/closed. I am planning on doing this exact setup to my steam shower and will post pics when it’s done, but it will be a month or two after I get my v2.


as you can see in the picture of my door sensor there is a terminal block that you can use in lieu of the magnet

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I like that. This would work really well for all the windows and doors I already have traditional magnets on. Very cool.

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I know this is an old thread, but this is exactly what I need to monitor if my solar panels are running on a Hayward solar controller. Do you happen to know the make and model of that sensor? I have several spare sensors… none have that block.

I think it’s going to be pretty confusing to people when an eight year old thread pops up at the top of their feed. :thinking:

There are several current threads on this same topic which will refer to devices that work with the 2023 smartthings architecture. Why don’t you start with the community FAQ:

FAQ: List of devices with dry contact input from external sources