I’ve tried using a Multi to detect the doorbell ringing as suggested in another thread. Unfortunately this also detects the pantry door closing and my kids running down the stairs. Is anyone aware of a device that would wire in parallel with the doorbell directly that is compatible with SmartThings? I see some of the door sensors have contacts but it looks like they are only for a dry pair.

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What event are you looking to trigger when the doorbell is rang?

Possible a relay switch will work (LFM-20). I have one installed now to trigger the garage door to open, but I’ve only looked at it for sending it a signal and can check if I manually make the contact (similar to door bell button push) if the hub see’s the contact real time (versus polling over some time interval on the switch’s status).

But if it is real time, and since ST handles the LFM-20 as a switch, then you can have any event occur when the switch goes on.

I’ll check tonight.

I’m looking to get a notification, and probably in the future turn the porch light on and/or activate a camera. My constraints are the button is mounted in brick, and not easily replaced. To keep the family happy, I also need to current chime to continue to function even if SmartThings is down. I’ve done some searching but there doesn’t seem to be any z-wave device designed for low-voltage current monitoring or the like.

@bazfum - How comfortable are you working with the Arduino? This sound like something that is definitely doable with the SmartThings Shield.

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Have you looked at Skybell or Doorbot? I think they are being planned for integration into ST.

FYI - Holding down the garage door button, that my relay switch (LFM-20) is connected to in parallel, did not register real time status change in ST.

The Doorbot and Skybell a are neat products. Where have you heard ST is looking at them?


Sounds like a job for Remotec Z-Wave ZFM-80
Here’s one link, but they are available other places too. No idea of the best price out there.

The Remotec is a z-wave relay BUT it has a spot where you can connect an external switch to it. Right now I’m using one of these to control my gas fireplace. I have the external switch on my fireplace connected to this relay. Now I can use SmartThings to turn on/off the fireplace and can also use the external switch to turn on/off my fireplace.

Here’s how I’d install it for what you’re looking at:

Find your doorbell transformer. This is what converts between house current and the lower voltage used by the door bell. Here’s where you’re going to install this unit. Connect main line house current to the power inputs on the relay. Then wire the doorbell in parallel to the external switch contacts on the relay as well as the transformer. What I mean by this is that the wires from your doorbell will go to BOTH the transformer and to the relay. You’re going to basically pig tail or spit the wires so they go to both devices.

You are NOT going to connect the load from this relay to anything. In other words, when this relay turn on it is NOT going to power anything other than itself.

Okay, so once the hardware work is done, here’s what should happen: When someone presses your door bell, it will still ring your build in doorbell chime/ringer/whatever like normal. But it will also turn on your newly installed relay.

Now for the software side: Add the device to SmartThings. Now in the IDE you’ll want to change the device type to a momentary push button. This basically tells SmartThings: As soon as you see this relay turn on, turn it back off.

Okay, so once this is done what will happen is when someone presses your door bell your normal doorbell chime/ringer/whatever will go off AND this relay will turn on, then off. So, setup your notification program to subscribe to that relay and watch for it to turn on. Once it goes on, execute your program as needed.


@chrisb - I’d be carefully hooking up the door bell button to the ZFM-80, while still having it connected to the door bell itself. The ZFM-80 is a dry contact module, and all sorts of badness might occur if the door bell button is not dry. Maybe I am misunderstanding, but it sounds like you will need to do some investigation with a multimeter, to make sure you’re not blowing up the module.

@FlorianZ I’m leaning toward trying a ThingShield, I wanted to make sure I wasn’t missing something commercial that would be plug and play.

@twack Unfortunately the current doorbell is a small button epoxied in a hole in the brick just large enough for it. I’m not sure there is an easy way to install one of those devices. Also they would not be high enough for the camera to be useful. I am following the development of that sort of device though. Would be nice.

@chrisb That looks like it might work, I found a manual online that does show the switch connection. Based on the pictures I’d seen I had assumed you had to use the button on the front. Do you know if it is capable of handling voltage on the input? Most devices I’ve looked at require a dry contact. Also, does it send notifications to the hub when the button is pushed? It looks like that would be good for rining the bell from SmartThings with the button on the input and the chime on the relay, but I’m not sure it would let me get a notification when the button is pushed. That would also prevent the doorbell from ringing if the relay died, which the family would not like.

Thanks for any suggestions.


I’m looking at the instructions myself right now ( and I’m not seeing if it say it can take a load on the switch… but I could swear I read somewhere that it could take all the way up to house voltage on the external switch line.

Yes, it does send notification to the hub when tripped by the external switch. When I turn on my fireplace via the external switch it shows up in smartthings nearly instantly that it’s been turned on.

If you wired in parallel it would NOT prevent the door bell from ringing if the relay died. If you did in parallel then when you push the door bell button you’re completing two circuits at the same time. You’re completing the ‘door bell chime’ circuit and you are completing the independent relay circuit.


I think “dry contact” just means that circuit between the incoming power and the circuit closed by the relay are separated.

I think I’ll go ahead and get a ZFM-80 to play with. If it can take voltage on the input and sends a notification it would be perfect. If it doesn’t work for this I’m sure I’ll find something to use it for.

@chrisb - Ah, thanks. I always thought it meant: “Don’t apply voltage across contacts. Just short wires.”

Anyone know of a store that has the ZFM-80 in stock? Not finding it anywhere.

What if you took one of the contact sensors that have the screw terminals and wired it in parallel at the transformer? Write the app that when triggered,sets a “ding-dong” state to true and starts a 1 minute timer to set ding-dong to false.

Now when you push the bell the circuit is energized, the sensor reports, and you’re good.

At least I think?

Thinking some more, you should wire the sensor in series on the low voltage side of the transformer.

I just ordered a MIMOlite, it specifically says in the manual that it supports up to 24VDC on the input. I should be able to connect that to the doorbell wiring via a bridge rectifier. If I can get that working I’ll try rigging up the relay to ring the bell via SmartThings as well.

I have SkyBell but I didn’t think they published an API yet. It has a motion sensor and of course the door bell button as well as the camera. It would be nice to have a ST interface.

+1 for Skybell integration.

I have a sky bell, but

So, not until they have an API