Fibaro dimmer as doorbell?

Hello Everyone,

I’m running Openhab2 & have several Fibaro dimmers, one of which is near my front door.
Would it be possible to connect a second momentary switch to it & use it as a doorbell?


Yes, you can attach a second input to FGD-21X devices.
But be aware that
a) an installed doorbell is usually using it’s own circuit, often 8VAC powered (yep, pretty strange one), you may not have that power source in the circuit (power to the switch comes from the FGD device)
b) that will just notify openHAB of the button being pressed (btw: you can distinguish single, double, triple presses, press-and-hold)
You will have to code in openHAB rules what is to happen when the button is pressed.
I, for instance, am playing a MP3 sound through my Pi’s soundjack, plus I make the ceiling lights blink in a couple of rooms I might be in where I wouldn’t hear the bell, such as in my office in the basement.


I’d agree that input S2 of a Fibaro FGD-212 could be wired to a momentary push button and programmed to trigger speech or audio as a door bell, this is likely to be dangerous.

Fibaro dimmers typically use a simple capacitive dropper power supply which means it is not isolated from the mains.

As @mstormi says, doorbells use an unregulated but fully isolated transformer providing 8-12V AC. This means bell push switches are simple mechanical designs without the insulation and waterproofing needed to protect a visitor from 220-250V AC mains voltage.

Whilst you could rig up something like a 6-12v relay to provide some isolation between the LV bell supply and HV dimmer, I’d suggest it’s simpler to try something like…

The script for the door bell is the easy bit - playSound(“doorbell.mp3”) , add speech, or even send an email complete with an attached web cam image of the visitor.

I haven’t measured the Fibaro FGD, but my Qubino dimmer just pushes 55V through the switch circuit, right below those 60V where (at least in Germany where I live) the border line is drawn between ‘low voltage’ and ‘dangerous’.
But @FloatingBoater is right, to insert a relay is definitely a better idea than this is. A 55V shock still is … well :slight_smile:

I myself have wired my doorbell to a Fibaro Universal Sensor (which is capable of running on 12-30VDC). Couldn’t reuse the existing 8VAC transformer, though, had to put in a higher voltage one.


The hidden danger with capacitive dropper power supplies is they are not isolated from the incoming mains electricity supply like older linear transformer suppliers were.

Between the PSU output terminals could be a low voltage, but referenced to earth (e.g. what you stand on in a rain storm…), a non-isolated supply can still deliver a mains voltage shock.

Although European standards are nominally the same for inter-working of CE-marked appliances and mains supply is deadly, it is true that some countries can be seen as being more deadly than others (and not just due to the beer…).

My local UK electricity supply is arranged +240V AC / OV, whereas some countries actually supply +110V AC / -110V AC halving the potential to earth with the same AC voltage between the supply terminals with a centre-tapped consumer-side transformer.

Could that be why you saw a lower 55V? - sounds like referenced to earth as the kit itself is probably more like 12 or even 3.3V.

Mind you, I still used to jump with 48V telephone ringing voltage close to the kit in the exchange despite BS7671 and IEC saying it’s only SELV!

This reminds me of a tale told to me by German relative who returned from the US with a fantastic new vacuum cleaner - after replacing the plug it apparently worked amazingly well for two weeks … until the 220V AC supply finally burnt out the 110V AC American motor! :smile:

Hi Everyone,

That for the replies.

I don’t have an existing doorbell to worry about & I had already anticipated the voltage issue, so was planning to use something like This.

Mostly I’m just not sure how to reference that switch in Openhab.
Was planning to use the say command & audio sink to squeezebox.

On a FGD-21X attached to S2, set zwave parameter to have it be a scene controller and use something like

Switch GarageEins “Aussen Garage” (Szenen) { zwave=“19:command=SCENE_ACTIVATION,scene=26,state=1” }
Switch GarageZwei “Doppeldruck Aussen Garage” (Szenen) { zwave=“19:command=SCENE_ACTIVATION,scene=24,state=1” }

And, once the hardware is in place, you can create a rule to play sounds, speak or even send email:

rule "Doorbell Trigger"
    Item Doorbell changed from CLOSED to OPEN
    logInfo("Doorbell", "Rule entry...")
    logInfo("Doorbell", "State: " + cHall_Doorbell.state.toString())


    say("There's somebody at the door!")

    sendMail("", "OpenHAB Doorbell", "The doorbell has been pressed.", "")

    logInfo("Doorbell", "Rule exit...")

Thanks for all the tips everyone!
Now just need to find time to sit down & tinker.

I’m trying to kind of the same.
Is using a Fibaro dimmer2’s S2 input as a scenecontroller.
My rule is:

rule "turn off all on ground floor with scene 26"
    Item Kitchen_SceneNumber changed to 26

My problem is that the rule is only triggered the first time, so I have to switch the dimmer2’s scene number between each activation (like activating S1).

I guess this is a problem with the Fibaro dimmer2?


Item Kitchen_SceneNumber received update 26

Damn Scott, it worked!
I felt confident that that wasn’t the problem since I only saw updates in the event.log when the scene number changed, therefore assuming that the dimmer only sent updates on changes…

Great. Thanks for your help, I love this forum!

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