Fibaro Universal Binary Sensor with Door relay - Problem & advice needed

Hi All,

I am considering this device and hope someone can confirm that it would do what I need.

I have a Doorbird, which has a 2 wire, 0 voltage relay which allows the Doorbird to trigger the gate release using a mechanical switch or button. The issue I have is when I installed the Doorbird and the wiring, I only use Cat5E cable and it appears that the lengthy distance is causing a voltage drop (is that even possible?) causing the mechanical button to only trigger the door release occasionally (multiple fast presses of the button usually get it to trigger but its problematic). I tried many switches all with the same result.

Unfortunately running thicker cable to the Doorbird is no longer possible as the cables are buried under the ground in conduit that wont allow more cables to be pulled through.

About half way along this cable run there is a possibility to join the cable into something like a Fibaro Universal Binary Sensor and power this sensor using DC power (the cable goes into my attic and theres power and so on up there).

Would it be possible to plug this 2 wire from the Doorbird into the Binary Sensor and then use something like a Fibaro ‘The Button’ somewhere in the house to trigger the relay?

What I find is the gate is unlockable using OpenHab2 but really its so much more convenient to have a nice large button somewhere in the house (or multiple buttons) to easily allow the gate to be unlocked by a visitor leaving or someone arriving)

Would it be possible to also use this sensor for a Doorbell sound input from the Doorbird?

See a drawing


I’ve also just released I can just use a standard zwave button (Fibaro or other) to just trigger the gate release without the universal sensor ! Derrrr

Perhaps this is better.

Yes of course, DC voltage drops significantly with the distance and the size of the cable.
This is why PoE uses 48v
This is why Edison plan to power the world with DC failed and Tesla’s AC won.



Can’t you just increase the voltage?

Hi Vincent,

The wires have no voltage on them according to Doorbird


There must be something of a voltage for the doorbird to detect that the switch has been closed
Time to get the old multimeter out again… :smile:

When you press the switch the voltage on the 2 doorbird connectors WILL drop to 0 because the switch is closed

OR maybe that’s the problem. It DOESN’T drop to 0 because of the length of the wires. Wires have a resistance. And doorbird don’t detect the closed switch.

Your fibaro solution would work. Or a hacked up sonoff basic with the power traces cut off and used as a dry relay. A bit like a sonoff 4CH but with only 1 relay.
The closing relay needs to be quite near the doorbird to ensure a good detection

I think ill use the Fibaro or Aeotec button and use the relay like this - no wires, no issues :stuck_out_tongue: and less hardware!