Shelly Plus I4 always detects ON-Signal when 230V-motion detector output is connected

[matt]

Hi all,

I have connected the signal of a normal 230V motion detector (Link to motion detector) to an input of a Shelly Plus I4.

Unfortunately the Shelly always detects On on this input.

So I did some measurements when the motion detectors output is connected to the Shellys input (SW1).

The motion detector and the Shelly are supplied by the same circuit (phase and neutral).

- Output of the motion detector when switched on: 235 V AC

- Output of the motion detector when switched off: 114 V AC

 

My first thougt was that maybe there is some voltage is inductively coupled on the connection. So in parallel to the Shellys input i connected a 230V relay to have some additional load on the signal. Here are the voltages of the signal in this setup.

- Output of the motion detection when switched on: 234 V AC

- Output of the motion detector when switched off: 55 V AC

So even with a load the voltage is still too high when the motion detectors output is switched off.

 

Based on that i measured the motion detectors output while there is nothing connected to it.

- Output of the motion detector when switched on: 235 V AC

- Output of the motion detector when switched off: ~ 4 V AC

From my point of view these voltages seem to be ok.

 

I measured the voltage of the Shellys input (SW1) when nothing is connected to it.

- Voltage on Shellys input while nothing is connected: 25 V AC, 105 V DC

From my point of view these voltages coming from the SW1-input could cause my problem.

Can someone confirm that there is some voltage on the Shellys input even there is nothing connected?

Does someone also has recognized some similar behaviour?

 

Thanks

matt

[Olsche]

This is normal behavior for the Shelly's SW inputs. There are 2 options: Either install a coupling relay between the motion detectors and the input or get a motion detector with correct potential-free switching contacts.

[terae]

Like already told, you need dry relay between those if the supposed to be triggering one leaks voltage. If any voltage difference, it will trigger Shelly SW input. There's about half of voltage at input with small energy (partial wave), so it will trigger to any difference (to L or to N or something else if leaks to different potential).