With no snubber Arduino has malfunctions when damper relay swith on/off.
With the snubbers installed, the Arduino malfunctions have been resolved, but I am now measuring a constant 230VAC downstream of the relays (on the damper close/open pins), regardless of their ON/OFF state.
In fact When I turn on the 'open relay', the damper opens. But when I turn it off, the damper should stay in place, but it closes.
The snubber has R=220ohm, C=100nF and a 10D471K varistor.
You are measuring leakage through the capacitor of the snubber. This voltage will drop to almost zero with a load attached.
Another way to use the snubber is to put it across the load instead of across the relay contact.
Snubber circuits are available from the big resellers. eBay, Ali, Amazon etc.
They usually have a 100n/630V cap, a 220Ohm resistor and a varistor fitted.
Leo..
The two relays provide power (phase) to the damper's "open" and "close" pins.
When the "open" relay is activated, the damper opens correctly.
The issue is that when both relays are open, the damper unexpectedly closes. This suggests that a current or phase connection is being made to the 'close' pin even when it should be disconnected.
so this “leakage” current is suffcient to move the damper…
