Simulate pushbutton for 24vac relays

  • Hi all,

    I'm looking for a solution to simulate the push of a button to control my lights.
    Right now i have wall push buttons installed to control my lights. These buttons close a low voltage 24VAC circuit to operate a DIN mounted relay on my electrical control board to switch my lights.

    Is it possible to build an Arduino sensor that (preferably) fits inside my wall switch, and can simulate a pushbutton that closes the 24VAC circuit for a second to act like someone is pushing a button? I would like this to work parallel with the current setup, so it can sense manual buttons pushes as well and report this to my controller.
    If not possible to build it very small it would also be possible to mount it at the electrical board.

    Any help or tips would be awesome!

  • Hero Member

    I'm doing something similar with mysensors but not behind my wall switch. My Relay is near the DIN mounted relay.

    I use a modified version of:

    With a code like something like this:

    The code is not tested! I'm using a more complex installation with 4 relay and 8 SSR.

  • Hero Member

    @gizzmo You can build a very small sensor (even battery powered) to simulate the switch. I don't understand from your post how you want operate the relays. To operate them directly from the Arduino you will need some kind of amplification (Mosfet) and a power supply (24V to 5v, buck) This will take some extra space.

  • @TimO Would you mind showing a sketch of your setup, and the used components?

    The thing I don't understand is how you simulate the button push ...
    It looks like you use a relay, but is a relay not always on or off? so sending a 24V pulse to the DIN Relay only requires the relay to switch on for 1 sec.

    is that what you are doing here?

         // Change relay state
         // WE ONLY EXPECT a 1 == on HERE
         digitalWrite(message.sensor-1+RELAY_1, message.getBool()?RELAY_ON:RELAY_OFF);
         digitalWrite(message.sensor-1+RELAY_1, RELAY_OFF);

    @AWI I think you are right looking that the size to accomplish my goal, the sensor in wall scenario is going to be to big.

  • I'm thinking about a similar project. One thing I'm struggling with is how to detect the current relay status. You will not notice when another push button is used, so your MySensors device in your controller will only switch between on and off without any meaning to the physical relay on/off. Maybe it is possible to use a mosfet with the 24v relay connected as gate to sense a switch-event triggered by any push button to update the status of your light. Just an idea at the moment, maybe someone with more knowledge on electronics can form a curcuit out of that.