Use a latching relay. Here is one I found on Amazon. https://www.amazon.com/dp/B015MRQNXS/?coliid=I3LXTGKX4GEPUR&colid=31WWM91JAUE22&psc=1&ref_=lv_ov_lig_dp_it If you are trying to use with existing 3 ways use https://www.amazon.com/dp/B015MSYQ8Q/?coliid=I3RP8X9OMYWU97&colid=31WWM91JAUE22&psc=1&ref_=lv_ov_lig_dp_it Use an optocoupler to indicate lamp status...see the last diagram in this post. https://forum.arduino.cc/index.php?topic=435506.0 ELECTRONICS-SALON Panel Mount Momentary-Switch/Pulse-Signal Control Latching SPDT Relay Module,12V $9.99 2 available ELECTRONICS-SALON Panel Mount Momentary-Switch/Pulse-Signal Control Latching DPDT Relay Module,12V $11.99 2 available