From FB comment
Monty Ross
It’s true that optocouplers are used for isolation. But I have seen whole sections of PC boards with a hole burned where the optocouplers used to be. It is incredible how much damage the power lines do to the PC boards due to high voltage spikes in the power. Transformers are safer. I think the cheapest way would be to wrap a half meter of thin gauge solid wire around the power wire and tape over it with electric tape. The capacitance will pick up enough AC to be amplified and turn on the controller. It takes up minimal space.