This year for our Halloween display I purchased a fogger at my local Lowe’s store. It worked exceptionally well. My only complaint was it didn’t automatically produce fog. It required someone to manually operate a rocker switch.
The existing hand control is 115v AC based. The green light indicates the fogger is ready and the red rocker switch sends power to the fogger’s pump and produces fog.
The main concern is to isolate the 115v AC from the lower voltage circuitry both for the indicator and to drive the fogger.
I chose to use the H11AA1 Optocoupler to handle the indication that the fogger is ready (Green Light). The H11AA1 is designed to accept AC on one side (pin 1 and 2) and DC on the other (B,C,E). When the AC side is hot two tiny LEDs inside the chip will turn on. The DC side has a photodiode that will detect the light and allow DC current and voltage to flow via pins B, C, and E.
I chose to use a mechanical relay to handle driving the fogger to produce fog.