I'm currently building a project that involves a 2-stroke engine. I have tapped into the wires where you would normally place a kill switch in order to get power for some electronics. The voltage is 9VAC. The first half wave is used to supply my battery and logic circuitry with power. The second half wave, I've discovered, that if you draw more than a few mA it will mess with the ignition and stop the engine, so I didn't use it for power.
But then I found the need to be able to use my MCU (an ATtiny84A) running on the first half wave's power to short the other half wave so it can stop the engine if something goes wrong.
- I can't use a relay: it draws too much power.
- I can't use a MOSFET: the two waves have the opposite potential.
- I can't use a latching relay: not in stock where I live (can't buy
online due to shipping restrictions).
- I can't use a reed relay because the ones I find are NO but I need it to be NC.
- I can't use an SSR: only available for higher voltage range.