/diy/ - Do It Yourself

>>1616322
The most fatal error is Q1. You used the wrong symbol (n-channel instead of p-channel) and you forgot the drain-source diode which will do exactly what you wanted to prevent in case of reversed battery polarity: it pulls the input down to -Vbat and kills the amp/comp (which also has the wrong input polarity if you want a hysteresis action). I'd suggest to scrap the entire circuit and start from scratch. It's perfectly normal, that's how you learn.