got the whole board mostly done. had that horrible moment of asking myself wait what problem am I trying to solve again? was originally using USB and 12V because I wanted more flexibility for closed-loop temperature control. ...but with this board I'm not actually using closed-loop temperature control. Just a dimmer knob. I can use a 120v bulb and a shitty triac dimmer like it's 1991. I do not feel clever about this realization. I feel bad about sinking time into such a misguided pcb.