First, the coil you refer is pretty small... so no.
yes 3v3 is fine, it only establishes a reference voltage.
Any power fet will do.... we are only dabbling with 200ma at most... so 4110 is great..
Was fiddling with the board today, and hooked it to the house AFTER I had set the voltage... It ran local loads of up to 4kw perfectly and stably..... when I hooked it to the house circuit... without even turning the contactor on... the voltage moved by 15v.. down.
Tried all sorts of things to see why.
1. replaced the 14007 with high speed fr107... small difference.... changed the position of diodes with the 50k resistors... ie rectify first, then through the 5ok resistors.... small change again... cut off the 10k resistor in parallel with the pot... small change.... but have not solved it at all really.
If I set it to the house circuit... it tracks fine within a few volts over a 5kw range... but there is something of a high impedance fault I can't get to grips with yet....
Small filter before the 240v goes to the voltage sense network helps a bit too.
,,,,,,,,,,,,,,,,,,,,,oztules
Always something I didn't think of apparently... it is annoying, not a game changer though.