I have a breadboard circuit that controls some solenoid valves and am trying to move it to a PCB along with improving it for ESD and EMI.
This is the circuit I have on the breadboard that I want to add ESD protection to:
Should I add the TVS diodes before or after the flyback diode?
So far, my thinking is that I should put them after because I want the coil discharge current to go through the flyback diode (which can sustain that current steady-state) instead of the TVS diodes.
Everything below the blue line is on one board. Everything above the blue line is off board. There's a connector and a few feet of wire in between the two.
I'm mainly worried about ESD damaging the FET when people touch the connector to plug or unplug the cable. The only thing on the +12V net is more copies of this circuit for additional valves, so I don't think there's anything else sensitive there.
Basically my question is whether the left or right layout for the diodes better and why: