OK, if the input is mechanical, and basically shorts-to-GND for turnin, then you're OK because the resistors you have will act as a pullup, and shut off the MOSFET.
Next, we need to look very carefully at the circuit layout, because there are ways the free-wheeling diode could en-up not helping at all. If at all possible, mount the main free-wheeling diode directly at the solenoid/relay because it is the source of the kickback. Having a secondary free-wheeling diode near the MOSFET will help, in case the relay is mounted remotely. Next, what does the relay control ? If it's contacts are switching power from the same source that drives the MOSFET (+12V, gnd, or both), you could have other unexpected glitches from shared inductance. Years ago, I fried an expensive transistor because it shared 6 inches of wire with another transistor that shorted-out. Lastly, is it possible the mechanical gizmo that turns-on the MOSFET got stuck-on for an extended period of time ? For example, if a motor/gearbox drives it, it seems very possible the motor could stop with the contacts closed if power got pulled at the wrong moment of time. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/4613a5b0-dac9-41b9-9bcd-8e385df4d467%40googlegroups.com.
