As we are talking of an event that took days to happen, on a solenoid coil that can take up to 5 amps and in an automotive environment I wouldn't discount that repetitive effects of seemingly negligible effects and perhaps marginal components and unexpected power surges could fry a MOSFET that drives a relay that uses an 1N4007 as freewheeling diode.
We also know nothing about the car itself and we cannot assume that we have the old watch in a new car. Actually I think it is reasonable to assume that the situation is quite the opposite: an old car with extreme power transients all over it at crank up time. One of this cranks, or a failing alternator or dynamo regulator plus a weak (high internal resistance) battery can send even hundreds of volts transients through the power line, zap the MOSFET and then burn the coil. On Monday, January 13, 2020 at 4:33:33 PM UTC-3, gregebert wrote: > > If the MOSFET turns off very fast, it's possible the free-wheeling diode > will not turn-on sufficiently fast to clamp the spike to a safe level; > given the currents involved in this circuit, I doubt this would happen. But > if this was an electric vehicle, engineers will be spending a lot of time > optimizing the design tradeoffs and probing around with a scope. > > -- 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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/fd889588-69bc-4513-9fca-5117f2ac9c04%40googlegroups.com.