I think I know the issue, but it the evidence just seems conflicting.
I built a PWM circuit based on a 555 timer (link to circuit) and it worked well enough the few times I tried it, except it suddenly would not turn back on after turning it off. It's running 4 fuel injectors (4-5 amps) at a relatively low frequency.
I originally designed it to run a single 5.4 watt solenoid, but later addapted it to run 4 injectors (~12-15 watts each). However I was thinking of the flyback diode in terms of voltage, not current - so I ran 4-5 amps using a single 1 amp diode (1n4003). Could that have fried the 555 chip?
I've already checked the mosfet and flyback & steering diodes, all seem fine. The 555 chip is won't come out easily, so I can't readily test it. One last thing is the injector +12vdc wire was unsoldered when I initially inspected after failure, but resoldering it didn't fix anything. [It had to have happened as I picked it up, since it initially turned off as I turned the switch off]
So all I can guess atm is a voltage spike killed something from the flyback diode not rated for enough current, or the possitive lead on the motor coming off induced some destruction...
I built a PWM circuit based on a 555 timer (link to circuit) and it worked well enough the few times I tried it, except it suddenly would not turn back on after turning it off. It's running 4 fuel injectors (4-5 amps) at a relatively low frequency.
I originally designed it to run a single 5.4 watt solenoid, but later addapted it to run 4 injectors (~12-15 watts each). However I was thinking of the flyback diode in terms of voltage, not current - so I ran 4-5 amps using a single 1 amp diode (1n4003). Could that have fried the 555 chip?
I've already checked the mosfet and flyback & steering diodes, all seem fine. The 555 chip is won't come out easily, so I can't readily test it. One last thing is the injector +12vdc wire was unsoldered when I initially inspected after failure, but resoldering it didn't fix anything. [It had to have happened as I picked it up, since it initially turned off as I turned the switch off]
So all I can guess atm is a voltage spike killed something from the flyback diode not rated for enough current, or the possitive lead on the motor coming off induced some destruction...