Topic: Inductors and voltage and electro-destruction
Nearly all of the LEDs on the Tinyvette's instrument panel have died. They are simply wired to the 12V power of the car, then to ground, of course with a current-limiting resistor so that they work properly in a 12V system. All very normal, and they only draw about 10-20 mA.
I'm pretty sure that what is happening is that various inductive loads in the system are spiking the voltage and killing the LEDs. These loads come from the electric fan, starter solenoid, and possibly the starter motor itself. For you non-engineer types, an inductor can be a simple coil, and once current is flowing through it it tends to try to keep the current flowing. If you stop the current, such as when you turn off the fan, the inductor will send the voltage up as it tries to maintain the current flow. I wouldn't be surprised if the voltage spike is close to 100 volts. Have you noticed how when you unplug certain appliances that are running that you can get a pretty good arc. At around 10k volts per inch even a 1/8' arc means your seeing a pretty high voltage on disconnect.
So, how to deal with this? Do I install a shunt resistor across the motor's terminals, or an MOV, or a diode? And if so, how do I rate them, such has how much power they can handle?
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