Clearly I'm doing something wrong because I've built this basic circuit and my mosfets are failing and locking ON. I'm not sure why thought.
Application: I want to be able to control a flipper on a pinball machine using a microcontroller. This circuit is just a concept for the final design.
The pinball machine has DC power supplies for 5v, 12v, 24v, 48v.
The flipper coil circuit is very simple. One side of the coil is connected to 48v, a button is pressed which closes a switch giving the current a path to ground and that actuates the flipper. You can take the "ground side" of the coil connect a test lead to it and touch it to ground and it will fire.
Attached is a picture of what I'm trying. I am connecting the Drain of an NPN mosfet (
http://www.mouser.com/ds/2/149/RFP12N10L-100355.pdf) to the "ground side" of the coil. The Source is connected to ground. I have a wire going to the 5v power supply, through a switch, connected to the gate and a 10k pull-down resistor connected between the gate and ground. Here is a sketched schematic.
I'm finding that with this setup, when I press the button to send 5v to the mosfet, the coil will fire and lock on. After the first firing, the mosfet is damaged and the connection between Source and Drain is a short.
It seems like everything on the mosfet is within spec, but I'm damaging it and it locks on. Is it that I need a resistor limiting the current to the gate? Is that where I'm causing the damage?