I'm creating a power supply with an input fuse and and output fuse, and I'd like to have blown fuse indicators. However, the circuits I have found typically have set voltages and thus set resistors, which would give me varying levels of brightness, or not work at all. I'm using chassis mount fuse holders.
Input Fuse: 12V to 24V variable, but I'd like the same brightness regardless of voltage. If there's such a thing as a constant-current LED driver that's not very complex, this could work - there will always be 12V-24V on this when I'd expect the LED to be lit if the fuse was blown.
Output Fuse: 0V to 20V variable, and I'd like the LED to indicate blown even if the output voltage is 0V, but wouldn't want this voltage or current affecting the load (or requiring that there be any).
I do have a microcontroller on the board, and I could thus drive the LEDs with the digital output pins, but would prefer a solution that does not use it. Is such a circuit possible?
Essentially, I'd like to power the LEDs with a set voltage (I have 5V and 12V rails), irrespective of the voltage on the fuses themselves.