Incandescent to LED Circuit Tester

Found one of those old school 12v circuit testers that had a blown bulb.

Noticed that the bulb was the same size as some fuses I had nearby.

Using the heat from a soldering iron, the end caps were very easily removed from the fuse.

Also had a 3mm red LED lying around nearby, which just happened to fit nicely inside of the glass fuse.

Since I normally work with 12v or less, I picked a 510-Ohm resistor, to pass 20 milliamps at max voltage.

Works from 2 to 12 volts, but of course the brightness decreases the lower the voltage is.

Sure, you can buy these things cheap:

From places like Harbor Freight Tools, but maybe the idea of inserting an LED into a fuse casing could be useful to someone out there :-)