Whilst I wait for yet another batch of Morse Practice Oscillator boards to be fabricated and shipped, I’ve been working on a really simple fuse tester. Rather than have the usual continuity circuit, I want this to be a little different and be educational.

I decided to include LEDs to indicate either a good or bad fuse. Green for good, red for bad. The circuit is quite simple. It is triggered by a tact type switch on the board where a transistor either switches on or not depending on the validity of the device under test.

Simple Fuse Tester Schematic

I have included two fuse holders for the two main sizes of fuse and the option to use either two single LEDs or a BiColour LED. I am hoping to have the CR2031 3V battery on the rear of the board to save some space.

The fuse holder pins and the battery holder components are en route at the moment. When they arrive, I will measure them up and create custom symbols/footprints if I can’t find them in the current KiCad libraries.