There was a hand held probing device build from my scratch, it is so far ok but it was not so really handy, why ? Need one hand to hold two probes and then the other hand press the button to test, hum, it was handy but not really.
One picture inspires to a better design and I did finish the build, now, it is real handy tool for LED sorting, no switch, only load the battery to test or remove the battery off, this battery can be last for at least 50 hours continuous operation. Brightness is able to adjusts (turn Variable Resistor) and dimmed a lot with more eyes safety. The probing operation good indicator (amber LED) is light when it is ready for test, if no, replace a battery at least 0.4V.
materials : wood chassis, 1″ and 1/2″ bronze plated tacks, AA battery holder, button head screws, wires, wire terminal, prober circuit
This assignment is done.