Help designing my own diode tester with decent drive circuitry

The "diode test" is simply a resistor from a voltage source to put current though the diode, with the multimeter reading the voltage across the test terminals.

A battery and resistor are all you need, with 4mm sockets and patch leads if you want to make a really fancy version rather than just hold the meter leads to the same places.

The battery should be something in the 6 - 9V range, so the current does not change too drastically with different LED voltage drops, and there is still sufficient voltage when the batteries are near flat (2/3 of the nominal voltage).

A 1K resistor should be suitable with either voltage, or 470 Ohm for more output; anything less than 20mA should be pretty safe on most things.

amateur_24 said:

I have a not so cheap multimeter from rapid electronics. It doesn't have a decent diode mode as it can't even light a regular led. I tried it on a ir led, it wouldn't even give me a forward volt drop reading.

Is it possible I can build a diode tester using my uno? It has to use through hole components since am hopeless at smd. I want it to have decent drive circuitry. If possible as good or better than what you would typically find in an expensive meter ie bryman or a fluke.

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Diode test range on a multimeter isn't intended to test, or light, LED's - I would strongly suggest you order yourself a 'component tester' kit like one of these:



There are numerous different types, great fun to build (I think I have four different ones ) and indispensable for checking all kinds of components, including LED's. Everyone should have (at least) one

If you ant to build your own from scratch, here's a nice simple example - which is basically an Arduino Uno with most of the bits left off:


All these devices are based on the same original design, from a German guy if I remember correctly?, and the software is freely available.