If you have anything to do with DIY electronics, circuit bending, or just messing around with microcontrollers, you will undoubtedly amass quite a collection of LEDs. A great majority of these will be clear, and will only show a color after applying a voltage to them. Also, if you order a batch, some of them will not work, and the only way to find out is to test them. So I'd been wanting to build an LED tester for a while. It seems like every time I wanted to make a project involving LEDs, and when first powering up my circuit, of course the LEDs don't light up. You know that it is probably in the wiring or programming, but you're not quite sure if maybe the LED is bad. Now you won't have to wonder anymore. And of course, I made it out of something fun...

This tester will allow you to test any LED and will provide a constant current, avoiding damage to the LEDs.

Here's the top, allowing easy testing...

  And it's easy to put together...

As you can see, it is a pretty simple circuit. Here is the circuit board assembled and soldered.

And this is the back. (Click on any image to enlarge.)

And here it is wired up. I just used an exacto knife to cut open the bottom of the Lemon juice holder, hooked up a 9 volt and shoved it all inside. I then soldered the 2 leads onto some headers I had laying around, drilled into the lid.

Here is the schematic and PCB design. I made the circuit on a pre-fabbed breadboard since it was such a simple circuit. All of the parts are easy to come by, so building this should not be too much trouble.

And here's the finished product. This provides an easy way to add "juice" to your LEDs without having to wire them up every time. Enjoy.