I admit it: I'm a total geek. I love electronics, programming, 3D art, vintage Apple hardware, and whisky. I'm always juggling half a dozen projects. I also enjoy documenting it all: my successes, my failures, my experiences... and everything geeky along the way.

Seeed Studio Fusion - $9.90 for 10pcs 2 layer 10x10cm boards


LED Tester | Kevin Rye.net - Main

Kevin Rye

Geek Extraordinaire. Yeh, I said it.

LED Tester

I’ve made a few devices already that have used 0603 SMD LEDs. 0603 LEDs are beyond tiny and they’re a little trickier to work with when orientation matters.


If you look closely at the back of the LED, you’ll notice some markings that indicate which end is the cathode, but in reality it’s really easy to lose track of which end is which.


When I was assembling one of my Button Breakout boards, one of the LEDs didn’t work. I didn’t know if I over-soldered it (unlikely) or if I had somehow flipped it the wrong way when I soldered it (more likely).

It would be so much easier if I had a quick and dirty means of testing the orientation before soldering one.

I decide to put together a small LED Tester board. It’ll be powered by a small coin cell battery. I can pick up an LED with a pair of tweezers and just simply tap it to the solder pads. If it lights up, I know I’m holding it the right way, or not.

As far as a PCB, I want it to be super simple and super cheap. I really don’t want to spend $10 bucks on something so simple. However, I don’t want it to be a one-trick pony either. Ideally, it should work for through-hole LEDs as well, as 1206s and whatever other sizes I can’t think of right now. Do SMD LEDs come in an 0805 package? I’ve never seen one, but it’s probably a good idea to place some large pads on it so that it’ll work for anything.

Screen Shot 2013-12-06 at 8.46.40 PM

The PCB measures 0.8” x 0.8” and is as small as I could make it. I included a little notch so that it’s easier to remove the battery. I have a pad for PTH LEDS, 0603s, 1206s, and some large pads for whatever else.

Screen Shot 2013-12-06 at 8.45.21 PM

Here’s the OSH Park render.

LED Tester v1.0 front

LED Tester v1.0 back

It looks pretty big, but in reality, it’s about the size of a quarter.


After about 2 weeks, my PCBs arrived. They look great.

LEDtester_0001 1

This had to be the easiest assembly ever. All I needed to do was solder in the battery holder along with a 68 ohm resistor. Testing through-hole LEDs couldn’t be any easier!

LEDtester_0006 6

As far as SMD LEDS of the 0603 variety, I just have to hold one with a pair of tweezers and tap the pads in order to see if the LED is good or not; at the same time identifying which end is the cathode.

LEDtester_0004 4

What a handy little trinket! I can already tell this will be one of those silly little things that’ll make you wonder what you did without it.