Picture of Make a simple LED tester.
This is a very simple but useful LED tester that lets you test, compare and check the colour of just about any two pin LED.

To make it you will need the following:-

A PP3 battery connector.
A 470 ohm resistor.
A bit of heat-shrink sleeving to cover the resistor.
A two pin Molex style 0.1" (2.54mm) pitch miniature socket.
Two contacts for the socket.
A PP3 9V battery. Alkaline preferred.

And some LEDs to play with.
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Step 1: The battery connector.

Picture of The battery connector.
The main part of this instructable is a cheap and common PP3 battery connector used to connect to the small rectangular 9V batteries.

Step 2: Adding a resistor.

Picture of Adding a resistor.
The tester needs a resistor to limit the current through the LED. I generally use a 470 ohm resistor which has the colour code:-
Yellow, Violet, Brown and gold. (For a standard four band resistor.)

To put the resistor in line the red lead is cut about 2" (50mm) from the end and the wire stripped, the resistor soldered in and a piece of heat-shrink tubing shrunk over the resistor and solder connections to protect them.

The three steps are shown in the image.

Step 3: The LED socket.

Picture of The LED socket.
This project uses an ordinary two pin Molex style socket to connect to the LED. To use the socket you need to crimp or solder wires to the contacts before they are pressed into an empty socket shell. The crimping tool for these contacts is quite expensive, so you may find it cheaper to just solder the wires to the contacts as shown.

Since the red lead may be slightly longer with the inline resistor, it's may be a good idea to trim the red and black leads down to the same length.

The easiest way to solder these contacts is to tin both the contact and wire with a touch of solder and then touch them both together and reflow the solder with your soldering iron.

Step 4: Assembling the socket.

Picture of Assembling the socket.
Once both the contacts have been soldered to the wires they are pushed into the housing so that their little latches click into place in the matching slots in the socket.

Simple, direct and easy to build. A suggestion and a question.

Using a 9V Battery holder, and gluing the molex to the plastic battery holder would make a more compact tester, no? I believe that there are holders(sockets) made for LEDs that you could use as well (Smaller, easier to solder to) but (on dialup) I can't locate them on the web just know.

Do you know if there are LEDs 'out there' that might be damaged by the 9V power source? I assume you added the resistor to prevent this. I ask because I have salvaged LEDs from various boards and have no idea of the specs for them and was looking for a test device that would serve without possibility of burning up the subject LED.

OR, why use a socket/holder at all!

Multimeter Probes - Tweezers


Description: Testing surface-mount components with
standard test leads is anything but easy. Everyone has their own method:
some people tackle it with teamwork and have a friend (or grad student)
hold the probes, some people have adapted a sort of chopsticks-like
technique, but the best way by far is probably just to buy these handy
tweezer probes! Tweezer probes connect to your existing instrumentation
with shrouded banana connectors and allow you to easily test small parts
with one hand. The large plastic tweezers are easy to grip and are
marked for polarity.

Dimensions: Tweezers are 6" long with 10mm open clip distance. Wire lead is 16" from tweezers to jacks.


Jenn Nelson5 years ago
Really easy, and super useful.
Mudbud5 years ago
Nice job dude.****
Goodhart6 years ago
Simple and elegant. I like this. :-)