LED TESTER

Sure, with a hand full of dime priced parts and a little time and you can build this gadget, but put your time to better use. Look in the current Digi-Key catalog, page 1071, Stock# 67-1398-ND You can buy it for only $38.00!

Now, get back to the order screen and
buy this tester from ALL Electronics (before they read this and increase their price!)

This is a inexpensive knock off of the LUMEX LED Tester Box at 1/4 the cost. It does however use a cheaper header than the screw machined header on the LUMEX tester so the insertion
life will be less. If you need to test hundreds of LEDs you would need a ZIF socket which even the LUMEX tester does not have. The new LUMEX tester now tests 3 terminal devices for the same price but the price is still closer to 40$ than 10$. Good addition to the tool box.

This is a good little tester but I've had mine for a few months and the sockets (where the LEDs plug in) are already getting loose. Even in the ones that I use infrequently (like 2 & 5 ma) I have to wiggle the LED around to get it to light. And, though I have used it on several hundred LEDs so far, this started happening right away. But, I do use it a lot, and asside from the sloppy sockets, it's still working.

Also, it uses resisters to limit the current, not constant current sources, so as the battery runs down, the current level changes.

But heck, for 9 bucks, it ain't bad.

Forgot to mention: because this device uses resistors to limit the current, the actual current that flows through the LED is going to be affected by the LED voltage. For instance: the "20ma" slot is limited by a 390 ohm (or 0.39K) resistor. So, assuming the battery supplies 9 volts, when a red LED, that runs at 1.8 volts, is tested, it will draw (9 - 1.8)/0.39 = 18.5ma A blue LED running at 3.6 volts will draw: (9 – 3.6)/0.39 = 13.8ma. Quite a difference. BUT, a nice feature is the seven 10ma slots (though I would have preferred that it be seven 20ma slots, since that’s the current level I generally run LEDs at). The 7 equal current slots makes it possible to compare the brightness between from 2 to 7 LEDs. So, it’s good for relative brightness, but not so good for absolute brightness – I mean, don’t rely on it to give you an accurate picture of how an LED is going to look at say 20ma, unless you come up with some kind of compensation chart based on LED color (though, even among LEDs of the same color there is variation in the voltage). But then, what do you want for a measly nine bucks ;)

There was a defect in mine. The current-limiting resistor for the 30mA branch is 3300 Ohms (the same as the 2mA branch). Other than that, it works fine. I figure it should be around a 230 Ohm resistor instead. It seems like this is an isolated problem, since it works for others.