LED tester

[TC Chris]

There's one born every minute, as P.T. Barnum observed, and it seems that his name is Chris.

I was aiming to watch a sailboat review video, and since I don't pay YouTube, they subject me to ads. This one was from Jameco, a company I've bought electronic stuff from (most recently, two little Christmas tree kits that flash their LEDs). This one was for another kit, an "LED Buddy."

It's a little device with a readout screen. You lay the LED across the contacts and it tells you the series resistance and the current for various voltages, or the voltage and resistance for a selected current draw. You don't have to know the characteristics of the LED.

So Chris raised his hand and handed over his credit card number and an LED Buddy kit is on the way. More reports later.

Chris Campbell

[TC Chris]

I've been assembling the little Velleman kit from Jameco. It's a high quality little thing, with sturdy circuit boards with through-grommets. I had to grind a point on my old Radio Shack pen-style soldering iron to be able to head just the solder pad I wanted. They are tiny so I check afterward with a magnifying glass to verify good joints.

The instructions are basic, mostly told in pictures. There are special cautions abut polarity of diodes and such. The resistors are called out by value and color code.

Chris Campbell

[electra225]

Keep us posted on how it works for you, Chris. You never know when one of us will come upon something that will help everyone.

[TC Chris]

I finished the kit tonight and it works. Here are pix of the circuit board I assembled, and the LCD screen board that was preassembled with surface mount components. There's a 6-inch rule for scale.

Then I put the two sections together. Add a 9-volt battery, turn it on and it greets you with "LED BUDDY" on the screen before saying "Touch LED." I did. First try, it did not show anything, which meant I had the polarity reversed. I knew which was which for this new LED, but with a mystery device, it's either dead or backward. With the polarity right, here's what I got.

It had two little pots, one for voltage and one for current. You can vary both and it calculates the LED's proper voltage and the series resistor to match your E and I. Very handy. It will allow me to use LEDs more readily.

Chris Campbell

[William]

Nice job, Chris. So this little device is to check LED lights?

Bill

[TC Chris]

It's not so much to test them good/bad as to test how to use them in a given circuit. Figure out what the voltage is where you want to use them, and it will calculate the series resistor you need for the LED you are hoping to use. It will let you fiddle with current to get the brightness you need. You can see all the data it gave me on the screen in the photo. I set the voltage and I set the current.

I suppose its helpful to know the max current rating for the device under test, but it will let you choose any current, which affects brightness. There are probably limits--exceed the current rating and it will likely die like an incandescent subject to over voltage.

Chris Campbell

[TC Chris]

Ordered up the Velleman component tester last night. It got a thumbs-up on an FM tuners forum. Of special interest, it tests transistors, and tells you which lead is which and what kind it is. It also does inductors, resistors, and caps.

https://www.jameco.com/z/WSMI8115-Velle ... 45343.html

Looks useful. I've got a stash of mystery transistors, coils, etc.

Chris Campbell