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.


 
 
 
 
 

Testing 200 White LEDs | Kevin Rye.net - Main

Kevin Rye

Geek Extraordinaire. Yeh, I said it.

Testing 200 White LEDs

Jameco wanted .89 cents for a white LED. That’s insane when you need 100 of them. eBay to the rescue! I grabbed 200 LEDs from a seller in China for $9 bucks!

word_clock_0015

I only need 100 for the Word Clock I’m designing. Why did I order so many extras? I’ll tell you.

I found a post from another guy who was building something similar. He too needed a good 100 LEDs for his project and was also reluctant to drop $100 bucks on LEDs. He hopped on eBay and picked up a few hundred “China LEDs” for just a few bucks. Unfortunately, every other LED he tried was either of a different brightness, or they were just dead.

Armed with that knowledge, I picked up twice as many as I really needed in anticipation that there would be a high failure rate.

I just received the LEDs. Delivery was surprisingly quick considering the shipping was free. Before I do anything with them, I’ll need to test all 200 just to see what I’m dealing with. To be quick, I ran 2 LEDs in series through a 1K resistor.

Here’s ~100 LEDs:

100LEDtest

Those looks like crap. The brightness is very inconsistent. Some are whiter than others. Some just look a bluish/gray. Looks like they’re not running at their full intensity. If I used a 330 or 470 Ohm resistor, I’m sure they’d be better. I guess running 2 LEDs through a 1K resistor is too much of a voltage drop. I pulled the LEDs out of the last few rows to test that theory.

50LEDtest2

Wow, they look so much better now. That’s nice and bright! I proceeded to just test the rest of the LEDs in batches of 50. They even miscounted and gave me 3 extra. All 203 LEDs work perfectly and are all of similar brightness.

50LEDtest

That’s awesome. $9 bucks for 200 LEDs and a zero failure rate.

See this project from start to finish:
Word Clock
Testing 200 White LEDs
Started the Word Clock
Completed The Word Clock PCB
Finishing the Word Clock Display
Started the Word Clock PCB Build
Completed the Word Clock