Author Topic: Identifying unknown LED colors  (Read 2712 times)

Bret608

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Identifying unknown LED colors
« on: May 16, 2012, 02:22:02 PM »
What's a good way to find out what color LEDs are if you have a mess of unmarked ones? Without frying them (as I've recently managed to accomplish), that is?  :P

pickdropper

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Re: Identifying unknown LED colors
« Reply #1 on: May 16, 2012, 02:30:48 PM »
Personally, I would just use a breadboard.  Put the CLR on the board and just plug in each LED, making sure you have the right orientation.  It'll go pretty fast.
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TNblueshawk

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Re: Identifying unknown LED colors
« Reply #2 on: May 16, 2012, 03:29:45 PM »
Buy a 3v coin battery. That is what I do. Just split the legs with the battery and presto.
John

Bret608

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Re: Identifying unknown LED colors
« Reply #3 on: May 16, 2012, 03:47:04 PM »
Thanks to both of you! Folks here usually give me a variety of solutions--both low and high tech--and I love that!

DutchMF

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Re: Identifying unknown LED colors
« Reply #4 on: May 17, 2012, 02:32:29 AM »
You could also use a DMM, that's how I double check the orientation of them before soldering. Set it to diode testing, and when it lights up, the leg where the black lead is should go to ground (at least with my DMM)
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Bret608

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Re: Identifying unknown LED colors
« Reply #5 on: May 18, 2012, 12:36:16 PM »
Paul, thanks, I do have a DMM so that could be the ticket!

Just to make sure I'm understanding, are you saying I'd put the black lead on the negative/short leg and the red one on the positive/longer leg?

culturejam

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Re: Identifying unknown LED colors
« Reply #6 on: May 18, 2012, 04:40:27 PM »
Some DMMs do not output enough voltage to work with LEDs. Neither of the DMMs I own will measure the forward voltage on an LED. But my Atlas LCR lights 'em up.

You can also get one of these:

http://www.allelectronics.com/make-a-store/item/LT-100/LED-TESTER/1.html

oldhousescott

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Re: Identifying unknown LED colors
« Reply #7 on: May 18, 2012, 07:10:46 PM »
Take a battery snap and solder a resistor in series with either lead, something in the range of 1k to 4.7k. Plug in your 9v and test your LEDs by touching the legs to the leads. Alligator clips make this easier.

alanp

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Re: Identifying unknown LED colors
« Reply #8 on: May 18, 2012, 08:24:08 PM »
I remember which way around LEDs go by looking inside them -- the small tab is positive, and the large tab is negative.
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DutchMF

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Re: Identifying unknown LED colors
« Reply #9 on: May 19, 2012, 06:00:31 AM »
Paul, thanks, I do have a DMM so that could be the ticket!

Just to make sure I'm understanding, are you saying I'd put the black lead on the negative/short leg and the red one on the positive/longer leg?

I'll have to get back to you on this one, as I don't exactly remember what goes where..... As I said in my earlier post, if it lights up, the leg where the black lead is needs to go to ground. Don't know if that is the long or short one, I'll grab me an LED this afternoon and check it out.
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Bret608

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Re: Identifying unknown LED colors
« Reply #10 on: May 21, 2012, 09:56:10 AM »
I appreciate all the suggestions on how to do this--I haven't had a chance to try my DMM on an LED yet, but will report back. I have to say I'm liking that LED tester that Culturejam provided the link for!

Bret608

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Re: Identifying unknown LED colors
« Reply #11 on: May 23, 2012, 08:04:30 AM »
Hi all,

My DMM accomplished this in spades. Thanks for the tip, Paul! It's a $6 Centech multimeter from Harbor Freight tools at that.

I just touched the black test lead to the short leg and the red one to the long leg.

Cheers,

Bret