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Author Topic: Mismarked LEDs  (Read 946 times)

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SavannahLion

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Mismarked LEDs
« on: June 16, 2013, 06:40:41 pm »
Given that a TPH LED is typically oriented as such that the long lead is the anode and the short lead/flat side is the cathode. Is it unusual to come across a bunch of leds where the orientation is mixed up?

I opened up a bag of blue LED's and tested them based on their lead lengths and had no problems. So I was doing another test where I clipped the leads and forgot which side was which and used the flat side as a reference. It wouldn't work. Tested the circuit with a different color LED and it worked perfectly. So I pulled out another blue LED and still no go. WTF?? I was pulling out my hair until I inadvertently installed the LED backwards and it lit up like a star.

These are 3mm so they're rather small but I finally realized that the flat side is on the anode and not the cathode.

Thought I was smoking crack and double checked online which is supposed to be the flat side, yep, cathode.

Is this sort of thing common with LEDs? This particular batch is the cheap Chinese crap and I did get them cheap on eBay so I imagine that part of the low cost is due to the defect. Which was oddly not mentioned on the description. Checked elsewhere on line and see no mention of LED's being mismarked. Guess I'll break out the ol' sharpie and mark them correctly.
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MonMotha

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Re: Mismarked LEDs
« Reply #1 on: June 16, 2013, 11:23:56 pm »
Decidedly not standard.  Do you have a real datasheet for these?  Sometimes deviations like that are called out in the datasheet, but I'm guessing it's just a production error, which might explain the cheapness.
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kahlid74

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Re: Mismarked LEDs
« Reply #2 on: June 17, 2013, 11:36:25 am »
I've experienced this before, especially with Chinese manufactured LEDs.  I always test them when I get them just to make sure it is all working as expected.
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SavannahLion

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Re: Mismarked LEDs
« Reply #3 on: June 17, 2013, 11:37:30 pm »
Quote from: MonMotha on June 16, 2013, 11:23:56 pm
Decidedly not standard.  Do you have a real datasheet for these?  Sometimes deviations like that are called out in the datasheet, but I'm guessing it's just a production error, which might explain the cheapness.

not really, just what was in the ebay description. IIRC 3.3v and20mA. I just needed a bunch of 3mm LED and didn't want to pay an arm and leg for them.

Just as well I guess. Get what you pay for. At least the AVR stuff on Digikey has better pricing.
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