Paul discussed buying LEDs and I decided to write about some of my experiences with buying LEDs in this blog.
I bought some LED assortments from an eBay seller, I think he’s from Canada. He’s still selling stuff.
Most of the LEDs had bubbles in them. I dealt with him through email, and I said that the LEDs were seconds or rejects, and he agreed to replace them. His prices are not inexpensive but after dealing with him I can vouch for his honesty.
I bought LEDs from another eBay seller, and they also had bubbles in them. I emailed the seller and the witch replied and told me that there was nothing wrong with the LEDs and if I filed a dispute complaint with eBay she would tell all the other sellers that they should not sell to me – to try to ban me. Needless to say I filed a dispute, and I finally got my money back but I had to pay a few dollars for return postage and a tracking number. I’ve never had to deal, before or since, with an eBay seller with such an argumentative and bad attitude.
So if you buy inexpensive LEDs you can expect some or all of them to have defects. They may put out enough light to meet your needs, but they most likely won’t meet the specifications. Common defects are bubbles, and mechanical errors that cause the beam to be out of spec, such as the chip being off center in the clear epoxy lens. One electrical defect is the wire lead is not bonded properly to the chip and may cause intermittent or dim light output.
But the biggest problem I’ve had with white LEDs was with the ones I bought from Hong Kong or China. I did a lot of 24/7 tests for thousands of hours with white LEDs and wrote them up in my late watsonseblog, After a few thousand hours, those LEDs put out a small fraction of their initial light output. to the point where four of those ‘used’ LEDs were much dimmer than a single identical new LED. The only maker that I tested that had long lasting LEDs was Nichia.
For low power projects where the LEDs will be turned on for only a few hours a year, such as flashlights (torches), any white LED will last years. For low power, where the LED will be putting out 20 percent or less of its maximum power, the same applies: any white LED will last a long time.
I looked at some of the LED packages to find out where I got them. I purchased one package at SuperBright LEDs a few years ago, they’re still selling them and a lot more. I purchased at least a few hundred from Nichia, when they were a dollar apiece. These white LEDs survived 24/7 testing for more than a year, probably more than 10 thousand hours, and I would buy their LEDs for any LED lighting where long lifetime is important.
Oh well I have ordered some white ones from DX and I will await my fate. There seem to be some (in various devices) that are quite good that seem to have a small cup / disk of yellow phosphor in them but mounted in a package like the old ones with an anvil and a small wire going to a point. I have not seen any with bubbles in yet. They are 10 for ~ £2 so I have not risked much. Interestingly my very old (and unused) ones seem very poor judged by the standards of newer ones.