Power & reliability issues for UV leds

If LEDs are not current limited, then what you have observed is execatly the End Result. It's all Made In China crap now-a-day -- so I would question the 'design' behind it. Maybe, just maybe, it was designed to 'ruin' the LED at about the same time the 'non-replaceable' battery died. Their junk - our landfills.

Separate topic, I guess? Duuno 'bout UV LEDs -- even if they exist. (It's only been recently that blue LEDs have reached The Masses.)

Jonesy

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  Marvin L Jones     | jonz          | W3DHJ  |  linux
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Most of the cheap keyfob LED lights are like that. They are designed with the idea that the internal resistance of the batteries is sufficient to limit the current, and that although the LED is overdriven very hard, it should last the couple of hours the batteries last. Also, they generally have a momentary switch which may extend their life a bit as the LED is unlikely to be powered for more than a few seconds at a time..

Don't know, but my blue keyfob drew 60mA, and taking the resistance of my AVO into account, it was probably much higher than that. No standard LED is going to survive that sort of abuse for long.

Dave

Exactly right on the use of the internal battery resistance to limit the current. A local inventer in Bend had us build a bunch of LED light units for him. They go in skate board lights! The units had two coin batteres and three LEDs, as I recall. These were white LEDs and I think they would run for a couple of hours and then the batteries had to be replaced.

We were way too expensive for him, so he is having the units mfg. elsewhere.

I wonder what the UV LEDs are being used for and how did the poster know if they worked or not?

Paul, Jodeco, Inc. Redmond, OR

AIUI some UV LEDs emit a lot of visible violet light, though I've never played with them myself.

Dave

Thanks for all the observations...Some additional comments:

I've worked with LED's since their introduction way back when, but this little keychain model is my first UV led. It is indeed a true UV, probably 395nm or so. I didn't get much use out of it, the mom switch allowed for quick on-off use on some fluorescent items I had laying around. I don't think it lasted more than 60 seconds in total time. It was quite bright in the UV with a bit more visible light than a traditional "black light" tube UV-B source. I wanted it as a small convenient UV source for quick document checks but just as a little toy really. (something I can admit to this group)

The seller said he will send a replacement. If he does, I'll check and see what current typical UV leds run at and figure what resistance I need with 2 2016 lithiums, maybe I can run it on a single 2016 for a lower, more reasonable voltage, and leave some space for a resistor.

I questioned the reliability for a few reasons, mostly web chatter, but in fact Inova, a reliable company, dropped their UV offering. I wonder if reliability issues lead to that decision, or simply lack of market interest.

Dennis Harper snipped-for-privacy@gmail.com

You might have better luck with a blacklight CCFL, that technology is pretty robust and the blacklight performance is comparable to a standard blacklight fluorescent tube.

Thanks to James Sweet for the CCFL tip. I totally forgot All Electronics had these things. Its currently out of stock but they had a

25mm CCFL for 8 bucks or so, they also have the necessary inverter to provide the proper juice. It's not as small as my little keychain led but it would make a very nice "robust" portable UV source. I can probably find the Velleman CCFL elsewhere. Curiously, All doesn't carry UV LED's. BTW, you can see the keychain version I got on ebay. Search under UV LED, you'll see just one HK seller offering the small keychain coin-cell type. A guy in the states has a different pointer style UV LED light.

Dennis H.

Hi...

And for those in Canada, if you have a chequing account with the Royal Bank of Canada, next time you need more blank cheques you can ask for the cheque "kit", rather than just more blank cheques.

You'll get one in that kit.

Take care.

Ken