I was shopping at a bookstore today together with a friend for pens with fluorescent ink. We found a shelf full of them, but could not determine which ones were UV reactive. So my friend pulls out a battery and a blue 8000 MCD LED from his pocket, and starts lighting up the test lines we drew on a piece of paper. I would never have guessed that the UV glow effect could be so strong just from a blue LED. But it seems logical, as the border between blue and ultraviolet on the light spectrum is 400 nm, and a blue LED is close to 400 nm. So when I got home, I did some test runs. I didn't have one of those UV-reactive pens (I'll buy when I get a UV cathode), but I had a yellow highlighter, with which I drew an X on a paper just to try. I first tried with 3000 MCD blue LEDs, but the effect was rather faint, so I tried with a 8000 MCD blue LED instead. And the X lit up completely! The test was a success! I took some pictures with my video camera, but it couldn't capture the UV glow very well, as video cameras are the most sensitive around 500-550 nm. But here's the pic. To see the effect, you'll have to try it yourself, using a highlighter and a bright blue LED.
Actualy BLUE and White LEDs are really just UV leds in disguise. They have a flourencent coats on the surface of the LEDs chip, that makes it glow blue or white. Take a look when it is off, you can't see the actual chip. Just a white haze, or patch. So his let out a little extra UV. (Also btw.. this is how a normal flourencent tube light works also)
*a bit scared* i discovered EXACTLY the same thing last night... Modded a mini LED torch (blown LED)... i put in a sunbeam LED.. (8000mcd) wich is probably the same as you used. then i tested it in the dark... then i discovered that a pricetag (you know those neon orange ones) lit up.. tested it on a piece of self glowing tape (??) you know those you charge in sunlight and it will glow for a while... the led actually charged it... and it's only UV that does that... ( i think)
Thats strange. I thought, the higher the frequency, the more difficult it is to find a substance that will emit at that frequency? hence how long it took after the introduction of the green LED until Nichia developed the blue? surely it would be easier to use a substance that emits blue than to emit UV and strike a blue phosphor. I know that the white LEDs operate using phosphors, but are you sure that blues do?
did my physics research on the construction of leds, i generally found that most blues these days dont use the phosphour coated technique, they are just standard diodes with a large band gap. If you look inside a white led you can see the yellow phosphour coating, which can be activated by blue photons, hence why white and blue leds were available before uv ones
But how about my Sunbeam LEDs? Are they UV LEDs with a phosphor coating, or are they blue LEDs that emit around 400 nm?
I have some white LEDS they have that white/yellow stuff inside.. but I also have some UV ones.. but they have a normal black ship... the blue red and greens too...
You know those skanky flashy flouro yellow posters you can get? I had one on my wall in uni, and I've got a 28" widescreen Tosh tv, and we were watching a video, when the video finished I switched the vid player off, and if there's no signal going into the TV it goes to a blue screen.. the effect on the poster was mad! It was insanely reactive it was cool!! As you can imagine I had my tv on bluescreen a lot from then on!
This is actually nothing new. The wavelenght of blue LEDs edges into that of purple/UV LEDs a bit. I though you knew?
Nexxo, that was my theory too. Looking at my blue LEDs, I find no diffusity in them; i can see the chip.
That's because CCs work by converting UV to visible light, and a little UV always escapes without being converted.
I found out that if you overclock blue LEDs in the right way, you get more UV. http://members.misty.com/don/ledbl.html 430nm blue LEDs will produce quite a bit of UV at stock, though.
That's interesting! I wish I had some of those 555s. But I will be buying a UV CCFL soon, and might pick up some UV LEDs while I'm at it.
pfff... 555timers are 50-75 cents each. and you could jsut get a 556 too, which is 2 555 timers in one chip.
Yeah, if you live in any other country than Norway they are. I would probably have to pay like $20 in shipping from ELFA.
