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UV LED

Discussion in 'General Electronics' started by Bob Urz, Aug 18, 2004.

  1. Bob Urz

    Bob Urz Guest

    I am trying to trouble shoot the AC in my truck. I am going to put UV
    dye in it for leak detection. I see they sell these cheap looking UV
    flash lights with a single LED in the end with two AAA batteries.

    Now, my question is what kind of LED do they use? Is it just a infrared
    type or something else to illuminate the UV dye? I figured i could roll
    my own for a few bucks if i could ID the LED type they use to detect the
    UV dye.

    Any suggestions?

    Bob
     
  2. There are ultraviolet LEDs. They require a forward voltage of about 4.0
    volts and a current-limiting resistor of (V - 4)*50 ohms, where V is the
    supply voltage. For example, 400 (or 470) ohms with 12 volts.

    If they light a UV LED with 2 AAA cells, it's by using some kind of step-up
    converter (for circuits see www.maxim-ic.com).
     
  3. ceraboy

    ceraboy Guest

    They are indeed UV emitting LED's. The ultraviolet wavelength range is
    100 - 400 nanometers as opposed to the visible light range of 380 - 780
    nanometers. UV led's are readily available, just be careful, they can
    damage your eyes if used inappropriately.

    http://www.theledlight.com/UV.html
     
  4. Sofie

    Sofie Guest

    Bob:
    For a one-shot application such as this you might be better off to use and
    off the shelf portable black light such as used for currency inspection.
     
  5. James Sweet

    James Sweet Guest


    Or one of those blacklight CFL spiral lamps you can get at Fry's and some
    other places for about 10 bucks.
     
  6. Jerry G.

    Jerry G. Guest

    The UV frequency used for your application is 365 nm. You will have a
    difficult time to have a UV LED powerful enough to be practical for
    automotive leakage inspection. You would have to invest in the proper lamp
    unit for this. If you are to use this in an environment where the ambient
    light is not too bright, you can get away with an 8 Watt or so UV tube type
    lamp. If you are going to use this in a brightly lit environment, you would
    be best to get an inspection lamp of upwards of 50 Watts. These lamps have
    the proper band filter built in, to make sure that the proper wavelength for
    your application is leaving the lamp unit.

    When using industrial UV lamps, even in the low UV spectrum, it is strongly
    suggested to use the proper UV protection eyewear. Standard specials with a
    UV rating are not good enough for these types of high intensity UV lamps.
    There would be also too much side light getting through. The proper UV
    goggles cover the eye area in a manner that there is no UV leakage to the
    eyes at all.

    http://uvp.com/new/index.php?module=ContentExpress&func=display&ceid=111

    --

    Jerry G. GLG Technologies GLG
    ==========================


    I am trying to trouble shoot the AC in my truck. I am going to put UV
    dye in it for leak detection. I see they sell these cheap looking UV
    flash lights with a single LED in the end with two AAA batteries.

    Now, my question is what kind of LED do they use? Is it just a infrared
    type or something else to illuminate the UV dye? I figured i could roll
    my own for a few bucks if i could ID the LED type they use to detect the
    UV dye.

    Any suggestions?

    Bob
     
  7. Bob Urz

    Bob Urz Guest

    Well, the one i saw in the autoparts store used two AAA batteries and
    had a SINGLE LED in the end. Like a small mag light only with a UV led.
    If it was usable, i should be able to duplicate it. Finding the UV
    LED's through normal replacement part sources is a little tougher. MCM
    did not have them listed in there catalog.
    There are some specialty places that sell them.

    My kids have a incandescent bulb black light i might try to see if it
    works.

    Bob
     
  8. jakdedert

    jakdedert Guest

    I have a small 6" flourescent one that I snagged when my wife threw it out.
    I think it was originally designed for drying nail polish....

    jak
     
  9. James Sweet

    James Sweet Guest

    I've had blue LED's from Radio Shack that put out enough UV to fluoresce
    dyes.

    Those incandescent blacklights are just about worthless, find a small
    fluorescent one, either one of the screw in compact fluorescent types or a
    small linear one, often you can get them at novelty shops and a big place
    like Wal Mart (as much as I hate to support them) would probably have
    something.
     
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