UV LED

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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

 

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).

 

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

 

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.

 

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

 

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

 

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

 

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

 

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.