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What wavelength UV LED do I need? (and cheap source for them) Answered

Alright less of what kind I need more than what will work. I want to buy one of those LED work lights (that go for around 40 bucks) to UV, however according to this list I would need 365 nm LEDs


so my question is, would it be better to go with 365 nm? Thing is those are way more expensive than 380 nm leds, but you can do some neater stuff with them.
So, would it be worth spending the extra on them,  and do any of you know a place I can get them that don't charge a ridiculous amount for them?

Also, would it be a good idea to perhaps mix the LEDs that way I get the stuff you can do in 380 nm and 365 nm? would that work?


11 Replies

scaplan1 (author)2013-11-04

You people seem to be in the know, using Radio Shack UV LEDs I can see the strips in US currency, but not their individual colors. The light does work as I can see other hidden UV items in things such as credit cards, etc.

Am curious what I need? Is it a strength factor, or a wavelength factor? And if it's the latter, does anyone know where I can purchase them?

Many thanks ahead of time for any future answers.

Radio Shack UV LED
*5mm High-Brightness Ultraviolet LED (2-Pack)
3.3V typical
4.0 max

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frollard (author)2013-03-14

You keep saying you think you need 365nm but they are expensive and 380 are cheaper...

365 is proper UV that would be used in medical equipment with very little visible portion to it - used for hardening uv resin, etc.

If you want to make stuff glow - the 380's will be just fine. as iceng points out there are a bajillion led suppliers out there for super cheap. search ebay for a china based seller (to get the factory cost), one that offers free shipping...
and find a strip or board that has what you want.

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XOIIO (author)frollard2013-03-25

Well what I did was order 100 380nm leds, and 20 365nm leds, then I'll buy a 40 LED work light, and alternate between the two wavelengths, so that I get both. I got some good information about the wavelengths here: http://www.riskreactor.com/Black_Lights_UV_LEDs/Black_Lights_UV_LEDs_Main.htm

The price difference is really clear because I bought both orders of leds for the same price.

Anyways according to that site I'll be able to use it for these things.

Anqitue glass (uranium glass, vasceline glass)
Forged document detection
A/C coolant leak detection (using dye)
Carpet inspection
Bathroom inspection
Animal urine
Human urine
Arson Investigation Flashlights Lanterns
Hotel room inspection
Mineral Hunting (diamonds, etc.)
Salmonella and Shigella bacteria detection
Contaminate inspection (clean environment)
Drivers licence UV markings
Dye penetrant inspection (NDI/NDT)
Magnetic surface analysis
Counterfeit currency detection
UV Curing (requiring 365nm)

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frollard (author)XOIIO2013-03-27

Just make sure the series resistor is correct; it may need changing for the voltage requirements of your leds.

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XOIIO (author)frollard2013-03-27

Thanks for reminding me, I totally forgot.

MY led's voltages are mismatched though. the 380nm ones are 3.1 to 3.4 volts and 365nm are 3.6 to 4 volts, so I'll have to have the 365nm ones running lower which is too bad but should work fine, after all I modified a 14 LED flashlight with the 380nm ones and its working well enough. (yeah the 380nm ones got in, I am just waiting for the 365s and then I'll be able to finish the project and make an instructable.

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frollard (author)XOIIO2013-03-27

remember you can always add them up in series - find out the forward voltage and figure out whats left to figure out the resistor value.

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XOIIO (author)frollard2013-03-27

Well they are on a printed board in parallel, the input voltage is 4.2 right after charging, so I'll drive all the LEDs at 3.4 volts using a couple 1.5 ohm resistors instead of the 2.2 ohm that was there. (I used 2 because I am replacing a bigger one with 1/4 watt resistors)

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frollard (author)XOIIO2013-03-28

that's fair, aim for 'safe' resistance rather than brightest or you'll have a short lived light! ...lastly...make an ible!

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XOIIO (author)frollard2013-03-28

Yup, I've got it all ready to go, I just neede the 365nm leds to come in then I can post it.

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iceng (author)frollard2013-03-14

Didn't know 365nm was available,

Starting to search for just the LED...

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iceng (author)2013-03-13

Try here for a $13 UV flashlight hex sides so it doesn't roll away.

I have two and like them.  Particularly to show diamonds that
phosphorus glow under the beam on my ring...


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