DIY UV LED Light - See the World in a New Light

I've always liked experimenting with things, and seeing things in new ways or from different perspectives, so I got interested in UV Lights, however I don't like tube technology, it offers easier use and us much cheaper but an LED version is a neat project, if rechargeable and doesn't generate heat, as well as being much more portable, so read on if you'd like to see how I made it and if you want to make one yourself.

P.S. Sorry that some of the images are sideways, I didn't have time to rotate them.

So for this project first thing you need to do is source UV LEDs, but more importantly, the wavelength you need. I used this site to find which ones I needed, which are 380 nm and 365 nm, and ordered them off ebay.

I chose 365 nm and 380nm leds because they are really the only available UV LEDs, they are reasonably priced, and give the UV light a wide range of use.

For parts, this is what you need. The total cost of this project was just under $70, but you get all the extra UV leds as well.

Prices are in CAD

x100 380 nm LEDs - 30.49 (free shipping)
x20   365 nm LEDs - 21.12 (without shipping)
3mm clear green LED - 1.50 (bought locally)
LED Worklight - I chose one that was already cheap and turned out to be on sale for 9 bucks, with a 4 LED flashlight and 28 LED work light that sprung out.

Other Supplies:

Soldering Iron
Solder
Wire Cutters
Flathead Screwdriver
Resistors

*Notes*

As you can see 380nm LEDs are much cheaper than 365nm, and that's good because most uses are in the 380nm range, so I used them to modify a few flashlights, and have spares for whatever I'd like.

The flathead screwdriver is for opening this light as it does not have any screws, yours will probably differ.

So, according to the site I linked to earlier, my finished UV light will be able to be used for all 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
Semen
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)

Note that blood requires 465nm wavelengths, so it won't work with this, however if you use luminol, which reacts to the iron in the blood, it might work.

First step is to open up your worklight, this one doesn't have any screws, so I pried around with a small flathead, and it just snaps into place, making it easy to take apart. Inside the worklight section (which is what you want), you see the LED board which seems to be of quite nice quality, and the wires leading down to the mechanism that slides and turns it on. There are just four screws holding the board in, so take those out, desolder the two wires, and you're ready to start.

Now, since we are using two types of LEDs, we want to make sure they have an even spread, you could go with rows vertically or horizontally, but I decided to go with an alternating pattern, so that it gave optimal coverage, and wouldn't have any gaps or areas where one wavelength dominated too much.

So, now that you have the board out, you want to clamp it or secure it however you like, fire up your modified soldering iron, turn on some good music and get started. I find having a desoldering pump a great tool to have, but you don't absolutely need it. Then, desolder the LEDs and make sure the holes are nice and clean. Don't heat the board up too much because you can cause the pads to lift and break them off if you aren't careful. I had my soldering iron at 480 celcius (896 farenheight) but didn't encounter that problem.

This is an extra step that you don't need to do, but I did anyways, because I like to modify things a lot, I replaced the standard diffused red LED with a greed non-diffused one, didn't take long and is just a little thing to make it more unique. I had to take two screws out and take off the sliding section to open the main part up, and the small circuit board was also helt in by two screws.

So, now that the board is cleared off, you need your UV LEDs, so open up the package and pick out however many you need. (14 of each for me). Then, put them in the circuit board in the pattern you decided on, bending their leads to hold them in place. Afterwards flip the board, and soldering them in place, I use a smaller solder that I do for wires so that there is a smaller connection. Also I went down the rows doing one lead at a time, then starting over doing the other lead so that the LEDs did not get heat damaged.

As always practice good soldering and make your joints flow nice and smoothly, and make sure they are shiny when cooled so you know they are nice and strong.

Now, open up your 365nm LEDs, grab 14 of them, and place them in the available spaces, insuring of course that the polarity is correct. Each time you place one in bend the leads to the side so that it does not fall out. Once all the LEDs are in place, turn the board over, solder the connections with fine solder, making sure to alternate as to avoid any chance of heat damage. Once all the LEDs are soldered, trim the leads off and make sure your connections are proper.

Now, the old white LEDs most likely used a lot less voltage than the new UV ones we are putting in. I found that the 380nm leds use 3.2-3.4 volts, while the 365nm ones use 3.6-4 volts, which is a bit of a problem since they are all in parallel.

I decided to run them all at 3.4 volts, the voltage supplied is 4.2, so using an online calculator I found that I needed a 1.5 ohm resistor, which I grabbed from my newly received pack of 112 assorted resistors, with 10 pieces of each. Now, the resistor I am replacing looks like its a one watt resistor, however mine are 1/4 watt. However since the rechargeable batteries this thing uses look simillar to AAA's, I figure 1/4 watt is fine, I did use two though to make in 1/2 watt to be safe.

Now, place the board back in it's spot and put the four screws back in, then solder the positive and negative wires to where they were.

After this, snap the cover back in place and you are ready to try it out.

Congratulations! Your UV LED light is finished! Now you can go sleuthing around, playing with fluorescent materials, UV dies, pretty much anything.

Here's a demonstration video, thanks for reading my instructable and be sure to vote for it in the lighting contest.