Blacklights are both entertaining and useful. They can make posters glow, detect blood and other crime scene evidence, and even sterilize food and water. When you make your own black light out of LEDs, you can use it nearly anywhere. Install it in a picture frame to make a painting glow, put it in a flashlight for portable light or wire it into a light fixture for party lighting.
Things You'll Need
Black Light Leds
Black Light Bulbs
12 Volt Power Source
Consider just plugging a black light bulb into a normal light socket. Both Incandescent and fluorescent light fixtures accept black light bulbs just like normal bulbs. Follow the link below for black light bulbs.
Decide on what sort of black light you want to use. The common black lights used in clubs are called "black light blue," and are safe for use without protective eye wear. There are also other black lights with shorter wavelengths used for various industrial and medical uses. Some of these lights are not safe for human eyes, so take extreme care with them unless you know what you are doing. See the link below for info about the wavelengths of black light.
Decide what sort of light fixture you want to use. LED's are extremely compact and use very little energy compared to incandescent and fluorescent lights, so they are probably the best choice for most people.
Order 3.6v ultraviolet LEDs such as the ones found in the link below. Each LED will have two pins, a long one called the anode and a short one called the cathode. Get a 12v power source such as a lantern battery.
Solder 3 LEDs together in a row, with the long pin of one LED joining to the short pin of the next. There should be a long pin on one end of the chain and a short one on the other. Solder an 82 ohm resistor to one end of the LED chain.
Attach the anode end of the chain to the positive terminal of the power source. Attach the cathode end to a switch and attach the switch to the negative terminal of the power source.
To make the light brighter, make several other strands of 3 LEDs and a resistor. Attach them in parallel between the positive terminal and the switch.
If you want a more portable black light, you can make one with 1.5 volt AA batteries. Follow the link below for information on how to wire LEDs.