Among the projects that define electronic design, a UV exposure box is right up at the top of the list. These boxes shine UV light on a work piece and are used for everything from exposing photosensitive PCBs to erasing EPROMs. [carlolog] decided to build his own and ended up with a fairly impressive array of ultraviolet LEDs perfect for making PCBs or tanning the back of your hand.
One important thing to remember when making large arrays of LEDs is current consumption and power needed to light the device up. [carlolog] naive assessment of how much power would be required used a 12 volt supply with 135 LEDs and 135 resistors, wasting a lot of energy and producing 24 Watts of heat.
Of course this power consumption can be reduced by putting a few LEDs in series, so [carlolog] wired 3 LEDs together with a 150Ω resistor. This array requires just over 11 Watts and consumes less than 1 Amp; perfect for a desktop UV box.
The enclosure for the box was crafted out of three Ikea photo frames, and a small timer circuit powered by an ATmega8 was added. Now whenever [carlolog] needs to wipe an EPROM, he can put the chip in the box, set the timer, and walk away.
A very nice build, but when dealing with a lot of UV we must remind our readers: do not look into the UV array with your remaining eye.