I built a light box with florescent tubes and it works well. The uv tubes I'm using for my box are Corallife True actinic tubes. LEDs are temperamental. They need a steady and good DC power source. The high powered LEDs need to be heat sinked or else they'll cook when they overheat. I'm currently trying to build an 8x10 enlarger head with (9) 3 watt LEDs. I'm gluing them with heat sink glue on a 1/8 " aluminum plate. Those LEDs are expensive and I'd hate to see them blow due to bad power or die from being over heated. If you're going to build your led exposure box, the parts are a available on eBay for cheaper direct from China.