Some updates:

I've tried a few sets of UV LEDs. Turns out that most of them will barely work at 3V. However, on close inspection I was able to get slight-to-some glow from them using a 3V button cell (2032). But, it seems that most of them want 3.2-3.4V My most recent effort was to step away from the eBay sources and get some LEDs that have better defined specifications. So, I got a couple of LEDs from Mouser. I got the LEDs in these wavelengths: 405 nm (http://www.mouser.com/ProductDetail/...cHs3daTdohk%3d) and 385 nm (http://www.mouser.com/ProductDetail/...vZdh3xyLUCg%3d).

Both of these worked really well with the button cell battery. Both charged the BB fully within 10 seconds (about the cycle time for the HL airsoft gun). The 405 nm LED left a brighter BB. But, I'm not sure if that is a function of the wavelength or the brightness of the bulb. I believe it's probably the brightness of the bulb (200 mcd vs 100 mcd) rather than the wavelength. I doubt these BBs are manufactured with materials that sensitive to differences in wavelength. That said, the 385 nm bulb left far less visible "residue" light than the 405nm bulb.

However, once I put the 405 nm bulb into my PzIII turret, it glowed a lot less than the button cell battery. In fact, it barely charges the BBs, even after letting it sit for several minutes. I don't have a meter or device that lets me check the currents coming from the battery or the Taigen control board. If someone does, do you know the current supplied to the headlight circuit? These seem to be optimized for 20 mA. I think I'm getting less than that.

One other observation of these with the BBs...light intensity appears to be everything when charging the BBs. A dim light will not charge a BB over a longer period of time. Instead, the BBs seem to come to an equilibrium in which they emit as much light as they absorb. The BB doesn't store much energy to emit as light. So, in a dim light, it reaches equilibrium quickly at a low level and stays there. In brighter light, it absorbs more and emits more.

Question for Perry or Shen: can you provide a source to your UV LEDs (ebay seller, online ventor, etc)? I'm thinking I might need something that needs a lower current.

TIA