Microblog: A very long article Wikipedia article on the orientation of toilet paper [Jun 7th, 22:52] [R]

Saturday, October 13th, 2007


Translation: [ Google | Babelfish ]

Categories: [ DIY ]


I bought some time ago Die Nacht der Magier, which is a board game with phosphorescent pieces, played in the dark. I read on the Web (therefore it has to be true) that phosporescent paint is getting “recharged” much faster with UV light than with white light. So I had to build a UV lamp. I bought UV LEDs at LSDiodes.com, and I finally built the device.

It has 10 LEDs, connected in parallel two by two with an 18 Ω resistor for each pair of LEDs, and is powered with a 4.5 V alkaline battery. Each diode is supposed to draw 20 mA and to have a forward voltage of 3.6 V, while the battery, providing 200 mA, sees its voltage drop to 4.3 V. In practice, it seems that the battery is not always able to do so, and during the first test after building the lamp, it provided only 80 mA. Another time, it was 130 mA.


UV do recharge the phosphorescent paint quicklier than while light. Also, I discovered that teeth are fluorescent, as well as soap (but not fluor toothpaste), white paper, many colored plastics in children's toys and white cloths (including those which have been washed with washing powder supposed not to contain optical brighteners). Also, the UV lamp allows to see the pattern of the mattress through the bedsheet. UV light is lots of fun.

[ Posted on October 13th, 2007 at 22:53 | no comment | ]