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Archive for December 21st, 2012

Large UV LED Self-Fluorescence

Just got an ultraviolet LED in a 10 mm epoxy package that’s water-clear in visible light and slightly fluorescent in its own UV:

10 mm dia 405 nm UV LED

10 mm dia 405 nm UV LED

The epoxy usually has some fluorescence, but this seems more dramatic than usual. In any event, the die’s wide beam angle shows clearly; the beam along the axis out in front is actually pretty tight.

It’s sitting on the back of a white ceramic tile and the colors came out surprisingly close to real life.

Adding this to an Arduino would follow the same logic as, say, the pager motor: power the LED + resistor + MOSFET from a +5 V external regulator that won’t heat the Arduino board, then define an unused bit in the shift register as, say UV_LED.

It runs at 20 mA and drops around 3.3 V.

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