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Wow, this is a really nice design... - "Speleogroup is experimenting with circuits for driving high-power LED devices, such as the White LED Luxeon Star from Lumileds ». This device is rated at approximately one watt, giving typically 18 lumens at its rated current of 350mA. Their high dome Amber Luxeon star gives 36 lumens at a similar power, with a colour similar to that of a sodium street lamp.
To use these devices safely at maximum power, and provide switchable power levels, it is best to use a constant-current circuit. To maximize battery life, we are investigating switched constant-current circuits using off-the-shelf power control ICs and microcontrollers.
This page describes one circuit we've developed, using the Atmel » ATtiny15L microcontroller. An earlier design used the Linear Technology » LT1512 chip, a current mode switching regulator. " [via] - Link.
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