SMJLED puck on Li-Ion


Flashlight Enthusiast
Jun 15, 2008
I've hooked up the SMJLED puck from Sandwich Shoppe to my power supply (wanted to check some current draws and see what's the lowest voltage it still gives any illumination at all) and accidentally bumped the voltage knob...

Lo and behold - it turned out it works quite happily at >3 volts. Up to and including 4V+, in fact. Heats up noticeably, but it works and seems to give off noticeably more light. Anyone tried using one in a cut down 1AA minimag with a 14500?

Oh, BTW, it still lights up at as low as oh-point-a-few volts!
Pretty nifty!

Edit: One more thing. There's a "jump" as you cross 3.1-3.2V or so, at which current and light output suddenly drop significantly, then ramp back up @ around 3.5-3.6V. Probably the point at which it stops working as a boost circuit and goes into direct drive. Current climbs to about 300-ish mA near 4V. Anyone knows what's the Vf of the SMJLED's?
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