LED replacement bulb with stepup built in!

White LEDs

Thanks to Bertrand H. for sharing this very compact LED bulb mod with us. Here is the account of the work he did in his own words.


'LED bulb' for 2.4 Volts:

I use the E10 base LED lamp below for caving. A very popular headlamp is the FX2, but it is based on 2 NiCd cells, so only 2.4 Volts.

I designed a tiny circuit wit 2 transistors to be fitted into to E10 base, so its a real plug-and-play replacement!

It works fine from 1.0 V, and is optimised to deliver 25mA per LED at 2.4V. Input current is around 130mA @ 2.4V for 3 LEDs

For the schematic see below. All parts are SMD (0805 & SOT23). The inductor is from coilcraft. Both transistors may also be BC847 without sacrifying efficiency too much.

You can build it together by using the inductor as carrier.

Many thanks, Bertrand!


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