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this uses LEDs from a broken GU5.3 bulb and a spent CR2032 battery to make a small night light.
there are six LEDs surface mounted onto an aluminium frame and are wired in series. I measured the light output with a 10K LDR and an ohmmeter, and tried all sorts of things to find the brightest circuit with the least current.
the Transistor I used was a BC337. the transformer is a pot set line isolation transformer. I used a trim pot to find the base drive resistor value. I tried all sorts of other transformers, wound a bunch of small toroids, tried putting capacitors on the base to hold it up, adding base bias resistors, base diode, etc etc
in the end this was the most efficient and brightest combination I found using 1V 50mA. no capacitors anywhere.
it works with any voltage above 0.6V, higher voltages just make brighter output up to about 9V.
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