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Example Micro-torch Circuit
Running an LED off just 0.75 volts to make a
Micro-torch
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An Ultrabright yellow LED usually needs at
least 2 volts across it before it will light.
This simple circuit by Z. Kaparnik was
published in "Everyday Practical
Electronics" magazine (page 804 November
1999). It uses a single transistor and a
transformer comprising just a few turns of wire
on a tiny ferrite bead to form an oscillator.
The circuit will operate off an almost dead
battery (just 0.75 volts) and produces around 30
volts with the LED disconnected.
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With the LED connected, the voltage is clamped and the
circuit produces short duration high-current pulses which
drive the LED to full brightness without destroying
it.
The result is an extraordinarily bright beam of light.
The circuit is so small that it can be built into a key
fob, a walking stick knob and many other common items
into which a torch would normally not fit. The beam is
bright enough to allow you to find your way along a path
in complete darkness.
Available as a kit from SatCure.
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