In article ,
Michael Kennedy wrote:
It may not work with a simple variable resistor because at higher
settings, the current will increase enough to probably just burn out
the small piece of the pot track that's still in circuit. A fixed
resistor will also still be needed to limit the full brightness
current. In order to get a decent control range, without risk of
over-running the pot's track and wiper, I would suggest that a small
transistor needs throwing into the mix to control the LED current,
whilst the pot is left the low-current job of controlling the
transistor's base. If I get time today, I'll give it a try.

Arfa


Arfa, How much current are we talking about here? If this is what I'm
immagining in my head with 2 or 3 led's it shouldn't draw much power. I
guess he could have one of those 5w led flashlights, but that was not
what I had in mind when he said dollar store.

The 'usual' LEDs found can only be driven to about 30mA from a constant
current source. So a 1/4 watt pot would likely be ok at the sort of
voltages found in a torch.

--
*The statement below is true.

Dave Plowman London SW
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