Re: Running a 1 watt LED of 6 volt lantern battery

In article
<904f5e87-56b8-4aa1-a26b-4df351c06430@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Dave.H" <the1930s@xxxxxxxxxxxxxx> wrote:

I'm looking to convert a flashlight I have to LED, the flashlight uses
a 6 volt "lantern battery but the LED's max voltage rating is 3.1
volts DC. What value resistor would I need for this? I also want to
run it off a 9 volt supply, again I need to know the value of the

Do you have any interest in max light out, or max battery life?

This is basics, so perhaps just slapping in a resistor is as far as you
want to go - but you could run 2 in series from the 6 volt battery, and
3 from the 9 volt battery, at no increase in power drawn - just making
more into light, and less into heat from resistors.

Alternatively, you could get somewhat more complicated and build a small
switch-mode driver circuit to get 2-3 times the battery life, with the
same light out, by converting more voltage at less current into less
voltage at more current, again reducing the power lost as heat from
resistors.

If you need more power dissipation, you can use resistors in parallel
and/or series to increase power without having to go track down a
high-power resistor. i.e., if you need 20 ohms at 2 watts, you can
parallel 2 1-watt 40 ohm resistors (39 in practice), or run 4 5 ohm (5.1
in practice) 1/2-watt resistors in series.

--
Cats, coffee, chocolate...vices to live by
.

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