Re: ATM DIY LED Flashlight Conversion

[gwoods@albany.net (Gary Woods)]

>I sure don't want to use a resistor or current limiter: I would end up
>wasting a lot of power.  What happens if you charge a small capacitor and
>then connect it (through a fet) to the LED?  Perhaps you do no damage if the
>capacitor is small enough.  And the brightness is proportional to the
>frequency.
>

OK, Ok, I can't stand it any longer!  As someone who loves Rube
Goldberg and Tim Allen as much as the next testosterone junkie, let's
get real!

We're trying to build an LED flashlight, not the guidance system for
the lunar lander.  Sure, if you use a switch-mode variable current
supply, you'll only have to change that 9-volt battery every three
years instead of annually, but at such a complexity of design that it
really isn't worth it.  All you need is:  (everything in series)
super-bright red led-fixed resistor (to set max current)-variable
resistor (10K would be nice)-switch (on the variable resistor)-9V
battery.  You don't really need 9 volts, but you can't beat the
convenient package and handy terminals.  

I've got one of these critters I bought several years ago from Orion
(8 bucks, I think; nice professional package) which is still on the
original battery.

Even better, maybe Mel could add a module to his software to have the
computer produce a PWM output to drive the LED flashlight under
software control.  That ought to win the "Most complicated flashlight"
at Stellaphane (-thant?) for sure!

(calmer letter follows).



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