On Jan 3, 2009, at 2:25 PM, Olin Lathrop wrote:

> Joseph Bento wrote:
>> My junkbox doesn't have any LM317s,
>> so an this immediate moment, another regulator choice isn't possible.
>
> What's more important, the immediate moment, or a few hours or days  
> later to
> get the righ parts?

This is strictly an experimental project.  Proper parts will come later.

> A quick and dirty and maybe good enough variable supply would be a  
> 7805 with
> a diode in its ground lead.  The output goes into a pot with the  
> divider
> output driving the base of a emitter follower.  That will give you  
> about 0V
> to 5V variable.  The 7805 is only used as a voltage reference with the
> emitter follower being the pass element.  This is crude but good  
> enough for
> many purposes, including running PICs from.  Of course there should be
> several capacitors on the emitter and something like a 10uF 10V  
> ceramic on
> the base.

That is worth a try.  I can manage a pass transistor.

Thanks!

Joe

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