On Tue, 10 Mar 1998 08:49:32 +0200, Pasi T Mustalahti wrote:

>On Mon, 9 Mar 1998, Dan Larson wrote:
>
>> Recalling the relaxation oscillator basaed LED driver from a while back,
>PTM: I threw it in here
>It worked FB with 0.51V. An AA cell lasted about two weeks.
>We do not see any use of going under 0.6V, because there really isn't any
>juice in the cell below that. I was surpriced even with what we got.
>
>We tried to make a regulated power source of it with minimum count of
>parts, but run out of time. We added one FET and potentiometer.
>We tried to take 50mA@5V out of it but didn't succeed. Regulation worked
>somehow with about 5..10 mA, but 50mA (100 Ohm) was too much for a load.
>
>If you find some simple ideas, please tell us !
>

I know that it would be much easier to just use one of the 1.5V to 5V switchers
or DC-DC chips, but the simplicity of the circuit you posted is giving me reason
to avoid them.  First of all, the switcher chips are not cheap.  Secondly I
 can't
imagine that they could be nearly as efficient.  Thirdly, I am learning a lot
 more
about DC-DC conversion by hacking your circuit. I have been driving a pair of
 white
LED's for three days now from a single AA cell.  The main reason to go to .5V or
 lower
is the possibility of using solar cells.  The relaxation circuit could be used
 to charge
more conventional NiCad's, which could then be the source of a conventional
 regulator.

Now, I know you can put several solar cells in series, but the panel becomes
 rather
large when you do that.  I am interested in making something very small.  It
 would even
be interesting to see what I could do with a "lemon juice" battery...

This is all off topic of course, but again, I reiterate that I am eventually
 going to
put this knowledge to work with powering PIC's, mini-bots, etc...

Dan