Apptech wrote:
> It's interesting that it both output voltage and output current
> limits.

This is really a regulated current supply since it's job was to drive a
string of LEDs.  The output voltage limit was only to prevent damage in case
the output was ever left open circuit.

Since Bob wants voltage regulation, he can dispense with the current limit
altogether and make the voltage limit more accurate.  Something like a 4.3V
zener into transistor base with a little resistance to ground is probably
good enough, and will be a lot less temperature sensitive and more accurate
than what I had.  My voltage limit was only there to keep the voltage below
damaging levels, so it didn't need much accuracy.

> IF you can find an acceptable way to start

That's the tricky part.  I originally was trying to create something that
would run from a single cell.  If I remember right, I got this topology with
maybe different value to run from around 900mV.  Since I wanted it to work
from rechargable batteries, I didn't think 900mV was acceptable.  In the end
I used two batteries in series.  But Bob specifically said alkaline, which
start at around 1.5V with very little of the total energy left at 1V.


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