Peter L. Peres wrote:
>
> You can save on transistors and switchoff logic by using a capacitance
> multiplier with a single transistor. This saves a PIC pin (required to
> hold the power on) (I suspect you are using a 8-pin PIC). The required
> capacitor will be small, too.

Very clever! I had thought of a way to get
the PIC to pulse a line capacitor coupled to
the transistor, to give a turn on period and
get rid of the bias problems when just using
one transistor for the power.

Your way is better, and has less parts count
and much simpler.

What about getting rid of the transistor
all together, just charging a large cap with
the button, which then takes X time to discharge
powering the zener reg and PIC?? Assuming the
PIC draws regular amount of current it would
give predictable time to go down. Hmm. Maybe
battery voltage could cause problems as
battery starts getting flat?.. But this would
be even simpler. :o)
-Roman

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