Hi All,

I need a cheap battery saver circuit. This is for legacy electronics-it
shuts the appliance off if the user forgets to-which prevents the battery
from draining if the user forgets to turn the power switch off.

So far, internet sources for conventional solutions have been an enormous
terrific disappointment.

I found a nanopower comparator with a built in 2v reference voltage. I
designed it with a mosfet switch that kills the power to the appliance and
to the comparator itself when voltage across the capacitor on the input
drops below the reference voltage. But, this removes the connection between
the battery and the power input pin while the comparator input is at 2
volts-which I believe is a big no-no......leaving an input at 2 volts while
the Vcc terminal is at zero volts. The specs for my comparator say the
inputs must never go above or below .2v relative to the gnd and vcc voltage.

Am I misinterpreting the specs, or is my plan technically correct????

If anyone knows of a better circuit that does not require an additional
switch (uses the stock power switch), I'd sure like to hear from them. The
circuit needs to be very cheap and needs to consume zero power when the auto
shut off activates. I'd prefer a non PIC solution with no exotic parts. The
circuit can consume a few ma while the device is powered up. And, it should
run on 9 volts (or higher) non regulated power. It needs to work with the
stock power switch (not requiring an additional momentary pushbutton
switch).

Thanks,

T
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist