Hi,
my 16F84 -based datalogger (16F84 running at 4MHz with a DS1820) have a
current
consumption of about 0.7 ma  at 4.5V, 3AA cells (when sensor is off).
I'm not sure, but It is at least 1 month of continuous use without excessive
discharge of the cells.
This is enough for my most uses but not for all...
For long-time measuremets I would put the logger in "sleep": at this time I
have two (or more?) ways:

- Use a 32 Khz crystal clock.
- Use an external circuit ( a 4060 CMOS  with 32 Khz crystal ) that send an
interrupt to wake-up the PIC.

The first solution isn't valid for DS1820 (timings, i think) but in this
event I can change with a DS1721.
I must also modify all the code delays, but this is obvious, but the board
is more compact.
The second is more complex to assemble but is still cheap and the pic's
clock remains 4Mhz.

My questions:

1) Is 32 Khz solution too limited if used for other types of measure?
( for example, i want use other sensors with frequency output )
2) Are there other CHEAP solutions for low current consumption?


Thanks,

Marco Genovesi

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