>
>I am back with the question on PIC and power consumtion. I need to make
>measurements with PIC every 5 minutes, keeeping power consumption to the
>minimum between measurements. My first thought - to turn power to PIC
>off and to turn it on by external timer (what is 50-100 uA by itself).
>Does anybody know of better way to do it? And second - how can I keep
>track of what PIC is doing if I power it off and don't use NVRAM?


Hi Gennady,

Others on the list can give you a good idea of how much the particular PIC
that you are using consumes in sleep mode (I can't - I haven't had to do
that yet) but I have built timers that draw only about 1.5 uA average using
a 4007 CMOS package and several resistors.  There are also some new op-amps
available from Maxim that will allow somewhat worse performance (5 - 10 uA)
but with fewer passive components.

What you might want to do is characterize your requirements.  Figure out how
much current your circuit will consume while it is powered up, and for how
long.  Look at how much capacity your battery has, then calculate what
standby current you can tolerate while still leaving enough energy in the
battery to operate your circuit at the end of the usful battery life.  There
is no sense spending time and money to get your standby current lower than
you actually need.

Do specify which PIC you want to use.  I do know that the brownout detector
built into some of the newer PICs consume much more current than the actual
PIC itself does.  If you need to use that function, you will have to account
for the extra current.

Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, Alberta, CANADA
(403) 489-3199 voice     (403) 487-6397 fax