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'Automatic shutdown'
1997\06\30@171716 by Matt Calder

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       The other day someone mentioned the automatic shutdown feature of
most modern calculators. My question is can I do this on a PIC? I have a
project that will be on for about 1 minute two or three times a week and I
would like it to turn off during the down times. In a semi-dream state I
imagined something with a relay and a mercury switch but when I actually
tried to write it down it didn't really work. Any help is appreciated.

Matt

/*****************************************/
/* Matt Calder, Dept. of Statistics, CSU */
/* http://www.stat.colostate.edu/~calder */
/*****************************************/

1997\06\30@195055 by Gerhard Fiedler

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At 15:16 30/06/97 -0600, Matt Calder wrote:
>        The other day someone mentioned the automatic shutdown feature of
>most modern calculators. My question is can I do this on a PIC? I have a
>project that will be on for about 1 minute two or three times a week and I
>would like it to turn off during the down times. In a semi-dream state I
>imagined something with a relay and a mercury switch but when I actually
>tried to write it down it didn't really work. Any help is appreciated.


AFAIK, setting it to sleep is the easy part -- just put the command SLEEP
in your code. (You want to make sure that all your inputs & outputs are in
a proper state, in order to really get into a low power state...)

How you get it to wake up is more dependent on your application: is it a
fixed time (which precision needed?) or is it some external action (which,
and how do you handle it?), and which PIC do you use (they have different
features regarding wake up from sleep)?


(I'm not at all experient here, I have just browsed the data sheets while
picking the PIC for my first PIC project... :-)

-------------------------------------
Gerhard Fiedler <spam_OUTgerhardTakeThisOuTspampobox.com>
S‹o Paulo - Brazil


'Automatic shutdown'
1997\07\01@034847 by STEENKAMP [M.ING E&E]
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>         The other day someone mentioned the automatic shutdown feature of
> most modern calculators. My question is can I do this on a PIC? I have a
> project that will be on for about 1 minute two or three times a week and I
> would like it to turn off during the down times. In a semi-dream state I
> imagined something with a relay and a mercury switch but when I actually
> tried to write it down it didn't really work. Any help is appreciated.

If you want to totally remove power from the PIC, you could do something
like this:
                                      --------------
          R/S Latch                   |   PIC xxx
         ----------                   |
         |       Q|-------------------|Vdd
         |        |                   |
         |        |                   |
   ----  |        |                   |
---o  o--|S      R|-------------------|I/Ox
+5V     | |        |       |           |
       | ----------       /           |
       |                  \           |
       \                  /           |
       /                  \
       \                  |
       /                 GND
       |
      GND

Pressing the button will set the latch and supply power to the PIC.  The
I/O pin will come up in three-state(tm) ;) and the pull down will stop
the latch from being cleared.  Setting the I/O will clear the latch and
power will be removed from the PIC.  The S/R latch has to be powered
pemanently so using one of the CMOS 4000 series devices will limit power
consumption.

Undoubtedly, one of many possibilities
Niki

1997\07\01@153511 by David W. Duley

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In a message dated 97-07-01 14:52:40 EDT, you write:

<<
        The other day someone mentioned the automatic shutdown feature of
most modern calculators. My question is can I do this on a PIC? I have a
project that will be on for about 1 minute two or three times a week and I
would like it to turn off during the down times. In a semi-dream state I
imagined something with a relay and a mercury switch but when I actually
tried to write it down it didn't really work. Any help is appreciated.

Matt >>
Hi Matt,
I did this with a hand held laser device I designed.  Use a TOKO (or other
such as MAXIM) voltage regulator with a shutdown input.  Wire your ON button
to the regulator shutdown input from the battery (make sure the regulator
that you choose has an active high shutdown input (High = ON low = OFF).
This turns the system on.  The PIC also has an I/O line connected to the
shutdown input of the V.R.  The first thing your code in the PIC does is
assign this bit to an output and set it true.  Now the PIC is in control of
its own power.  Do whatever you application does and then set this bit false
and all will shut off!

If you need more just holler
Dave Duley
V.P. DreiTek Inc.

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