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PICList Thread
'[STAMPS] Accelerometer Project = Kludge'
1997\06\29@182050 by paulb

Quentin Lewis wrote:

> I know this is going to sound like a kludge....but what if you took one
> of these cheap "give-away" calculators and simply replaced the press of
> the buttons with output bits from the PIC or STAMP?
> That is, you could "press" the buttons by connecting some sort of
> "decoder" on stamp outputs, and wiring the outputs up in place of the
> push-buttons. One of the outputs could be the Clear that
> you could "clear" the display.

 A version of the classic application whereby you use CMOS switches
to press firstly the "1" then "+" buttons of the calculator, then use
"=" button to count events up to 2 or three a second.

 You know what really fouls up this plan?  Virtually all later model
calculators are "auto-off" after a certain number of minutes and the
way to get them back on is to use the "AC" button!  And there is no
which just keeps them alive without affecting the result.

       Paul B.

'[STAMPS] Accelerometer Project = Kludge'
1997\07\01@050233 by Tim Forcer
Just a couple of suggestions for those considering using calculators for
event counting.  I haven't tried it, so please don't have a go at me if it
doesn't work or can't work.

1. Auto-defeat of auto-off (1).  Using a very slow clock (don't ask me
where it comes from) with a period approximately that of the auto-off
timer, add 1 on every +ve edge, subtract 1 on every -ve edge.  Only take
readings while this clock is low.

2. Auto-defeat of auto-off (2).  Using the same clock as in 1, activate
"M+" on +ve edges, "M-" on -ve edges.

3. Add built-in timing at the same time as auto-off defeat.  Use a stable
clock with period well below that of the auto-off, but some nice round
figure like 2 minutes.  On every +ve clock edge swap memory and display,
add 1 to display, swap memory and display.  This gives event count in
display, elapsed time in memory.  (Avoid event increments near +ve clock

4. Make auto-off irrelevant.  My calculator's "memory" register is
non-volatile.  Therefore, event counting only requires: "AC/On" to turn the
calculator on, "1", "M+" and then into sleep mode.  I've no idea what the
calculator's current drain is - it's one of those which runs off solar
cells, with no battery at all.

Tim Forcer     
Department of Electronics & Computer Science
The University of Southampton, UK

The University is not responsible for my opinions

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