Motion Timer

[Lewis Anderson]

I am looking for some guidance in designing a timer circuit. I have a
pneumatic cylinder that has 2 hall effect switches, one at either end
of the stroke. What I need to do is measure the time it takes the
piston to travel between the 2 switches and then display the time,
preferably on an lcd display. It has to be capable of timing the
piston in both directions and preferably autoreset the display when
the direction is reversed. The total time will be ~2 sec and I'm
looking for ~1/1000 accuracy.

It's been about 10 years since I've done any electronics design so I'm
looking for a little help getting started with this project. Can
someone please suggest a direction to take with this project and
suggest some components to consider.

Thank you.

 

[CWatters]

"Lewis Anderson" <lewis@wfoondirt.com> wrote in message
news:59bb5081.0411141748.30082415@posting.google.com...

I am looking for some guidance in designing a timer circuit. I have a
pneumatic cylinder that has 2 hall effect switches, one at either end
of the stroke. What I need to do is measure the time it takes the
piston to travel between the 2 switches and then display the time,
preferably on an lcd display. It has to be capable of timing the
piston in both directions and preferably autoreset the display when
the direction is reversed. The total time will be ~2 sec and I'm
looking for ~1/1000 accuracy.

Perhaps a standard counter/timer would do the job...

http://users.erols.com/bakinc/3-11.html

...plus some switches to swap the start and stop inputs over to measure the
reverse direction. If you use something like a rotary wafer switch it should
be possible to hook it up to momentarily trigger a reset when changing over.
(eg use a three position switch - Forward, Reset, Reverse)

Do you need the display to reset and remeasure on each stroke or just one
stroke after changing direction? If you want a continiously updated display
you may need a buffered display and/or play around with the gate input.

 

[John Fields]

On Mon, 15 Nov 2004 17:26:12 -0600, John Fields
<jfields@austininstruments.com> wrote:


Oops... X.XXX seconds = 4 counters, etc.

---
If you want to do it brute-force in hardware, you'll need five decade
counters, five BCD to seven-segment LCD decoder-drivers, a suitable
clock oscillator, a five digit static LCD display (reflective or
transflective if you want to use it with ambient light or
transflective if you want to use it with ambient light or a
backlight), some glue logic to latch the accumulated time of the
current stroke into the display and reset the counter to time the
cylinder's next stroke, and maybe a couple of comparators to crispen
up the outputs from the Hall sensors.

If you want a schematic, ask and I'll draw one up for you and post it
to alt.binaries.schematics.electronic.

--
John Fields

 

[John Fields]

On 14 Nov 2004 17:48:32 -0800, lewis@wfoondirt.com (Lewis Anderson)
wrote:

I am looking for some guidance in designing a timer circuit. I have a
pneumatic cylinder that has 2 hall effect switches, one at either end
of the stroke. What I need to do is measure the time it takes the
piston to travel between the 2 switches and then display the time,
preferably on an lcd display. It has to be capable of timing the
piston in both directions and preferably autoreset the display when
the direction is reversed. The total time will be ~2 sec and I'm
looking for ~1/1000 accuracy.

It's been about 10 years since I've done any electronics design so I'm
looking for a little help getting started with this project. Can
someone please suggest a direction to take with this project and
suggest some components to consider.

---
If you want to do it brute-force in hardware, you'll need five decade
counters, five BCD to seven-segment LCD decoder-drivers, a suitable
clock oscillator, a five digit static LCD display (reflective or
transflective if you want to use it with ambient light or
transflective if you want to use it with ambient light or a
backlight), some glue logic to latch the accumulated time of the
current stroke into the display and reset the counter to time the
cylinder's next stroke, and maybe a couple of comparators to crispen
up the outputs from the Hall sensors.

If you want a schematic, ask and I'll draw one up for you and post it
to alt.binaries.schematics.electronic.

--
John Fields