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Creating An Activity Meter From A Pulse Width

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If you look at post #24 circuit that the OP is using, I am not satisfied with some of the component values/timings also the description on how the circuit works.

I originally tried in another posting, to utilize the fact that
the coil produces voltage when induced, but nobody could
direct me how to integrate that into making the servo move.
I happened to series it into the circuit, and believe it or not,
with a few weeks of refinement, it actually does work. I can
pick up cars driving by in the parking lot, and neighbors when
they walk across the floor in adjacent apartments. This is SO
much more than I managed to get by attempting amplification
of the coil's voltage. I just know it does work, and it is VERY
sensitive (it actually moves when the A/C runs and I don't
have the pendulum/magnet/coil enclosed, simply due to airflow).
This part of the circuit is done. I don't actually work for the
USGS anyways, so having the stylus draw a 1/4" line when a
car drives by or a neighbor walks around on my floor, is more
than acceptable (considering the last quake we had here moved
pictures on the walls!). I simply wish to get a heads up (via the
meter), when activity is about to begin...

https://www.electro-tech-online.com/threads/control-a-servo-by-a-small-voltage-signal.99716/
 
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hi mhs,
I did a LTSpice simulation of the full circuit, but using the values shown for the bistable 555 I could not get any where near 20ms for the frame rate.
I will relook and repost the results.
EDIT:
refer to Post #35 for the results, this circuit should give the voltage that could drive a LM3914.
 
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Hi.
I see what is bothering you. The rep rate is only a little over 2 ms. But, that's ok the servo doesn't mind being over sampled it just makes it quicker and stiffer. Hmmm.
 
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