Subject:
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Re: multiplexed touch sensors [was: Re ideas for a RIS 2.0]
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 26 Aug 1999 00:24:29 GMT
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Viewed:
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769 times
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Robert Munafo <munafo@gcctechNO.SPAMcom> wrote:
> Other people writing in this thread have been saying that the
> intermediate resistance values result from intermediate amounts of
> pressure being applied to the touch sensor's moving element, which would
> imply that the intermediate resistance values could persist for quite a
> long period of time if the touch sensor were being affected by a
> mechanism that could sustain such intermediate pressure for a long time.
I don't doubt that there are reasonable creations that e.g. press a touch
sensor button halfway for extended periods of time, but I can't think of
any off the top of my head. Can anybody help me out here?
My point was that in what I would presume to be the common case (not the
one above), the touch sensor is activated quickly enough (even if several
tens of ms, as Ralph suggested it might require) that reasonably simple
debouncing logic can handle the situation, even for multiplexed touch
sensors, as long as the multiplexed sensors are not switching so often or
so quickly that the voltages never settle between button events.
To change topics, regarding the time it takes to debounce the touch sensor,
I had previously said 3 ms was enough, but I take that back, since the only
measurements I've done (now that I've thought about this a bit more) have
been for the buttons on the face of the RCX, and not the touch sensors.
The buttons on the face of the RCX can certainly be debounced by simply
sampling every few ms, but I never verified this for the touch sensors.
Oops. To gauge the touch sensors better, somebody ought to measure what
sampling rates are reasonable for presses of the touch sensor. And while
whoever does that is at it, it would also be nice to understand what the
waveforms look like for short presses. Perhaps I am completely wrong about
everything, and voltages never settle when the touch sensor is
pressed/tapped quickly.
I might take a look into this later, but if somebody beats me to it, that
is fine too.
-Kekoa
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