Subject:
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RE: touch sensors aren't just switches (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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Wed, 25 Aug 1999 16:13:22 GMT
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Viewed:
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699 times
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> You could always make a multiplexing circuit which does the thresholding and
> debouncing for you. Once the status of each switch has been turned into a
> binary state you could then use resistors to create a sort of D/A which
> works reliably -- just as you wanted.
The debouncing isn't the real problem, it's the variable resistance as the
switch is being pressed which alaises the touch sensor. By building a
MUX circuit which does thresholding and debouncing you effectively make
the system way more complicated than it has to be.
By using good microswitches (from a mouse) you get the clean resistive
transitions you need, the sampling algorithm can take care of the debounce.
One VERY easy method is to take successive samples at an interval greater than
the switch bounce (from the spec sheet for the switch) and just make
sure you have two identical readings before processing it as a state
change...
Cheers,
Ralph Hempel - P.Eng
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Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbFORTH>
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Reply to: rhempel at bmts dot com
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