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 18:31:06 GMT
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Original-From:
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Jim Thomas <jim.thomas@trw.ANTISPAMcom>
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Viewed:
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618 times
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I believe what we have got here is two solutions.
1) replace the Lego hardware with better microswitches
2) Make a multiplexor capable to work well with the Lego touch sensors
Either one will work. I think I would rather make the multiplexor than
start cutting up blocks to make my own touch sensors. I think it can be
done with a '14 and some resistors (in addition to the standard sensor
circuitry). In this application I would prefer to debounce by hysterisis
rather than delay. Debouncing multiplexed switches in software is more
difficult than you proposed unless you make some limiting assumptions.
My $.02.
JT
-----Original Message-----
From: Ralph Hempel [mailto:rhempel@bmts.com]
Sent: Wednesday, August 25, 1999 9:13 AM
To: lego-robotics@crynwr.com
Subject: RE: touch sensors aren't just switches (was Re: ideas for a RIS
2.0
> 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
--------------------------------------------------------
Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbFORTH>
--------------------------------------------------------
Reply to: rhempel at bmts dot com
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--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 2 Replies:
 | | Software builds LEGO structures..
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| (URL) don't know if this has been posted to the list, but I thought it might be of intrest.. Looks like all us bot builders could be out of a job soon.. :-P "Evolution, until now the unchallenged domain of living organisms, may soon become possible (...) (25 years ago, 25-Aug-99, to lugnet.robotics)
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