Subject:
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RE: Cybermaster Sensors
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 30 Nov 1998 19:38:51 GMT
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Original-From:
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Tilman Sporkert <tilman@nscale*NoMoreSpam*.activesw.com>
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Viewed:
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2463 times
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> > In message <4.1.19981128213514.00961de0@mail.telepac.pt>, Laurentino
> > Martins <lau@mail.telepac.pt> writes
> > > In the future, I'm going to put the 3rd. touch sensor in a • bumper in the back
> > > of
> > > the unit since it might impact on some object when reversing • and I would never
> > > know.
> > > I haven't done that already because I'm a bit out of ideas how • to make flexible
> > > a bumper for the whole rear (the CyberMaster is my only LEGO).
> Any ideas?
The trick with bumpers is to mount them on the long end of a lever. Mount
the touch sensor so that the short end short end presses it in when the
bumper is not touching anything. A rubber band pulls the short end against
the touch sensor, pressing it when not bumped. The bumper then releases the
touch sensor. With this arrangement, you can build a bumper that triggers
the sensor immedietately when touched, but has a long way of travel. I.e. if
your robot can't stop on the spot, you aren't putting any stress on the
bumper assembly. It simply swings back. This arrangements is also convenient
for programming - you can wait for a touch sensor being pressed inside a
task, but not for release. I.e. you can write a task that triggers when the
sensor gets released (bumped), reverse, and then wait until it gets pressed
again ("un-bumped"), followed by whatever code you want to use to get out of
the situation.
For a "whole rear" bumper, you could use a horizontal beam for the bumper.
Mount it on one or two shorter vertical beams. Use grey pegs to mount the
vertical beams a couple of holes up, so that the horizontal beam can swing
back and forth. Mount a touch sensor behind one of the short vertical beams,
on the opposite side of the bumper. Use a rubber band to pull the vertical
beam into the touch sensor.
It took me a while to figure this out. My first bumpers were all the other
way round - the bumper presses the sensor. The problem is that you have no
flexibility, and need to build a very strong bumper assembly. It's also a
lot more difficult to adjust.
The Mindstorms Robosports expansion set manual shows some very nice examples
of bumpers.
Tilman
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Message is in Reply To:
 | | Re: Cybermaster Sensors
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| (...) Thinking ahead, and also if I recall because the set had the idler gear in it, I bought several of the rubber-skirted hovercraft some years ago. It isn't flexible but it's soft and it looks cool. And implausibly enough it's real LEGO. Haven't (...) (26 years ago, 30-Nov-98, to lugnet.robotics)
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