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[DPRG] Contests at the Science Place

Subject: [DPRG] Contests at the Science Place
From: Ed Koffeman edk at kinetric.com
Date: Tue Feb 5 10:11:07 CST 2002

I used to make autocross timers for timed automotive events.

The beams were low, triggered by the tires.

The first triggering starts the clock, and the timer ignores all other triggers for a set period (2 seconds in that case) that
allows all the wheels to go past the beam.

The set "ignore" time just has to be shorter than the shortest possible real time to be measured.

After that time, the next beam break stops the timer.

(The actual autocross timer could also use separate start and stop beams, time multiple cars at once etc. but we don't need to do
that.)

If we wanted to do without the delay, then the first beam break would start the timer, and the timer wouldn't stop until a judge had
pushed a manual button to arm the timer so that the next beam break would stop the timer.  This button just needs to be pushed some
time after the robot has cleared the beam at the start and before it arrives back to the beam at the finish.

Ed Koffeman



----- Original Message -----
>From: "Ed Okerson" <eokerson at fw.telenic.net>
To: "R. Bickle" <rbickle at swbell.net>; "'Mike McCarty'" <jmccarty at ssd.usa.alcatel.com>
Cc: <DPRGlist at dprg.org>
Sent: Tuesday, February 05, 2002 9:48 AM
Subject: Re: [DPRG] Contests at the Science Place


> Rick,
>
> I don't know if the 1/4" hole itself would cause a gap for IR detectors
> following the wall, but would the laser cause problems for IR detectors?  I
> would think it would swamp them and prevent them from seeing the IR signal
> they are looking for.  But your point about height also brings up a whole
> other topic, how high should the laser be?  If we put it 2" from the floor,
> and someone shows up with a 1" robot, we never detect it crossing the line.
> On the other hand if we put it 1/2" from the floor, we will likely get
> multiple triggers from tires going by and miss the robot body all together.
> I would really like to see this problem solved however.  It would really be
> nice to have 100% accurate timing for all the competitions.  It would also be
> cool to have the running clock that could be seen by all the spectators as
> the robot maneuvers around the course.  Maybe an array of beams 3 or 4 high
> and at least 2 long.  As cheap as laser pointers are now days it should be
> easy to do.
>
> Ed Okerson
> President DPRG
>
> ----- Original Message -----
> From: "R. Bickle" <rbickle at swbell.net>
> To: "'Mike McCarty'" <jmccarty at SSD.usa.alcatel.com>; "'Ed Okerson'"
> <eokerson at fw.telenic.net>
> Cc: <DPRGlist at dprg.org>
> Sent: Tuesday, February 05, 2002 9:26 AM
> Subject: RE: [DPRG] Contests at the Science Place
>
>
> > Ed,
> >
> > Sure, this was more or less my default solution, but you would only be
> > sensing the passage of the robot at a given height. Some robots may have
> > pieces protruding back above or below the height of the lasers which would
> > change the time. Bill's little dragster robot comes to mind. It's rather
> low
> > to the ground. (And it has transparent wheels)
> >
> > What's the big deal about drilling holes in the walls? It would only take a
> > 1/4 inch hole or so to insert the emitters and detectors. I don't think
> that
> > this would interfere with the robots sensors.
> >
> > Rick
> >
> >
> > -----Original Message-----
> > From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org]On Behalf
> > Of Mike McCarty
> > Sent: Monday, February 04, 2002 9:37 PM
> > To: Ed Okerson
> > Cc: DPRGlist at dprg.org
> > Subject: Re: [DPRG] Contests at the Science Place
> >
> >
> > On Mon, 4 Feb 2002, Ed Okerson wrote:
> >
> > > Why?  All you need is two lasers, parallel to each other at the same
> > height
> > > with detectors on the other side of the course.  The real problem is how
> > to
> > > get the lasers across without drilling holes in the course walls.  I also
> > > suspect that lasers shining into the IR detectors will cause problems
> with
> > > many robots.  Most of our robots are probably not heavy enough to trigger
> > any
> > > pressure sensitive contacts.  I guess we could mount microphones at the
> > > corners of the course and do surface wave acoustic analysis to
> triangulate
> > > the bots position.  I saw this approach used once for very large touch
> > screen
> > > monitors that did not have any overlay on the CRT.
> > >
> > > Ed Okerson
> > > President DPRG
> > >
> > > ----- Original Message -----
> > > From: "Ralph Tenny" <rten at metronet.com>
> > > To: "R. Bickle" <rbickle at swbell.net>
> > > Cc: "'Rodent'" <daweasel at swbell.net>; <dprglist at dprg.org>
> > > Sent: Monday, February 04, 2002 7:04 PM
> > > Subject: RE: [DPRG] Contests at the Science Place
> > >
> > >
> > > > It is easy to detect when the front of the robot crosses the line; not
> > > > easy to detect when the back end crosses!
> > > > Ralph
> >
> > while (BeamSeen())
> >     DoNothing();
> >
> > do {
> >
> >     while (!BeamSeen())
> >         DoNothing();
> >
> >     ExitEpoch = GetEpoch();
> >
> > } while (BeamSeen() && GetEpoch()-ExitEpoch < MaxWaitTime);
> >
> >
> > ExitEpoch is the moment that the robot completely exited the arena.
> >
> > IOW, we wait until we can't see the beam. Then we wait until we can see
> > the beam. Then we "debounce" by forcing a wait until MaxWaitTime has
> > lapsed with the beam constantly visible. If the beam goes away again,
> > then we reset the timer. This way, if the beam sneaks through a hole in
> > the robot for a moment, it doesn't fool us into thinking that the entire
> > robot has gone by.
> >
> > Mike
> > --
> > char *p="char
> > *p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}
> > This message made from 100% recycled bits.
> > I can explain it for you, but I can't understand it for you.
> > I don't speak for Alcatel      <- They make me say that.
> >
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>
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