Subject:
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Re: "No Contact" Homebrew Train Sensor for Mindstorms
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Newsgroups:
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lugnet.trains, lugnet.robotics
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Date:
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Tue, 5 Dec 2000 20:58:20 GMT
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Viewed:
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1657 times
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James,
Are they directly wired to the RCX or is there a resister in series. BTW
where is the web page on the electrical specs of the RCX and home brew
sensors? I can't remember.
SteveB
In lugnet.trains, James Trobaugh writes:
> Chris,
>
> Another great little sensor for train detection, via Radio Shack, is the
> little photo sensors they sell. I put them inside of a 2x4 technic plate and
> then snap them face up on the track. This way they use the omni light from
> the room as the light source, when the train crosses over the sensor the
> light source is removed and the train's arrival is detected. By placing one
> on both sides of the crossing you can tell if the train is still in the area
> of the crossing. The basic logic is if either sensor is triggered lower the
> gates, once both sensors are clear raise the arms back up.
>
> The only problem I had with this was at some of the shows I've done they
> don't turn on the main lights till the show starts (i'm sure to save money),
> and sometimes the sensors wouldn't work till the lights were all turned on.
> Not a big deal, just that I couldn't test the sensors till show time. I did
> start carrying a flash light for testing reasons though.
>
> Here are a few pictures of the sensors I've built:
>
> http://www.ngltc.org/novgats/image50.htm
> http://www.brickshelf.com/cgi-bin/gallery.cgi?i=20391
>
>
> In lugnet.trains, Chris Phillips writes:
> > As has already been reported by others, I built an automated railroad
> > crossing for the NELUG train display at last weekend's Greenberg show. I
> > wanted to take a moment to describe the "homebrew" sensor that I used to
> > detect an approaching train so that others might benefit in their own layouts.
> >
> > I originally tried several techniques to detect the presence of a train,
> > including the touch sensor, the light sensor opposite a light source, and
> > the good old infrared "radar" technique that has been well-documented on the
> > robotics forum in the past. I also considered using Vision Command, but I
> > didn't want to have a PC in the loop if I could avoid it. None of these
> > techniques was very reliable: I couldn't find a good way to trip a touch
> > sensor without derailing the train, and the other techniques required a lot
> > of highly visible and unsightly "plumbing" somewhere along the track. I had
> > pretty much abandoned the idea of using an RCX to detect a train before I
> > remembered an idea that I had awhile back but never tried, due to my
> > semi-irrational aversion to non-LEGO solutions.
> >
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