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 20:17:27 GMT
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Viewed:
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1623 times
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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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