Subject:
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Re: Mindstorms Automatic Train Control Questions
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Newsgroups:
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lugnet.trains
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Date:
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Sun, 28 Oct 2001 04:47:58 GMT
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Viewed:
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583 times
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In lugnet.trains, David Niemann writes:
> Hello,
> I am building a Lego subway line and I want to try to automate it. I am new to
> Mindstorms and I do not know how to get started. I saw there are now several
> starter sets, and three versions of the RIS. What I want to do is run 3-4 two
> car trains simultaneously on my two track layout, having them automatically
> speed up, slow down, and stop at each station for a few seconds. I might also
> try having a switch track at the end of the line change direction each time a
> train enters and leaves that station (so the train can cross to the other • track
> at the terminal station). Does this all sound possible?
Sure, it is _possible_. How I would approach it follows.
If so, which set would
> be the best for me to start with? Will I need a seperate RCX for each train?
> Also, I seem to remember reading something about the RIS version 1 having an • AC
> adapter and the RIS 1.5 and RIS 2 needing batteries. I think it said the RIS 1
> could control a train stationarily, but the RIS 1.5 or 2 would need to be
> onboard the train. Is this true?
Nope, any one of them can be fitted to either the train or ground. If you are
going to have stationary RIS's, it would be better to have 1.0's, since there
are no structural changes to 1.5, and few to 2.0, except for the deletion of
the 9v input jack.
As for approach, I would use an RCX for each station, but located in a manor
which would allow them to "talk" to each other, if at all possible. So, if you
have 4 stations, that means 4 RCX's too (and only 3 trains) (about $480USD-S@H
sells just the brick). The prime reason for using them this way is because of
sensor limits. To control a crossover at each end would take a single output
(fixed) on each end (so, it is perfectly possible to do it with train mounted
RCX's too...which might be better if you want to have 10 stations, and only 4
trains...)
To control the trains, I would use mostly light sensors. Again, S@H has them.
To do a good job, I think you would need 2 sensors per station, one at the
start and one at the end of each platform.
Program would look something like this:
Ask next RCX if track clear
(wait if not)
Power up track, send train on way
Wait until train clears EOP (end of platform sensor)
Answer all requests now that track is clear into section
(put the EOP sensor so that the train masks it when it is at the end of the
platform, a BOP (beginning of Platform) sensor is also required
Keep track power at nominal level until next train arrives at BOP sensor
then reduce at a appropriate rate to stop the train in the station.
Repeat above after time delay
Note, that you will need one extra RCX (or a combination of sensors& outputs
totalling 2 input, 1 output) to make this setup work. (above the number of
trains you want to move-also note, that not all the trains can move at once!)
It would take 2 inputs, and 1 output per station, so 3/6/9 stations would be
most efficent. 3 stations would give you 3 extra outputs-these could be used
to reverse track switches, although there is a easier way to acchieve
unidirectional running on most of the track, because the switches are spring
switches...
Feel free to ask here some more...I've set FUT to trains, because I think that
it is more appropriate than .robotics-the mechanical side of this is probably
harder than the programming side of things.
(also, at least one person sells reed switches...they would work better than
light sensors for this application, but are a non lego pure solution...)
James P
(the RCX is 119 USD, light sensors are 20)
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Message has 1 Reply:
 | | Re: Mindstorms Automatic Train Control Questions
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| Snipped most of James's explanation, I just want to comment on one point (...) This is overkill. Just use the fact that you can align the switches AGAINST the incoming subway train and when it reverses, it will cross over to the other track with no (...) (23 years ago, 28-Oct-01, to lugnet.trains)
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