Subject:
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Re: Help me convert this train program to use events (NQC)
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Mon, 28 Nov 2005 17:39:46 GMT
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Viewed:
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5984 times
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In lugnet.robotics.rcx.nqc, Brian Davis wrote:
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In lugnet.robotics, Jordan Bradford wrote:
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the original version works as a prototype, but I don’t have
enough cords to reach the touch sensors I would have put at
each “station” in the full layout.
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Speaker wire and small alligator clips will make a dandy solution for
extending the basic wires - after all, you really only need one very long
wire here (to the “remote station”), and yoiu have a working set-up.
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I wanted the layout to be pure LEGO, but if I run out of time building this I’ll
break down and use non-LEGO wire and my original setup.
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So now I’m going to power the train motor directly from an RCX
that rides along as one of the cars.
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Have you built and tested this yet? “Hiding” an RCX on a 6-wide isn’t very
easy (it can be done, it’s just not easy). A bigger problem is the power
issue - the RCX will not be able to run the train for long (the batteries
will run down fairly rapidly, and the weight of the RCX isn’t going to help),
and the speed will change over time. Worse yet, when the power runs low the
RCX is likely to corrupt the firmware unless you put in code to monitor the
battery level (something I’d suggest if you go this route).
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I wasn’t worried about hiding the RCX, but I have seen the batteries run down
very quickly. In the course of testing just the RCX on a motor I had to adjust
the SetPower() function call a couple times because of this. NQC reports the
battery level after every upload, and it was down to 8.5V pretty quickly.
I didn’t know that low voltage will corrupt the firmware. That’s good to know
for future reference.
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I’ll use light sensors on each end of the train to
look for white tiles placed between the track rails
at each “station.”
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That should work, within the constraints above. As another poster mentioned,
you might need periodic recalibration. Not a big problem, just run a
calibration task every few minutes when you *know* the train is not i na
station (like a few seconds after it pulls out of one). Note that for events,
you will need to redefine the upper or lower limits to recalibrate.
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Here’s a new version of main()... Is this going to work?
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Not yet. For one thing, the sum of two sensors is not a legal source for
an event - a single sensors is. More to the point, if the (single) light
sensor is looking down from the moving train, why do you need two sensors?
You’re just looking for changes in the state of a single light sensor, right?
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That’s a good point. I guess I was thinking of putting the “stations” at the
extreme ends of the track, but one of them could be more inward based on the
length of the train. As long as the cars don’t run off the end it’s fine. The
same would be true of touch sensors -- I’d only need one if it’s mounted on the
train.
As for the event setup, thanks for the tip. Most every convenience function in
NQC allows combinations of inputs/outputs. But as you pointed out, I only need
one sensor, anyway.
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Also, if you are looking for a event to transition to a “high” state, that
implies brighter the way you’ve defined your sensors. So you need bright
tiles under the track - reflective tape works really well in some of these
setups. As mentioned, I would have the code autocalibrate. The task main()
will execute the monitor command only once - once it falls out of the monitor
command, it will execute the catch code (if the event was tripped), and then
fall out of main(), end of program. Within the monitor() body itself, a
single “Wait(32767)” will work - yes, it will hang there, but it will be
immediately pulled out if the event triggers, so it doesn’t get “stuck in a
Wait()”. Those are issue I see immediately.
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I was wondering about that monitor block and whether it would only execute once.
Should I put the monitor block inside a while(true) ?
Thanks for the information.
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