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In lugnet.lego, Brian Davis wrote:
> Stalled, the train motor pulls 950 mA, while the stall current of the NXT
> motor is a whopping 2 Amps. So a single NXT motor output should easily
> handle a twin-engine train loaded to the point where it stalls the
> engine(s)...there's the matter of what the peak voltage is, which for a
> system driven by the NXT will be slightly lower than what I *think* the peak
> voltage is from a train controler, but not by much.
So it sounds like a single loop should be no problem under most situations,
since I'm not sure I've heard of anyone running three motors on a single train
(there's the same issue with how much amperage a power regulator can push).
> > I'm not sure a 1:3 pulse of power would be enough to sustain
> > a desirable speed on many AFOL trains.
>
> You lost me here. I was proposing pulsing the power ("pulse width
> modulation") on a motor output, to simulate a more standard PWM scheme. With
> an NXT motor attached, you might actually get away without a bunch of
> rapid "on off" command in the software, because by watching the motor
> encoders for feedback the firmware on the NXt would do it for you.
It sounds like what you'd want to do is run three loops where only one loop is
receiving power at any given moment. Based on that, what I was saying is that
I'm not sure a train will run nicely if it's only getting power 1/3rd of the
time. It seems like if you're giving it full power for one second and no power
for two seconds, it's roughly equivalent to giving it a steady 33% power.
> Use an on-screen menu and the on-brick buttons to select which bank of loops
> to control, and then use the three motors as three inputs to "set the
> throttle". No, you wouldn't have a console of nine analog-appearing
> throttles sitting in front of you, but it would certainly work. Start small
> is good, and I agree... but I'm pointing out the level of flexibility
> inherent in the system.
Well, if you don't mind the fact that many people would have difficulty
operating it under emergency circumstances (such as one train derailing over the
tracks of another approaching train). And don't ever hand it to anyone whose
VCR still flashes "12:00". Actually, if you include the use of buttons in the
control scheme, you could control four single-loop NXTs by using three motors as
analog throttle controls, and the left/right arrow buttons as a fourth digital
throttle.
> And this is a good reason, but it would need more testing to see what the
> limits are. Conservative is good, but very few of us have 4 NXTs to try this
> out with as yet (yeah, I do know a few folks who could, but theytend to be
> hyperactively busy with their HW).
No one person should need to own all involved NXT bricks. Since this is
something that would ultimately likely appeal more to an LTC than a robotics
group, having a few members donate NXT bricks for any shows would allow one
person to do all of the programming without having to drop a bunch of extra cash
on the project. For instance, in our club, Steve Ringe does a lot of work with
the older Mindstorms, but I doubt he'd have bought four NXT sets (I'm not sure
he's even bought one), but all told I believe our club has at least six within
the greater Detroit area (more if you include all of our far-flung members).
> I agree, but it's not large buildings that worry me, but tunnels and multi-
> level layouts. If the Hobby train IR remote is anything like the PF remote,
> just point it at the ceiling. I can control my PF Bulldozer from the other
> side of a island counter just by pointing it up at the ceiling and bouncing
> the IR. But no way will it work for tunnels.
Heh. So I guess that wouldn't work at all for one of Ringe's more devious
systems...
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Message has 1 Reply:
 | | Re: The Future of Trains
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| (...) Philo kindly corrected me, pointing out that the NXT outputs are regulated down to 1 A, so you couldn't run a dual-truck train all the way to stall. You could still get a good bit of the way there, however. Does anyone know what the peak (...) (17 years ago, 8-Oct-07, to lugnet.lego, lugnet.robotics.nxt)
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Message is in Reply To:
| | Re: The Future of Trains
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| (...) Stalled, the train motor pulls 950 mA, while the stall current of the NXT motor is a whopping 2 Amps. So a single NXT motor output should easily handle a twin-engine train loaded to the point where it stalls the engine(s)... there's the matter (...) (17 years ago, 7-Oct-07, to lugnet.lego, lugnet.robotics.nxt)
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