| |
In lugnet.lego, David Laswell wrote:
> The ports may be able to pour out power, as you say, but I'd
> say it's equally well established that large trains with heavy
> cars will suck it like water in a desert.
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.
> 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. The neat thing about this second is
that when the train hits a hill and tries to draw more power, the amount of
power to the NXT motor on the circuit with it will drop, and it will slow down
just like the train... until the NXT firmware detects this, and increase the
power out to maintain a constant speed on the motor. I've not tested this, but
it's a possibility that might be very interesting for NXT-driven trains.
> While it might be possible to pull off nine loops, I think
> your first problem would be in setting up independant control
> of all nine through a single control NXT.
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.
> > the AC power supplied through the Li-ion limits the motor
> > ports (in other words, you can draw more current from the
> > three ports together than the wall transformer can supply
> > in a steady-state situation).
>
> Again getting back to a reason for limiting this to one loop
> per slave unit, and three loops per control unit.
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).
> Remember, this is a system where train clubs will turn
> the trains on in the morning and let them run for maybe
> eight hours straight in a single day, with the only
> breaks being to swap out trains or to recover from a
> derailment. I don't think a battery-only solution is
> going to cut it...
I agree... but if you are using conductive tracks, use good old analog train
controlers. If you want automation, you could control the train controler with
an NXT motor (if you've got the hardware, this gets around a number of
problems). And since folks have run their trains using LDCC off an RCX, running
a similar set-up off an NXT using the Li-ion battery and a wall wart should be
easy in terms of power (the transformer is the limit in the system, and if it
could power 1.5 amps out of the RCX under LDCC, it should certainly handle
something similar for the NXT).
> they'll never get the LTC's to switch over to a system
> that requires constant line-of-sight to keep a train
> moving.
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. Yes, a system that allows the reciever to enter a
"latched on" state would be ideal... and while you're at it, if the PF receiver
(in the new yet-to-be-seen trains, for instance) could do PWM, then other than
battery life a lot of the problems have been solved: you could use IR to "talk"
to a receiver on a train going by, and set it's speed. The train then holds its
speed until the next communication window.
--
Brian "not actually a train-head" Davis
|
|
Message has 2 Replies:
 | | Re: The Future of Trains
|
| (...) 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). (...) It (...) (17 years ago, 8-Oct-07, to lugnet.lego, lugnet.robotics.nxt)
| | | Re: The Future of Trains
|
| (...) Some precisions here: - NXT stall current is 2A but only for a short time: internal thermal protection will trip at a current much lower than that (exact value depends on temperature and overload duration). A practical value is about 1A - NXT (...) (17 years ago, 8-Oct-07, to lugnet.lego, lugnet.robotics.nxt)
|
Message is in Reply To:
| | Re: The Future of Trains
|
| (...) Fair enough, but clearly the idea has sparked some interest, so I'm sure I'll see it get put into use at some point. (...) The ports may be able to pour out power, as you say, but I'd say it's equally well established that large trains with (...) (17 years ago, 7-Oct-07, to lugnet.lego, lugnet.robotics.nxt)
|
124 Messages in This Thread:
(Inline display suppressed due to large size. Click Dots below to view.)
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
