Subject:
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Re: RCX Output (Train applications)
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Newsgroups:
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lugnet.robotics, lugnet.trains
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Date:
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Thu, 16 Dec 1999 23:09:43 GMT
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Viewed:
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102 times
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This sounds interesting, but trying to understand it in the middle of class has
my head swimming ;-)
Any chance of diagrams and pics? I ust picked up my first trains and RIS last
week, so I want to hook them together and have some fun with my cats ;-) Maybe
set the trains to speed up if the light sensors detect a cat hanging over the
train ;-)
In lugnet.robotics, "Avery, Amos E." <Amos.E.Avery@disney.com> writes:
> Wow, what an excellent description. I look forward to trying this out over
> the holidays. I had one other idea that may explain my initial failure.
> The track layout I was using was rather large, in fact it took up the entire
> living room using nearly every piece from 5 train sets. I will try again,
> thanks to your encouragement, with a smaller layout. Also, the plastic
> insulation you are talking about, is that a thin plastic film cut to 1/4" x
> 1/8" such as scotch tape? I'm having a hard time visualizing anything other
> than really thin material. Many thanks.
> F'amos
>
> -----Original Message-----
> From: Ted Michon [mailto:tedmichon@home.com]
> Sent: Thursday, December 16, 1999 9:20 AM
> To: Avery, Amos E.
> Cc: lego-robotics@crynwr.com
> Subject: Re: RCX Output (Train applications)
>
>
> Avery-
>
> With 1 RCX running on AC (with batteries installed), I could run both
> complete Railway Express trains (engine and 2 loaded long cars each) just
> fine. We ran them at a max RCX speed setting of 4 - any higher and they were
> prone to fly off the rails around curves. Because of the isloation blocks in
> the layout, the loops were each electrically open at one spot so we made a
> point of putting the track connector in the middle to minimize the maximum
> resistance to the farthest points.
>
>
> I only noticed a problem if I started both trains simultaneously at slow
> speed, which was necessary when doing the track swap. So instead of using
> speed 3 for this, I chose speed 4 and had no further trouble.
>
>
> I don't have any processed photos yet that show the layout, but perhaps I
> can give a better description. I'll start by defining some terms for the
> switches. Consider a switch oriented like your right hand with the straight
> side going from your wrist toward you middle finger and the curve flowing
> toward your thumb and your palm flat on the layout. I'll call this a "right
> hand" switch. I'll call the part the corresponds to the thumb the "curved
> node", the part for the middle finger the "straight node", and the part for
> the wrist where the opposite ends of the curve and straight meet the "common
> node".
>
>
> This particular layout was made by first making a 180 degree half circle
> (imagine it at the top of the layout, if we were working on a sheet of
> paper, with the open ends pointing down). Attached to the right side of the
> half circle is the curved node of a right hand switch. Attached to common
> node of this switch is another 180 degrees of curve (with some straight in
> the middle) followed by the common node of a left hand switch. The curved
> node of this second switch attaches to the remaining spot on the original
> half curve.
>
>
> At this point, there is a complete inner loop and two unconnected straight
> nodes from the two installed switches.
>
>
> Attached the straight node of another right hand switch to the straight node
> of the first installed switch. Attach the straight node of another left hand
> switch to the straight node of the second switch. Now add a 180 degree
> section with some straight track in the middle to connect the common nodes
> of switches 3 and 4 across the top of the layout. Finally, add a 180 degree
> section with some straight track in the middle and on each end to link the
> curved nodes of switches 3 and 4. These sections complete the outer loop.
>
>
> Set all switches so that the yellow balls point to the right. This will
> force a clockwise running train on the outer loop to stay on the outer loop
> and a clockwise running train on the inner loop to stay on the inner loop.
> When either train reverses, however, it will swap to the opposite loop.
>
>
> The two small piece of 1/8 inch by 1/4 inch plastic insulation goes at the
> junctions where the straight nodes of the switches meet - but only on one of
> two rails in each junction. For the pair of switches on the right side of
> the layout, the inner most rail gets the plastic. For the pair of switches
> on the left side of the layout, the outermost rail gets the plastic.
>
>
> The outer track sensor goes at the top of the outer loop on the inner side.
>
>
> The inner track sensor goes at the bottom of the inner loop on the inner
> side.
>
>
> Power the outer loop from the bottom right corner. Power the inner loop from
> the bottom left corner.
>
>
> -Ted Michon
>
>
> "Avery, Amos E." wrote:
>
>
> When I tried this, my train only ran at about 1/2 speed at full output from
> the RCX plugged into the train power supply and batteries removed. Any
> ideas why? My trains are a little old and I'm considering cleaning the
> tracks. Maybe I'll try again with a new train set. Do you have any
> pictures or can you show with sketches the sensor configuration or a detail
> of the track layout and the plastic weggies? I'd be very grateful for any
> additional info I could get. Thanks!F'amos
>
> -----Original Message-----
> From: Ted Michon [ mailto:tedmichon@home.com <mailto:tedmichon@home.com> ]
> Sent: Wednesday, December 15, 1999 3:11 PM
> To: Avery, Amos E.
> Subject: Re: RCX Output
>
> Amos -
>
> We drove the trains directly from the RCX. In fact, everything in the system
> was an "all LEGO" solution except for the 2 small pieces of insulating
> plastic wedged between two pair of rails and for one axle in each sensor
> whose end I filed a trifle to give a small bevel and eliminate the dimple
> which was making the sensor button stick a little.
>
>
> -Ted
>
>
> "Avery, Amos E." wrote:
>
>
> Wow! Did you drive the trains directly through the RCX or did you do
> something different?
>
> -----Original Message-----
> From: Ted Michon [ mailto:tedmichon@home.com <mailto:tedmichon@home.com> ]
> Sent: Wednesday, December 15, 1999 2:45 PM
> To: Avery, Amos E.
> Cc: lego-robotics@crynwr.com; Joel Shafer
> Subject: Re: RCX Output
> Avery-
>
> For the Orange County (CA) Festival of Trees (South Coast Plaza, Costa Mesa,
> CA December 2 - 6 ), we entered a LEGO decorated tree with 2 Railway Express
> sets underneath run by an RCX (the lucky winner of the tree got the complete
> Mindstorms and trains, an autographed copy of The Ultimate LEGO Book, a 5
> foot diameter octagon base with a LEGO village and track layout, 150 LEGO
> ornaments, 84 glass globes, and 1300 lights).
>
>
> We designed the track as two concentric layouts linked by two pairs of
> switches. The switches were set so that trains would run continuosly on
> their track (inner or outer) in the clockwise direction but would change
> tracks if run in reverse (counter clockwise). We placed one RCX touch sensor
> on the outer track and one touch sensor on the inner track (it took awhile
> to design the mechanics of the sensors, but we eventually got a design that
> worked reliably).
>
>
> Because LEGO switches isolate one rail according to the position of the
> switch, we completely isolated our inner loop from our outer loop by
> inserting a small piece of plastic (1/8 inch x 1/4 inch, cut from an
> ordinary blister card packing) on the non-isolated rails (two total). One
> RCX motor output controlled the inner loop and one controlled the outer
> loop.
>
>
> With this arrangement, we ran the trains independently and randomly for a
> time (they looked pretty good starting up slowly, running at speed, slowing
> down, and stopping) and then synchronously. In this latter mode, the outer
> train started, rain 3 loops (we counted passes by the sensor), slowed a
> notch, and then stopped at the outer track sensor. The inner track did the
> same thing, phase delayed about 30 seconds. With both trains stopped, we
> backed the outer train to clear it's sensor and then backed the inner train
> to clear its sensor. Then we ran both trains backwards until one of them hit
> a sensor (this switched the outer train to the inner track and the inner
> train to the outer track), then ran the other track until its sensor was
> hit, and then ran each independently (still backwards) to clear their
> sensors. Then we repeated the whole thing.
>
>
> The tree was pretty popular with kids and adults and we got a crowd whenever
> we ran the trains.
>
>
> I was amazed how reliable the whole thing was, though we knew better than to
> leave the trains running when we weren't there.
>
>
> -Ted Michon
>
>
> "Avery, Amos E." wrote:
>
>
> Thanks for the much-needed input. My goal was/is to eventually build a
> fun, interactive multiple train layout with seemingly random events
> triggered by multiple networked RCX's. It looks like I may be designing
> a machine that manually turns the train rheostat to achieve my goal. The
> holidays could be interesting.
> F'amos
>
> -----Original Message-----
> From: Nick Taylor [ mailto:ntaylor@iname.com <mailto:ntaylor@iname.com> ]
> Sent: Wednesday, December 15, 1999 11:05 AM
> To: lego-robotics@crynwr.com
> Cc: Joel Shafer
> Subject: Re: RCX Output
>
>
> Hello Joel,
>
>
> Attempting to drive an RC servo directly from the RCX is NOT a good
> idea! The servo is a three wire device; +4.8V to +6.0V for power
> (usually the red wire), an approximately 40Hz pulse train of 1.0 to
> 2.0ms pulses at 0V and +5V logic levels (white or yellow wire), and
> ground (black wire). The pulse train does NOT power the servo motor,
> it only tells the chip in the servo where to go ... the red wire
> supplies power to drive the motor until an internal pot is turned
> to the point where the position of the servo equals the position
> commanded by the pulse width on the white wire.
>
>
> The RCX delivers a two wire output which changes polarity when a
> command is sent to reverse the motor ... and the servo's logic chip
> would not be very happy.
>
>
> I'm sure that you could build external circuitry to let the RCX
> control a servo, but I'll leave that exercise to the reader.
>
>
> Play well,
> - Nick -
>
>
> Joel Shafer wrote:
> >
> > So if you need a 1, 1.5 & 2ms pulse for controlling a servo and you said
> > the low setting in NQC = a 1ms pulse, are there other matching motor speed
>
> > settings to get a 1.5 or 2ms pulse?
> >
> > At 05:14 PM 12/15/99 +0000, you wrote:
> > > Hi F'Amos,
> > > I just now put a scope on the motor output ran an NQC motor test
> > > program. At OUT_FULL the motor output is about +7V DC. At OUT_LOW
> > > the motor output is a pulse train of 1ms 7V pulses at about 125Hz.
> > > The low level depends on the motor load ... almost 7V with no motor
> > > connected and approaching 0V with a stalled motor. NQC provides
> > > seven motor speeds ... and by increasing the duty cycle of the pulse
> > > train the average DC level to the motor is changed.
> > >
> > > RC servos are also controlled by varying the pulse width. For most
> > > servos a 1.5ms pulse tells the servo to go to the center position.
> > > Increasing the PW toward 2.0ms turns the servo CW and decreasing
> > > toward 1.0ms turns the servo CCW. The exact pulse width determines
> > > the exact stopping position. Servos that are modified for use as
> > > motors can never find a null position so they continue to turn
> > > seeking the nonexistent null. Unless the PW sent to the servo is
> > > very close to the null PW, the servo will turn at full speed. If
> > > the null PW is 1500us, then a 1550us PW will result in a slower
> > > speed.
> > >
> > > Hope this helps,
> > > - Nick -
> > >
> > > "Avery, Amos E." wrote:
> > > >
> > > > --- Nick Taylor <ntaylor@iname.com> wrote:
> > > > > If I'n not mistaken, the RCX output is pulse width
> > > > > modulated to control motor speed, while the train controller
> > > > > varies the DC voltage.
> > > >
> > > > Can anyone confirm the output characteristics of the RCX?
> > > > It is my understanding that PWM is used to control RC servos
> > > > and not to power them. Has anyone put a scope on the RCX's
> > > > outputs to see what they look like? If the info is available,
> > > > I'd be interested to know the exact output specs (eg. 0-9v 200ma).
> > > > F'amos • <http://www.crynwr.com/lego-robotics>
> >
> > Joel Shafer joel@connect.net
> <http://www.crynwr.com/lego-robotics>
> <http://www.crynwr.com/lego-robotics>
>
> -- Did you check the web site first?: http://www.crynwr.com/lego-robotics
> <http://www.crynwr.com/lego-robotics>
>
>
>
> --
> MIME ATTACHMENTS DISCARDED:
>
> 1. Content-Type: text/html;
> charset="windows-1252"
> Content-Length: 16899
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Message is in Reply To:
 | | RE: RCX Output (Train applications)
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| Wow, what an excellent description. I look forward to trying this out over the holidays. I had one other idea that may explain my initial failure. The track layout I was using was rather large, in fact it took up the entire living room using nearly (...) (25 years ago, 16-Dec-99, to lugnet.robotics)
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