Standard RCX Train controler

[elicend]

Hi all ;)

I'm starting this post in order to try to put on a standard for RCX controling Train

Aim of the project :

The aim is to define and share a standard to control train by RCX bricks.

Why RCX brick :

There is severals reasons : the first one is that it is a full lego solution, instead of an arduino solution, the second one, the RCX can be powered by 9v pickup from rails. Then, the RCX is able to control 3 outputs, that should be 2 motors, and one light, it can use swiths, rotation captors, optic captors, and it is now not really expensive.

What i have found at this time :

best RCX integration in a loco (most of mine would be in a wagon and not loco) : http://railbricks.com/instructions/gp40-rcx/

more integration and exceptionel controling (for RCX septics) : http://www.eurobricks.com/forum/index.php?showtopic=45440 (here!! if the member can help me:)

another here, with interaction with track : http://www.eurobricks.com/forum/index.php?showtopic=45495 (if member can help me too !!)

My wish :

my wish is a mix of those link. I would like to control train by RCX, if possible by controling the speed, as on the second link and had track reading by swich of bar code reading, in order to not only have a train moving, but had stops (fret and passenger should have different stops), speed increasing or decreasing, pause, and, why not with technic, having optional bar code (if two train are too near one from the other). I think for the begining, i'll do wagon with RCX, and loco motorised, later, i'll look for more RCX and dedicates them in spécific loco as in the third link.

List of action (work open and in progress) :

1 Stop in passenger station

2 Stop in fret station

3 increase speed

4 decrease speed

5 pause x second (different than stop, because follow by every train, RCX shoud know if it is a fret or passenger train in order of good interpreting bar code)

6 not identified at this time ?

so... what do you think about this,

Edited November 29, 2013 by elicend

[zephyr1934]

There are several approaches to controlling a train with RCX and all sorts of ways to tell where it is. Though if you are using an RCX, you probably cannot use a barcode reader. You'll likely have to rely on simpler sensors. If you are a good programmer, the most reliable I have seen are break-beam light sensors (but there goes one of your outputs to power the light... that is assuming the RCX is on the wayside rather than on the train). A few other complications to keep in mind, first, the RCX cannot provide nearly as much power as the 9v train controller (and for that matter, if you are running on batteries, things will start to also lose power (e.g., the light level for your break beam sensor). Also, the RCX uses PWM to vary the speed and I THINK that can be extra hard on the train motors (there was a good post on that about 6 mo back somewhere in the forum). Also, the RCX has very limited memory, I had to use two of them to control a pre-scripted switching maneuver. It is a fun challenge and will keep you busy for a while, but also keep in mind that it is a little Rube Goldberg-esq (excessively complicated but fun to do).

Another alternative would be the IR link and an NXT, but the IR link has a limited range because it is a "sensor" and thus, must comply with the sensor specifications (although the IR link is a 3rd party product, it is/was sold by lego too).

[Heppeng]

I think all lego train motor controllers use pwm, I know that the grey 12v lego train one does, and I would expect all subsequent ones would too, so I think it is unlikely that any motor problems will surface. Counter intuitively, PWM is most likely to damage motors when they are run at low speed.

[mikezang]

There are several approaches to controlling a train with RCX and all sorts of ways to tell where it is. Though if you are using an RCX, you probably cannot use a barcode reader. You'll likely have to rely on simpler sensors. If you are a good programmer, the most reliable I have seen are break-beam light sensors (but there goes one of your outputs to power the light... that is assuming the RCX is on the wayside rather than on the train). A few other complications to keep in mind, first, the RCX cannot provide nearly as much power as the 9v train controller (and for that matter, if you are running on batteries, things will start to also lose power (e.g., the light level for your break beam sensor). Also, the RCX uses PWM to vary the speed and I THINK that can be extra hard on the train motors (there was a good post on that about 6 mo back somewhere in the forum). Also, the RCX has very limited memory, I had to use two of them to control a pre-scripted switching maneuver. It is a fun challenge and will keep you busy for a while, but also keep in mind that it is a little Rube Goldberg-esq (excessively complicated but fun to do).

Another alternative would be the IR link and an NXT, but the IR link has a limited range because it is a "sensor" and thus, must comply with the sensor specifications (although the IR link is a 3rd party product, it is/was sold by lego too).

NXT and EV3 are too big and expensive to control one train.

[elicend]

If you just have a look to this video, from one of the first 3 link :

from http://www.eurobricks.com/forum/index.php?showtopic=45495

the 1 stud bar code is possible

then, on this vidéo :

from http://www.eurobricks.com/forum/index.php?showtopic=45440

controling train, with different configuration, with RCX don't seem to be a problem :)

in fact, both ar from Toastie, i hope he is still here and will can help me, because, everything is already done i think ;)

[JopieK]

It is not that difficult, as with all programming, one should start off very simple and work your way up from there to the bigger solution (I currently teach robotics in 'sophomore' year (first year bachelors), so I over and over again see that that is the problem with novice programmers: first decompose your larger problem into manageable chunks and then combine the chunks to solve the large problem).

[Duq]

I think all lego train motor controllers use pwm, I know that the grey 12v lego train one does, and I would expect all subsequent ones would too, so I think it is unlikely that any motor problems will surface. Counter intuitively, PWM is most likely to damage motors when they are run at low speed.

Really? I'm pretty sure the 9V controller does not use PWM. As far as I know that was only introduced with PF.

[mashsladies]

I think it is unlikely that any motor problems will surface. Counter intuitively, PWM is most likely to damage motors when they are run at low speed.

Edited December 1, 2013 by mashsladies

[JopieK]

the 9V adapter indeed does not use PWM at all. There is a special print inside that regulates the voltage. PWM does not regulate the voltage.

[1974]

PWM does not regulate neither voltage nor current, it governs the time that power is applied

The 9V regulator is just an LM317 Vreg and I believe the old grey 12V transformer is an ever more simple with no actual active regulation

Really? I'm pretty sure the 9V controller does not use PWM. As far as I know that was only introduced with PF.

The 7898 IR train is also PWM and that predates PF

[JopieK]

@1974, thanks for your correction :)