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Power Functions and 9V


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#1 Unitron6991

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Posted 15 September 2009 - 01:24 PM

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Has anyone had success using them with Mindstorms and the 9v system? Is it possible to use a PF motor in the Emerald Night and have it pick up off of 9v track? Or is there somehow a way to put a IR receiver between the speed controller and the track?
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#2 TaltosVT

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Posted 15 September 2009 - 05:29 PM

View PostUnitron6991, on Sep 15 2009, 09:24 AM, said:

Has anyone had success using them with Mindstorms and the 9v system? Is it possible to use a PF motor in the Emerald Night and have it pick up off of 9v track? Or is there somehow a way to put a IR receiver between the speed controller and the track?
You can put the IR receiver between the controller and track.  See the discussion on the Flickr Lego Trains group:

http://www.flickr.co...57617947835040/

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#3 BMW

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Posted 16 September 2009 - 04:49 PM

Several people have used Mindstorms to control 9v trains.  Myself, John Gerlach of GMLTC, and Benn Coifman to name three.  The upshot is that it isn't practical but I'll try to summarize

My experience - In 2001 I wired a mindstorm 1.0 to control a 9v point to point shuttle mechanism.  The logic worked fine but I had problems with speed control.  Since MS power levels use pulsed with modulation instead of discrete voltage levels like the 9v system, the motors respond differently.  My trains would just sit an hum at low power levels until they got to a certain level and would then lurch forward at too fast a speed.  I never fully understood this since, in theory, electric motors have higher torque with pulsed power than constant voltage.  I attributed it to the choice of power levels (% duty cycle) the MS design team made.  My workaround was to wire a MS motor w/ rotation sensor (for indexing) to an arm that drove a regular TechII power pack.  Kinda complex, and a major non-lego part, but it worked.  

Gerlach/GMLTC - Shortly after my experience John wired an MS unit to control a roundhouse turntable.  Very clever in that it placed a lok onto the bridge, then rotated to the next open stall, moved the lok into that stall, and then repeated the operation over and over.  I recall him saying the logic worked well but he encountered a similar issue as myself with loks "shooting" on and off the turntable bridge.  Not sure if he ever worked past this.

Benn Coifman - At Brickworld this year Benn demonstrated the most impressive MS train control I've seen to date.  It automatically controlled two trains simultaneously, switching them on and off sidings, and I think I recall seeing it even decouple and shunt individual cars.  The trains operated at decent speeds too.  I think he said he achieved this by pulsing the power in software (which I interprited as looping power on/off quickly.... effectively pulsing pulsed power at a lower frequency).  He believed this would eventually burn out the motors and didn't plan to run much past the show.  I didn't have time to followup with Benn on this yet so ping him if you are inclined as this would be the place to start.

Today you could use Mindstorms to directly control the power functions variable speed control through BT so consider that too.  Either with the receive on multiple loks (for independent operation) or wired into the 9V track (for unmodified loks).

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#4 Captain Zuloo

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Posted 17 September 2009 - 06:34 AM

If you want to know about Mindstorms control, check out pe668's website. He is without doubt the king of Mindstorms layout control:

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#5 BMW

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Posted 17 September 2009 - 06:23 PM

Yes, he certainly has an impressive array of Mindstorms controlled accessories.  But I don't see any evidence that he uses MS for actual power control of the trains.  Is it burried down on one of the pages?

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#6 missouri_bb63

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Posted 20 September 2009 - 04:54 PM

This is a great topic. I just read throught the Flickr discussion as well. From what I can figure (and correct me if I am wrong), one could also leave out the RC controler if one could live with the trains all going in one direction. Cheap, high torque PF motors without all the expensive RC add-ons and no battery limitations. Very, very tempting!




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