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What if you could have your 9V and PF, too?

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#1 fred67


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Posted 18 March 2010 - 05:20 PM

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NOTE: This is all theory, as far as I know.  If someone has already done this, I would love to hear about it.

For the sake of clarity, I'm going to refer to three different kinds of motors:

9V - the traditional 9V/electrified rail motor.
RC - the 9V battery operated motor that is similar in size and shape to the 9V motor.
PF - an XL or M power functions motor.

So, I'm one of these guys hanging on and beating a dead horse about the death of 9V.  I'm not worried about the track, as I think the O-Scale track method (although I haven't tried it myself) solves that problem both for curves and straight sections of track - and also gives you the versatility of flexible track.  The conductive metal (copper or silver) tape over plastic solution is interesting me but I have doubts about it's longevity.

I also don't worry about powering the rails; although I'd love to stick with LEGO, you can probably use without problem a number of other speed regulators available from other companies (being sure to cap off at 9V).

That leaves motors.  The problem with the RC and PF motors is they seemingly need an on-board battery.  Batteries are the whole reason I hate the idea of converting to PF, I simply don't want to deal with them, I don't want to stop my train to recharge my batteries, I want to be able to run them for hours at a time, and probably the most important issue - I want the flexibility of not having to design trains around the size of the battery packs, and I don't want to have to open up my trains just to change batteries.

But what if you could use the RC or PF motors with power from the rails?  I know this has been discussed before, although I seem to see more people wanting to power their 9V motor from a battery (the worst of both worlds, if you ask me).  The only sticking point is you need some way to pick up the power from the rails.  Some people are gutting burned out 9V motors, which is probably the best solution, but then you are still stuck with the fact that there is a dearth of 9V engines... especially dead ones, and I know I'm not going to destroy a working one.  Moreover, I don't have that many to begin with.  But let's assume you use this method.

A recent Brick Journal article (that I've referenced in other posts) describes how to modify the connector on an 8886 conversion cable.  Now, generally speaking, this conversion cable will allow you to control 9V motors using PF battery packs with either a switch or IR receiver, but it doesn't work the other way around (through in IR receiver).  The article describes how to modify it to make it work... to power an IR receiver using a 9V source, be it an older battery pack or rails (which the article specifically mentions).

So here is the setup...

1. Speed/Voltage Regulator to power the tracks.
2. *** Gutted 9V motor to pick up voltage, connects to
3. Modified conversion cable connector, connects to
4. IR Receiver, connects to
5. Either a PF motor, or an RC motor using an unmodified 8886 conversion cable.

You would run the trains with the speed regulator turned all the way up (I would imagine).  The train won't go until you use the remote, but the train is still getting full power.

- No batteries needed, no need to model around battery packs.
- Remote control.
- Non-motive functions get full power, even when train isn't moving... in other words, your lights remain on and bright even if the train is not moving.
- Here's the kicker... here's the "real" advantage PF had over 9V... you can control MULTIPLE TRAINS on the SAME TRACK.
- You can control OTHER PF functions you've added to your train (like a crane or operating doors).

and, AND, if you DON'T WANT RC, you can eliminate the modified connector and IR receiver and connect your pick-ups (dead 9V) directly to an RC or PF motor.  You then control the train with the speed regulator (but your other powered functions would be affected also... i.e. dim or no lights when the train is stopped).

- If you're using a dead 9V and an RC motor to actually move the train, you need to incorporate both bogeys into your design.
- Dead 9V are not easy to come by.

I'm really busy this week (and spending far too much time here, but it's stuck in my head and I can't concentrate on other things, if you can believe it... if you're truly addicted to LEGO like me, you'll know what I mean when you get an idea stuck in your head that you can't test for some time!).  Hopefully either Saturday night or Sunday I can try to set something up, but I don't have any dead 9V and refuse to mess up one of the few working ones I have.

*** I'm desperately trying to find a non-9V solution to picking up voltage from the rail.  While I'm in the hobby shop picking up O-Gauge flex track, I will look into options, but I'm definitely open to ideas.

EDIT: I want to make it clear that I KNOW people have used gutted 9V motors to power RC and PF motors, and I know it works... the idea here is to use that modified converter connector in order to make your 9V train gain the advantages of the PF system.

Edited by TheBrickster, 19 March 2010 - 02:10 PM.

#2 roamingstop


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Posted 18 March 2010 - 05:28 PM

You have phrased something I have been thinking about - identically. Basically the bogey's would need to have metalled wheels to pick up the power supply; and a zenner diode bridge to compensate for reversed polarity (when doing a loop for example). Alternatively use a couple of small power MOS-FETS. Thus you could in principle have a small brick which picks up the voltages (any polarity) and delivers them into a 9V PF style format (+9V, 0V, CC1 and CC2).

It could also provide a link into the IR remote control - making (in my eyes) the best of both worlds. i.e. Powered track which allows full PF remote control (unfortunately not as powerful as the Marklin digital controls which control encode pulses onto the power supply rails).

Feel free to PM me if you want to discuss things - I was also quietly looking out for a dead 9V motore but since you wrote up the idea independantly I will creep out of the wood work.

#3 fred67


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Posted 18 March 2010 - 05:50 PM

Ahh... yes... I'd forgotten about looping a track back on itself.  I don't know when I'd do this (being old school about model railroads), but I can see the appeal.  Personally I would just avoid it.

Edited by fred67, 18 March 2010 - 05:50 PM.

#4 legoboy3998


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Posted 18 March 2010 - 06:24 PM

Fred, your theory is very tempting, in that, if you can get the RC motor to pickup track power, your whole system could be relatively commercially available at the present time.  I also agree that using "O gauge track" would be nice, hand laying is common in traditional model railroading, the only sticky part is witches but with a little effort and patients it would be possible.  

have you thought about the metal brushes from slot-cars?  there should be enough room in the RC motor to connect them and you could probably mount them between the front and rear axles.  most hobby shops, I would think carry them, the shop I go to has a large selection of slot-car stuff.

Since most traditional model railroad systems are 12V putting resistors in the circuit between the transformer and the track would limit the power to the track automatically.  

I like the possibilities of the new PF system, (I dont have a lot of 9V stuff, Im just starting out,) however the battery pack is the sticking point.  I have a loco designed like the BNSF GP38 LEGO produced 6 wide with the rechargeable battery in it, the only downside is I need to make decals to cover up the battery box.  to recharge the battery all I need to do is remove one 4 x 6 plate from the roof and plug it in.  Ill post before and after pics once i make and install decals.


#5 roamingstop


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Posted 18 March 2010 - 06:36 PM

View Postfred67, on Mar 18 2010, 06:50 PM, said:

Ahh... yes... I'd forgotten about looping a track back on itself.  I don't know when I'd do this (being old school about model railroads), but I can see the appeal.  Personally I would just avoid it.
Loopbacks are not really such a big issue - more that I believe the PF supply expects the supply rails to be a certain way around to work properly - and that would mean you would always need to place the engine the same way around on the track. The beauty with a voltage bridge is that you should not have to care anymore.

For those with an electronics edge...
Key words reverse polarity protection
or Full Bridge Diode Rectify

Next time I go through a Marklin shop I will look to see how they could pick up voltage. The Scaletrix brushes approach is probably the easiest.

Edited by roamingstudio, 18 March 2010 - 10:00 PM.

#6 legoboy3998


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Posted 20 March 2010 - 07:03 PM

To deal with loop tracks ("reversing loops" as traditional model railroaders call them) traditionally there is a electrical break at the switch (this can just be a plastic between two pieces of track)  However you will need to tell the locomotive somehow that forward is now backward and vice versa.  Its not simply turning the train around like is possible with the PF trains because the motor is powered by the battery.  DCC systems require reversing modules (exactly what they do I dont know) a local hobby shop may be able to help explain whats involved with reversing loops or you can look up DCC reversing loops on the internet, model railroader magazine and their website modelrailroader.com may also be of interest.


#7 Dan-147


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Posted 20 March 2010 - 09:16 PM

View Postlegoboy3998, on Mar 18 2010, 02:24 PM, said:

have you thought about the metal brushes from slot-cars?  there should be enough room in the RC motor to connect them and you could probably mount them between the front and rear axles.  most hobby shops, I would think carry them, the shop I go to has a large selection of slot-car stuff.

That makes me think of the old Playmobile train that ran on LGB track (gauge 1).  They had a sprung slider on each side between the front and rear wheels of the truck that picked up power from the metal track.  Playmobile eventually gave up on track-powered trains and switched to battery-powered IR-remote on plastic track for pretty much the same reasons LEGO did (cost and upcoming legislation about wall-powered electrical toys).  It might be possible to make brick-mounted sliders to pick up power from the track.  They would have the advantage (compared to gutted 9-volt motors) of being smaller and easier to mount on any truck or two-axled car, plus they wouldn't destroy a 9-volt motor.

I'm not all that worried for those of us who already have a sizable 9-volt train collection (not my case, unfortunately) when I see how many Europeens are still runnimg 12-volt layouts with components that are 20+ years old.  It's more the newcomers (and older fans like myself who couldn't afford to stock up on 9-volt components when they were still available) who will be "stuck" with the new Power Functions based system.  However, I like to look at it as a challenge rather than as a problem.


P.S.  I still have a grudge against LEGO for not distributing the 12-volt train line in North America in the 1980's!!

Edited by Dan-147, 20 March 2010 - 09:18 PM.

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#8 birdie100


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Posted 21 March 2010 - 02:55 AM

For reference, my father had the original Lego 12v motor system trains. He is an electrical engineer so when I was a child he electrified the original blue tracks he had, initially soldering copper strips onto the track, later taking the grey 12v tracks and putting copper tape on. At each end was a flat surface, so each track had a copper flap that would tocuh the next track, held in place on white 2 by 8 plates. How this system could be modified for the clip arrangement I'm not sure, but it must be possible. The copper strips can be relied upon to at least give 7/8 years faithful service. The pickups for the motors were modified 2 by 4 bricks, that clipped in the "ledge" under the classic 12v motor, and utilised twisted metal bead paper fasteners! Add a couple of special sleepers that accepted a 12v wire, and a special signal box, and some of the best lego railways I have built were in operation! Excitingly, this was done long before the internet and AFOLs! Sadly though, now I have progressed to real 9v it's hard work setting up all the sleepers and fiddly connections for this modified system as compared ot the ease of 9v tracks, so it hasn't had much of an outing recently.

#9 skaako


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Posted 27 April 2010 - 12:04 PM

Yes a few of us here in NZ have been thinking of a 9V pickup from a standard wheel set, when i get the time i might machine some wheels and see what i can think up for the pick up. Any ideas for the pick-up from the wheels would be helpful, i was thinking of something like spring steel contacting to the inside of the metal wheel, similar to the 9V train motor design, its a proven design so if i can make something similar would be good.

#10 Mark Bellis

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Posted 27 April 2010 - 05:25 PM

An empty 9V train motor would work well.  A single wheelset is prone to losing power more easily, but multiple single wheelsets could be connected together.  Consistency of manufacture and reliability would be important.

For a track-powered scheme you would need some sort of battery or large capacitor on the train, simply because track power is not continuous on metal track, especially over points.  One reason I connect the 2 motors on a large loco with a wire is because a single motor can find a dead spot on the points and hence would be pushed or pulled by another motor, not something that would aid motor life!  The wire ensures that both motors receive equal electrical power as long as one makes contact.

If a PF-powered train with track pickup hit a dead spot, the speed setting in the IR receiver would be lost, stopping the train.

If a pickup were used with a connection to the DC input of the LiPo battery, you would have to overcome the tendency of the battery to stop the train every time power came back after crossing a dead spot, since it has that function in the battery's control logic.  I would have to check whether this applied to the 9V and 0V outputs for an IR receiver, but it definitely applies to the C1 and C2 outputs of the battery.  Anyway, since the DC input is 10V, you would have to apply the 10V to the track, in which case you couldn't run 9V locos on the same layout.

The best scheme would use a boosting switch mode power supply, working from a variable input of 3 to 9V at either polarity and converting this to 10V DC to charge the LiPo battery.  The SMPS would include a capacitor to keep the battery input voltage constant over dead spots, so that its logic would not trip.  this would mean a PF loco could run on any powered 9V track that had a voltage sufficient to move an unloaded 9V train motor.  The circuit would have to be a variable current source with good stiffness of voltage regulation, without dissipating too much heat in the output transistors!  This scheme would enable a PF loco to double head with a 9V loco, as long as the PF handset and 9V controller were kept at similar output power levels.

I'd also like a PF battery output device, to facilitate using two LiPo batteries together, with current balancing, to get up to 800mA from each one and power more than 2 motors.  Some of my trains have 4 train motors as well as auxiliary motors and lights, with a total current requirement of 1300mA up hills!  Such a device should also aim to overcome the 7.4V limit and get up to 9V, perhaps with a DC-DC converter, but this would be large if it had to handle 12W!

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#11 roamingstop


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Posted 27 April 2010 - 09:15 PM

Small Traco Power Adapters?

From memory no reverse polarity units... but never mind. Two dual wired bogeys would also help - they could be placed apart so current can always flow when train crosses a dead switch. Actually a trickle charger would somehow be ideal as then not all track would need to be expensive 9V stuff...

#12 Helmantel


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Posted 28 April 2010 - 08:45 AM

I actually bought two broken 9V motors, to use as power pick ups. Another alternative would be to open a (working) 9V motor, disconnect the motor from the wheels, connect the wheels (or rather the metal pieces that pick up current from the wheels) to two of the four PF wires, connect the wire to a IR sensor and power the motor with the other two PF wires.

That would of course require some creativity and a hole in the motor housing to feed the PF wire through, but would result in an IR controlled 9V motor.

#13 CommanderP5


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Posted 28 June 2011 - 09:22 PM

Hi all ^_^

Actually, the last Christmas i powered my Emerald Night cutting an old 9V cable
(compatible with the original 9V motor)and soldering the wires to the terminals
of a standard PF battery box (the bulky original one).

At this point i'm able to connect the empty battery box to the 9V motor, powering
the lights i placed in the engine and in the wagon, while the original unmodified
motor pulls the train.

To embed the battery box (used in place of a PF switch because it costs less) i
rebuilt the tender (making a much bigger version: it's almost long as the engine ^_^ ).

It worked very well, even if the original engine wheels tended to obsatcle the
movement, slowing down the train until it stops.

I forgot to say that the speed is directly regulated by the original SR, making the
lights turning off if the voltage fades away while slowing down the train.

As soon as i found my Camera ill post some pictures of the modified train ;)

p.s. sorry for my clumsy english: i'm italian

Edited by CommanderP5, 28 June 2011 - 09:24 PM.

#14 Bojan Pavsic

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Posted 04 July 2011 - 01:29 PM

It's a pretty old topic, but i'll share my experiment anyways (it's from the beginning of 2011).

The difference from the idea that fred67 proposed is, that i took a working 9V motor. That way the same bogey was used as a motor and as power pickup.

Here's the video i made to show how it works.

I took a working 9V motor apart and disconnected the motor from the wheels. Then i cut a PF extension cable (50cm) in half and made a hole into the motor where usually the PF motors have the wire. I put a diode bridge in there (i didn't use MOS-FET bridge, because i'm not that good with electronics and the voltage drop is not that important anyways, since you can drive everything with higher voltage anyways). I put some capacitors in there too, just to have a small "power reserve" for the IR receiver.

When i took the IR receiver apart, i found out a very nice thing. The output lines 9V/GND are connected to the input lines 9V/GND. That means the receiver can be powered from the output and the input doesn't need to be connected to anything (as seen on the video).

Inside the bogey i connected the wheels to the diode bridge, then to the capacitors and then to the 9V/GND. The C1/C2 lines where connected to the motor. (so 1 PF cable to get the power and to drive the motor).

Basicly it's something that Helmantel and Mark Bellis already wrote.

Edited by Bojan Pavsic, 04 July 2011 - 01:37 PM.

There's always a way to include Technic in any Lego creations.

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