Motorizing switch point with a Technic Power Functions motor

, by  Philippe "Frogleap" LABEL
[English] [français]

Following the motorization of switch point with a Technic mini-motor, here is a solution to operate your switch points using the Technic Power Functions size M motor produced by LEGO during summer 2007.

When the railway layout grows, we all finally try to find a way to operate that nasty switch point far away on the track. Don’t look further! Here a simple and relatively cheap solution to move your remote switch points using a Technic Power Function size M (PF-M) motor.

This MOC adapts the very efficient mechanism of Mark Riley designed quite a long time ago for the Technic 9V mini-motor.

The PF-M motor produces a higher mechanical power than its ancestor the mini-motor. Have a look at Philo’s webpages to see a full description of their features. Because of this elevated power, the assembly we propose has a risk of... violently disassembling under full 9V operations :) But thanks to this power, you can use it to operate a regular 9V switch point without any modification or oiling. However, to limit this mechanical power, we recommend lowering the electrical tension delivered to the PF-M motor. To do this, plug this motor to a 9V train regulator through the 9V-PFS adapter . You will avoid the use of polluting batteries and you will be able to integrate it into a more comprehensive system were are going to see below.

Assembly requires common parts. Here is what it looks like.
Le montage complet {JPEG}
The assembly file in MLCad format is available here and if you prefer there is also a webpage for this assembly.

For real on a switch point, here is what it could look like.
En situation sur l'aiguillage {PNG}
You don’t need to choose your parts’ color with so much care... :) But notice that you can add a semaphore signal to help visualize the remote position of the switch point. More pictures here.

Now that it is built, lets try to see the easiest way to use it. If you really have nothing else handy, just use a Power Functions battery box with its integrated switch. Everything is plug n’ play. At least it’s convenient to operate that silly remote switch point you couldn’t access. But if you plan to use several of these assemblies, then the best solution is to feed the motor using a 9V train regulator. The most integrated solution is then to use an old 9V inverter to switch the point. To connect the PF-M device to the inverter, just use a 9V-PFS adapter.. Finally, grab ideas from this former article which describes how to build a train command lever from the inverter, an idea adapted and size-reduced from Dave Koudys’ original MOC. The 9V train regulator will be preferably used instead of the old 9V battery box show in the pictures. Using this regulator is the second advantage of this system, because you will be able to limit the electrical tension fed to the PF-M motor and thus limit its mechanical power. Reduce the tension to about two thirds or even one half, just try and test so the assembly becomes more stable at use.

Finally for the most fanatics, it is also possible to use such a PF-M motor to operate LEGO switch points through a DCC interface. We recommend the Lenz LS150 accessories interface connected to the track. In that case, adjust the pulse duration to its lowest value of 0.1 seconds and feed the PF-M motor through the interface with alternate 12V. Interface outputs being semi-alternate filtered, it will produce an averaged 5.7V digital current to the PF-M motor.

Play well,

Niconico57 and frogleap.


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