PF polarity reversal (3rd party part idea?)

[andythenorth]

For both technic and trains, it sometimes would be handy to be able to reverse polarity in less space than the PF switch requires.

I'm guessing that a third party wouldn't see a financial return on a specialist part for such a niche use. But eh, it's a thought.

The part-modifying solution is to snip the wires and resolder. Anyone know which wires are +ve / -ve and which are control?

[Heppeng]

I think there may be an alternative - get 2 x short extension cables, which have contacts for the old 9v system. Attach the light grey ends either end of a 2x4 or 2x8 conducting plate and it should reverse the polarity. You may even be able to substitute a short 9V lead instead of the plate.

For modifying, the two center wires are the control, the outside are +ve/-ve, but I don't know which way round.

Edited December 29, 2014 by Heppeng

[dr_spock]

You can probably experiment using a bread board. Or take apart the PF switch to reverse engineer it.

An ideal new part would be a 2x2 plate or brick with contacts wired for reverse polarity. Really handy if you're running multiple train motors in the same train.

[Splat]

For Power Function information my first stop is always Philo's Home Page.

The information on this page should help you work out which wires are which in the PF cable.

[andythenorth]

So flip 9v and 0v, leave C1 and C2 untouched? I can start chopping up wires to figure it out, just wondering if anyone has done it before...

[Heppeng]

No, flip C1 and C2, that's the variable supply to the motor. The 9V and 0V are constant and not used by the motor - essentially in the diagram above the dotted lines represent unused wires. You might find that altering the two middle wires of the motor cable is easier if you cut back the outer wires to give yourself more room to make the connections - no need to reconnect as the motor does not use them, but wise to make sure any loose ends are adequately insulated.

Edited December 30, 2014 by Heppeng

[andythenorth]

Thanks for that, very useful :)

Out of interest, is there a constant supply on the 9v wire when connected to the PF receiver _output_ ? Thinking about powering lights from it...

[andythenorth]

I found this very useful post while looking for a way to use 8 AA batteries (for ~9v output from NiMH).

http://texbrick.com/tjab/?p=127

The important bit for PF hackers being to not connect certain some of the wires to power, quoting: "DO NOT DO THIS! This will make smoke come out of the PF IR receiver box."

[aminnich]

could you connect one motor to one battery box turned on to the right and on motor connected to another battery box turned on to the left? idk this is just the simplest way I can think to do it

[andythenorth]

Nah, the polarity coming out of the battery box is ignored by the PF IR receiver, so the switch direction makes no difference

[aminnich]

oh... ok

[1974]

No, flip C1 and C2, that's the variable supply to the motor. The 9V and 0V are constant and not used by the motor - essentially in the diagram above the dotted lines represent unused wires. You might find that altering the two middle wires of the motor cable is easier if you cut back the outer wires to give yourself more room to make the connections - no need to reconnect as the motor does not use them, but wise to make sure any loose ends are adequately insulated.

The "0" and "9V" is for daisychaining raw power

Edited January 4, 2015 by 1974

[Brickthus]

The easiest way to reverse polarity without using a PF switch is to cut the two centre wires of a PF extension lead (C1 and C2) and swap the connections.

12V single-pin plugs would be the easiest way to reconnect the wires either way round. I have used these for PF train experiments.

You would need to separate the 4 wires for about 2cm each side of the break, and probably fold the cable when C1 and C2 are connected.

I doubt the whole solution would fit in a much smaller space than the switch, considering the need to accommodate the cable.

The cost would not be cheaper than a switch by the time you've bought the plugs.

Mark

[andythenorth]

Thanks Mark.

The other issue with the switch (other than space) is that it is quite low friction (which is nice if actuating it mechanically). When the kids crash the trains, or in Technic vehicles on rough terrain, the switch can jog back to centre (off).

This can be easily missed, for example on a twin-motored train with PF train motors, a powered motor will drive through another one that is accidentally unpowered on the same unit. L motors will do the same in Technic. The £0.02 solution is probably to tape the switch in position.