Sunday, January 27, 2008

TBs TechReview 01 - PF/9V conversion cable, Review & Usecases

This week my order with some units of 'PF/9V conversion cable' or 'PF extension wire', as it is their official name, arrived.

They are ~25 studs length (20cm / 8") or ~29 studs including the connectors at both ends. These cables also look very nice and well done.
Each cable has a standard PF plug at one side and an hybrid plug on the other side, which is PF on top and have a 9V form factor on bottom. This combination would allow to:

  • Make easy conversion between systems and bring PF electrical compatibility to legacy 9V parts.
  • Extend wires that came attached and with fixed size, on the new PF elements.

The first good surprise, I was not expecting, is the plug color differentiation. 'Dark Bluish Gray' (DBG) for the PF connector and 'Light Bluish Gray' (LBG) for the PF/9V connector. A good idea and not exactly as in the LEGO marketing material, as you can compare from the images below.

Another surprise concerns with the way plugs are connected. If you flatten the cable you see one plug is upside-down in relation to the other. Still didn't decided if this an advantage or disadvantage...

However personally had preferred if LEGO put them straight, but with the wire leaving the PF/PF plug (DBG) from the studs side. This would allow to connect extension wires without having to bend them backwards like in the image below (despite this may be the desired configuration in some cases, like at star or 'Y' configurations, on the right side).

This limitation derivate not specifically from a characteristic of this cable, but from the new PF connector in general and its inability to be turned by 90º or 180º, like the 9V predecessor.

Cables could of course be arranged in different ways from the one above left, but the linear extension is not optimally achieved also.

Below a few more images that suggest how this cable, can be used as a PF extension wire, or to interconnect PF and old 9V elements (motors, battery boxes, etc...). Click on images to enlarge and see the details.

Direct conversion (some 9V elements, those with bottom or non-stud contacts only, require the use of an electric plate)

Simple PF extension (left), and conversion plus extension with PF cable (center) or 9V (right)

Multi span for longer extension lengths.
PF only (left); Combined with 9V cable for bigger flexibility due to large range of lengths available (center); Multispan with conversion and extension (right)

Chain of 3 different devices (PF and 9V)

Simple Star configurations (also with extension on the rigth)

Some larger combined configurations (some also with the IR Receiver included)
Note that with the extension/conversion wire and IR Receiver, it is possible to control old 9V motors direction with PF remote

Finally, this cable should also bring wired compatibility from PF motors with the NXT, when combined with 8528 (Converter Cables for MINDSTORMS® NXT) and the NXT-G programming Block for standard motors.
This kind of compatibility was already possible wireless, but via IR with OEM parts like HiTechnic 'NXT IRLink Sensor' and others (see video with application example, here).

One possible setup for a PF motor connection to NXT (left) and respective connections detail (right)

A few more variations, can be also seen from this Brickshelf folder.

According to the information on this post at Eurobricks, it was recently found that the configuration on the red crossed photo above, is not allowed. Appart from the PF battery box and remote, the 9V black battery box was the only one without batteries when I took the photos (Murphy...).
Sadly it was found that the IR Receiver does not work when powered by the an old 9V battery box! It was a design flaw, that LEGO only recently discovered when playing around with the new system...
On the same topic there are a few workarounds possible to make it work. One can be seen from this image (bottom left), another is to connect the old battery box into one of IR Receiver outputs instead of using the cable attached to it. This only leaves you with one output left to control remotely, instead of two. Not really that handy, but if you only want to control one function it might be sufficient.
Well... a minor issue IMHO.

Last Update:
2008.Feb.06 19:35 GMT


Anonymous said...

Another surprise concerns with the way plugs are connected. If you flatten the cable you see one plug is upside-down in relation to the other. Still didn't decided if this an advantage or disadvantage...
Actually this is mandatory. Since the plugs are polarized, connectors placed on the same side would result in a crossed cable.

TechnicBRICKs said...

Got it!

You are right, about your observation. Thanks!

TechnicBRICKs said...

Well... but if it wasn't upside down and rotated 180º as I suggested in the sentence bellow, guess it would be Ok, again. ;)
No crossover in this case.

"However personally had preferred if LEGO put them straight, but with the wire leaving the PF/PF plug (DBG) from the studs side."

Anonymous said...

yes but thats a whole new plug design, fingers crossed anyway and for some longer ones!

Anonymous said...

Where'd you get the clear 9V motor?

Anonymous said...

Clear motor comes from 4094. It makes too much noise though, maybe mine is broken?

I wish those wires were straight. And I wish they were longer... Mine are still on the way..

TechnicBRICKs said...

No, the clear motor is not the one from Creator Series (4094, 4895)!

This one is identical to the latest 9V standard version, and should be a prototype made in Trans-clear.
I got it from a seller at BrickLink who have some more available.
According to the seller they came from an factory in Hungary, where LEGO 9V motors where produced while ago.
This is also something, that I have in my long post queue for TBs... In this specific case, the post is already started (in draft), but not finished. Sooner or later, I'll finish it. ;)

TechnicBRICKs said...

...and added a paragraph making a reference to the compatibility with NXT. How could I had forgot this while making the photos!?...
Must add photos soon.

Alex Campos said...

The issue with the cable length isn't very serious: just use a standard 9V cable with the length you want, with a converter cable at each end.
This new cable is much more versatile than I imagined!

BlueToothKiwi said...

Informative article - I wish I read it months ago. Also Thanks for the link into my IRLink video of the Bulldozer.

Anyone know what is in that little box of the Item #: 8528 Converter Cable for MINDSTORMS NXT?

I want to make some custom cable from NXT to the PF - and sure could do with some advise before I waste two PF motors cables (I wouldneed to chop off).

This is an excellent blog - I will be visiting this regularly from now on and would be visiting this regularly from now on.


TechnicBRICKs said...

Hi, thanks for the positive comments!

For the 8258 box, I believe it to be a Ferrite Bead, like those we see at some power cords, to suppress certain signal frequencies into the transmission line.

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