I'm considering the possibility of making my own Power Functions-compatible sockets for a project.

I'm designing a module board for a single-board-computer with motor drivers and would like to encase the SBC and module board in a 3D-printed LEGO-compatible case. Now, my current solution for plugging PF motors to the drivers is to cut PF extension cables and use just half of them, which is expensive (~3€/cable if memory serves), a bit tricky (the wires are fickle), and damaging LEGO products really hurts my feelings.

Some projects, like the SBrick came up with their own PF-compatible socket designs and I'm wondering if there are any readily-available open-hardware socket designs (CAD files and building instructions). I couldn't find any for the moment.

If there's no such thing, I'm willing to design it myself. I think I could manage to make a working CAD model of the plasic part but I'm looking for suggestions and advice as to how to make the electrical contacts.

This project would ultimately be open-sourced for anybody to reproduce it.


  • I'm looking into the same, but not yet far enough advanced to have done a lot of research. One thought I had is to see if it is easier to make a connection with the old 9V connector present at the bottom of this official conversion cable. Did you consider this as an option?
    – Phil B.
    Oct 1, 2015 at 12:28
  • I haven't really started to look at how I could do it myself either, just searched for existing solutions. The old 9V connectors might indeed be easier but then extension cables would still be needed for modern PF motors and there would be no way of controlling a PF servo which needs all four lines. I guess I will start making experiments at my local hackerspace with pins inserted in a 3D printed socket.
    – Shadocko
    Oct 1, 2015 at 12:49
  • 2
    I've got a working CAD file for the socket. I 3D-printed it with PLA filament and the connector snaps in nicely. The next step is to put actual electrical contacts in there. Still looking for options as to how to make durable contacts. Will share the model when I have some time.
    – Shadocko
    Oct 12, 2015 at 8:07
  • When you share - make sure to put it somewhere easily accessible (if you're willing to do so) and post the link (plus a short description) as an answer to this question - as it is truly an answer to your own question.
    – Phil B.
    Oct 12, 2015 at 15:27

2 Answers 2


I eventually made my design available for download over at Shapeways with a CC BY-NC-SA license (login is required in order to download the STL file).

I tested it at my local maker space in PLA on a µDelta 3D printer.

For the electrical contacts, I tried with pins scavenged from a DIP IC socket like Cyril suggested but the pins were a bit fickle and easily broke. I ended up cutting a sheet of conductive metal I had handy (iron alloy?) in thin bands with a paper cutter, folding the bands in two then using that as the base for the electrical contacts. Paper clips should also work.

The holes in the 3D-printed socket might have to be enlarged a bit, especially in the first layers of the print, with a needle heated with a ligher or dipped in acetone.

The resulting socket works nicely. Only time will tell how good they fare in the long run.

Cutting the metal sheet: cutting the metal sheet

Resulting thin metal band: metal band

The metal band is folded in two: folding the metal band

The folded band is inserted through one of the holes, folded again, then through the opposite hole: inserting the contact

Once the electrical contacts are in place, they are secured with hot glue on the back of the socket: hot glue

End result: end result

Snap! snap


I make a print (with silicon) of the Lego PF socket, in 2 halves.

I just need the C1 and C2 electrical contacts, so I'm just dealing with them, but you can go for the 4 contacts.

So in the bottom half, I insert two small pins from a DIP socket (for integrated circuits) in 2 tiny cuts I do with a kind of bistoury and insert the 2 pins in those two slots.

After that I pour some acrylic resin (red for that case) in the silicon mold, including the 2 pins.

The bad point is that it only deal with one half.

The other one could be done the same way, and maybe, if they are thin enough, you can join both.

On the pictures, the top face of the resin PF socket would need a kind of grounding, to make it flat and nice.

To connect it to a NXT brick, I pick up a RJ12 socket on a old electronic device and solder it with both electric wire (+some resistors)

Silicon print 1 Silicon print 2 Silicon print 3 Silicon print 4 Silicon print 5 Silicon print 6 Silicon print 7 Silicon print 8 Silicon print 9 Silicon print 10 Silicon print 11 Silicon print 12 Silicon print 13

  • 1
    @Cyril, fixed your answer to include all pictures.
    – Shadocko
    Oct 15, 2015 at 7:17
  • Nice work with your mold! Scavenging the pins from a DIP socket is a clever solution. I have yet to check that this will work with the other side of the connector.
    – Shadocko
    Oct 15, 2015 at 7:26
  • @chicks : the site doesn't let me post more than 2 pictures for each answer.Now i can't post anymore pictures (i have some more of the finished thing)
    – Cyril
    Oct 15, 2015 at 8:32
  • @Shadocko , if you could post you CAD file, it would be nice
    – Cyril
    Oct 15, 2015 at 10:38
  • @Cyril If you create a composite picture of 4 or 6 of your individual pictures together, you can put 2 composite pictures in one single answer (ideally the one that already has upvotes). The remaining answers can then be deleted. A little more work, but it'll make the answer much cleaner.
    – Phil B.
    Oct 15, 2015 at 12:26

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