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    NXT® plugs crimping tool

    Mindsensors sells NXT-style RJ12 connectors. Unfortunately regular RJ12 crimping tools are not suited for them because of their offset latch. Since adapted crimping tools are not available you need to hack a RJ12 one... Here is how I modified mine. This is just for illustration purpose and to give you ideas on how it can be done, since there are so many different models.

    See also Michael Brandl crimping tool. Here is his method (in German).

    R J McNamara modified another model of crimping tool, see here.

     

    Mindsensors plugs.

    The RJ12 crimping tool that I used.

    Close-up before hacking.

    There is a plastic insert used to maintain the plug. Left part of image shows the front side (where the plug is inserted) of an unmodified piece, with yellow line showing where to remove plastic to make room for the offset latch. I used a retractable blade knife to carve out thin plastic shavings.

    Warning: Take care of your fingers while doing this!

    Bottom side of the insert. A corner is to be removed here too.

    Warning: Take care of your fingers while doing this too!

    In the end, the plug should fit easily and completely in the hole, with a click of the latch that should be able to retain the plug from one side.

    Note that this modification doesn't prevent you to use the tool to crimp regular RJ12 plugs.

    Unfortunately I also had to remove a corner of the tool itself, this time using a metal saw and a file.

    Top view of the modified tool.

    Bottom view. Note that the retaining plate had to be modified too.

     

    Using the crimping tool

    In addition to the plugs, you will need cable. Flat RJ12 cable with 6 wires is of course well suited. The end of the cable must be stripped, most crimping tool provide a blade to strip cable at the right length.

    Standard NXT cables have the white wire placed on the side of the latch.

    Alternatively you may use 1mm pitch flat cable. This kind of cable, not very common, is manufactured by 3M under reference 3625 (datasheet). This cable is similar to the one used by Mindsensors for their Flexi-Cables. Don't confuse with other pitch cables:

      1. Regular 1.27mm pitch flat cable, used for floppy disks and IDE hard disk drive cables
      2. 0.635mm pitch used for Ultra-DMA hard disk drive cables
      3. 1mm pitch flat cable, the only one that matches RJ plugs.

    I bought 5 meters of 26 wires 3625 cable (it is easy to split into 6 wires wide cables) for about 25 euro.

     

    • Don't make too long cables. 1 meter is about the maximum recommended length to guarantee proper working of all sensors and motors connected to your NXT. If you need and build longer cables, test them thoroughly in your application to make sure they work reliably enough for you.
    • Important: NXT cables are "straight" cables. That means that the same wire must be connected to matching contacts at both ends of the cable. With a flat cable, the connectors latches are thus placed on the same side, and on opposite face: 

         

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