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
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
Take care of your fingers while doing this!
Bottom side of the insert. A corner
is to be removed here too.
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
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
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:
- Regular 1.27mm pitch flat cable, used
for floppy disks and IDE hard disk drive
- 0.635mm pitch used for Ultra-DMA hard
disk drive cables
- 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
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
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