Lego com nxt

The RJ12 connector and the LEGO NXT
If you are interested in driving a LEGO NXT motor using your own board (i.e.: Arduino) you will have to face the problem of connecting your controller to the motor. Instead of cutting an original LEGO cable it is possible to adapt an RJ12 to fit a LEGO NXT motor. You can follow the guide that you find at: www.philohome.com/nxtplug/nxtplug.htm and do a neat job. But if you are in a hurry you can simply cut the latch and file as much as it is needed: try iteratively until the wire fits and stays in place.

In the figures above: an unmodified RJ-12 cable, a partial solution, and a neat job.
An RJ-12 cable has 6 small wires: how are those used by the Lego NXT motor? • Motor power (first signal): 0 to 9 V • Motor power (second signal): 0 to 9 V • Ground • Encoder power: 5 V • Encoder (first signal) • Encoder (second signal) This means that if you are interested in driving the motor you have to make use of the first three signals. If the voltage provided on the first one is greater than the voltage provided on the second one then the motor will turn in one direction, otherwise in the other. If you also provide 5 V on the first signal you will be able to read the encoder signals, which changes once every degree of rotation (360 times in a complete turn). A good explanation of how an incremental rotary encoder works is given on Wikipedia: http://en.wikipedia.org/wiki/Rotary_encoder#Incremental_rotary_encoder For more information on Arduway, the robot I built: http://tinyurl.com/arduway-2008