A Closer Look at the NXT Motors

Contained in the new Lego Mindstorms NXT kit are three newly designed servo motors. Compared to the old 9v square motors contained in the original Robotics Invention System the NXT motors are much slower, but make up for their speed in the amout of power they hold...


The servo under no load runs at 170 rpm compared to the old style motor which ran at 360 rpm. The difference however is in the amperage drawn by the motors. The servo draws 60 mA of power whereas the old motor drew 3.5 mA.

This increased power draw in turn provides more torque. The NXT servos stall out when put under a load of 50 N cm. At the stalling point the servo draws 2 A of current.

Slower speeds are the result of an internal gear train that provides the extra torque. A computer generated image provided by Lego Education shows the servo internals here:
The actual internals of the motor can not be completely seen due to the construction of the servo. To view the inside of the servo the motor would have to be broken and would no longer work. You can check more internal pictures at Philo's NXT Motor Page



This article is only a glimpse into the internals and statistics of the new NXT servos. For more information you should check out Philo's NXT Motor Page where much of this information was found.