VEX Robotics

VEX Robotics is a great way to build a robot.  VEX 3 wire motors and servos can be controlled by almost any servo controller.

Members: 4
Latest Activity: May 18, 2012

Interfacing VEX 3 wire servos and motors to TWR-MECH boards

VEX Robotics sells erector sets on steroids!  These are great robotics kits both kids and adults.


Depending on the kit you have,  it contains either 2wire or 3wire servos and motors. The TWR-MECH board can only drive 3wire motors and servos directly.  A three wire female to female cable is required, you can order one here:


Specification for the VEX servos can be found here:

  • Rotation:100 degrees
  • Stall Torque:6.5 in-lbs
  • Voltage:4.4 - 9.1 Volts (Motor life will be reduced operating outside this range)
  • PWM Input:1ms - 2ms will give full reverse to full forward, 1.5ms is neutral
  • Black Wire:Ground
  • Orange Wire:Power
  • White Wire:PWM signal
  • Current Draw:20mA to 1.5 A per Servo

Note: Performance varies slightly due to variations in manufacturing.


The RobotSee servo and servos command create a pulse duration of (0)500us to (255)2500us.  The VEX motors and servos only work correctly between 1000us and 2000us.


In RobotSee, simply limit your servo values between 65 and 191.

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