Brand: VEX Robotics
Product Code: 276-1321
Availability: In Stock

This product replaces the plastic cap on the back of a VEX 2-Wire Motor 393 with a quadrature encoder. Install this product and connect it to your Cortex Microcontroller via I2C to receive direct feedback from the motor. This encoder provides information on how fast the motor is going, how far it has traveled, and what direction it is moving.

  • Increased feedback from your motors allows for more control.
  • Communicates via I2C via included 4-wire Cable.
  • Not compatible with the PIC Microcontroller.
  • Programming Required! Consult your software provider for details.


Firmware Bug Note from VEX

We've recently discovered that some of our users are experiencing issues with their robot running after it is disabled. This error is due to a bug in the VEX Cortex Microcontroller firmware.

In very rare situations, the user processor inside the Cortex Microcontroller may encounter a partial reset (caused by a static shock, or intermittent power connection) while the master processor continues to operate normally. In this situation, the Cortex Microcontroller firmware could continue to send the last received command to the motor controllers, causing the motors to continue to run even if the robot has stopped communication with the joystick.

This error is rare, and very difficult to reproduce. We have identified that robots using the VEX Integrated Motor Encoders may be susceptible to this failure as the result of a static shock to the Cortex Microcontroller's I2C port. Users who experience such a failure should power-cycle their robots, which will reboot the Cortex processors and resume normal operation.

This bug is not something caused by user software programs. We are working to correct this issue with a firmware update in the coming months and apologize for any inconvenience this may have caused you.


Do not over-tighten screws when installing the Integrated Motor Encoder. Over-tightening can affect encoder performance.

Up to (8) I2C devices can be chained together and connected to (1) I2C port on the Cortex Microcontroller.

Technical Specifications

Kit Contents
  • (2) Motor Encoder Caps for the 2-Wire Motor 393
  • (2)Replacement Gears with White/Black Encoder Wheel
  • (10) Cap Mounting Screws
  • (2) 12" Long, 4-Wire Extension Cable
Downloads & Docs Documentation
Inventor's Guide - Motor 393 Integrated Encoder Module
Compatibility 2-Wire Motor 393
Cortex Microcontroller
4-Wire Extension Cables
Outputs 4-Wire Cable
Connect to I2C port on microcontroller or another encoder
  • Black:ground
  • Red:+5V
  • Yellow:control signal
  • White:control signal
Function Measures 627.2 ticks per revolution of the output shaft. (High Torque Configuration)
Measures 392 ticks per revolution of the output shaft (High Speed Configuration)