Wheel Watcher Rotation Encoder for GM2/3/8/9


This Product Has Been Discontinued, This Page Is For Reference Only.

20.95 USD
$20.95 ea.

Sometimes you need to measure how fast a wheel is going on your GM 2/3/8/9 gear motor. Here's your solution!

Description [Hide]

This "Incremental quadrature encoder system" is specially designed by Nubotics to retrofit to our GM2, GM3, GM8 or GM9 gear motor. If you need to control a robot for dead reckoning, tracking odometry (distance travelled), stalled motor, or closing the feedback loop for position/velocity/acceleration, this is your solution.

 It features:

  • 32 stripe codewheel
  • Hardware quadrature decode with 4x multiply for 128 clocks per rotation
  • Mates with GMPW / SW wheels
  •  Compatible with GM-2, GM-3, GM-8 and GM-9 gearhead motors. The GM2 & GM3 need GMWWS spacer for proper operation, due to their longer output shafts. So unless you're comfortable in cutting down the shafts on your own, these are the ideal solution.
  • Easy installation
  • Simple interface
  • Raw quadrature
  • Smart serial mode
  • Designed for use with standard injection-molded robot wheels – any color
  • Adapts to many wheels and articulated mechanisms with optional CS-040 codewheel spacer
  • Code examples for common robot controllers available

The Nubotics documentation and FAQ contains all assembly & application notes to successfully implement your Wheel Watcher. This kit contains a single preassembled sensor board, codewheel, and wiring kit. Large plastic wheel and gearmotor not included.

Note: When the WheelWatcher encoder is added to a motor, it accurately senses direction, distance, velocity and acceleration. Installation is easy using the provided hardware.


  • Dead reckoning
  • Odometry (how far has it gone)
  • Closed-loop position, velocity, and acceleration control
  • Stall detection


The WW-12 WheelWatcher low cost incremental encoder system enables robot builders to quickly add closed-loop control to their robots. Standard ChA/ChB raw quadrature outputs, decoded Clock and Direction signals, or 38400 baud serial interface modes are available. When in Sign/Magnitude mode, the clock signal toggles at each transition of ChA or ChB, providing a 4x increase in resolution – 128 clocks per servo rotation – while the direction signal indicates the decoded direction of rotation, making it very easy to add to any microcontroller. Serial mode outputs the distance travelled and current velocity, both in terms of encoder ticks.

Proper spacing depends on the board being held tightly against the top of the motor using appropriate mounting hardware, and also depends on the use of standard injection molded wheels designed for the GM-8 and GM-9 gearhead motors. The WW-12 WheelWatcher low cost encoder system also works with the GM-2 and GM-3 motors, but due to their longer motor shafts, you will also need the CS-100 codewheel spacer. This .1" thick spacer lowers the codewheel sticker close enough to be in range of the sensors.

 WW-12 encoder

  • Printed circuit board, preassembled
  • Self-adhesive codewheel
  • 6" five lead color-coded cable
  • Mounting hardware

Also see Example code.


Documentation [Hide]

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