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WW-02 WheelWatcherTM Encoder

End of Life Notice: this product has been replaced with the WW-12.

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


  • Easy installation
  • Simple interface
  • Preprinted 32 stripe self-adhesive codewheel included
  • Hardware quadrature decode with 4x multiply for 128 clocks per rotation
  • Raw quadrature also provided
  • Compatible with Solarbotics GM-2, GM-3, GM-8 and GM-9 gearhead motors (CS-100 recommended with GM-2 & GM-3, which have longer motor shafts)
  • Designed for use with standard injection-molded robot wheels any color
  • Code examples for common robot controllers coming soon


The WW-02 WheelWatcher low cost incremental encoder system enables robot builders to quickly add closed-loop control to their robots. Both standard ChA/ChB raw quadrature outputs (90 phase shift between channels), as well as decoded Clock and Direction signals are provided. The clock signal produces 25s pulses at each transition of ChA or ChB, providing a 4x increase in resolution 128 clocks per motor rotation while the direction signal indicates the decoded direction of rotation, making it very easy to add to any microcontroller.


Proper spacing between the photodetectors and codewheel, as well as alignment of the photodetectors to the codewheel, is essential to proper operation.

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-02 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-02 PartsWW-02 Motor Encoder

  • Printed circuit board, preassembled
  • Self-adhesive codewheel
  • 6" four lead color-coded cable
  • Two extra wires provided for use with raw-quadrature output
  • Motor and wheel not included
  WW-02 Installed

WW-02 Side WW-02 Top

Click photo to enlarge.

WheelWatcher encoder shown with motor and wheel sold separately.

 * Requires Adobe Acrobat Reader:

Connector Pinout - J1: 2mm
Decoded Quadrature Grouping:
1.   Clk: violet
2.   Vcc: red
3.   Dir: orange
4.   Gnd
These are the left 4 pins in the diagram.
Standard Quadrature Grouping:
5.   ChB: blue (optional)
6.   Vcc
7.   ChA: yellow (optional)
8.   Gnd: black
These are the right 4 pins in the diagram.
This connector is fully compatible with the Nubotics WW-01. Early versions of the WW-01 have pin numbering that differs from the WW-02, but the signals are on the same pins. Only the silkscreen pin numbers are different.

Connector - J1:2mm

Note: the triangle mark indicates pin 1 on both the header and the connector.

Block Diagram

Block Diagram


 2004-2010 Noetic Design, Inc. All Rights Reserved. Nubotics, WheelWatcher and WheelCommander are trademarks of Noetic Design, Inc.