WW-12 – WheelWatcher^TM Encoder

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

Applications

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

Features

• Easy installation
• Simple interface
• Preprinted 32 stripe self-adhesive codewheel included
• Hardware quadrature decode with 4x multiply for 128 clocks per rotation
• Raw quadrature
• Smart serial mode
• 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
• Adapts to many wheels and articulated mechanisms with optional CS-040 codewheel spacer
• Code examples for common robot controllers available
• Fully compatible with Wheel Commander WC-132

Description

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.

Differences with the WW-02

The WW-12 differs in these ways:

• 5 pin, 0.1" pitch connector rather than 8 pin (2 rows of 4) 2mm connector
• 3 operating modes which can be selected by selectively pulling down certain connector pins:
• quadrature (ChA/ChB)
• sign/magnitude (CLK/DIR)
• serial (38400 baud); outputs distance traveled as well as velocity
• sign/magnitude mode toggles the clock line on either edge of either quadrature channel, rather than the 50us low pulse on either edge generated on the WW-02
•  no 0.1" pitch 2x4 alternate connector area (this was stuffed instead of the 2mm connector for a special build for the Seattle Robotics Society Workshop Robot, level 3) 

WW-12 encoder Printed circuit board, preassembled Self-adhesive codewheel 6" five lead color-coded cable Mounting hardware Motor and wheel not included
Two wheel WW-12 kit Two WW-12 encoders Motors and wheels not included.

Click photos to enlarge.

WheelWatcher encoders shown with motors and wheels (motors and wheels are sold separately).

• Frequently Asked Questions
• User's Manual v1.02; 1.06MB PDF* (New! Updated 11-30-2011)
  
• Code Examples (examples specific to the WW-12 coming soon)

 * Requires Adobe Acrobat Reader: