Nubotics WheelWatcher

WW-01 – WheelWatcher^TM Encoder

When the WheelWatcher servo encoder is added to a standard-size RC servo, it accurately senses direction, distance, velocity and acceleration. Installation is easy using the provided hardware and alignment tool.

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 also provided
Compatible with standard-size servos from Hitec, Futaba, and GWS
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-01 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, as well as decoded Clock and Direction signals are available. The clock signal produces 25µs pulses 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.

Board installation consists of removing the adhesive backing, aligning the board with the shaft, then attaching the board and servo to the robot chassis with the supplied mounting hardware. Codewheel installation is just as simple: peel off the backing, and lower onto the spline-side of the wheel; the raised hub helps align the codewheel to the axis of rotation. Accurate alignment to the servo output shaft is easy to do with the included AL-02 alignment tool.

The new Rev C version of the kit is even simpler to install than before. There are no more washers, but instead we have replaced the need for them by buying custom manufactured spacers that fit standard Futaba and Hitec servos perfectly. We also include a spacer that is just right for GWS servos. Further, the silkscreen for the connector now is consistent with the connector's pin numbering and now matches the silkscreen on the WW-02 WheelWatcher.

WW-01 encoder with alignment tool

Printed circuit board, preassembled
Alignment tool
Self-adhesive codewheel
6" four lead color-coded cable
Two extra wires provided for use with raw-quadrature output
Mounting hardware (note: Rev C kits no longer contain washers)
Servo and wheel not included

Two wheel WW-01 Kit

Two WW-01 servo encoders
One alignment tool
Servos and wheels not included.

Click photo to enlarge.

WheelWatcher encoder shown with servo and wheel sold separately.

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Connector Pinout - J1: 2mm
Rev C	Rev B
Decoded Quadrature Grouping:
1.	7.	Clk violet
2.	8.	+5v red
3.	5.	Dir orange
4.	6.	Gnd
These are the left 4 pins in the diagram.

Standard Quadrature Grouping:
5.	3.	ChB blue (optional)
6.	4.	+5v
7.	1.	ChA yellow (optional)
8.	2.	Gnd black
These are the right 4 pins in the diagram.

This connector is fully compatible with the Nubotics WW-02. The silkscreen on Rev B (older) boards have the nonstandard and confusing pin numbering shown in the table above; newer Rev C boards have silkscreens that match the connector better and also match the WW-02. This is a cosmetic difference only -- a given cable will work with either a Rev B or Rev C board.

Rev C pinout

Note: this diagram shows pin numbering compatible with the Rev C board.

WW-01 – WheelWatcherTM Encoder