SRS Robot Level 3 Parts
The following are suggestions for components that you may want to add
to your robot.
Adding encoders to the motors/wheels of your robot will enable it
to measure distance traveled.
The SRS is selling WheelWatcher encoders designed specifically for the
SRS Robot. There is a PCB that mounts to each motor, a striped sticker for
the inside of each wheel, and cables that connect to the motor headers on
the ARC board. The WheelWatchers were designed and manufactured by
Pete Skeggs / Noetic Design, who makes the WheelWatchers for servo motors.
Our version is similar to the
but without the quadrature decoder. We will be doing the quadrature decoding
We are able to sell the SRS version of the WheelWatchers to SRS Robot owners
for $35/pair. If you have purchased multiple kits, you may buy as
many pairs as kits. (See the Kit Purchasing page
If you would like WheelWatchers for a project other than the SRS Robot, you
can buy the WW-02 (with the quadrature decoder) from
The documentation for our version is included in the standard WW-02
documentation, which is on the
Look for the section "J2: .100" Connector Pinout" for
details on the wiring. Pins 1-6 correspond to the 6 pins on the motor headers
on the ARC board. You will need to connect the wires from the motors to the WW-02
boards; those signals are connected to the ARC board as part of the 6-pin
connection. On the WW-02, pin 2 (Motor+) is connected to SH1; connect the orange motor
wire to SH1. Pin 4 (Motor-) is connected to SH2; connect the red motor wire
You can download a 9KB zip file with Sample C
code in the "Level 1" style (using Util.c and Util.h). Check back
for code using classes as in Level 2.
Digital Rate Gyroscope
One way to determine heading for your robot is to use a digital rate gyroscope
(also called an angular rate sensor) to measure the rate at which your robot
is turning. You can integrate this to figure out how far it has turned.
A gyroscope measures rotation; an accelerometer measures
One popular device is the
Devices ADXRS150; the Evaluation Board version comes in a convenient DIP
package that will work nicely in the breadboard.
Also check out the options in SparkFun's
"Accelerometers" category (which also contains gyros).
For a balancing robot, you need to measure tilt, which can be done with
a dual-axis accelerometer. Some options are the
Devices ADXL203 and
Devices ADXL320 (evaluation boards), and the selection of boards in
If you are interested in both a gyroscope and accelerometer, look at
the Combo Boards at SparkFun.
The Level 2 kit introduced infrared (light) sensors for measuring distance.
Sonar (sound) is another way to measure distance, and is generally more reliable
outdoors where sunlight tends to saturate light sensors.
The SRS Robot has a chassis plate designed to hold the
Ultrasonic Range Finder. This and various other interesting components
can be found at the Mark III
One popular compass is the