Motor-Sensor Expansion Board
The Handy Cricket Motor-Sensor Expansion Board adds two DC motor
outputs (with power control) and four analog sensor inputs.
The DC motor outputs are named c, and d,
and work just like the Cricket's built-in motor ports a and
b. Commands on, off, thisway,
thatway, rd, onfor, and
setpower are used to operate the motors.
Power for the motor outputs is drawn from the Handy Cricket's 4xAA
supply. PCB holes are provided for running an alternate motor power
source into the Expansion Board.
The four sensor ports have the same pin-out as the two sensor ports
built into the Cricket. The command sens reads the value
of the sensor port. E.g., sens 1 reports the value of
sensor port 1. The sensor ports have 8-bit A/D converters; converted
readings are in the range 0 to 255.
The sensor ports come with encoder software. Each of the four ports
can provide raw counts and velocity readings when used with simple
single encoders. The commands are counts n to report the
number of counts on encoder n (n is a value from 1 to 4), velo
n to report the velocity on that encoder (counts per 64
millisecond period), and resetc n to reset the counts
reading to 0.
Sensors to be used as encoders must provide a signal that rises
above 3.75v (a reading of 192 or higher) and falls below 1.25v (a
reading of 63 or lower). When the encoder sensor value rises above
192, an encoder count is registered. When the sensor value falls below
63, another encoder count is registered. Each encoder input is sampled
at a rate of 500 Hz.
When used pairwise, ports (1 and 2) and (3 and 4) provide two
quadrature decoders. These accept signals from a pair of single
encoders in the quadrature configuration (signals 90 degrees out of
phase) to provide direction-sensitive counts information. The commands
quad12 and quad34 report counts;
resetq12 and resetq34 reset the counts to
zero. Velocity information can be obtained with the single-encoder
routines; e.g., velo 1 or velo 2 will report
the velocity of quadrature encoder quad12.
Here is the Logo driver file for the Motor/Sensor Expansion Board.
Shipping weight: 0.20 lbs.