Page 107 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Sound and ultrasonics
Sound may be used for games, range finding, and collision and
obstacle avoidance. To play a game of robot tag, robots are fitted
with a two-tone oscillator and receiver. Each robot can generate
and recognize two tones. Let’s say the A tone is 3000 Hz and the B
tone is 6000 Hz. Tones are generated for 1 s whenever a robot’s
bumper switch is activated.
The robot that’s “it” generates the B tone whenever its bumper
collides with another robot. A “not it” robot generates the A tone.
Upon collision, the “it” robot generates the “B” tone. The “not it”
robot hearing the B tone changes states and becomes “it.” And the
“it” robot hearing the A tone from the “not it” robot changes states
and becomes “not it.” Two “not it” robots will both generate the A
tone and leave the collision with their states unchanged. Although
we are using sound as an example here, be aware that this tech-
nique can be applied using infrared light.

Ultrasonics are often used for range finding and collision detection.
Many robotists have written on the Polaroid Company’s ultrasonic
modules (see Fig. 5.33). These modules are used in Polaroid cam-
eras to quickly measure the subject’s distance from the camera
86 and focus the lens to produce sharp pictures. When interfaced to
a microcontroller, the units can accurately measure distance.

If one needs or wants distance measurements for the robot, the
Polaroid sensor is the way to go. The ping can measure distances up
to 30 ft. The sensor may also be rotated (using a servo or stepper
motor) like a radar to build a navigation map and find an obstacle-
free path.

5.33 Polaroid ultrasonic ranging module
Team LRN
Chapter five