Sports two eyes:These eyes help Sam figure out where to go. Sam’s
eyes— phototransistors pointed at the floor — sense infrared (IR) light
that is sent out by IR LEDs and then reflected by the floor. By laying
down a track of black electrical tape on the floor, you create an area that
reflects less of the IR light.
We set up the circuit so that when Sam’s eyes hover over reflective floor,
the motors turn. If one eye is over the black tape or other nonreflective
surface — for example, where a bend comes in the tape track — the
motor connected to that eye shuts off, causing the cart to turn and
follow the tape. When the eye is back over the reflective floor, the motor
turns back on, and the cart goes in a straight line again.Responds to a remote control:This remote uses radio waves to send its
commands to Sensitive Sam. (This is the same technology that a key
chain remote control device uses to open the doors on a car.) You can
set the switches on the remote control to tell Sam to turn on/off, slow
down or speed up, or honk the horn. When you flip a switch and press
the transmit button, that effect kicks in.Sensitive Sam is shown in Figure 13-1 in all his glory.Figure 13-1:
Our very
own
Sensitive
Sam and his
feline friend,
Willoughby.302 Part IV: Good Vibrations