Here are the types of activities you’ll do in this project:- Put together the electronic circuit for the remote control transmitter and
then fit the breadboard into a plastic box with switches. - Put together the electronic circuit that decodes the radio signal and con-
trols the movement of Sam in response to his sensor eyes. - Mount the circuit onto a chassis along with DC motors, wheels, and a
few switches.
In the end, you create a cart that follows a track all by itself and responds to
your every command. It also has a cute little horn that you can toot.Scoping Out the Schematic .........................................................................
You need to get your arms around two schematics to master this project. The
first is the transmitter circuit that you use to send Sam his commands. The
second is the receiver circuit that helps him understand what the heck you’re
saying!Transmitting Sam’s commands ........................................................
You use the transmitter circuit to send signals to Sam to start, change speeds,
and sound his horn. Here’s an explanation of what’s going on in this circuit:VR1is a voltage regulator that takes the 6 volts supplied by the battery
pack and supplies a steady 5 volts instead. We added this because
although the IC specs say it should work with 6 volts, it blew out the
first time we tried using 6 volts. Better safe than sorry!
The transmitter modulesends out a radio signal at 433.9 MHz that’s
modulated with the code provided by the encoder.IC1is an encoder. The radio signal that the remote control sends out is
modulated, depending upon how you have the switches set, by this
encoding IC (see Figure 13-2). In this figure, the top line shows the code
that tells Sam to speed up, and the bottom shows the code that tells
Sam to slow down, based in the width of the fourth pulse from the right.
The radio receiver in Sam sends this code to a decoding IC to turn Sam
on/off, honk the horn, or change the speed.Chapter 13: Sensitive Sam Walks the Line 303