Making Things Talk

THE TOOLS 43

Figure 1-14

The Serial monitor in Arduino.

Figure 1-15

Arduino connected to a breadboard. +5V and

ground run from the module to the long rows of

the board. This way, all sensors and actuators can

share the +5V and ground connections of the board.

Control or signal connections from each sensor

or actuator run to the appropriate I/O pins. In this

example, two pushbuttons are attached to digital

pins 2 and 3 as digital inputs.

Making_Things_Talk.indb 43 11/13/09 4:49 PM

44 MAKING THINGS TALK

mines the voltage at the connection between them. If you

connect the analog-to-digital converter of a microcon-

troller to this point, you’ll see a changing voltage as the

variable resistor changes. You can use any kind of variable

resistor: photocells, thermistors, force-sensing resistors,

flex-sensing resistors, and more.

The potentiometer, shown in Figure 1-18, is a special type

of variable resistor. It’s a fixed resistor with a wiper that

slides along the conductive surface of the resistor. The

resistance changes between the wiper and both ends of

the resistor as you move the wiper. Basically, a poten-

tiometer (pot for short) is two variable resistors in one

package. If you connect the ends to voltage and ground,

you can read a changing voltage at the wiper.

Most of the circuits in this ...