Page 433 - Robot Builder's Bonanza

402 COMMON ELECTRONIC COMPONENTS FOR ROBOTICS

the device. Date codes can look like part numbers—9206 might mean the IC was made in
June 1992.

MICROCONTROLLERS AND OTHER SPECIALTY ICS
Chips like the 7400 (and all its kin) are considered standard building blocks and are available
from a variety of manufacturers. Add to these the thousands of specialty ICs that are unique
to specific chip makers and perform unique tasks.
For robotics, the most common of these specialty ICs is the microcontroller, a type of
all- in- one computer that is designed to directly connect with external inputs and outputs.
Microcontrollers are more fully detailed in Chapters 35 through 40.
Still other specialty ICs might perform any of the following tasks:
• Sense the tilt of your robot to let you know if it’s fallen over (accelerometer)
• Detect small changes in temperature and convert this information to a signal that can be
read by a microcontroller (temperature sensor)
• Convert one voltage to another, with very high efficiency (switching mode regulator)
• Create sound effects and intelligible speech (sound and speech synthesizer)
• Control the operation and speed of a DC motor (H- bridge motor driver)

and, of course, many others.
As with standard- building- block ICs, specialty chips carry markings that indicate the manu-
facturer name and part number, date code, and other important information.

Switches

Most robots use at least one switch— to turn it off or to reset the thing when its programming
goes bonkers. A lot of robots use multiple switches, for things like setting operating modes or
detecting when the bot has bumped into a wall, chair leg, or person.
Switches come in a variety of shapes and sizes, but their overall functionality is universal:
switches are composed of two or more electrical contacts. In one position of the switch, the
contacts are not connected, and current doesn’t flow through the device. The switch is said to
be open. In the other position, the contacts are connected together, and current flows. The
switch is said to be closed (see Figure 31- 20).

Poles: The most basic switch has a single pair— or pole— of contacts. But some switches
are composed of several poles, so there are extra pairs of contacts— one switch func-
tions as multiple switches all connected together. Multiple poles allow the switch to
control multiple circuits at the same time.
Throws: The basic switch has two positions, on or off. But some switches have more posi-
tions. Each position is called a throw. Instead of just on or off, a two- throw switch is
on- on. Each “on” can connect to a different part of the circuit. Most often, multiple
throws are combined with multiple poles to provide all manner of choices.
Momentary position: Switches that are spring- loaded are called momentary, because
when you release the switch it automatically goes back to its normal position. The most
common type of momentary switch is the push button: press it, and the switch closes;
release it, and the switch returns to open all on its own.

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