Electronics Basics - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 56

mA. Your electronics distributor will have more information about the specii c
model you are using, so consult their documentation.
Transistor s
Transistors are largely responsible for the proliferation of digital technologies, as
well as many of the advances in computing power and size. A transistor is like
a tiny switch but is solid state , meaning that there are no moving parts to wear
out and can turn on and off much faster than any mechanical device. There are
several sorts of transistors, but this tutorial talks only about the most common
type in hobbyist electronics: the bipolar transistor.
Using Transistors
Although there are dozens of uses for transistors, examples in this topic cover
only one possible use: a switch.
Imagine an Arduino system powered by 5 volts. This system is designed to
turn on and off an electric motor, one that needs to be powered by a 12-volt
power supply. The motor also requires more current than the Arduino can sup-
ply. How can the Arduino possibly power a 12-volt motor using only a 5-volt
output? The answer is, of course, by using a transistor as a switch.
A bipolar transistor has three leads. The Collector is connected to the positive
side of the circuit, and the Emitter is connected to the negative side of the circuit,
or the ground. Electrons will l ow from the Collector to the Emitter, depending
on the voltage at the Base. By supplying a relatively low voltage to the transistor's
base, current can l ow through the transistor into the collector and out of the
emitter. In short, the transistor conducts current through the collector-emitter
path only when a voltage is applied to the base. When no base voltage is present,
the switch is off. When base voltage is present, the switch is on.
Breadboards
Electronics is fun; there is a joy in assembling components to do a required task;
and it is hugely satisfying. When i nished, some electronics are akin to digital
art, in their function and in their implementation. Some circuit boards are a work
of art in their own right, because of placing LEDs at strategic places, and cutting
out the board to be the right shape. Have a closer look at your Arduino; notice
the pictures printed onto the board, the picture of Italy, and imagine the time
that was taken to make this board its current shape. It did take a lot of time, but
that is also what frightens some people; do you really have to make one of these
boards every time you make a design? Printed circuit boards like the Arduino
and shields can either be made at home using some specialized equipment and