inductor, but the real deal electronic
bits are normally encased in cylinders.
Sometimes the cylindrical
capacitors can be hard to tell apart
from the inductors, but the surefire way
to tell them apart is to see what units
appear on the casing. Capacitance is
given in farads (F) and inductance is
given in henrys (H). Thankfully, there
is no potential for confusion when it
comes to the schematic symbols.
Circuits with resistors, inductors, and
capacitors are referred to as RLC
circuits, and they can manifest
themselves in a variety of useful bits.
A low pass filter, for example, can be
used to attenuate (cancel out) high
frequency signals and is given in Figure 8.
Another circuit element very often
seen populating PCBs is the diode,
shown in Figure 9. A diode essentially
acts as a one-way valve for current. What
the diode does to a current (allowing
it to flow in only one direction) is
called rectification, so diodes are also
occasionally called rectifiers. One of
the most common flavors of the diode
seen in projects is the Light Emitting
Diode, or LED. The symbol for an LED
looks exactly like that for the regular
diode, but the LED also has two arrows
pointing away from the diode at an
angle. Arrows pointing towards the diode
symbol would indicate a photodiode.
The switch (shown in Figure 10) is another common
inhabitant of the schematic. A switch opens and closes all
or part of a circuit, allowing or disallowing current to flow
to that section. The switch shown in Figure 10 is a
normally open pushbutton switch. Switches also come
in a variety of flavors, like a normally closed pushbutton
switch, the Single Pole Single Throw (SPST) switch (like
an on/off switch), the Single Pole Double Throw switch
(SPDT), and many others.
Another useful tool is the operational amplifier, which
has inner workings that include resistors and dependent
sources, but is easily represented in Figure 11. Operational
amplifiers — or op-amps for short — perform a variety of
tasks such as amplifying (increase) voltage, inverting
(change sign) voltage, summing voltages from multiple
sources, and many more, but they will not be seen on
their own in schematics for electronics projects. Op-amps
are usually included as a part of Integrated Circuits, or ICs.
ICs are those little four to eight (or more) legged black
boxes, as shown in Figure 12. The setup in Figure 12 is the
Dual In-Line Package (DIP), which in my experience is one
often favored for robotics projects because it is compact
and easy to solder. ICs come in other packages, with one
of the more common packages being a vertical, black
rectangular prism with three thick, flat legs and a metallic
FIGURE 3. Alternating voltage source.
FIGURE 2. Direct voltage source.
FIGURE 4. Ground.
FIGURE 5. Voltage divider circuit.
FIGURE 7. An inductor.
tab coming off the top that acts as a heatsink.
The term “integrated circuit” is an umbrella phrase
that includes everything from sophisticated logic gates
to microcontrollers, but another specific type of IC that
pops up all the time is the transistor, shown in Figure 13.
Transistors can amplify and rectify signals, and they come
in a variety of flavors like NPN, PNP, N-JFET, and P-MOSFET.
Transistors, like most ICs, actually contain a whole web of
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