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in farads (F).An F is pretty darn big, so you have to use prefixes to show lesser

values. The prefixes used are micro- (millionth), nano- (thousand-millionth),

and pico- (the ever-popular million-millionth).

Although you can find several kinds of capacitors — based on what material

they are made of — three common types of capacitors you’ll run across in

electronics projects are electrolytic, tantalum bead, and ceramic. Here’s are

the basic characteristics of each:

Electrolytic capacitorsare typically made of some kind of foil material,

and you’ll find them with values of 1 microfarad and up. The two types are

• Axial:These have leads stuck on both ends.


• Radial:These have all the leads attached to the same end.
  We use the axial type for the projects in this book because they take less
  room on a breadboard. The value of this type of capacitor is printed on
  it along with a voltage rating and its capacitance.

Be careful to check the voltage rating required by your project and

choose a capacitor accordingly.

Tantalum (a metallic material) bead capacitorsare available with values

of 0.1 microfarad and higher. They cost more than the electrolytic capac-

itors but are useful if you have a circuit that requires more accuracy

because tantalum capacitors have less variation in value than elec-

trolytic capacitors.

Ceramic capacitorsare nonpolarized (see the sidebar, “Polarized counts”),

and you can find them with values from 1 picofarad to 0.47 microfarad.

Reading the value on these tiny components can be difficult. And to add to

the confusion, because many of these capacitors are too small to write the

value on in words and numbers, folks use a code. Table 3-1 helps you spot

common capacitor values based on their markings.

40 Part I: Project Prep

Polarized counts

Most electrolytic and tantalum capacitors are

polarized, so you will see a polarity symbol on

them. Typically, only one end is marked with

either a plus or minus sign, so you can conclude

that the other end is the opposite. With both types

of capacitor, the longer lead is the positive one,

which is probably the easiest way to identify it.

What’s important about being polarized? If a

capacitor is polarized, you have to be absolutely

sure to install it the right way around in your cir-

cuit. If you don’t, you will be left with one dead

capacitor and possible damage to other com-

ponents in the circuit.

Small-value capacitors, typically made of

ceramic or mica, are nonpolarized so you can

connect them any way you want.