resistor schematic symbols: resistor, variable resistor, photoresistor
Almost all electronic circuits are built out of just a few basic components. There are often different types of each component. For now you just need a general idea of what these things are and how to identify them and their values on a schematic diagram. Don't worry if you don't understand how they work.
resistor: A resistor impedes the flow of electrons through a circuit. A resistor has a value indicating its resistance in ohms. Resistor values range from 1ohm to several mega ohms. A color code on the resistor is used to indicate the value. Some resistors have a variable value; they're called variable resistors, potentiometers, or trim pots. Also important is a resistor's power rating, give in watts. That tells you how much power you can let flow through a resistor before it explodes. Generally the bigger the resistor the more power it can handle. Resistors are not polarized, which means that you don't have to pay attention to which end is which when you add it to a circuit.
If you need a resistor of a particular value and you don't have one handy, you can build it out of other smaller resistors. Resistors in series (one after another) add together. So if you need a 1k resistor, you can use two 500 ohm resistors instead.
resistor schematic symbols: resistor, variable resistor, photoresistor
capacitor: A capacitor (cap) is a device that can store a an electrical charge. A capacitor has a value indicating its storage capacity in farads. Capacitor values range from really really tiny (picofarads) to a few farads. A farad is huge, and all the circuits you're likely to deal with will use capacitors in the picofarad (pF) to microfarad (mF) range. Various mysterious codes printed on caps are used to specify their values. The bigger the capacitor value, the more energy it can store. Some capacitors are polarized, which means that you have to pay attention to their orientation in a circuit.
Like resistors, you can build a larger capacitor out of smaller ones. But instead of placing them in series, you place them in parallel with one another. That is, their left legs are joined together and their right legs are joined together, forming one massive world-conquering capacitor. I'll draw this on the board.
capacitor schematic symbols: non-polarized, polarized
diode: A diode is a semiconductor with a very special property: current can only
flow through it in one direction (more or less). There are lots of different types of
diodes with different properties. Generally you use a diode when you want to stop one part
of a circuit from affecting another part. One special type of diode is the Light Emitting
Diode (LED). All diodes emit light when current flows through them, but LEDs are specially
designed so that lots of light is emitted. The little lights on your stereo are LEDs.
All diodes are polarized, with current flowing from + to - in the direction of the arrow.
That means that in most cases you want to arrow to be pointing to the lower voltage part
of the circuit (usually ground). All diodes have a "voltage drop" across them. That means
that they "eat up" (not a technical term) a fixed amount of the voltage that passes through
them. The amount of the drop varies; for LEDs it's usually around 2v.
diode schematic symbols: diode, LED
transistor: Transistors are the basic building blocks of all integrated circuits
(ICs). A transistor can work as either a switch (turn the flow of electrons on or off) or as
an amplifier (take a small voltage and make it bigger). Transistors generally have three
pins, an emiter, a base and a collector. You've got to connect them the right way or they
won't work. They also come in two flavors, PNP and NPN. You have to use the right one in
your circuit or it won't work. Identifying trasnsistors by their packaging is maddening.
It's much easier to purchase the specific transistors you need than trying to use crusty
old ones you found in the bottom of a drawer.
transistor schematic symbols: PNP, NPN (Not Pointing iN)
IC: An IC (integrated circuit) is a bunch of circuits that have been miniaturized and
etched into a piece of silicon. They've got numerous pins, each of which has a specific
function. ICs are non-general. That is, you need to use a particular IC for a particular
purpose. A microcontroller is an IC. You might have a squarewave generator IC, an LED
display driver IC, an XOR (exclusive OR) IC, and so on. The pins of an IC are numbered
starting at the top left corner. There is almost always a dot or an indentation at the top
of an IC. That's how you know where pin one is.
IC schematic symbol
voltage source/power supply: Common voltage sources are batteries, wall warts, and surplus supplies removed from old computers. There are two types of voltage sources: A/C (alternating current) and D/C (direct current). It's very important that you use the correct one for a given task! You also have to pay attention to the voltage that the voltage source supplies, and the amount of current that it is able to provide.
voltage source schematic symbols: battery, +5v, ground