Electronic Components
Here I'll explain the different parts you'll need to know about to make some of the projects.
Resistors
Resistors come in dozens of sizes and shapes, but they all do the same thing: LIMIT CURRENT.
Resisto Color Code- See those color code bands in the picture? They're very important: they indicate the resistance of the resistor they decorate. Here's how:
somtimes there is a fourth band. It indicates the TOLERANCE of the resistor:
Gold---=-5%
Silver-=-10%
none---=-20%
Looks complicated the first time... but you will quickly learn how to use it. For example, what's the resistance of a resistor color coded yellow, violet and red? Yellow is the first color so the first number is 4. Violet is the second color so the secon number is 7. Since the third color is red, the multiplier is 100. Therefore, the reesistance is 47 x 100 or 4700 ohms. No fourth color band means the actual resistance is 4700 20%. 20% of 4700 is 940. Therefore, the ACTUAL value is between 3760 and 5640 ohms.
Substituting Resistors- What if you need a 6700 ohm resistor but only can find a 6800 ohm unit? You can almost always use any value within 10 or 20% of the required value so go ahead and use it.
Here are some other types of resistors-
Metal film resistors- various kinds of resistors that use a thin film of metal or a metal particle mixture to achieve various types of resistances.
Carbon Film Resistors- These are made by depositing a carbon film on a small ceramic cylinder. A spiral groove cut into the film controlds the length of carbon between the leads.
Wire-wound resistors- These consist of a tubular form wrapped with coils of resistance wire. They are very accurate and can take lots of heat.
Photoresistors- Also caleld photocells. Made from a light sensitive material like cadmium sulfide. Increasing the light level decreases the resistance.
Thermistors- This is a temperature sensitive resistor. Increasing the temperature decreases the resistance.
Capacitors
There are many kinds of capacitors, but they all do the same thing: STORE ELECTRONS. The simplest capacitor is two conductors separated by an insulating material called the DIELECTRIC. The dielectric can be paper, plastic film, mica, glass, ceramic, air or a vacuum. The plates can be aluminum discs, aluminum foil or a thin film of metal applied to opposite sides of a solid dielectric.
Specifying Capacitors- THe ability to store electrons is known as CAPACITANCE. Capacitance is specified in FARADS. A 1-farad capacitor connected to a 1 volt supply will store 6,280,000,000,000,000,000 electrons!!! most capacitros have much smaller values. Small capacitors are specified in PicoFarads (Trillionths of a farad) and larger capacitors are specified in MICROFARADS (millionths of a farad.
Kinds of Capacitors- Capacitors are often labeled according to their dielectric. Thus you'll see references to ceramic, mica, polystryrene and many others. All these are FIXED value capacitors. Some capacitors have a variable capacitry and a special class of fixed capacitros has much more capacity than other capacitors.
Variable Capacitors- These usually have one or more non-moving plates and one or more moving plates. The capacitance is changed by rotating a rod affixed to one side of the movable plates.
Electrolytic capacitors- Unique in that a thin oxide layer formed on aluminum or tantalum foil is the dielectric. Much higher capacitance than non-electrolytic types. Tantalum units have move capacitance per volume and a longer life than aluminum electrolytics. But they cost more. Most electrolytics are POLARIZED. They must be connected into a circuit in the proper direction.
Diode
Both P-type and N-type silicon conduct electricity. The resistance of both types is determined by the proportion of holes or surplus electrons. Therefore both types can function as resistors, and they will conduct electricity in any direction. By forming some P-type silicon in a chip of N-type silicon, electrons will flow through the silicon in ONLY ONE DIRECTION. This is the principle of the DIODE. The P-N interface is called the P-N JUNCTION.
How the diode works- Here's a simplified explanation of how a diode conducts electricity in one direction (foward) while blocking the flow of current in the opposite direction (reverse).
A typical diode- Diodes are commonly enclosed in small glass cylinders. A dark band marks the CATHODE terminal. The opposite terminal is the ANODE.
Types of Diodes- Many different kinds of diodes are available. Here are some of the major types.
Small signal: small signal diodes are used to transform low current AC to DC, detect (demodulate) radio signals, multiply voltage, perform logic, absorb voltage spikes, etc.
power rectifier: funcionally identical to small signal diodes, power rectifiers can handle MUCH more current. They are installed in large metal packages that soak up excess heat and transfer it to a metal hat sink, used mainly in power supplies.
Zener: The zener diode is designed to have a specific REVERS BREAKDOWN (conduction) VOLTAGE. This means zener diodes can function like a voltage sensitive switch. Zener diodes having breakdown voltages of from about 2 volts to 200 volts are avialable.
Light Emitting: ALL diodes emit some electromagnetic radiotion when foward biase. Diodes made from certain semiconductors emit considerably more radiation than silicon diodes. They're called Light Emitting Diodes (LED's)
Photodiode: ALL diodes respond to some degree when illuminated by light. Diodes designed specifically to detect light are called photodiodes. They include a glass or plastic window through which the light enters. Often they have a large, exposed junction region. Silicon makes good photodiodes.
From "Getting Started in Electronics" by Forrest M. Mims III ----------------Pictures by me :)
