Electronics Basic guide for beginners

Basic Concepts

Atoms and Electrical Charge Atoms are the building blocks of all matter. They are made up of protons, neutrons, and electrons. Every electron has a small negative (-) charge. The proton has the same amount of charge except that it is the opposite, positive (+) charge. Neutrons are electrically neutral and have no charge. The protons and neutrons are located in the center of atoms forming what is called the nucleus and the electrons revolve around them. It is very important to know that particles of like charges will repel and unlike charges will attract. For example, two protons or two electrons will repel each other. However, a proton and a electron will attract. That is how the electrons are held inside the atom. The attraction between the electrons and protons keeps the electrons in orbit much like the gravitational attraction between the sun and its planets.

Electricity is the flow of electrons so it is necessary to measure the charge. The basic unit for measuring charge is the coulomb or the letter C. 1 coulomb is equal to the charge of 6,250,000,000,000,000,000 electrons!!! 1C = 6.25x10^18 electrons

Current Electric current is the amount of electrons, or charge, moving past a point every second. It is basically the speed of electron flow. The faster the electron flow, the higher the current. Current is represented by the letter I. The basic unit for measuring current is ampere. Ampere can be abbreviated to amp or just A. 1 amp = 1 coulomb/sec Meaning for every amp, there are 6.25x10^18 electrons moving past a point every second.

Voltage To make sense of voltage, we will need to make an analogy. Lets imagine that electrons are represented by a marble on a flat plane. At this point, the plane is level and the marble does not move. If the plane is lifted at one side, the marble will roll down to the lower point. In electricity, the high point is a point with lots of electrons and the low point is a point with a lack of electrons. The high point is called the high potential and the low point is the low potential. The difference between these two points is called the potential difference. The larger the potential difference, the larger the voltage.

Voltage can be thought of as the measure of the pressure pushing the electrons. The higher the pressure, the higher the voltage. Voltage is represented by the letter E. The basic unit of measure is volts or the letter V. One volt will push 1 amp of current through 1 ohm of resistance. Resistance will be discussed in a later section.

Power Power is simply the amount of energy used or the amount of "work" a circuit is doing. Power is represented by the letter P. The basic unit for measuring power is watts or the letter W. To find power, all you need is a simple equation: P=EI or Power equals voltage times current. For example, if E = 9V I = 0.5A then P = 9 * 0.5 P = 4.5W

Resistance To better understand what resistance is, you must first get an idea of how electrons flow. When an electron is knocked out of an atom, it will fly off and hit another atom. If the electron strikes the atom with enough force, it will knock off another electron. The atom that was just knocked off will hit another atom and so forth. Note that every time an electron strikes another, it is transferring its energy. Some of the energy is converted into heat every time it is transferred. The voltage will drop as the energy is transferred over long distances. Thus a long wire has a higher resistance than a short wire.

Some materials - such as copper and silver - does not hold on to its electrons very tightly. Therefore it doesn't require much energy to knock off an electron. These materials are called conductors and has a very low resistance to electron flow. Materials such as clay and plastics hold on to their electrons more tightly than conductors. It takes more energy to knock off an electron from these materials. These materials are called insulators and has a high resistance to electron flow. Now, you must understand that this is NOT how electrons really flow; It serves only as something for you to work with. To really know how electrons flow, which we will not get into, you will need to study quantum physics. Resistance is represented by the letter R. The basic unit of measure is ohm or the symbol (Greek omega). In the next section (Ohm's Law), we will show you the relationship between Current, Voltage, and Resistance. Resistance will also be further discussed as we introduce the resistor

Ohm’s law Ohm's law is one of the most important concepts in electronics. Fortunately it's only a very simple mathematical relationship between current, voltage, and resistance. According to the Ohm's law, voltage equals current times resistance which is expressed in the following equation: E=IR where E = voltage, I = current, and R = resistance For example, if I = 0.1A R = 10k then E = 0.1 * 10k E = 1000 volts

Schematic Diagrams A schematic diagram shows how each component connect with another. It is a simple and easy to read outline of the circuit. Each type of component has a unique symbol and a name (usually 1-2 letters). All relevant values and component specific information are usually included. Below is an example of a schematic diagram: As you can see, this diagram has 3 components: the thing with 4 horizontal lines, the triangle in a circle, and the thing with the wavy lines. Can you guess which is the battery? Yes, the 4 horizontal lines. The triangle in the circle represents the light emitting diode and the wavy lines represent the resistor -- both of which will be discussed in the components section. Note the "R1" next to the resistor symbol and "R1 470 ohm" below the diagram. This tells you what value to use for that component. If there was a second resistor, the second resistor will be called R2.

Common Components

Introduction Resistor A component that resist the flow of electrons. Capacitor A mini rechargeable battery. Diode A "one way street" for electrons. Transistor A component used for switching and amplifying.

Resistors Resistors are one of the most commonly used components in electronics. As its name implies, resistors resist the flow of electrons. They are used to add resistance to a circuit. The color bands around the resistors are color codes that tell you its resistance value. Recall that resistance is measured in ohms. The tolerance bands indicates the accuracy of the values. A 5% tolerance (gold band) for example, indicates that the resistor will be within 5% of its value. For most applications, a resistor within 5% tolerance should be sufficient.

To get the value of a resistor, hold the resistor so that the tolerance band is on the right. The first two color bands from the left are the significant figures - simply write down the numbers represented by the colors. The third band is the multiplier - it tells you how many zeros to put after the significant figures. Put them all together and you have the value.

One last important note about resistors is their wattage rating One last important note about resistors is their wattage rating. You should not use a 1/4 watt resistor in a circuit that has more than 1/4 watt of power flowing. For example, it is NOT okay to use a 1/4 watt resistor in a 1/2 watt circuit. However, it is okay to use a 1/2 watt resistor in a 1/4 watt circuit.

Capacitors Capacitors are the second most commonly used component in electronics. They can be thought of as tiny rechargeable batteries -- Capacitors can be charged and discharged. The amount of charge that a capacitor can hold is measured in Farads or the letter F. However, 1F is too large for capacitors, so microfarads(µF) and picofarads(pF) are used. micro = 1/1,000,000 and Pico = 1/1,000,000,000,000 So 100,000pF = 0.1µF = 0.0000001F We will only be discussing two types of the most commonly used capacitors: Ceramic and Electrolytic.

Ceramic capacitors are brown and has a disc shape Ceramic capacitors are brown and has a disc shape. These capacitors are non-polarized, meaning that you can connect them in any way. To find the value, you simply decode the 3 digit number on the surface of the capacitor. The coding is just like the resistor color codes except that they used numbers instead of colors. The first 2 digit are the significant figures and the third digit is the multiplier. These capacitors are measured in pF. Electrolytic Capacitors has a cylinder shape. These capacitors are polarized so you must connect the negative side in the right place. The value of the resistor as well as the negative side is clearly printed on the capacitor. These capacitors are measured in µF.

Diodes Diodes let electrons flow through them only in one direction. Diodes flow from cathode to anode. The cathode side of the diode is marked with a band around it. There are basically three different types of diodes: Diodes, Zener Diodes, and Light Emitting Diodes. Zener diodes have a set voltage rating. When a voltage exceeds the voltage rating going the opposite direction (from anode to cathode), the diode allows the electrons flow. Light Emitting Diodes (LED for short) are just like the regular diodes except that it lights up when electrons are flowing through. Note: there aren't any bands to identify which pin is anode and which is cathode. However, one pin is longer then the other. The longer pin is the anode, the positive side.

Transistors Transistors are used as switches and amplifiers. We will discuss two types of transistors: PNP and NPN transistors. Both of these transistors has 3 pins: emitter, base, collector. There aren't any standards for where and what order the physical pins are on the transistors, so be sure to check the packaging when purchasing. To allow electrons to flow through the collector and emitter of a PNP transistor, the following must apply: The emitter is more positive than the base and the collector leads to the negative. The NPN transistor is the opposite: The collector must be more positive than the base and the emitter leads to the negative.

Integrated Circuits (ICs) Integrated circuits (IC) are usually referred to as chips. Inside them is a tiny piece of semiconductor (usually silicon) with large circuits built in. There are millions of different integrated circuits. The general types of integrated circuits include: Logic circuits These IC's are basically decision makers. most contain logic gate circuits. (logic gates will be discussed in a later section). Comparators These IC's compare inputs and gives an output. Operational Amplifiers These are amplifiers. Works very much like transistor amplifier circuits.

Audio amplifiers These are used to amplify audio. Timers These are counting IC's used for circuits that counts or needs to keep track of time. Switches Switching IC's are also very much like the switching circuits of transistors. Other There are thousands of other types. A lot of IC's are made for a special purpose like digital sound recording. Most IC's come with pinout information and how to use it. If not, you'll need one of those large reference books that have info on most of the IC's.

Switches Switches really don't need any introduction. It simply connects and disconnect a circuit. This section gives an overview of the contact configurations. There are 3 commonly used configurations: SPST, SPDT, and DPDT. SPST = Single Pole, Single Throw This is a two terminal switch that opens and closes a circuit. SPDT = Single Pole, Double Throw This is a three terminal switch that connects one terminal to either of the other two. DPDT = Double Pole, Double Throw This is a six terminal switch that connects a pair of terminals to either of the other two pairs.

Circuit Concepts

Resistors in Series & Parallel So what is a series circuit? A series circuit means connecting components one after the other. So when we say "Resistors in series", we mean connecting one resistor after the other: To find the TOTAL resistance, simply add up the resistance of the resistors in the series circuit. What happens when resistors are placed side by side -- in other words, in a parallel circuit? The result is the total resistance being lower than the lowest resistor. To calculate what the total resistance is, you must use this equation: Rt = (R1 * R2) / (R1 + R2)

Capacitors in Series & Parallel Unlike resistors in series, capacitors in series lowers the total capacitance. The total capacitance in a capacitor series circuit is less than the lowest capacitor in the circuit. To find the total capacitance, use the following equation: Ct = (C1 * C2) / (C1 + C2) Notice that it's the same equation as resistors in parallel Now if capacitors in series uses the same equation as resistors in parallel, how do you find the total capacitance of capacitors in parallel? Right! You just add it up! So if there are 4 capacitors in parallel and their values are: 2pF, 3pF, 4pF, and 5pF The total value is 2pF + 3pF + 4pF + 5pF = 14pF

Electronic Projects

Using Breadboard Breadboards are used for testing and experimenting with electronic circuits. They are very convenient since all you have to do is plug in the components. Oh the surface of a breadboard, there are many holes for plugging in components:

The bread board has many strips of metal which run underneath the board that connects the component. The metal strips are laid out as shown below: Each strip is a connection. So whichever components connected to a certain strip are connected to each other. The blue strips shown in the illustration are usually used for connecting the batteries and the green strips are for the components.

Simple Circuits