## Meet the 7-segment display

Displays convert electrical signals to visual representations that have meaning to people. The 7-segment display is a simple device to display numbers or even some characters. The project’s result is a 7-segment display set to display the capital character ‘E’.

## Objective

The project is an introduction to displays.

• You see how breadboards, resistors, and 7-segment displays look like .
• You understand how breadboard works.
• You understand the difference between schematic and real circuit.
• You understand what a 7-segment display does.

## The Schematic

This is the circuit of the project.

You can see a way to set up the circuit on the breadboard. Remember, there are many correct ways to transfer a circuit on the breadboard.

## Notes

• Every segment consists of a LED.
• Resistors role is to reduce the current to prevent and damages to the LEDs.
• By turning on a selected group of segments, a specific number or character is displayed.

## Resistors in Series and in Parallel

There are two ways arranging resistors, series circuits and parallel circuits.

In a series circuit, the resistors are arranged in a chain, so the current has only one path to take and is the same through each resistor. The total resistance is equal to the sum of the resistances:

In a parallel circuit the resistors are arranged with their heads connected together, and their tails connected together.

The current breaks up and flow among each different branch through the resistors and re-combining when the branches meet again. The voltage through each parallel resistor is the same. The total resistance is reduced and is given by the relationship:

## Ohm’s Law

The power source V, leads electric current I through the resistor R. Thus we can say that the three quantities obey the law of Ohm.

Ohm’s Law relates the voltage (V), the current (I) and resistance (R).

Ohm discovered that the current in a circuit is directly proportional to the voltage applied to the edges of a circuit and inversely proportional to the resistance of the circuit.

V = I x R

This relationship can be expressed in three ways:

I = V / R

R = V / I

V = I x R

where:

V    = voltage (Volts)

I     = current (Ampere)

R    = resistance (Ohm)

The corresponding relationship between units is: Ampere = Volts / Ohm

Thus in a given circuit, the voltage and the current are proportional to each other. This implies that if we double the voltage across the circuit, the current will be doubled; the higher the voltage, the greater the current. However, if we double the resistance of the circuit, the current will reduced by half; the greater the resistance, the less the current.

So by applying the relation V = I x R, if we know any two of the three quantities, we can find the third.

According to Ohm’s law if it is applied potential difference of 1 Volt to the edges of a circuit having a resistance of 1 Ohm, will be generate a current of 1 Ampere.

## Standard Electrical SI Units and Prefixes

Standard Electrical SI Units

In order that each of the SI units and quantities can be standardized across the globe, it is necessary to have exact definitions of each of them. The SI units are System International units that form the basis of the International System of Units.

Physical SI Units

Common Electrical Units

The standard SI units used in electrical or electronic circuits and systems are given in the following table. The table gives also a list of some of the standard electrical units of measure used as well as the electrical formulas and component values.

Metric Prefixes
In order to describe different values according to their size it is important to set up a range of metric prefixes for the values standard electrical units. By using multiples of the standard unit we can avoid having to write too many zero’s to define the position of the decimal point.

Try to convert

The conversion from one prefix to another it’s easy. The only thing you have to do is either multiply or divide by the difference between the two values.

Example: Convert 1MHz into kHz.

We know that: 1MHz  = 1,000,000Hz and 1kHz = 1,000Hz

So, 1MHz is one thousand times bigger than 1kHz.

To convert MHz into KHz we have to multiply MHz by one thousand, as 1MHz is equal to 1000 kHz.

This is a classic project. The IC (Integrated Circuit) NE555 is around and popular for many decades. Its main application is to form oscillator circuits. This project is about creating an oscillator with two LEDs connected to its output. The two LED blink alternatively in constant period.

## Objective

The project is an introduction to oscillator circuits and to ICs.

• You see how breadboards, resistors, capacitors, ICs and LEDs look like.
• You understand how breadboard works.
• You understand the difference between schematic and real circuit.
• You understand what an oscillator does.
• You can note that the function of an oscillator based on the charging-discharging cycle of a capacitor.

## The Schematic

This is the circuit in action.

You can see a way to set up the circuit on the breadboard. Remember, there are many correct ways to transfer a circuit on the breadboard.

## Notes

• The resistors which are in series with the LEDs has nothing to do with the charging/discharging the capacitor. So, it has nothing to do with the blinking frequency. Its role is to reduce the IC’s output current to avoid any damages to ICs or the LEDs.
• You can change the frequency of the blinking by using different capacitor or different resistors which are evolved in capacitor’s charging/discharging. For example use a capacitor with more capacitance and you will get a slower blinking.

This is a classic project. The IC (Integrated Circuit) NE555 is around and popular for many decades. Its main application is to form oscillator circuits. This project is about creating an oscillator with a LED connected to its output. The result is a LED which is blinking in constant period.

## Objective

The project is an introduction to oscillator circuits and to ICs.

• You see how breadboards, resistors, capacitors, ICs and LEDs look like.
• You understand how breadboard works.
• You understand the difference between schematic and real circuit.
• You understand what an oscillator does.
• You can note that the function of an oscillator based on the charging-discharging cycle of a capacitor.

## The Schematic

This is the circuit of the project.

You can see a way to set up the circuit on the breadboard. Remember, there are many correct ways to transfer a circuit on the breadboard.

## Notes

• The resistor which is in series with the LED has nothing to do with the charging/discharging the capacitor. So, it has nothing to do with the blinking frequency. Its role is to reduce the IC’s output current to avoid any damages to ICs or the LED.
• You can change the frequency of the blinking by using different capacitor or different resistors which are evolved in capacitor’s charging/discharging. For example use a capacitor with more capacitance and you will get a slower blinking.

## The basic electronic components

When building electronic circuits, you will need to become familiar with the basic electronic components including resistors, capacitors, diodes, transistors, and integrated circuits. These components are the bread and butter of most electronic projects. Here is a brief overview of the functions of each of these basic electronic components.

Resistors

The symbol of  a resistor in schematic diagrams is:

The resistance is an electrical/electronic component which is used in various circuits for controlling the current flow. The unit of electrical resistance in the International System of Units (SI) is the Ohm, which is denoted by (Ω) and got the name from the German physicist Georg Ohm (Georg Ohm). Georg Ohm’s law formulated Ohm, which states that the resistance (R) of an object can be calculated by dividing the potential difference (V) applied to the edges of the object to the current intensity (A) that is flowing.

Mathematically is denoted as:  R = V / I

wherein:

R: Resistance displayed by the object (in ohms)

V: The potential difference / voltage applied to the ends of the object (in volts)

I: The intensity of current flowing through the object (in amperes)

A breadboard is a reusable construction base for prototyping of electronics and is used to build and test circuits. It’s a quick and easy way to create temporary prototypes and experimenting before finalizing your circuit design.

Prototyping is the process of evaluating an idea, creating a preliminary model of a circuit. This is one of the most common usages of breadboards. If you are not sure how a circuit will respond under a given set of parameters, it is better to create a prototype and try it.

For beginners to electronics and circuits, breadboards are often the best place to start. This is the real beauty of breadboards – can manipulate both the simplest circuit, and very complex circuits. If your circuit current exceeds the breadboard, you can expand your circuit connecting other breadboard circuits to manipulate all sizes and complexity.

Another common usage of breadboards is to try new components, such as integrated circuits (ICs).

A typical breadboard is shown below:

Capacitor

The electrolytic capacitor is one type of capacitor which the plate used is made of ionized liquid form preparations. They usually have larger capacitance in proportion to their volume than do other types of capacitors. They are valuable regarding use in high current circuits and low frequencies. Specifically, their use in power supplies as filters for filtering the voltage output of a ballast circuit is very common. Electrolytic capacitors have high capacitance and allow us to construct filters with very low cut-off frequencies. Finally to be mention that the electrolytic capacitors are polarized and must be careful when connecting the polarity will be destroyed otherwise. In practice the positive pole of the cell is greater and the body of the capacitor, the negative pole is determined by a gray or white stripe along its length.

The typical capacitor is shown in the image below:

Diode LED

A LED is presented as:

LED, Light Emitting Diode, is called a semiconductor that emits a narrow-spectrum light when electrical voltage is granted at the proper bias direction (forward-biased).

The color of the emitted light depends on the chemical composition of the semiconductor material used, and can be ultraviolet, visible or infrared. The wavelength of the light emitted, and therefore its color, depends on the energy gap of the material used to generate the contact P-N.

P = material impregnated with recipients (Deficit Electron)

N = material impregnated with donors (Surplus Electron)

IC – Integrated Circuits

In electronics, a printed circuit (also known as a microcircuit, microchip, chip, silicon chip) is a micrograph of an electronic circuit, which is usually consist of semiconductor materials as well as passive components.

Integrated circuits was able to be manufactured after experimental discoveries showing that semiconductor elements could perform the functions of vacuum tubes and by technological progress in the field of manufacturing semiconductor elements occurred mid-twentieth century. The integration of a large number of tiny transistors on a thin silicon chip has very significant improvement over the manual assembly of vacuum tubes and discrete electrical components.

The opportunity provided by the integrated circuits for mass production, adding further complexity, reliability and significant cost savings contributed to the rapid dissemination displacing the vacuum tubes and discrete circuits. The significant reduction in costs has been made possible because all data is printed using a single photolithography is printed instead of each transistor individually. In 2006, the area of ​​a chip range from a few square millimeters to 250 mm2, with one million transistors per mm2. Their use is widespread in all electrical and electronic devices we are using today.

Transistor

A transistor is a three-terminal device in which a voltage applied to one of the terminals (called the base) can control current that flows across the other two terminals (called the collector and the emitter). The transistor is one of the most important devices in electronics.

Switch

A switch is a mechanical device that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. There are two states to activate the switch, it opens or closes the circuit.

The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: either “closed” (N.C.) meaning the contacts are touching and electricity can flow between them, or “open” (N.O.), meaning the contacts are separated and the switch is not conducting.

As switches get more complex they can both open one connection and close another when activated. This type of switch is called single-pole double-throw switch (SPDT). If you were to combine two SPDT switches into one single switch, it would be called a double-pole double-throw switch (DPDT). This would break two separate circuits and open two other circuits, every time the switch was activated.

Battery

An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.

Batteries are represented in a circuit by a series of alternating lines of different length. There are also additional marking for power, ground and the voltage rating.

Wires

Wires are used to connect things together on breadboard. Wire links can be made with single-core plastic-coated wire of 0.6mm diameter. Stranded wire is not suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.

## Current, circuits and resistance

Different kind of electronic devices broadcast sounds, display images, takes measurements, record and “remembers” information, perform calculations and regulate other devices. Electronics is the science and technology of the motion of electrons in gas, vacuum, or in any semiconductor. A device is called electronic if it is comprised of parts where the movement of tiny particles (electrons) generate electricity directly controlled by electric or magnetic fields. In electronic devices a power forms to control another. For example, in a computer the changes that occur when you press the buttons regulate the data written on the hard disk. Electricity in this way allows quick and inexpensive implementation of complex functions. Everyone today is exposed to electronic and circuit devices, so it’s important to gain the basic knowledge of electronics, electricity and circuits. If you are interested to learn some basic electronics keep reading the following information guide.

DC & AC current

Electricity is the movement of electrical charges directed along an electrified conductor.
The amperage is time dependent. Thus, there are two kinds of electricity, direct current (DC) and alternating (AC).

DC is defined as the constant flow of electrons in the same direction, for example in a cable. DC can also be considered as the current, which varies the price and not the polarity over time. This feature separates DC from AC.
The alternating current is the electric current where both the intensity and the direction changing periodically. Unlike direct current, alternating current is transmitted easily and with low cost. Fewer losses arising during transportation which can be done with thinner wires. The alternating current is considered dominant over DC because of the possibility of converting the voltage to lower or higher prices.

Electronic Circuit

An electrical circuit is called a closed electrical circuit if electric current flows through it. Observe a battery, the lamp or any other electrical device. You will find that each such device has two edges those two poles. If you connect the cable ends of a battery with the ends of a light bulb, you will notice that the lamp illuminates. Inside the cable and the lamp electrons move in the direction from negative towards the positive terminal of the battery. In addition are moving into the battery in the direction of the positive to the negative pole. Namely electrons follow a closed path. In this case we say that we have a closed electrical circuit.

An open circuit is when we stop the flow of electrical current to the circuit. Try to disconnect the wire by one pole of the battery or from one end of the lamp. We observe that the lamp goes out. This is because between the free end of the wire and the battery pole or terminal of the lamp interposed air which is an insulator. The electrons cannot move within it consistently and their movement within the bulb the battery stops. Thus, the electrical circuit is called an open circuit.

Resistance

From physics it is known that the property of a body to restrict the flow of electrical current through the electrical resistance is called. The resistance is denoted by the letter R (Resistance).
In order to understand the electrical resistance in depth you can check out the correlation between electrical and hydraulic systems.