Introduction to Electronics

Electronics

The study of the behavior and control of electrons under different conditions, particularly in electric fields, and how this behavior is used in electronic devices and circuits.v

Electronic Devices

Components that control or influence the flow of electric charge. Serve as the building blocks of electronic circuits. Examples: diodes, transistors, and integrated circuits (ICs).

Electric Current

The flow of electric charge through a conductor. In metal conductors, current is mainly due to the movement of electrons. Sources of electrical energy: Batteries and generators.

Digital Electronics

Deals with discrete signals, usually represented by binary values 0 and 1.

Analog Electronics

Deals with continuously varying signals.

Microelectronics

Focuses on very small electronic components and circuits.

Nanoelectronics

Studies electronic devices and phenomena at nanometer scales.

Optoelectronics

Combines electronics with light, such as in LEDs and photodetectors.

Semiconductor Devices

Studies devices made from semiconductor materials, such as diodes and transistors.

Digital Electronics

Analog Electronics

Microelectronics

Nanoelectronics

Optoelectronics

Semiconductor Devices

Branches of Electronics

J. A. Fleming

Developed the diode vacuum tube.

Lee De Forest

Developed the triode vacuum tube, which enabled signal amplification.

Bell Laboratories

Demonstrated the first working transistor in 1947.

Jack Kilby – Texas Instruments

Developed a pioneering integrated circuit in 1958; it was demonstrated in 1958 and patented in 1959.

Resistor

Limits electric current and reduces voltage in a circuit. • Protects components from excessive current.

Variable Resistor

Allows resistance to be adjusted. • Controls current or voltage levels. • Examples: Volume control, light sensitivity adjustment.

Electrolytic Capacitor

Stores electrical charge and helps filter voltage fluctuations. • Polarized; positive and negative terminals must be connected correctly. • Usually has a negative stripe on its body; the longer leg is commonly positive on a new component.

Ceramic Capacitor

Stores electrical charge and helps reduce electrical noise and fluctuations. • Non-polarized; can be connected in either direction. • Noise suppression and high-frequency filtering.

Diode

Allows current to flow primarily in one direction. • Rectifies AC into pulsating DC and prevents reverse current flow in suitable circuits.

Transistor

Amplifies signals or acts as an electronic switch. • NPN and PNP bipolar junction transistors. • Motor control, signal amplification, and switching circuits.

Voltage Regulator

Maintains a relatively constant output voltage. • Provides a stable voltage to electronic components. • Example: A 7805 regulator provides a nominal 5 V output under suitable operating conditions.

Integrated Circuit (IC)

Contains many electronic components in one compact semiconductor package. • Performs specific electronic operations or complex functions. • Examples: Timer ICs, microcontrollers, and operational amplifiers.

7-Segment LED Display

Displays numerical digits from 0 to 9. • Seven individual LED segments arranged to form digits. • Digital clocks, calculators, counters, and measuring instruments.

Relay

An electrically controlled switch. • Allows a control signal to switch a separate circuit. • Motor control, automation, and electrical control systems.

Programmable Logic Controller (PLC)

An industrial digital computer designed to monitor inputs, execute a programmed set of instructions, and control outputs in machines or processes.

Input

Information received from sensors, switches, push buttons, and other field devices.

Process

The CPU executes the user program and evaluates logic based on the input conditions.

Output

The PLC sends control signals to devices such as motors, valves, lamps, alarms, and actuators.

Power Supply

Provides the required electrical power to the PLC system. • The supply voltage and wiring must match the PLC model and installation requirements.

Input Modules

Receive signals from input devices and convert them into a form the PLC can process. • Common devices: push buttons, limit switches, proximity sensors, photoelectric sensors, and level switches.

Central Processing Unit (CPU)

The PLC's main processing unit. • Reads input status, executes the user program, performs logic and calculations, and updates output status.

Memory

Stores the operating program, configuration, and relevant data. • The exact data retained after power loss depends on the PLC model and memory type.

Output Modules

Send control signals to field devices. • Common output devices: indicator lights, relays, contactors, solenoid valves, and motor-control interfaces.

Programming Device / Software

Used to create, edit, download, monitor, and troubleshoot the PLC program.

Communication Interface

Allows the PLC to exchange data with other devices, such as HMIs, other PLCs, drives, or supervisory systems, depending on supported protocols.

Power Supply

Input Modules

Central Processing Unit (CPU)

Memory

Output Modules

Programming Device / Software

Communication Interface

Main Components of a PLC System

Digital / discrete

Represents distinct states, often ON/OFF or 1/0
Push button, limit switch, digital proximity sensor

Analog

Represents a value that varies over a range

Temperature, pressure, flow, level, position

Digital signals

commonly represent a state such as a switch being open or closed

Analog signals

represent changing quantities and may require analog input or output modules.

Input scan

The PLC reads the states or values from input modules and updates its input image/data.

Program scan

The CPU evaluates the user program using the input and stored data.

Logic execution

Instructions, conditions, timers, counters, comparisons, and calculations are processed in program order.

Output update

The PLC updates output states based on the program results.

Housekeeping / communications

The PLC may perform diagnostics, communication tasks, and other system functions before the next scan.

ON/OFF Control

an output fully ON or fully OFF depending on whether a measured value is above or below a set point or threshold.

Deadband / Hysteresis

separate ON and OFF thresholds—to reduce rapid switching.

Proportional–Integral–Derivative (PID) Control

It is a control method that calculates a control response from the difference between the desired value (set point) and the measured value (process variable).

Error

Set point − measured process value.

Proportional (P)

Responds to the current error.

Integral (I)

Responds to accumulated error over time and can help remove steady-state offset.

Derivative (D)

Responds to how quickly the error changes and can help anticipate changes; measurement noise must be considered.

ON/OFF

Output switches between states

Simple thermostats, level switches, basic pump control

PID

Output is adjusted to reduce process error

Temperature, pressure, flow, and speed regulation.

Programmable Logic Controller

PLC

Central Processing Unit

CPU

Input

Signal or data received from a field device

Output

Control signal sent to a field device.

Sensor

Device that detects a physical condition or quantity.

Actuator

Device that produces physical action, such as moving a valve or mechanism.

Set point

Desired target value for a controlled variable.

Process variable (PV)

The measured value of the variable being controlled.

Error

Difference between the set point and the measured process value.

Scan cycle

Repeated sequence in which the PLC reads inputs, executes logic, and updates outputs.

Human–Machine Interface

HMI

Input/Output

I/O

Interlock

A condition that permits or prevents an operation to improve correct or safe sequencing.

Proportional–Integral–Derivative

PID

Resistor

introduces resistance (opposes the flow of current in it) in a circuit to reduce current, divide voltage or for biasing other active components.

Inductor

stores energy in the form of magnet field. It is basically an insulated wire wounded in a coil around a core.

Capacitor

stores energy in the form of electric field. It is made from metal plates with dielectric between them.

Switch

used for breaking or making a circuit. They are used for stopping the current flow in a circuit or start its conduction.

Changeover Switch

type of switch used for changing or directing the current flow from one terminal to another terminal

Push-Button

switches that consist of a button which enable us to make or break the circuit by pressing it with finger.

Male Plug

connects an electrical cord to a female plug to complete an electrical circuit. it has two or three unshielded pins that inserts into a socket or female plug of the same design.

Female Plug

is a connector that has two or three holes instead of pins. used for connecting it to a matching male plug by inserting the pins of male plug into it.

Fuse

an electrical safety device that provides protection against overcurrent.

Electric Line

This symbol represents an electrical conductor such as cables, wires etc. in a circuit schematics.

Ground

represents a common reference point from where the voltages are measure & it is the return path for all the currents.

Diode

an active electronic component made up of semiconductor. The junction allows the current flow in only one direction.

DIAC

it is bi-directional semiconductor device with the analogy of a two diodes connected in antiparallel combinations.

Thyristor

or SCR (Silicon controlled rectifier), is a 4 layered PNPN semiconductor device. It has three terminals Anode, Cathode & Gate

TRIAC

made up of Triode for Alternating Current. it is a modified version of SCR that can conduct and also control the current flow in both directions.

IC (Integrated Circuit)

It is a small chip made up of semiconductor material upon which multiple micro electrical components are fabricated to perform specific task and reduce size.

Amplifier

used to amplify or increase the amplitude of a signal.

Transistor

a three terminal device made from semiconductor material. It is used for switching or amplification of weak signals.

Vacuum Tube

or electron tube is a sealed tight tube with vacuum and two electrodes.

AND Gate

performs the logical inclusive conjunction (True output only if all True inputs). It provides output of logic “HIGH” only when it’s all inputs are logic “HIGH” and provides logic “LOW” for any logic “LOW” at input.

OR Gate

performs the logical inclusive disjunction (True output for any True input)’.The output of OR gate is logic “HIGH” when any input is logic “HIGH”. The output becomes logic “LOW” when all of its inputs are logic “LOW”.

NAND Gate

is the Inverse of AND gate or “NOT of AND” gate. Its output is logic “High” for logic “LOW” at any input & it is logic “LOW” when all inputs are logic “HIGH”.

NOR Gate

Negative or inverse of OR gate or “NOT of OR” gate. Its output is logic “HIGH” when all inputs are logic “LOW” & it is logic “LOW” for logic “High” at any input.

NOT Gate

also known as logic Inverter, is a single input single output logic gate. It inverts the input logic. The output is logic “LOW” for input logic “HIGH” & it is logic “HIGH” for input logic “LOW”.

7 Segment Display

made of 7 LEDs in specific pattern. It is used for displaying decimal numerals and English alphabets. However it can be designed to display numerous characters

Ammeter

or ampere meter is a measurement instrument used to measure the current flow in a power line. It is connected in series with the line through which the current need to be measured.

Voltmeter

or voltage meter is also a measurement instrument used for measuring the voltage between two points on a circuit. it is always connected in parallel to the points of measurement.

Ohmmeter

resistance meter is a measurement instrument used for measuring the resistance of any component.

Frequency Meter

used for measuring the frequency of a periodic signal such as the frequency of an alternating current in a power line.

Wattmeter

used for measuring the electrical power supplied through a power line. The unit of electrical power is watt thus the name.

Electric Clock

a clock that is power by electricity in an electrical circuit schematic.

Electrical Counter

generic counter for counting a specific quantity such as energy unit counter.