The Engineering Projects

Introduction to 74HC595

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to explain all of you about Introduction to 74HC595. It is basically a shift register. It has an ability to store and to shift the data of 8 bits. First of all the data is written on the register serially and then it goes to the storage register. All of the output lines are controlled by this register. 74HC595 register is a very high speed device based on Complementary Metal Oxide Semiconductor (CMOS). 8 bit data register receives the data from the input DS. This data is then transferred from the input shift register to the output shift register. 74HC595 has a vey wide range of applications in daily life. It can be used as serial to parallel data converter, can receive and keeps the data for a long time etc. Moreover, It can be used in home appliances, for the industrial management, as computer peripheral. We will discuss further about this register later in this tutorial.

Introduction to 74HC595

74HC595 is a shift register having and eight bit storage register and an eight bit shift register. The data is written first and then stored into the device. It is high speed CMOS device. The data is usually entered in a serial format. Storage register is used to control the output lines of 74HC595. It has different real life applications e.g. in home appliances, computer peripherals, serial to parallel converter etc.

1. 74HC595 Pinout

• It has 16 pins in total out which eight are on left side and the remaining on the right side of the structure.
• The different function is associated with each of the pin.
• Some of the pins acts as an input to this device and receives data serially and transfer to the output pins to observe the received data.
• The pin diagram for 74HC595 is shown in the figure below:

• DS pin acts and receives the serial data.
• All of the lines with prefix Q acts as the output lines.

2. 74HC595 Pin Configuration

• In this section if the tutorial Introduction to 74HC595, I will tell you about the functions associated with each of the individual pin of 74HC595.
• All of the associated functions are describes in the table given below.

3. Functioning Diagarm

• The proper functional diagram of the shift register 74HC595 is shown in the figure below.

• From the above figure you can see that SHCP, master reset (MR) and the input DS are connected to 8 stage shift register.
• Pin number 12 i.e. STCP is connected to 8 bit storage register.
• The output enable (OE) is connected to 3 state outputs.

4. 74HC595 Functional Description

•  In this section of the tutorial Introduction to 74HC595, I will tell you about the functions of each line of the 8 bit shift register 74HC595.
• Complete description of the functions of 74HC595 is given in the table shown below.

5. 74HC595 Timing Diagram

• The arrow in the upward direction shows the rising edge of the each wave either received or applied.
• The shape of the signals applied and received and their relation with each other is shown in the figure below.

5. 74HC595 Logic Diagram

• The logic diagram for 74HC595 8 bit shift register is shown in the figure below.

• You can see that there are 8 different stages from 0 to 7 and latches are there in the logic diagram of 74HC595.
• Output enable (OE) and master reset (MR) are connected to latches with an inverted sign usually known as bubble.

6. 74HC595 Current/Voltage Rating

• The current, power and voltage rating along with their values and system international units are shown in the table given below.
• The values of operating temperature and storage temperature are also shown in the figure below.

7. 74HC595 Proteus Simulation

• I have a Proteus simulation for continuous control of the different LED's using 74HC595.
• The screenshot of the simulation is shown in the figure below.

• The complete Arduino source code is shown below.
• You need to just upload .hex file of this code into the Arduino of Proteus and run the simulation.

int RCLK = 5;
int SER = 6;
int SRCLK = 7;

#define TotalIC 1
#define TotalICPins TotalIC * 8

boolean Data[TotalICPins];

void setup()
{
  pinMode(SER, OUTPUT);
  pinMode(RCLK, OUTPUT);
  pinMode(SRCLK, OUTPUT);

  ClearBuffer();
}              


void loop()
{
   for(int i = TotalICPins - 1; i >=  0; i--)
   {
      Data[i] = HIGH;
      UpdateData();
      delay(300);
      ClearBuffer();
   }

   for(int i = 1;i < TotalICPins - 1;  i++)
   {
      Data[i] = HIGH;
      UpdateData();
      delay(300);
      ClearBuffer();
   }
   
}

• The running form of the above simulation is shown in the GIF below.

• You can download the complete simulation as well as the complete Arduino source code, here by clicking on the button below.

Proteus Simulation & Arduino Code

• Just download .rar file, extract it and enjoy the complete package having both Arduino source code as well as Proteus simulation.

So that is all from the tutorial Introduction to 74HC595. I hope you really enjoyed this tutorial. If you face any sort of problem regarding any thing, you can ask me anytime in comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in a way or the other. I will explore different IC's in my later tutorials and will surely share all them with all of as you as well. So, till then, Take Care :)

Introduction to 2N3904

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to give an Introduction to 2N3904. It is basically an NPN transistor made up of silicon material. It acts as a general purpose amplifier and switch. You should also have a look at Introduction to 2N2222, which is also an NPN transistor and considered as 2N3904 equivalent. It is mostly used for lower power amplifiers and switching applications. Its major functional area is enclosed in TO-92 package. Its a silicon NPN general purpose bipolar junction (BJT) transistor designed for switching purpose as well as for an amplifier. Its can bear lower amount of current, lower power and medium voltage levels. It is most commonly used BJT due to its smaller size, wide availability and low cost. It is less sensitive to fluctuations in voltages and currents as compared to other BJT's.

Where To Buy?
No.	Components	Distributor	Link To Buy
1	2N3904	Amazon	Buy Now

Introduction to 2N3904

• 2N3904 is a silicon NPN Bipolar Junction Transistor (BJT), enclosed in TO-92 package and is normally used for switching & amplification purposes.
• 2N3904 Pinout consists of 3 Pins i.e. Base, Emitter & Collector.
• As it's an NPN transistor, so major charge carriers are electrons caryying negative charge.
• Small voltage at base(around 0.7V) changes its state from reverse to forward biased and starts conducting.
• It has a wide range of applications i.e. used in televisions, home appliances, medium-load switches, PWM applications etc.

Now let's have a look at 2n3904 Pinout:

2N3904 Pinout

• 2N3904 Pinout has three pins in total:
  1. Emitter denoted by E
  2. Base denoted by B.
  3. Collector denoted by C.
• 2N3904 Pin Diagram is shown in below figure:

• 2N3904 Pinouts alongwith their symbols are shown in the table given below.

Let's have a look at the Datasheet of 2N3904:

2N3904 Datasheet

• In order to get in-depth knowledge on any component, must read its datasheet. Here's the link to download 2n3904 Datasheet:

Introduction to 2N3904 Let's have a look at the equivalents of 2N3904 NPN Transistor:

2N3904 Equivalent

Although common transistors such as 2N3904 are easily available in local/online electronics stores, but its wise to know the alternatives. So, 2N3904 equivalents are as follows:

• BC636
• 2N3055
• 2N2222
• BC549
• BC639
• 2SC5200
• 2N2369
• 2N3906

Now let's have a look at poewr ratings of 2N3904:

2N3904 Ratings

• Transistors are available in different ranges of power ratings and their selection depends on circuit's requirements.
• So, a circuit designer's task is to select an optimized transistor for its circuit, which should fullfill all its power equirements & must be cost efficient.
• If current/voltage passing through a transistor exceeds its ratings, the transistor may burnt out.
• Below table shows 2N3904 Ratings:

2N3904 Ratings
No.	Parameter Name	Parameter Value
1	C-E Voltage (VCEO)	40V (DC)
2	C-B Voltage (VCBO)	60V (DC)
3	E-B Voltage (VEBO)	6V  (DC)
4	Collector Current (IC)	200mA

Now, let's have a look at few applications of 2N3904:

2N3904 Applications

2N3904 is one of the most commonly used NPN transistor because of its low-cost, high-speed and small-size. Few of 2N3904 applications are as follows:

• It's normally used as a simple switch to control heavy loads, because of its low saturation voltage and high gain.
• It's used in home appliances i.e. TV, LCDs, stereo systems etc.
• It's also used in fast switching applications i.e. pulse width modulation(pwm), because of its fast switching speed.
• 2N3904 is also in signal amplification projects(i.e. sound amplifiers) as it has high current gain & thus can be used as an amplifier.

2N3904 Transistor as a switch

• In normal state, 2N3904 acts as reverse biased and there's no conduction between Collector & Emitter.
• When small voltage applies at its Base Terminal(normally 5V), 2N3904 converts its state from reverse to forward biased and conventional current starts flowing from Collector to Emitter.

Now, let's design a simulation to practically understand, how 2N3904 transistor acts as a switch?

2N3904 Proteus Simulation

• Let's first control a simple LED on/off state using 2N3904 NPN transistor
• As shown in below figure, power is supplied at Collector and LED is connected at the Emitter with resistor(to limit current) & grounded from the other end.

• As there's no voltage applied at Base Terminal, so 2N3904 is reverse biased and thus LED is OFF.
• Now when we have applied 5V at Base Terminal(using LogicState in Proteus), 2N3904 gets forward biased and now LED is ON, as shown in below figure:

• So, that's how we can use 2N3904 transistor as a switch.

In above simulation, we have controlled a simple LED and have used a manual switch. Now, I am going to control a DC motor with Arduino.

2N3904 Arduino Interfacing in Proteus

• I have made another simulation in Proteus ISIS for DC motor control using 2N3904.
• The screenshot of the simulation is shown in the figure below.

• The complete Arduino source code of the above simulation is given below.
• You have to get the hex file in Arduino to observe the results properly.

int MotorInput = 2;
int MotorOutput = 7;

void setup() 
{
    pinMode(MotorInput, INPUT_PULLUP);
    pinMode(MotorOutput , OUTPUT);
}

void loop() 
{
    if(digitalRead(MotorInput) == HIGH)
    {
      digitalWrite(MotorOutput, HIGH);
    }
    if(digitalRead(MotorInput) == LOW)
    {
      digitalWrite(MotorOutput, LOW);
    }
  
}

• The running form of the above simulation is shown in the below figure:

• From the above figure you can see that after uploading .hex file and running the simulation you need to change the level of logic state from 0 to 1, and the motor will start to rotate.
• You can download the complete Proteus ISIS simulation as well as complete Arduino source code, here by clicking on the button below.
• Just download .rar file, extract it and enjoy the complete package.

Introduction to 2N3904

• You should watch this below video to understand how to run this Proteus Simulation:

So that is all from the tutorial Introduction to 2N3904. I hope you really enjoyed this tutorial. If you face any sort of problem regarding any thing, you can ask me anytime in comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in a way or the other. I will explore different IC's in my later tutorials and will surely share all them with all of as you as well. So, till then, Take Care :)

Introduction to 1N4148

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to give an Introduction to 1N4148. It is basically a diode used for fast switching purposes. Switching diodes are usually single P-N diodes and their functionality is similar to that of normal switch. Below a specific voltage, switching diodes i.e. 1N4148 has high resistance. Whereas as above that specific voltage they show a low resistance. It is a most commonly used diode due to its smaller size, easy availability and low cost. Good switching diode can be chosen by its maximum reverse recovery time and its power dissipation ranging from 80mW to 1kW. Switching diodes such as 1N4148, 1N4007 etc. have very wide range of applications specially in Embedded Systems for switching purposes. It is mostly used in switches having extremely fast operation. It can be used for high speed rectification, general purpose switching and fast switching are also included in its applications, protection of telecommunication industries and homes etc.

Introduction to 1N4148

1N4148 is a standard diode made up of silicon and is used for extremely fast switching operations. It has two modes of operation named as:

1. Forward Biased
2. Reverse Baised

In Forward Biased operational mode, it allows the current to pass though it and it acts as a closed switch, while in Reverse Biased operational mode it acts as an open switch and doesn't allow the current to pass through it. I have explained it in below figure: I have designed the above simulation in Proteus and you can see in the above image.

• In forward biased state, diode IN4148 is acting as a closed switch and allowing the current to pass through it, that's why our LED is ON.
• In Reversed Biased state, diode IN4148 is acting as an open switch and there's no current flowing through it, that's why our LED is OFF.
• In the below figure, I have shown the equivalent circuit of both of these diode states:

1. 1N4148 Mechanical Design Parameters

• The different parameters for mechanical design of this diode are shown in the table given below.

• These are few of the parameters for mechanical designing of the zener diode 1N4148.
• Some of the other mechanical parameters are also shown in the table given below.

• The parameters given in the table above can be verified from the figure shown below,

• From the figure shown above, we can see that the diode has four major sides which are A, B, C and D respectively.
• Each of the side has its own different dimension as given in the table shown above.
• So, that was the brief discussion about the mechanical design parameters for this diode.

2. 1N4148 Pinout

• 1N4148 has only a single input terminal and a single output terminal.
• Input terminal is known as anode and output terminal is known as cathode.
• Anode is indicated by the positive (?ve) charge whereas the cathode is indicated by negative (?ve) charge.
• Pins and their charges are shown in the table given below.

3. 1N4148 Pins Diagram

• Pins diagram for this diode is shown in the figure below,

• This is the properly labeled diagram of 1N4148 showing anode on one side as A and cathode on the other side as B.

4. 1N4148 Power Ratings

• The current, voltage and power rating for the diode 1N4148 are provided in the table shown below.

• The table above displays the ratings of the particular diode along with their symbols and values.

5. 1N4148 Applications

The switching diode i.e. 1N4148 has a wide range of applications, a few pf which are given below:

• Extremely fat switching purposes.
• High speed rectification.
• General purpose switching.
• Protection circuits in telecommunication industries, offices, homes etc.
• These were few of the applications associated with this switching diode.

So that is all from the tutorial Introduction to 1N4148. I hope you really enjoyed this tutorial. If you face any sort of problem regarding any thing, you can ask me anytime in comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in a way or the other. I will explore different IC's in my later tutorials and will surely share all them with all of as you as well. So, till then, Take Care :)

Introduction to 2N2222

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to give you an Introduction to 2N2222. It is the most commonly used Negative-Positive-Negative (NPN) Bipolar Junction Transistor (BJT) available in the market now a days. 2N2222 can be used for different purposes e.g. switching and amplification of analog signals. I hope you have enjoyed the previous post on Introduction to ULN2003. The major functional area of 2N2222 is enclosed in TO-18 package. Due to the low cost and small size it is the most commonly used transistor. One of its key features is its ability to handle the high values of currents as compared to the other similar small transistors. Normally it is capable of switching a load current of 800mA which is really high rating as compared to other similar transistors. It is either made up of silicon or germanium material and doped with either positively or negatively charged material. Its applications may include amplification of analog signals as well as switching applications. While performing amplification applications, it receives an analog signal via collectors and another signal is applied at its base. Analog signal could be the voice signal having the analog frequency of almost 4kHz (human voice).

Introduction to 2N2222

2N2222 is the most common NPN bipolar junction transistor available in the market. It can be used for amplification of analog signals as well as switching applications. The major functional area of 2N-2222 is enclosed in TO-18 package. It is most common in the market due to the cost efficiency and the smaller size.

• It is shown in the figure shown below.

1. 2N2222 Pinout

• 2N 2222 has 3 pins in total, which are:
  1. Pin # 1: Emitter.
  2. Pin # 2: Base.
  3. Pin # 3: Collector.
• 2N2222 Pinout is shown in the figure below:

2. 2N2222 Pin Description

• The functions associated with each pin of 2N2222 along with the pin names are shown in the table given below.

• That was the description of the pins of the transistor.
• Pin configuration is shown in the figure below.

 

3. 2N2222 Voltage/Current Ratings

• The current, power and voltage ratings for 2N 2222 transistor are shown in the table given below.

• From the above table you can see the voltage across collector base junction is almost double as compared to the voltage across collector emitter junction.
• emitter base voltage is 12 times lesser than the voltage across the collector emitter junction.
• It can drive high amount of current loads as compared to the other similar transistors i.e. 800mA.
• This IC should be operated between the temperature ranging from -65 to 200 degree celcius.
• That was the brief description of the power, current and voltage ratings of the IC 2N2222.

4. 2N2222 Characteristics

The key characteristics associated with 2N2222 are given below.

• The total power of this component should not exceed by 500mW.
• The maximum capacity of handling frequency is 250MHz.
• For the collector current of 10mA and for 10 volts the DC current is around 75.
• Maximum tolerance of 2N2222 is 60V across its base and collector.
• Some of the other characteristics are shown in the table given below.

• That was the brief description about the key characteristics of the transistor 2N2222.

5. 2N2222 Simulation in Proteus

• I have also made a two different simple simulation in Proteus ISIS using the transistor 2N2222.
• The Proteus ISIS simulation for controlling an LED using 2N2222 is shown in the figure given below.

• If you change the state of the logic state from 0 to 1, current will be supplied to the collector and hence an LED attached to its emitter will be turned on.
• The running form of the above simulation is shown in the figure below.

• I have made another simulation in Proteus ISIS to control a simple DC motor using Arduino UNO.
• The simulation of the task is shown in the figure below.

• Source code for the above simulation is given below.

int MotorInput = 2;
int MotorOutput = 7;

void setup()
{
  pinMode(MotorInput, INPUT_PULLUP);
  pinMode(MotorOutput , OUTPUT);
}

void loop()
{
  if (digitalRead(MotorInput) == HIGH)
  {
    digitalWrite(MotorOutput, HIGH);
  }
  if (digitalRead(MotorInput) == LOW)
  {
    digitalWrite(MotorOutput, LOW);
  }

}

• You have to just copy and paste the entire code into the Arduino software.
• Obtain its .hex file and insert it into the Arduino of the Proteus ISIS.
• The running form of the above simulation is shown in the figure below:

• You can download the complete Arduino source code and simulation in one package, here by clicking on the button shown below.

Proteus Simulation & Arduino Code

So that is all from the tutorial Introduction to 2N2222. I hope you enjoyed this tutorial. If you face any sort of problem regarding any thing, you can ask me anytime in comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in a way or the other. I will explore different IC's in my later tutorials and will surely share all them with all of as you as well. So, till then, Take Care :)

Introduction to ULN2003

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to give you a detailed Introduction to ULN2003. We will also discuss the ULN2003 Datasheet, Pinout, Circuit Diagram & Proteus Simulation. If you have ever controlled any motor (i.e. DC Motor, Stepper Motor etc.) with a microcontroller (i.e. PIC, Arduino etc.), then you must have heard about drivers. Why do we need to use drivers? We use drivers (to control motors) because of two reasons.

• First: Microcontrollers operate at 5V while motors operate at different voltages (5V, 12V, 24V etc.).
• Second: Motors are Inductive loads thus they produce back emf, which may damage your microcontroller permanently (if not handled correctly).

Because of these two reasons, we have to use the driver in between the microcontroller & motor. There are different types of motor drivers available and ULN2003 is one of them. If we check its datasheet, then we can see that ULN2003 can handle up to 50V & 500mA. As its current rating is not that high, so it's used to control small motors. For heavy motors, we normally use relays in between ULN2003 & motor. In this case, the Microcontroller is sending a signal to ULN2003, which then forwards it to relays (connected at output). Remember, the relay is also an inductive load. So, we can control different types of loads with ULN2003 i.e. motor, relay, solenoid, actuator etc. You should also have a look at Relay Interfacing with Microcontroller using ULN2003A.

Now, let's have a look at what's inside ULN2003 in detail:

Where To Buy?
No.	Components	Distributor	Link To Buy
1	ULN2003	Amazon	Buy Now

ULN2003: Definition

• ULN2003 is a 16 Pin IC, consisting of 7 Darlington pairs (each pair protected with suppression diode) and thus has the capability to handle a maximum of 7 loads(could be inductive).
• In simple words, we have 7 drivers in a single ULN2003 chip and thus can control a maximum of 7 loads.
• Each Darlington pair can handle a maximum 500mA load, while the peak value is 600mA.
• Similarly, the maximum output voltage of each Darlington pair is 50V.
• In the below figure, you can see ULN2003 has 16 Pins, where inputs and their respective outputs are placed in front of each other(for ease of circuit designing).
• Other than I/O Pins, we have Ground Pin where we need to provide 0V & Vcc (Common) Pin.

ULN2003 Datasheet

• Here's the link to download ULN2003 datasheet, must read it once.
• I have also given the link to a reliable source, from where you can buy ULN2003 IC.

Download ULN2003 Datasheet

ULN2003 Pinout

• ULN2003 has 16 pins in total:
  • 7 Input pins (Pin # 1 to Pin # 7)
  • 7 Output pins (Pin # 10 to Pin # 16)
  • 1 Ground pin (Pin # 8)
  • 1 COM pin (Pin # 9)
• ULN2003 Pinout is shown in the below figure:

ULN2003 Pin Description

• The functions associated with each pin of ULN2003 along with pin names are shown in the table given below.

ULN2003 Darlington Pair

• ULN2003 consists of 7 identical Darlington pairs.
• A single Darlington pair consists of two bipolar transistors its maximum operating values are 50V & 500mA (peak 600mA).
• These two transistors of the Darlington pair have a common emitter, while their collectors are open.
• Here's the circuit diagram of a single Darlington pair, shown in the below figure:

ULN2003A Free-Wheeling Diodes

• ULN2003A has free-wheeling diodes, which protect from back emf.
• So, if we are using an inductive load (i.e. relays), then we don't need to add extra diodes if we are controlling it with ULN2003A.
• Logic Diagram of ULN2003A is shown in the below figure:

ULN2003 Features

There are a lot of key features associated with the relay driver ULN2003. A few of them are given below:

• 500mA of the rated collector.
• The high output voltage of around 50V.
• Relay driver applications.
• Output clamp diodes.
• Compatible input with popular logic types.
• Some of the key features are also given in the table below for a better understanding of the working conditions of ULN2003.

ULN2003 Applications

The relay circuit driver ULN2003 has a wide range of applications in real life. Some of the major applications associated with ULN2003A are given below.

• Logic buffers.
• Line drivers.
• Relay drivers (for driving different loads).
• Lamp drivers.
• LED display drivers (display devices).
• Motor (stepper and DC brushed motor) drivers.

ULN2003 Proteus Simulation

• I have designed a simulation in Proteus ISIS for LED control using ULN2003.
• The screenshot of the simulation is shown in the figure below.

• As you can see in the above figure that I have connected Logic State at all inputs of ULN2003A and have connected Leds at outputs.
• So, now when I make the Logic State HIGH then the respective LED will also go ON.
• The running form of the above simulation is shown in the figure below.

• If you change the state of the logic state from 0 to 1, the corresponding LED will be turned ON as shown in the above figure.
• You can download the Proteus simulation here by clicking on the button below.
• Just download the .rar file, extract it and enjoy the simulation.

ULN2003 Simulation in Proteus

• Here's the video in which I have shown how to use ULN2003A in Proteus:

So that is all from the tutorial Introduction to ULN2003. I hope you enjoyed this tutorial. If you face any sort of problem regarding anything, you can ask me anytime in the comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in one way or the other. I will explore different ICs in my later tutorials and will surely share them with all of you as well. So, till then, Take Care :)

Introduction to Relay

Hello everyone! I hope you will be fine and having fun. Today, I am going to give a detailed Introduction to Relay. In this tutorial, we will learn the basics of relays, the working principle of relays, the types of relays and their applications in detail.

A relay is a simple automatic switch that opens and closes the circuit(either electronically or mechanically) based on its input signal. A relay is an electromechanical switch that uses electromagnetism from a small current or voltage to switch higher current or voltage for different appliances. When a relay is in a Normally Open (NO) state, no current passes through it and when the relay is energized, the current starts to flow and we can say the relay is in a Normally Closed state. You should also have a look at Relay Interfacing with Microcontroller using ULN2003.

A Relay is used to control high-power devices with small current devices i.e. microcontrollers. When a small voltage is applied(normally from microcontrollers) to the input coil of a relay, it gets energized and the relay output changes its position from NO to NC. Relays are also used for protection purposes i.e. overload, reverse, under current, over current etc.

Now let's have a detailed overview of What is Relay???

What is a Relay?

Relay is an automatic switch, which opens and closes the circuit electronically. It uses electromagnetism from small voltage to provide higher voltages. It has two basic contacts i.e. NO (Normally Open) and NC (Normally Closed). When input voltage is applied across its coil, NC changes to NO and NO changes to NC. When input voltage is supplied, we say that the relay is energized. It has several features e.g. it can be used for switching smaller voltage to higher. But it can not be used in power-consuming devices. It has a wide range of applications. It can be used in home appliances, electronic circuits where there is a need of protection, robotics for controlling its motors for the proper motion and many more. A basic relay is given in the figure shown below.

1. Relay Pins

• Relay has total five (5) pins with different individual functions.
• Three pins are at one side of the structure.
• The other two pins are on the opposite side of the structure.
• All of these pins are provided in the table given in the figure shown below.

• I have also made a relay pin configuration diagram.
• Pin configuration diagram is shown in the figure given below.

2. Relay Pins Description

• Each pin has different functions to perform.
• So, we must know about each of the function before using it, for the better use of it.
• All these pin descriptions are listed in the table shown in the figure below.

3. Relay Internal Structure

• Internal structure of any electronic device leads to the better understanding about its working principle.
• I have made a completely labeled internal structure of relay along with its pin configurations.
• Relay internal structure is shown in the figure given below.

4. Relay Pinout

• If you want to know about the pin configuration of any electronic device you must have a look at its pinout diagram.
• Pinout diagram helps us to understand the pin configurations in a better way.
• I have made a pinout diagram which contains relay animation, internal structure and the real image.
• Relay pinout diagram is given in the figure shown below.

5. Relay Working Principle

• Relay works on a pretty simple principle.
• Initially when the power is not supplied and relay is in normally open condition, its contact will be opened.
• When relay is in normally closed condition, its contact will be closed.
• When power is supplied to its coil, it gets energized and its normally open condition is changed to normally closed and normally closed condition is changed to normally open.
• If we want to control the device via relay through a software then we have to attach this device to its normally open terminal.
• When the relay gets energized, that device will be turned on for the appropriate operation.
• Working principle of array can be understand from the visuals given in the figure shown below.
• Initially, when the power is not supplied and you can see the relay has normally closed contact as shown in the figure give below.

• As I have told earlier, when we supply power the normally closed contact will changed its state to normally open contact and vice versa.
• The explanation of the above step is given in the figure shown below.

• From the above figure, you can see contact has been changed to normally open contact.

6. Relay Functions

• Relay has the three basic functions to perform.
• All of these three functions are provided in the table given in the figure shown below.

• Air conditioning control (to limit & control a very high power load) are the examples of on/off control of the relay.
• Limit control includes motor speed control (to disconnect it if it is moving with slow or faster than the desired speed).
• Test equipment is an example of logic operation, which connects the device with no. of test points.

7. Types of Relays

• This section will focus on the major types of relays commonly used these days.
• There are several different types of relays.
• The basics types are listed in the table given in the figure shown below.

• Electromagnetic Relay is made up of magnetic, electrical and mechanical components. It has operating coil and mechanical contacts. When AC or DC supply is provided its mechanical contacts get either open of close. An electromagnetic relay is given in the figure shown below.

• Solid State Relay consists of solid state components. It is used to perform switching operation without any movement in its parts. Its power gain is higher than the electromagnetic relays because it requires low power as in input and provides high power at the output. Solid state is given in the figure shown below.

• Hybrid Relay is made up of electronic components and electromagnetic relays. Its input part consists of electronic circuitry which performs rectifications tasks. Its output part consist of electromagnetic relay. Hybrid relay is given in the figure shown below.

• Thermal Relay works on a very simple principle based on heat effect i.e. the rise in ambient temperature changes one position of the contact to another. Mostly it is used for the motor protection purposes. It consists of temperature sensors and control elements. Thermal relay is given n the figure shown below.

• Reed Relay has two magnetic strips. These strips are known as reed. These are sealed with a glass tube. The reed acts as blade as well as an armature. When magnetic field is applied to the coil. It wraps around the tube and reed start to move to perform the switching operation. Reed relays are given in the figure shown below.

8. Relay Applications

• Relay has a wide range of application in real life.
• Some of the major applications are listed in the table given in the figure shown below.

• Relay can also be used in relay boards for controlling either DC or stepper motor.
• One relay can control a single device, since two relay module has two relays so it can control two device simultaneously.
• Two relay board is given in the figure shown below.

• TV remote is another example of relay applications.
• TV remote is given in the figure shown below.

• Relay can also be used in mobile robots to control their motion properly.
• Visuals for the above step is given in the figure shown below.

9. Relay Simulation in Proteus

• I have made relay simulation in Proteus ISIS in order get a better idea about it.
• As the relay is energized, LED will be turned ON.
• A simple relay simulation in Proteus is given in the figure shown below.

• I have also made another relay simulation in Proteus ISIS as shown in the figure below.
• When the relay gets energized, LED will be turned ON, as shown below.

In the tutorial, Introduction to Relay, I have discussed the basics of relay. This is a fully detailed article the basically focuses on the the basics of relay including its pins configurations, its functions, types, working principle and many other things. I hope you have enjoyed the tutorial and I am sure you will appreciate my efforts. If you have any sort of problem you can freely ask us in comments anytime. Our team is always there to help you and to entertain you. I will also try my level best to answer your questions. I will share further interesting topics in my upcoming tutorials. Till my next tutorial, take care and bye :) strong>