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EMBEDDED SYSTEM INDIVIDUAL MODULES 1. Embedded System 2. Microcontroller unit 3. Power Supply 4. Liquid crystal display(LCD) 5. Motor driver 6. Seven segment display 7. Ultrasonic sensor 8. Bluetooth 9. Relay 10. Light emitting diode 11. IR reflector sensor 12. DC motors 13. RFID 14. MQ5

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EMBEDDED SYSTEM

INDIVIDUAL MODULES

1. Embedded System

2. Microcontroller unit

3. Power Supply

4. Liquid crystal display(LCD)

5. Motor driver

6. Seven segment display

7. Ultrasonic sensor

8. Bluetooth

9. Relay

10. Light emitting diode

11. IR reflector sensor

12. DC motors

13. RFID

14. MQ5

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1. EMBEDDED SYSTEM

1.1IntroductionMicrocontroller are widely used in Embedded System products. An Embedded product uses

the microprocessor(or microcontroller) to do one task & one task only. A printer is an example

of Embedded system since the processor inside it perform one task only namely getting the

data and printing it. Although microcontroller are preferred choice for many Embedded

systems, There are times that a microcontroller is inadequate for the task. For this reason in

recent years many manufactures of general purpose microprocessors such as INTEL,

Motorolla, AMD & Cyrix have targeted their microprocessors for the high end of Embedded

market.One of the most critical needs of the embedded system is to decrease power

consumptions and space. This can be achieved by integrating more functions into the CPU

chips. All the embedded processors have low power consumptions in additions to some forms

of I/O,ROM all on a single chip. In higher performance Embedded system the trend is to

integrate more & more function on the CPU chip & let the designer decide which feature

he/she wants to use.

1.2Embedded SystemAn Embedded System employs a combination of hardware & software to perform a specific

function. Software is used for providing features and flexibility hardware(Processors,

Memory...) is used for performance & sometimes security.An embedded system is a special

purpose system in which the computer is completely encapsulated by the device it controls.

Unlike a general purpose computer, such as a PC, an embedded system performs predefined

task’s usually with very specific tasks design engineers can optimize it reducing the size and

cost of the product.

Embedded systems are often mass produced, so the cost savings may be multiplied by millions

of items.The core of any embedded system is formed by one or several microprocessor or

micro controller programmed to perform a small number of tasks. In contrast to a general

purpose computer, which can run any software application, the user chooses, the software on

an embedded system is semi-permanent, so it is often called firmware.

1.3 Examples 1) Automated tiller machines (ATMS).

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2) Integrated system in aircraft and missile.

3) Cellular telephones and telephonic switches.

4) Computer network equipment, including routers timeservers and firewalls

5) Computer printers, Copiers.

6) Disk drives (floppy disk drive and hard disk drive)

7) Engine controllers and antilock brake controllers for automobiles.

8) Home automation products like thermostat, air conditioners sprinkles and security

monitoring system.

9) House hold appliances including microwave ovens, washing machines, TV sets DVD

players/recorders.

10) Medical equipment.

11) Measurement equipment such as digital storage oscilloscopes, logic analyzers and

spectrum analyzers.

12) Multimedia appliances: internet radio receivers, TV set top boxes.

13) Small hand held computer with P1M5 and other applications.

14) Programmable logic controllers (PLC’s) for industrial automation and monitoring.

15) Stationary video game controllers.

1.4Microprocessor (MPU) A microprocessor is a general-purpose digital computer central processing unit(CPU).

Although popularly known as a “computer on a chip” is in no sense a complete digital

computer. The block diagram of a microprocessor CPU is shown, which contains an

arithmetic and logical unit (ALU), a program counter (PC), a stack pointer (SP),some

working registers, a clock timing circuit, and interrupt circuits.

Figure 1.1: Block Diagram of Microprocessor.

1.5Microcontroller (MCU)Figure shows the block diagram of a typical microcontroller. The design incorporates all of

the features found in micro-processor CPU: ALU, PC, SP, and registers. It also added the

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other features needed to make a complete computer: ROM, RAM, parallel I/O, serial I/O,

counters, and clock circuit.

Figure 1.2: Block Diagram of Microcontroller.

1.6 Comparision Between Microprocessor And MicrocontrollerThe microprocessor must have many additional parts to be operational as a computer whereas

microcontroller requires no additional external digital parts.

1) The prime use of microprocessor is to read data, perform extensive calculations on that data

and store them in the mass storage device or display it. The prime functions of

microcontroller is to read data, perform limited calculations on it, control its environment

based on these data. Thus the microprocessor is said to be general-purpose digital

computers whereas the microcontroller are intend to be special purpose digital controller.

2) Microprocessor need many opcodes for moving data from the external memory to the CPU,

microcontroller may require just one or two, also microprocessor may have one or two

types of bit handling instructions whereas microcontrollers have many.

3) Thus microprocessor is concerned with the rapid movement of the code and data from the

external addresses to the chip, microcontroller is concerned with the rapid movement of the

bits within the chip.

4) Lastly, the microprocessor design accomplishes the goal of flexibility in the hardware

configuration by enabling large amounts of memory and I/O that could be connected to the

address and data pins on the IC package. The microcontroller design uses much more

limited.

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2. THE 8051 ARCHITECTURE

2.1 IntroductionThe Intel 8051 is an 8-bit microcontroller which means that most available operations are

limited to 8 bits. There are 3 basic "sizes" of the 8051: Short, Standard, and Extended. The

Short and Standard chips are often available in DIP (dual in-line package) form, but the

Extended 8051 models often have a different form factor, and are not "drop-in compatible".

Figure 2.1: Block Diagram of 8051.

All these things are called 8051 because they can all be programmed using 8051 assembly

language, and they all share certain features (although the different models all have their own

special features).Some of the features that have made the 8051 popular are:

4KB on chip program memory.

128 bytes on chip data memory (RAM).

4 register banks.

8-bit data bus.

16-bit address bus.

32 general purpose registers each of 8 bits.

16 bit timers (usually 2, but may have more, or less).

3 Internal and 2 external interrupts.

Bit as well as byte addressable RAM area of 16 bytes.

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Four 8-bit ports, (short models have two 8-bit ports).

16-bit program counter and data pointer.

1 Microsecond instruction cycle with 12 MHz Crystal.

8051 models may also have a number of special, model-specific features, such as UARTs,

ADC, OpAmps, etc.

2.2 Typical applications8051 chips are used in a wide variety of control systems, telecom applications, and robotics as

well as in the automotive industry. By some estimation, 8051 family chips make up over 50%

of the embedded chip market. The 8051 has been in use in a wide number of devices, mainly

because it is easy to integrate into a project or build a device around. The following are the

main areas of focus:

2.2.1 Energy Management: Efficient metering systems help in controlling energy usage

in homes and industrial applications. These metering systems are made capable by

incorporating microcontrollers.

2.2.2 Touch screens: A high number of microcontroller providers incorporate touch-

sensing capabilities in their designs. Portable electronics such as cell phones, media

players and gaming devices are examples of microcontroller-based touch screens.

2.2.3 Automobiles: The 8051 finds wide acceptance in providing automobile solutions.

They are widely used in hybrid vehicles to manage engine variants. Additionally,

functions such as cruise control and anti-brake system have been made more

efficient with the use of microcontrollers. So the microcontroller 8051 has great

advantage in the field of the automobiles.

2.2.4 Medical Devices: Portable medical devices such as blood pressure and glucose

monitors use microcontrollers will to display data, thus providing higher reliability

in providing medical results.

2.3 Pin out DescriptionPin 1-8 (Port 1): Each of these pins can be configured as an input or an output.

Pin 9(RST): A logic one on this pin disables the microcontroller and clears the contents of

most registers. In other words, the positive voltage on this pin resets the microcontroller.

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Figure 2.2: Pin diagram of the 8051 DIP.

By applying logic zero to this pin, the program starts execution from the beginning. Pin 9 is

the RESET pin. It is an input and is active high. Upon applying a high pulse to this pin the

microcontroller well reset and terminate all activities. This is often referred to as a power on

reset .Activating a power on reset will cause all values the registers to be lost. It will set

program counter to all 0s.In order for the RESET input to be effective it must have a minimum

duration of two machine cycles. In other words the high pulse must be high for a minimum of

two machine cycles before it is allowed to go low.

Pin 10-17(Port 3): Similar to port 1, each of these pins can serve as general input or output.

Besides, all of them have alternative functions:

Pin 10(RXD): Serial asynchronous communication input or Serial synchronous

communication output.

Pin 11(TXD): Serial asynchronous communication output or Serial synchronous

communication clock output.

Pin 12(INT0): Interrupt 0 input.

Pin 13(INT1): Interrupt 1 input.

Pin 14(T0): Counter 0 clock input.

Pin 15(T1): Counter 1 clock input.

Pin 16(WR): Write to external (additional) RAM.

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Pin 17(RD): Read from external RAM.

Pin 18, 19(X2, X1): Internal oscillator input and output. The 8051 has an on chip oscillator

but requires an external clock to run it. Most often a quartz crystal oscillator is connected to

inputs XTAL1 (pin 19) and XTAL2 (pin 18). The quartz crystal oscillator connected to

XTAL1 and XTAL2 also needs two capacitors of 30PF value. One side of each capacitor is

connected to the ground. Speed refers to the maximum oscillator frequency connected to

XTAL.

Figure 2.3: Oscillator Circuit and Timing.

Pin 20(GND): Ground.

Pin 21-28(Port 2): If there is no intention to use external memory then these port pins are

configured as general inputs/outputs. In case external memory is used, the higher address byte,

i.e. addresses A8-A15 will appear on this port. Even though memory with capacity of 64Kb is

not used, which means that not all eight port bits are used for its addressing, the rest of them

are not available as inputs/outputs.

Pin 29(PSEN): This is an output pin. PSEN stands for “program store enable”. If external

ROM is used for storing program then a logic zero (0) appears on it every time the

microcontroller reads a byte from memory.

Pin 30(ALE): ALE stands for “address latch enable. It is an output pin and is active high.

When connecting an 8031 to external memory, port 0 provides both address and data. In other

words the 8031 multiplexes address and data through port 0 to save pins. The ALE pin is used

for de-multiplexing the address and data. Prior to reading from external memory, the

microcontroller puts the lower address byte (A0-A7) on P0. In other words, this port is used

for both data and address transmission.

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Pin 31(EA): EA which stands for “external access” is pin number 31 in the DIP packages. It

is an input pin and must be connected to either VCC or GND. In other words it cannot be

unconnected. By applying logic zero to this pin, P2 and P3 are used for data and address

transmission with no regard to whether there is internal memory or not. It means that even

there is a program written to the microcontroller, it will not be executed. Instead, the program

written to external ROM will be executed. By applying logic one to the EA pin, the

microcontroller will use both memories, first internal then external (if exists).

Pin 32-39(Port 0): Similar to P2, if external memory is not used, these pins can be used as

general inputs/outputs. Otherwise, P0 is configured as address output (A0-A7) when the ALE

pin is driven high (1) or as data output (Data Bus) when the ALE pin is driven low (0).

Pin 40(VCC):+5V power supply.

2.4 PORTS P0-P3All the ports upon RESET are configured as input, since P0-P3 have value FFH on them. The

following is a summary of features of P0-P3.

2.4.1 PORT 0:

Port 0 is also designated as AD0-AD7 allowing it to be used for both address and data. When

connecting an 8051/31 to an external memory, port 0 provides both address and data. The

8051 multiplexes address and data through port 0 to save pins. ALE indicates if p0 has address

A0-A7.in the 8051 based systems where there is no external memory connection the pins of

P0 must be connected externally to 10k-ohm pull-up resistor. This is due to the fact that P0 is

an open drain, unlike P1, P2 and P3. Open drain is a term used for MOS chips in the same way

that open collector is used for TTL chips. In many systems using the 8751, 89c51 or

DS89c4*0 chips we normally connect P0 to pull up resistors.

2.4.2 PORT 1, PORT 2:

In 8051 based systems with no external memory connection both P1 and P2 are used as simple

I/O. however in 8031/51 based systems with external memory connections P2 must be used

along with P0 to provide the 16-bit address for the external memory. P2 is also designated as

A8-A15 indicating its dual function. Since an 8031/51 is capable of accessing 64k bytes of

external memory it needs a path for the 16 bits of address. While P0 provides the lower 8 bits

via A0-a7 it is the job P2 to provide bits A8-A15 of the address. In other words when the

8031/51 is connected to external memory P2 is used for the upper 8 bits of the 16 bit address

and it cannot be used for I/O.

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2.4.3 PORT 3:

Port 3 occupies a total of 8 pins 10 through 17. It can be used as input or output. P3 does not

need any pull-up resistors the same as P1 and P2 did not. Although port 3 is configured as

input port upon reset this is not the way it is most commonly used. Port 3 has the additional

function of providing some extremely important signals such as interrupts.

Port 3 Bit Function Pin

P3.0 RXD 10

P3.1 TXD 11

P3.2 INT0 12

P3.3 INT1 13

P3.4 T0 14

P3.5 T1 15

P3.6 WR 16

P3.7 RD 17

Table 2.1: Port 3 Alternate function

2.5 Programming Model of 8051In programming model of 8051 we have different types of registers are available and these

registers are used to store temporarily data is then the information could be a byte of data to be

processed or an address pointing to the data to be fetched the majority of registers is 8051 are

8-bikt registers.

2.6 Accumulator (Register A)Accumulator is a mathematical register where all the arithmetic and logical operations are

done is this register and after execution of instructions the outpour data is stored in the register

is bit addressable near. We can access any of the single bit of this register.A register is a

general-purpose register used for storing intermediate results obtained during operation. Prior

to executing an instruction upon any number or operand it is necessary to store it in the

accumulator first. All results obtained from arithmetical operations performed by the ALU are

stored in the accumulator. Data to be moved from one register to another must go through the

accumulator. In other words, the A register is the most commonly used register and it is

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impossible to imagine a microcontroller without it. More than half instructions used by the

8051 microcontroller use somehow the accumulator.

Figure 2.4: Accumulator Register.

2.7 B RegisterB register is same as that of accumulator of. It is also an 8 bit register and every bit of this is

accessible. This is also a mathematical register B which is used mostly for multiplication and

division.

Figure 2.5: B Register.

2.8 PSW (Program Status Word) RegisterProgram status word register is an 8 bit register. It is also referred to as the flag register.

Although the PSW register is 8 bits wide, only 6 bits of it are used by the 8051. The unused

bits are user-definable flags. Four of the flags are called conditional flags, meaning that they

Indicate some conditions that result after an instruction is executed. These four are CY (carry),

AC (auxiliary carry), P (parity) and OV (overflow).

Figure 2.6: Program Status Word Register

PSW register is one of the most important SFRs. It contains several status bits that reflect the

current state of the CPU. Besides, this register contains Carry bit, Auxiliary Carry, two

register bank select bits, Overflow flag, parity bit and user-definable status flag.

BANK RS1 (PSW.4) RS0 (PSW.3)

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Bank 0 0 0

Bank 1 0 1

Bank 2 1 0

Bank 3 1 1

Table 2.2: PSW Bit Bank selection.

P (Parity bit): If a number stored in the accumulator is even then this bit will be automatically

set (1), otherwise it will be cleared (0). It is mainly used during data transmit and receive via

serial communication.

Bit 1: This bit is intended to be used in the future versions of microcontrollers.

OV ( Overflow): Occurs when the result of an arithmetical operation is larger than 255 and

cannot be stored in one register. Overflow condition causes the OV bit to be set (1).

Otherwise, it will be cleared (0).

1RS0, RS1 (Register bank select bits): These two bits are used to select one of four register

banks of RAM. By setting and clearing these bits, registers R0-R7 are stored in one of four

banks of RAM.

F0 (Flag 0): This is a general-purpose bit available for use.

AC (Auxiliary Carry Flag): This is used for BCD operations only.

CY (Carry Flag): This is the (ninth) auxiliary bit used for all arithmetical operations and shift

instructions.

2.9 Data Pointer Register (DPTR)DPTR register is not a true one because it doesn't physically exist. It consists of two separate

registers: DPH (Data Pointer High) and (Data Pointer Low). For this reason it may be treated

as a 16-bit register or as two independent 8-bit registers. Their 16 bits are primarily used for

external memory addressing. Besides, the DPTR Register is usually used for storing data and

intermediate results.

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Figure 2.7: Data Pointer Register.

2.10 Stack Pointer (SP) Register

Figure 2.8: Stack Pointer Register.

A value stored in the Stack Pointer points to the first free stack address and permits stack

availability. Stack pushes increment the value in the Stack Pointer by 1. Likewise, stack pops

decrement its value by 1. Upon any reset and power-on, the value 7 is stored in the Stack

Pointer, which means that the space of RAM reserved for the stack starts at this location. If

another value is written to this register, the entire Stack is moved to the new memory location.

2.11 Internal MemoryThe 8051 has two types of memory and these are Program Memory and Data Memory.

Program Memory (ROM) is used to permanently save the program being executed, while Data

Memory (RAM) is used for temporarily storing data and intermediate results created and used

during the operation of the microcontroller. 128 or 256 bytes of RAM is used.

2.11.1 Internal RAM

As already mentioned, Data Memory is used for temporarily storing data and intermediate

results created and used during the operation of the microcontroller. Besides, RAM memory

built in the 8051 family includes many registers such as hardware counters and timers,

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input/output ports, serial data buffers etc. The previous models had 256 RAM locations, while

for the later models this number was incremented by additional 128 registers. However, the

first 256 memory locations (addresses 0-FFh) are the heart of memory common to all the

models belonging to the 8051 family. Locations available to the user occupy memory space

with addresses 0-7Fh, i.e. first 128 registers. This part of RAM is divided in several blocks.

The first block consists of 4 banks each including 8 registers denoted by R0-R7. Prior to

accessing any of these registers, it is necessary to select the bank containing it. The next

memory block (address 20h-2Fh) is bit- addressable, which means that each bit has its own

address (0-7Fh). Since there are 16 such registers, this block contains in total of 128 bits with

separate addresses (address of bit 0 of the 20h byte is 0, while address of bit 7 of the 2Fh byte

is 7Fh). The third group of registers occupy addresses 2Fh-7Fh, i.e. 80 locations, and does not

have any special functions or features.

Figure 2.9: RAM Memory Space Allocation.

2.11.2 Additional RAM

In order to satisfy the programmers’ constant hunger for Data Memory, the manufacturers

decided to embed an additional memory block of 128 locations into the latest versions of the

8051 microcontrollers. However, it’s not as simple as it seems to be… The problem is that

electronics performing addressing has 1 byte (8 bits) on disposal and is capable of reaching

only the first 256 locations, therefore. In order to keep already existing 8-bit architecture and

compatibility with other existing models a small trick was done. What does it mean? It means

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that additional memory block shares the same addresses with locations intended for the SFRs

(80h- FFH). In order to differentiate between these two physically separated memory spaces,

different ways of addressing are used. The SFRs memory locations are accessed by direct

addressing, while additional RAM memory locations are accessed by indirect addressing.

2.11.3 Internal ROM

The first models of the 8051 microcontroller family did not have internal program memory. It

was added as an external separate chip. These models are recognizable by their label

beginning with 803 (for example 8031 or 8032). All later models have a few Kbyte ROM

embedded. Even though such an amount of memory is sufficient for writing most of the

programs, there are situations when it is necessary to use additional memory as well. A typical

example are so called lookup tables. They are used in cases when equations describing some

processes are too complicated or when there is no time for solving them. In such cases all

necessary estimates and approximates are executed in advance and the final results are put in

the tables (similar to logarithmic tables).EA=0In this case, the microcontroller completely

ignores internal program memory and executes only the program stored in external memory.

EA=1In this case, the microcontroller executes first the program from built-in ROM, then the

program stored in external memory. In both cases, P0 and P2 are not available for use since

being used for data and address transmission. Besides, the ALE and PSEN pins are also used.

2.11.4 Memory Expansion

In case memory (RAM or ROM) built in the microcontroller is not sufficient, it is possible to

add two external memory chips with capacity of 64Kb each. P2 and P3 I/O ports are used for

their addressing and data transmission. From the user’s point of view, everything works quite

simply when properly connected because most operations are performed by the

microcontroller itself. The 8051 microcontroller has two pins for data read RD(P3.7) and

PSEN. The first one is used for reading data from external data memory (RAM), while the

other is used for reading data from external program memory (ROM). Both pins are active

low. Even though additional memory is rarely used with the latest versions of the

microcontrollers, we will describe in short what happens when memory chips are connected

according to the previous schematic. The whole process described below is performed

automatically. Similar occurs when it is necessary to read location from external RAM.

Addressing is performed in the same way, while read and write are performed via signals

appearing on the control outputs RD (is short for read) or WR (is short for write).

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2.12 Special Function Registers (SFRs)Special Function Registers (SFRs) are a sort of control table used for running and monitoring

the operation of the microcontroller. Each of these registers as well as each bit they include,

has its name, address in the scope of RAM and precisely defined purpose such as timer

control, interrupt control, serial communication control etc. Even though there are 128

memory locations intended to be occupied by them, the basic core, shared by all types of 8051

microcontrollers, has only 21 such registers. Rests of locations are intentionally left

unoccupied in order to enable the manufacturers to further develop microcontrollers keeping

them compatible with the previous versions.

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3. POWER SUPPLY

3.1 IntroductionIn most of our electronic products or projects we need a power supply for converting mains

AC voltage to a regulated DC voltage. For making a power supply designing of each and

every component is essential. Here to discuss the designing of regulated 5V Power Supply.

3.2 Block Diagram of Power SupplyFigure 3.1 show the block diagram of power supply. It can be divided into following stages:

Stage1: Transformer

Stage 2: Rectifier

Stage 3: Filter

Stage 4: Regulator

Figure 3.1: Block Diagram of Power Supply.

Figure 3.2: Circuit Diagram of Power Supply.

3.2.1 Transformer

A transformer is a static electrical device that transfers energy by inductive coupling between

its winding circuits. A varying current in the primary winding creates a varying magnetic flux

in the transformer's core and thus a varying magnetic flux through the secondary winding.

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This varying magnetic flux induces a varying electromotive force (EMF) or voltage in the

secondary winding. Commonly, transformers are used to increase or decrease the voltages of

alternating current in electric power applications.

A wide range of transformer designs are used in electronic and electric power applications.

Transformers are essential for the transmission, distribution, and utilization of electrical

energy.

Figure 3.3: Centre Tapped Transformer.

3.2.2 Rectifier

A rectifier is an electrical device that converts alternating current (AC), which periodically

reverses direction, to direct current (DC), which flows in only one direction. The process is

known as rectification. Physically, rectifiers take a number of forms, including vacuum tube

diodes, mercury-arc valves, copper and selenium oxide rectifiers, solid-state diodes, silicon-

controlled rectifiers and other silicon-based semiconductor switches. Historically, even

synchronous electromechanical switches and motors have been used. Early radio receivers,

called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead

sulfide) to serve as a point-contact rectifier or "crystal detector".

A more complex circuitry device which performs the opposite function, converting DC to AC,

is known as an inverter.

Rectification based on Full Wave Rectifier either using 4-diode or using 2-diode shown in

Figure 3.4.

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Figure 3.4: Rectification.

3.2.3Filter Capacitor

Filter capacitors are capacitors used for filtering of undesirable frequencies. Figure 3.5 show

the Full wave rectifier with a capacitor filter.

Figure 3.5: Full wave rectifier with a capacitor filter.

They are common in electrical and electronic equipment, and cover a number of applications,

such as:

a) Glitch removal on Direct current (DC) power rails

b) Radio frequency interference (RFI) removal for signal or power lines entering or leaving

equipment

c) Capacitors used after a voltage regulator to further smooth dc power supplies

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d) Capacitors used in audio, intermediate frequency (IF) or radio frequency (RF) frequency

filters (e.g. low pass, high pass, notch, etc.)

3.2.4 Voltage Regulator

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage

regulator may be a simple "feed-forward" design or may include negative feedback control

loops. It may use an electromechanical mechanism, or electronic components. Depending on

the design, it may be used to regulate one or more AC or DC voltages.

Figure 3.6: LM7805 – Pin Diagram.

Electronic voltage regulators are found in devices such as computer power supplies where

they stabilize the DC voltages used by the processor and other elements. In automobile

alternators and central power station generator plants, voltage regulators control the output of

the plant. As we require a 5V we need LM7805 Voltage Regulator IC shown in Figure 2.6.

7805 IC Rating:

a) Input voltage range 7V- 35V

b) Current rating Ic = 1A

c) Output voltage range VMax=5.2V ,VMin=4.8V.

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4. LED LED falls within the family of P-N junction devices. The light emitting diode (LED) is a diode that will

give off visible light when it is energized. In any forward biased P-N junction there is, with in the

structure and primarily close to the junction, a recombination of hole and electrons.

LED is a component used for indication. All the functions being carried out are displayed bled The LED is

diode which glows when the current is being flown through it in forward bias condition.

Figure 4.1: LED.

The LEDs are available in the round shell and also in the flat shells. The positive leg is longer

than negative leg.

 Crystal oscillators are oscillators where the primary frequency determining element is a quartz

crystal. Because of the inherent characteristics of the quartz crystal the crystal oscillator may be held to extreme

accuracy of frequency stability. Temperature compensation may be applied to crystal oscillators to improve

thermal stability of the crystal oscillator. Crystal oscillators are usually, fixed frequency oscillators

where stability and accuracy are the primary considerations. For example it is almost impossible to

design a stable and accurate LC oscillator for the upper HF and higher frequencies without

resorting to some sort of crystal control.

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5. LIQUID CRYSTAL DISPLAY

5.1IntroductionLiquid crystal displays (LCD) are widely used in recent years as compares to LEDs. This is

due to the declining prices of LCD, the ability to display numbers, characters and graphics,

incorporation of a refreshing controller into the LCD, their by relieving the CPU of the task of

refreshing the LCD and also the ease of programming for characters and graphics. HD 44780

based LCDs are most commonly used. The LCD, which is used as a display in the system, is

LMB162A. The main features of this LCD are: 16 X 2 display, intelligent LCD, used for

alphanumeric characters & based on ASCII codes. This LCD contains 16 pins, in which 8 pins

are used as 8-bit data I/O, which are extended ASCII. Three pins are used as control lines

these are Read/Write pin, Enable pin and Register select pin. Two pins are used for Backlight

and LCD voltage, another two pins are for Backlight & LCD ground and one pin is used for

contrast change.

5.2 LCD Pin DescriptionLCD voltage The LCD discuss in this section has the most common connector used for the

Hitachi 44780 based LCD is 14 pins in a row and modes of operation and how to program and

interface with microcontroller is describes in this section.

Vcc

1615141312111098

654321

7

1615141312111098

654321

7

D7

E

Vcc

D4

ContrastRS

Gnd

R/W

Gnd

D0

D3

D6D5

13

2

D2D1

Figure 5.1: LCD Pin Description Diagram

5.1.1 VCC, VSS, VEE: The voltage VCC and VSS provided by +5V and ground respectively

while VEE is used for controlling LCD contrast. Variable voltage between Ground and

Vcc is used to specify the contrast (or "darkness") of the characters on the LCD screen.

5.1.2 RS (register select): There are two important registers inside the LCD. The RS pin is

used for their selection as follows. If RS=0, the instruction command code register is

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selected, then allowing to user to send a command such as clear display, cursor at

home etc.. If RS=1, the data register is selected, allowing the user to send data to be

displayed on the LCD.

5.1.3 R/W (read/write): The R/W (read/write) input allowing the user to write information

from it. R/W=1, when it read and R/W=0, when it writing.

5.1.4 EN (enable): The enable pin is used by the LCD to latch information presented to its

data pins. When data is supplied to data pins, a high power, a high-to-low pulse must

be applied to this pin in order to for the LCD to latch in the data presented at the data

pins.

5.1.5 D0-D7 (data lines): The 8-bit data pins, D0-D7, are used to send information to the

LCD or read the contents of the LCD’s internal registers. To displays the letters and

numbers, we send ASCII codes for the letters A-Z, a-z, and numbers 0-9 to these pins

while making RS =1. There are also command codes that can be sent to clear the

display or force the cursor to the home position or blink the cursor.

We also use RS =0 to check the busy flag bit to see if the LCD is ready to receive the

information. The busy flag is D7 and can be read when R/W =1 and RS =0, as follows:

if R/W =1 and RS =0, when D7 =1(busy flag =1), the LCD is busy taking care of

internal operations and will not accept any information. When D7 =0, the LCD is ready

to receive new information.

5.3 Interfacing of micro controller with LCD displayIn most applications, the "R/W" line is grounded. This simplifies the application because when

data is read back, the microcontroller I/O pins have to be alternated between input and output

modes.

In this case, "R/W" to ground and just wait the maximum amount of time for each instruction

(4.1ms for clearing the display or moving the cursor/display to the "home position", 160µs for

all other commands) and also the application software is simpler, it also frees up a

microcontroller pin for other uses. Different LCD execute instructions at different rates and to

avoid problems later on (such as if the LCD is changed to a slower unit). Before sending

commands or data to the LCD module, the Module must be initialized. Once the initialization

is complete, the LCD can be written to with data or instructions as required. Each character to

display is written like the control bytes, except that the "RS" line is set. During initialization,

by setting the "S/C" bit during the "Move Cursor/Shift Display" command, after each

character is sent to the LCD, the cursor built into the LCD will increment to the next position

(either right or left). Normally, the "S/C" bit is set (equal to "1")

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LC D

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

8 Bit Data Busof LCD To MCUPort

Control Pins ofLCD To MCU PortPins

VC C

Figure 5.2: Interfacing of Microcontroller with LCD.

5.4 LCD Command Code

Code

(HEX)

Command to LCD Instruction

Register

1 Clear the display screen

2 Return home

4 Decrement cursor(shift cursor to left)

6 Increment cursor(shift cursor to right)

7 Shift display right

8 Shift display left

9 Display off, cursor off

A Display off, cursor on

C Display on, cursor off

E Display on, cursor blinking

F Display on, cursor blinking

10 Shift cursor position to left

14 Shift cursor position to right

18 Shift the entire display to left

1C Shift the entire display to right

80 Force cursor to the beginning of 1st line

C0 Force cursor to the beginning of 2nd line

38 2 line and 5×7 matrix

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6. SEVEN SEGMENT DISPLAY

6.1 IntroductionA seven-segment display (SSD), or seven-segment indicator, is a form of electronic display

device for displaying decimal numerals that is an alternative to the more complex dot

matrix displays.

Figure 6.1: Seven segment

6.2 Displaying LetterHexadecimal digits can be displayed on seven-segment displays. A combination of uppercase

and lowercase letters is used for A–F;[6] this is done to obtain a unique, unambiguous shape for

each hexadecimal digit (otherwise, a capital D would look identical to an 0 and a capital B

would look identical to an 8)..

Figure 6.2: Zero Display On a & segment

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7. ULTRASONIC SENSOR

7.1 IntroductionThe ultrasonic sensor is used for obstacle detection. Ultrasonic sensor transmits the

ultrasonic waves from its sensor head and again receives the ultrasonic waves reflected

from an object. There are many applications use ultrasonic sensors like instruction alarm

systems, automatic door openers etc. The ultrasonic sensor is very compact and has a very

high performance.

Figure 7.1: ultrasonic sensor

7.2Working principle The ultrasonic sensor emits the short and high frequency signal. These propagate in the air

at the velocity of sound. If they hit any object, then they reflect back echo signal to the

sensor. The ultrasonic sensor consists of a multi vibrator, fixed to the base. The multi

vibrator is combination of a resonator and vibrator. The resonator delivers ultrasonic wave

generated by the vibration.  The ultrasonic sensor actually consists of two parts; the emitter

which produces a 40 kHz sound wave and detector detects 40 kHz sound wave and sends

electrical signal back to the microcontroller. The ultrasonic sensor enables the robot to

virtually see and recognize object, avoid obstacles, measure distance. The operating range

of ultrasonic sensor is 10 cm to 30 cm.

Figure 7.2: ultrasonic working principle

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7. 3 Applications of Ultrasonic Sensor Automatic change over’s of traffic signals

Intruder alarm system

Counting instruments access switches parking meters

Back sonar of automobile

7.4 Features of Ultrasonic Sensor Compact and light weight

High sensitivity and high pressure

High reliability

Power consumption of 20mA

Pulse in/out communication

Narrow acceptance angle

Provides exact, non-contact separation estimations within 2cm to 3m

The explosion point LED shows estimations in advancement

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8. MOTOR DRIVER

8.1 IntroductionA H bridge is an electronic circuit that allows a voltage to be applied across a load in any

direction. H-bridge circuits are frequently used in robotics and many other applications to

allow DC motors to run forward  & backward. These motor control circuits are mostly used in

different converters like DC-DC, DC-AC, AC-AC converters and many other types of power

electronic converters. In specific, a bipolar stepper motor is always driven by a motor

controller having two H-bridges.

8.2 L293D Motor Driver ICL293D IC  is a typical Motor Driver IC which allows the DC motor to drive on any direction.

This IC consists of  16-pins which are used to control a set of two DC motors instantaneously

in any direction. It means, by using a L293D IC we can control two DC motors. As well, this

IC can drive small and quiet big motors.This L293D IC works on the basic principle of H-

bridge, this motor control circuit allows the voltage to be flowing in any direction. As we

know that the voltage must be change the direction of being able to rotate the DC motor in

both the directions. Hence, H-bridge circuit using L293D ICs are perfect for driving a motor.

Single L293D IC consists of two H-bridge circuits inside which can rotate two DC motors

separately. Generally, these circuits are used in robotics due to its size for controlling DC

motors.

8.2.1 Pin Diagram of a L293D Motor Driver IC Controller

Pin-1 (Enable 1-2):  When the enable pin is high, then the left part of the IC will work

otherwise it won’t work. This pin is also called as a master control pin.

Pin-2 (Input-1):  When the input pin is high, then the flow of current will be through

output 1

Pin-3 (Output-1): This output-1 pin must be connected to one of the terminals of the

motor

Pin4 &5: These pins are ground pins

Pin-6 (Output-2):  This pin must be connected to one of the terminals of the motor.

Pin-7 (Input-2): When this pin is HIGH then the flow of current will be though output

2

Pin-8 (Vcc2): This is the voltage pin which is used to supply the voltage to the motor.

Pin-16 (Vss): This pin is the power source to the integrated circuit.

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Pin-15 (Input-4): When this pin is high, then the flow of current will be through

output-4.

Pin-14 (Output-4): This pin must be connected to one of the terminals of the motor

Pin-12 & 13: These pins are ground pins

Pin-11 (Output-3): This pin must be connected to one of the terminals of the motor.

Pin-10 (Input-3): When this pin is high, then the flow of current will through output-3

Pin-9 (Enable3-4): When this pin is high, then the right part of the IC will work &

when it is low the right part of the IC won’t work. This pin is also called as a master

control pin for the right part of the IC.

Figure 8.1: motor driver IC

8.3 H Bridge Motor Control Circuit Using L293d ICThe IC LM293D consists of 4-i/p pins where, pin2 and 7 on the left side of the IC and Pin 10

and 15 on the right side of the IC. Left input pins on the IC will control the rotation of a motor.

Here, the motor is connected across side and right i/p for the motor on the right hand side.

This motor rotates based on the inputs we provided across the input pins as Logic 0 and Logic

When a motor is connected to the o/p pins 3 and 6 on the left side of the IC. For rotating of the

motor in clockwise  direction, then the i/p pins have to be provided with Logic 0 and Logic

1.When Pin-2= logic 1 & pin-7 = logic 0, then it rotates in clockwise direction.

Pin-2=logic 0 & Pin7=logic 1, then it rotates in anti clock direction

Pin-2= logic 0 & Pin7=logic 0, then it is idle (high impedance state)

Pin-2= logic 1 & Pin7=logic 1, then it is idle In a similar way the motor can also operate

across input pin-15 and pin-10 for the motor on the right hand side. The L4293D motor driver

IC deals with huge currents, due to this reason, this circuit uses a heat sink to decrease the

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heat. Therefore, there are 4-ground pins on the L293D IC. When we solder these pins on the

PCB (printed circuit board), then we can get a huge metallic area between the ground pins

where the heat can be produced.

Figure 8.2: block diagram of motor driver circuit

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9. BLUETOOTH

9.1 IntroductionHC-05 module is an easy to use Bluetooth SPP (serial port protocol) module designed for

transparent wireless serial communication setup. Serial port Bluetooth module is fully

qualified Bluetooth V2.0+EDR(enhanced data rate) 3Mbps modulation with complete 2.4Ghz

radio transceiver transceiver and baseband. It uses CSR Bluecore 04 External single chip

Rluetooth system with CMOS technology and with AFH (Adaptive Frequency Hopping

Feature).

Figure 9.1: Bluetooth

9.2 Hardware Features1. Typical 80dBm sensitivity.

2. Up to +4dBm RF transmit power.

3. Three to five Volt I/O.

4. PIO(Programmable Input/Output) control.

5. UART interface with programmable baud rate.

6. With integrated antenna.

7. With edge connector.

8. Software Features

9. Slave default Baud rate: 9600, Data bits:8, Stop bit:1,Parity:No parity.

10. Auto connect to the last device on power as default.

11. Permit pairing device to connect as default.

9.3 Pin DescriptionThe HC-05 Bluetooth Module has 6pins. They are as follows:

9.3.1 ENABLE:

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When enable is pulled LOW, the module is disabled which means the module will not turn on and it

fails to communicate. When enable is left open or connected to 3.3V, the module is enabled i.e the

module remains on and communication also takes place.

9.3.2 VCC:

Supply Voltage 3.3V to 5V

9.3.3 GND:

Ground pin

9.3.4 TXD & RXD:

These two pins acts as an UART interface for communication

9.3.5 STATE:

It acts as a status indicator.When the module is not connected to / paired with any other

bluetooth device,signal goes Low.At this low state,the led flashes continuously which denotes that the

module is not paired with other device.When this module is connected to/paired with any other

bluetoothdevice,the signal goes High.At this high state,the led blinks with a constant delay say for

example 2s delay which indicates that the module is paired.

Figure 9.2: Pins of Bluetooth

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10. IR REFLECTOR SENSOR

10.1 Introduction

An IR transmitter or source converts an electrical signal to an optical signal. The two most

appropriate types of device are the light-emitting diode (LED) and semiconductor laser diode

(LD). LEDs have a naturally wide transmission pattern, and so are suited to non directed links.

Eye safety is much simpler to achieve for an LED than for a laser diode, which usually have

very narrow transmit beams. The principal advantages of laser diodes are their high energy-

conversion efficiency, their high modulation bandwidth, and their relatively narrow spectral

width. Although laser diodes offer several advantages over LEDs that could be exploited, most

short-range commercial systems currently use LEDs.

A receiver or detector converts optical power into electrical current by detecting the photon

flux incident on the detector surface. Silicon p-i-n photodiodes are ideal for wireless infrared

communications as they have good quantum efficiency in this band and are inexpensive.

Avalanche photodiodes are not used here since the dominant noise source is back-ground

light-induced shot noise rather than thermal circuit noise.

1) Transmission wavelength and Noise

The most important factor to consider when choosing a transmission wavelength is the

availability of effective, low-cost sources and detectors. The availability of LEDs and silicon

photodiodes operating in the 800 nm to 1000 nm range is the primary reason for the use of this

band. Another important consideration is the spectral distribution of the dominant noise

source: background lighting.

2) Safety

There are two safety concerns when dealing with infrared communication systems. Eye safety

is a concern because of a combination of two effects: the cornea is transparent from the near

violet to the near IR. Hence, the retina is sensitive to damage from light sources transmitting

in these bands. However, the near IR is outside the visible range of light, and so the eye does

not protect itself from damage by closing the iris or closing the eyelid.

10.2 IR Reflector Circuit

This Circuit is works on reflection of white surface. There are two cases, In First case when IR

LED emits IR rays and reflects from white surface then it is received by photodiode. When IR

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rays fall on photodiode then it passes 5V to base of transistor (BC 547).Transistor gets turn on

and passes 5V from collector to emitter. The output of reflector circuit is 0. This zero send to

MCU then MCU take action according to condition which is written in program.

VC C

100K

13

2

D 2

PHOTODIODE1

2

Q 1

BC 5 4 72

31

47 E

D 1

IR LED10K

5V

O/ PtoMCU

Figure 10.1: block diagram of IR sensor

In second case when IR LED emits IR rays and absorb by black surface then it is not received

by photodiode. Photodiode remains OFF and it is not pass 5V to base of transistor (BC

547).Transistor remains OFF. The output of reflector circuit is 1.This one send to MCU then

MCU take action according to condition which is written in program.

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11. RELAY

11.1 IntroductionA relay is an electrically operated switch. Many relays use an electromagnet to mechanically

operate a switch, but other operating principles are also used, such as solid-state relays. Relays

are used where it is necessary to control a circuit by a separate low-power signal, or where

several circuits must be controlled by one signal. The first relays were used in long

distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit

and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges

and early computers to perform logical operations.

Figure 11.1: pins of relay

11.2 ApplicationsRelays are used wherever it is necessary to control a high power or high voltage circuit with a

low power circuit.  The first application of relays was in long telegraph lines, where the weak

signal received at an intermediate station could control a contact, regenerating the signal for

further transmission. High-voltage or high-current devices can be controlled with small, low

voltage wiring and pilots switches. Low power devices such as microprocessors can drive

relays to control electrical loads beyond their direct drive capability. In an automobile, a

starter relay allows the high current of the cranking motor to be controlled with small wiring

and contacts in the ignition key.

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12. DC MOTOR

12.1 IntroductionElectrical motors are everywhere around us. Almost all the electro-mechanical movements

we see around us are caused either by an A.C. or a DC motor. Here we will be exploring

this kind of motors. This is a device that converts DC electrical energy to a mechanical

energy.

12.2 Principle of DC Motor Structurally and construction wise a direct current motor is exactly similar to a  DC

generator, but electrically it is just the opposite. Here we unlike a generator we supply

electrical energy to the input port and derive mechanical energy from the output port

Figure 12.1: left hand rule for finding direction

A DC motor relies on the fact that like magnet poles repel and unlike magnetic poles attract

each other. A coil of wire with a current running through it generates an electromagnetic field

aligned with the center of the coil. By switching the current on or off in a coil its magnetic

field can be switched on or off or by switching the direction of the current in the coil the

direction of the generated magnetic field can be switched 180°. A simple DC motor typically

has a stationary set of magnets in the stator and an armature with a series of two or more

windings of wire wrapped in insulated stack slots around iron pole pieces (called stack teeth)

with the ends of the wires terminating on a commutator. The armature includes the mounting

bearings that keep it in the center of the motor and the power shaft of the motor and the

commutator connections. The winding in the armature continues to loop all the way around

the armature and uses either single or parallel conductors (wires), and can circle several times

around the stack teeth. The total amount of current sent to the coil, the coil's size and what it's

wrapped around dictate the strength of the electromagnetic field created. The sequence of

turning a particular coil on or off dictates what direction the effective electromagnetic fields

are pointed. By turning on and off coils in sequence a rotating magnetic field can be created.

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These rotating magnetic fields interact with the magnetic fields of the magnets (permanent

or electromagnets) in the stationary part of the motor (stator) to create a force on the armature

which causes it to rotate. In some DC motor designs the stator fields use electromagnets to

create their magnetic fields which allow greater control over the motor. At high power levels,

DC motors are almost always cooled using forced air.

The commutator allows each armature coil to be activated in turn. The current in the coil is

typically supplied via two brushes that make moving contact with the commutator. Now, some

brushless DC motors have electronics that switch the DC current to each coil on and off and

have no brushes to wear out or create sparks.

Different number of stator and armature fields as well as how they are connected provide

different inherent speed/torque regulation characteristics. The speed of a DC motor can be

controlled by changing the voltage applied to the armature. The introduction of variable

resistance in the armature circuit or field circuit allowed speed control. Modern DC motors are

often controlled by power electronics systems which adjust the voltage by "chopping" the DC

current into on and off cycles which have an effective lower voltage.

Since the series-wound DC motor develops its highest torque at low speed, it is often used in

traction applications such as electric locomotives, and trams. The DC motor was the mainstay

of electric traction drives on both electric and diesel-electric locomotives, street-cars/trams

and diesel electric drilling rigs for many years. The introduction of DC motors and

an electrical grid system to run machinery starting in the 1870s started a new second Industrial

Revolution. DC motors can operate directly from rechargeable batteries, providing the motive

power for the first electric vehicles and today's hybrid cars and electric cars as well as driving

a host of cordless tools. Today DC motors are still found in applications as small as toys and

disk drives, or in large sizes to operate steel rolling mills and paper machines.

If external power is applied to a DC motor it acts as a DC generator, a dynamo. This feature is

used to slow down and recharge batteries onhybrid car and electric cars or to return electricity

back to the electric grid used on a street car or electric powered train line when they slow

down. This process is called regenerative braking on hybrid and electric cars. In diesel electric

locomotives they also use their DC motors as generators to slow down but dissipate the energy

in resistor stacks. Newer designs are adding large battery packs to recapture some of this

energy.

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Figure 12.2: motor

DC Motor has two leads. It has bidirectional motion

If we apply positive to one lead and ground to another motor will rotate in one

direction, if we reverse the connection the motor will rotate in opposite direction.

If we keep both leads open or both leads ground it will not rotate (but some inertia will

be there).

If we apply +ve voltage to both leads then braking will occur.

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13. DC MOTOR

13.1 IntroductionRFID or Radio Frequency Identification is a method in which electromagnetic waves are used

for transmitting data for the purpose of identifying tags attached to objects. An RFID system

consists of a transmitter (tag) and a reader. The tag is encrypted with a unique code and the

reader scans this code for the identification purpose. The tags are generally of two types:

active and passive. Active tags have a battery fitted to it and it transmits the unique code

periodically or in the proximity of the reader. Passive tags are powered using the

electromagnetic induction from the signal transmitted by the reader. Typical applications of

RFID are access control systems, ID cards, human identification, animal identification,

payment systems, tagging books, replacing bar codes, tagging merchandise in stores etc .

RFID tags are available in different shapes but the most common shape is in the form of a

card. The RFID readers are available in the market in the form of a module with all the

supporting hardware. This article is about interfacing RFID to 8051 microcontroller. The

images of a typical RFID card and reader are shown below.

Figure 13.1: RF Card and Reader

The RFID card is available in different sizes and shapes and the most commonly used type is

shown above. The image of a typical RFID reader module is also shown above. Basically it

contains a semiconductor memory for storing the unique ID code, modulating circuit and a

coil. The coil acts as the power source by means of electromagnetic induction while in the

vicinity of the reader and it also serves as the antenna for propagating the ID code. The

modulating circuit modulates the unique code into the transmitted wave. The reader basically

contains a coil and an electronic circuit. The coil serves as exciter for the card and also the

antenna for receiving the signal propagated by the card. The electronic circuit demodulates

this signal and converts it into a form suitable for the next stage (microcontroller). Circuit

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diagram for interfacing RFID module to 8051 microcontroller is shown below. he full circuit

diagram for interfacing RFID module to 8051 is shown above. The unique ID code in the

RFID card is read by the circuit and displayed on the LED which is connected P0.0 and fake

ID code is detected on P0.7.

Figure 13.2: Interface RF Card and Reader with MCU

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14. MQ5

14.1 Introduction

In this guide, we learn how to interface MQ5 Gas sensor (which is a generic Gas

Sensor more suited to detect and determine LPG concentrations) with MCU.

In this tutorial, we are using the MQ5 Gas sensor module (which is widely

available in market) . This module has two output possibilities – an analog out

(A0) and a digital out (D0). The analog out can be used to detect Gas leakage

and to measure volume of Gas leakage (by doing proper calculation of the sensor

output inside program) in specific units (say ppm). The digital out can be used to

detect Gas leakage and hence trigger an alert system (say a sound alarm or an

sms activation etc). The digital out gives only two possible outputs – High and

Low (hence its more suited for detection of gas leak than to measure volume of

gas presence).

We have developed a Gas Leakage Detector using MCU and MQ5 with SMS

Alert, Sound Alarm and Relay activation. You can try this interesting project to

gain more knowledge and build a practical application using MQ5 sensor.

MQ5_LPG_Sensor_Module

Interfacing MQ5 Gas Sensor Module to Arduino using Digital Out Pin

This is pretty simple. Connect the D0 pin of MQ5 module to any digital pin of

arduino. Lets connect D0 to pin of MCU. Now we need to give power supply

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(Vcc) and complete the circuit by connecting to ground (Gnd). Refer the circuit

diagram given below. Take a +5V connection from arduino and connect it to Vcc

of MQ5 module. Finally connect the GND pin of MQ5 module to GND of

arduino. That’s all and we have finished the circuit.

Circuit Diagram of Interfacing MQ5 to MCU (Digital Out)