Theory - Basic Electrical and Electronic Components

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Tuesday, July 10, 2012

WELCOME




BASIC ELECTRICAL AND

ELECTRONIC COMPONENTS

• RESISTORS

• DIODES

• CAPACITORS

• INDUCTORS

• TRANSISTORS

• BATTERY

• TRANSFORMER • VOLTAGE REGULATORS

• LDR (LIGHT DEPENDENT RESISTOR)

• RELAYS




The first band gives the first digit

The second band gives the second digit

The third band indicates the number of zeroes.

RESISTOR:

A resistor is a device which opposes the flow of

current.




Colour Number

Black 0

Brown 1

Red 2

Orange 3 Yellow 4

Green 5

Blue 6

Violet 7

Grey 8

White 9




DIODE:

A Diode is a two terminal electronic component that

conducts electric current only in one direction.

Based on applications diodes are divided into two

types

-> PN junction

-> ZENER diode




PN junction diode:

The most common function of a diode is toallow an electric current in one direction (called

the forward direction) while blocking current in

the opposite direction (the reverse direction).




ZENER DIODE:

A Zener diode is a type of diode that permits current inthe forward direction like a normal diode, but also in the

reverse direction if the voltage is larger than the

breakdown voltage known as "Zener knee voltage" or

"Zener voltage".




LIGHT EMITTING DIODE (LED)

A light-emitting diode (LED) is a semiconductor light

source. LEDs are used as indicator lamps in many

devices, and are increasingly used for lighting.

k

A




capacitors easily pass AC (changing) signals.

capacitor block DC (constant) signals.

s

CAPACITOR:




INDUCTOR:

• An inductor or a reactor can store energy in a

magnetic field created by the electric currentpassing through it. It is denoted in Henry.

• Typically an inductor is a conducting wire shaped

as a coil, the loops helping to create a strongmagnetic field inside the coil due to Faraday'sLaw of Induction.




TRANSISTORS:

A transistor is a semi conductor device commonly used

to amplify or switch electronic signals. A voltage orcurrent applied to one pair of the transistor's terminals

changes the current flowing through another pair of

terminals. Because the controlled (output) power can be

much more than the controlling (input) power, the

transistor provides amplification of a signal.







Transformer:




VOLTAGE REGULATOR:

• A voltage regulator is an electrical regulator designed

to automatically maintain a constant voltage level.

• It may use an electromechanical mechanism, or passive or active electronic components. Depending

on the design, it may be used to regulate one or more

AC or DC voltages.




The voltage regulators are classified into two types.

positive series(7805)

negative series(7905)

7805

I/P GND O/P

7805SERIES Output

voltage

7905

I/P O/PGND




Light Dependent Resistor (LDR):

An LDR is an input transducer (sensor)which converts brightness (light) to

resistance. It is made from cadmium

sulphide (CdS) and the resistance

decreases as the brightness of lightfalling on the LDR increases.




RELAY:

A Relay is an electrically controllable switch widelyused in industrial controls, automobiles, etc…

inductor




OPERATION OF RELAY:

• The relay's switch connections are usually labeled COM,

NC and NO:• COM = Common, always connect to this, it is the

moving part of the switch.

• NC = Normally Closed, COM is connected to this whenthe relay coil is off.

• NO = Normally Open, COM is connected to this whenthe relay coil is on.

• Connect to COM and NO if you want the switchedcircuit to be on when the relay coil is on.

• Connect to COM and NC if you want the switchedcircuit to be on when the relay coil is off.




N/C

COM

N/O

AC230V

BULB

I ND U C T OR

IRON

ARM

ON

OFF

Diagrammatic explanation:




WINE YARDT E C H N O L O G I E S

REGULATED POWER SUPPLY:




7812

7805

C1

C2

5V

12V

REGULATED POWER SUPPLY CIRCUIT:

C

C=1000uF C1,C2=104pF R1,R2=330

R

R2




RECTIFIER:

• The primary application of rectifiers is to derive usable

DC power from an AC supply. Virtually all electronics

except simple motor circuits such as fans require a DC

supply but mains power is AC so rectifiers find usesinside the power supplies of virtually all electronic

equipment.




FILTERS:

• Electronic filters are electronic circuits which

perform signal processing functions, specifically toremove unwanted frequency components from thesignal, to enhance wanted ones, or both.

RECTIFIER

OUTPUT FILTER PURE DC

AC+DC DC

AC




How the Transistor act as a switch ?

what is a transistor?

A transistor is a semi conductor device commonlyused to amplify or switch electronic signals.




What is a switch? In electronics, a switch is an electrical component

that can break an electrical circuit, interrupting

the current or diverting it from one conductor to

another.




Transistor as a switch:

• Transistor can be used as an electronic switch, in

grounded-emitter configuration.

• Transistors are commonly used as electronic

switches, for both high power applicationsincluding switched mode power supply and low

power applications such as logic gates.




• In a grounded-emitter transistor circuit, such as

the light-switch circuit shown, as the base voltage

rises the base and collector current rise

exponentially, and the collector voltage drops

because of the collector load resistor.

• If the emitter-base and base-collector are in

forward bias then it act as a switch.• At that instant the collector to emitter is shorted,

it act as a closed switch.

V




N/C

COM

N/O

LDR

100K

PRESET

Vcc

relay

330

LED

LIGHT VB<0.7V

T-OFF

NO

LIGHT

VB>0.7VT-ON

R

LOAD

Transistor as a switch

example







• In general, "embedded system" is not a strictly

definable term, as most systems have some element

of extensibility or programmability.

• For example, handheld computers share some

elements with embedded systems such as the

operating systems and microprocessors which power

them, but they allow different applications to be

loaded and peripherals to be connected or a few

dedicated functions", and is thus appropriate to call

"embedded".




• Moreover, even systems which don't expose

programmability as a primary feature generally

need to support software updates. On a continuum

from "general purpose" to "embedded", large

application systems will have subcomponents atmost points even if the system as a whole is

"designed to perform one or a few dedicated

functions", and is thus appropriate to call

"embedded".




Embedded system

• An embedded system is a special purpose computer

system designed to perform one or a few dedicatedfunctions, often with real time computing

constraints.

• It is usually embedded as part of a complete device

including hardware and mechanical parts.

• Since the embedded system is dedicated to specific

tasks, design engineers can optimize it, reducing the

size and cost of the product, or increasing thereliability and performance.

• Embedded systems span all aspects of modern life.

Ch i i




Characteristics:

• Embedded systems are designed to do some

specific task, rather than be a general-purposecomputer for multiple tasks.

• Embedded systems are not always standalone

devices. Many embedded systems consist of small, computerized parts within a larger device

that serves a more general purpose.

• The program instructions written for embedded

systems are referred to as firmware, and arestored in read-only memory or Flash memory

chips.




Applications:

• Telecommunications• Consumer electronics like PDA’s, mp3 players,

mobile phones, digital cameras, DVD's, ovens,

washing machine, to control lights, to provide

security, climate, etc..




User Interface

• Embedded systems range from no user interface

at all — dedicated only to one task — to

complex graphical user interfaces that resemble

modern computer desktop operating systems.

• Simple embedded devices use buttons, LEDs,

graphic or character LCDs (for example popular

HD44780 LCD) with a simple menu system.




• A more sophisticated devices use graphical

screen with touch sensing or screen-edge

buttons provide flexibility while minimizing space

used: the meaning of the buttons can change

with the screen, and selection involves the

natural behavior of pointing at what's desired.




• Serial Communication Interfaces (SCI): RS-232,RS-422, RS-485 etc

• Synchronous Serial Communication Interface: I2C,

SPI, SSC and ESSI (Enhanced Synchronous Serial

Interface)

• Universal Serial Bus (USB)

• Multi Media Cards (SD Cards, Compact Flash etc)

Peripherals




• Networks: Ethernet, Controller Area Network,

LanWorks, etc

• Timers: PLL(s), Capture/Compare and Time

Processing Units

• Discrete IO: aka General Purpose Input/Output

(GPIO)

• Analog to Digital/Digital to Analog (ADC/DAC)

• Debugging: JTAG, ISP, ICSP, BDM Port, BITP DP9

port …

Peripherals




• Embedded system means the processor is embeddedinto that application.

• An embedded product uses a microprocessor or

microcontroller to do one task only.

• In an embedded system, there is only one applicationsoftware that is typically burned into ROM.

• Example: printer, keyboard, video game player.

Overview of Embedded System







Contents

IntroductionBlock Diagram and PinDescription of the 8051

I/O Port Description

Led InterfacingSwitch Interfacing

Led And switch Interfacing

LCD Interfacing

Serial communicationRelay Interfacing




Why do we need to learn

Microprocessors/controllers?

• The microprocessor is the core of computer

systems.

• Nowadays many communication, digital

entertainment, portable devices, are controlledby them.

• A designer should know what types of

components he needs, ways to reduce

production costs and product reliable.




Aspects of a microprocessor/controller

• Hardware :

Interface to the real world. Ex- LCD, LED,printers, keyboard etc.

• Software :

order how to deal with inputs. By usingsoftware we can control the hardware to

obtain the desired outputs.




Tools for a microprocessor/controller:

• CPU: Central Processing Unit

• I/O: Input /Output

• Bus: Address bus & Data bus

• Memory: RAM & ROM• Timer

• Interrupt

• Serial Port

• Parallel Port




CPU

General-

Purpose

Micro-

processor

RAM ROM I/O

PortTimer

Serial

COM

Port

Data Bus

Address Bus

General-Purpose Microprocessor System

• CPU for Computers.

• No RAM, ROM, I/O on CPU chip itself.

• Example: Intel's x86, Motorola’s 680x0.

Many chips on mother’s board

General-purpose microprocessor:

Microprocessors:

Microcontroller:




RAM ROM

I/O

PortTimer

Serial

COM

PortMicrocontroller

CPU

• A smaller computer.

• On-chip RAM, ROM, I/O ports...• Example: Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and

PIC 16X.

A single chip

Microcontroller:




Microprocessor

• CPU is stand-alone,RAM, ROM, I/O,timer are separate

• designer can decideon the amount of ROM, RAM andI/O ports.

• Expansive,versatility.

• general-purpose

Microcontroller

• CPU, RAM, ROM, I/O

and timer are all on a

single chip

• fix amount of on-chipROM, RAM, I/O ports

• for applications inwhich cost, power and

space are critical

• single-purpose

Microprocessor vs Microcontroller




1. Meeting the computing needs of the task efficientlyand cost effectively

• speed, the amount of ROM and RAM, the numberof I/O ports and timers, size, packaging, power

consumption• easy to upgrade

• cost per unit

2. Availability of software development tools

• assemblers, debuggers, C compilers, emulator,simulator, technical support

3. Wide availability and reliable sources of themicrocontrollers.

Three criteria in Choosing a

Microcontroller:




Block Diagram:

CPU

On-chip

RAM

On-chip

ROM for

program

code

4 I/O Ports

Timer 0

Serial

PortOSC

Interrupt

Control

External interrupts

Timer 1

Timer/Counter

Bus

Control

TxD RxDP0 P1 P2 P3

Address/Data

Counter

Inputs




Feature 8051 8052 8031

ROM (program space in bytes) 4K 8K 0K

RAM (bytes) 128 256 128

Timers 2 3 2

I/O pins 32 32 32Serial port 1 1 1

Interrupt sources 6 8 6

Comparison of the 8051 Family Members




4K Bytes On Chip ROM

128 bytes On Chip RAM

6 Interrupts

32 I/O channels

Bit Addressability

2 Timers

Features of 8051:




Pin Description of the 8051:

1

23

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

40

3938

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

P1.0

P1.1P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

RST

(RXD)P3.0

(TXD)P3.1

(T0)P3.4

(T1)P3.5

XTAL2

XTAL1

GND

(INT0)P3.2

(INT1)P3.3

(RD)P3.7

(WR)P3.6

Vcc

P0.0(AD0)P0.1(AD1)

P0.2(AD2)

P0.3(AD3)

P0.4(AD4)

P0.5(AD5)

P0.6(AD6)

P0.7(AD7)

EA/VPP

ALE/PROG

PSENP2.7(A15)

P2.6(A14)

P2.5(A13)

P2.4(A12)

P2.3(A11)

P2.2(A10)

P2.1(A9)

P2.0(A8)

8051




8051 Description:

Vcc, gnd and xtal:

• Vcc pin 40

–Vcc provides supply voltage to the chip.

–The voltage source is +5V.

• GND: pin 20 ground

• XTAL1 and XTAL2 pins 19,18




8051 Description:

• Reset: pin 9 reset

– It is an input pin and is active high normally low .

• The high pulse must be high at least 2 machine

cycles. – It is a power-on reset.

• Upon applying a high pulse to RST, the

microcontroller will reset and all values in

registers will be lost.• Reset values of some 8051 registers

Figure (b). Power-On RESET Circuit:




Figure (b). Power On RESET Circuit:

30 pF

30 pF

8.2 K

10 uF

+

Vcc

11.0592 MHz

EA/VPP

X1

X2

RST

31

19

18

9




Pins of 8051:

• EA: pin 31 external access – There is no on-chip ROM in 8031 and 8032 .

– The EA pin is connected to GND to indicate the

code is stored externally.

– PSEN ALE are used for external ROM.

– For 8051, EA pin is connected to Vcc.

• PSEN: pin 29 program store enable

– This is an output pin and is connected to the OE

pin of the ROM.

Pins of 8051:




Pins of 8051:

• ALE: pin 30 address latch enable

– It is an output pin and is active high.

– 8051 port 0 provides both address and data.

– The ALE pin is used for de-multiplexing the

address and data by connecting to the G pin of the 74LS373 latch.

• I/O port pins

–

The four ports P0, P1, P2, and P3. – Each port uses 8 pins.

– All I/O pins are bi-directional.

Pi f I/O P t




Pins of I/O Port:

• The 8051 has four I/O ports

– Port 0: pins 32-39, P0 P0.0-P0.7 – Port 1: pins 1-8 , P1 : P1.0-P1.7

– Port 2: pins 21-28, P2 : P2.0-P2.7

– Port 3: pins 10-17, P3 : P3.0-P3.7

– Each port has 8 pins.

• Named P0.X ,X=0,1,...,7, P1.X, P2.X, P3.X

• Ex: P0.0 is the bit 0, LSB of P0

• Ex: P0.7 is the bit 7, MSB of P0

• These 8 bits form a byte.

• Each port can be used as input or output (bi-direction).




Other Pins:

• P1, P2, and P3 have internal pull-up resisters.

– P1, P2, and P3 are not open drain.

• P0 has no internal pull-up resistors and does notconnects to Vcc inside the 8051.

– P0 is open drain.

• However, for a programmer, it is the same to

program P0, P1, P2 and P3.• All the ports upon RESET are configured as

output.




Port 0 with Pull-Up Resistors:

Pull-up resistors are used in electronic logic circuits to

ensure that inputs to logic systems settle at expected logic

levels if external devices are disconnected.

Pull-up resistors may also be used at the interface

between two different types of logic devices, possibly

operating at different power supply voltages.




P0.0P0.1

P0.2P0.3P0.4P0.5P0.6P0.7

DS5000

8751

8951

Vcc

10 K

P or t

0




Port 3 Alternate Functions:

17RDP3.7

16WR P3.615T1P3.5

14T0P3.4

13INT1P3.3

12INT0P3.2

11TxDP3.1

10RxDP3.0

PinFunctionP3 Bit







ADDRESSING MODES:

There are five addressing modes available in the8051:

• Register

• Direct

• Indirect

• Immediate

• Indexed




REGISTER ADDRESSING:

• 8051 has access to eight working registers (R0

to R7)

• Some instructions are specific to a certain

register, such as the accumulator etc.

Example: ADD A,R7Example: MUL AB




Direct Addressing:

• Direct addressing is so-named because thevalue to be stored in memory is obtained by

directly retrieving it from another memory

location.

Example: MOV A,30h




Indirect Addressing:

• In 8051 assembly language, indirect addressing is

represented by an @ before R0 or R1.

Example: MOV A, @R0

Moves a byte of data from internal RAM atlocation whose address is in R0 to the

accumulator.




Immediate Addressing:

• In assembly language, immediate operands are

preceded by #.

• Operand my be a numeric constant, a symbolic

variable or an arithmetic expression using

constants, symbols and operators.

Example: MOV A,#12




Indexed Addressing:

• Indexed addressing uses a base register (either the

program counter or data pointer) and an offset

(the accumulator) in forming the effective address

for a JMP or MOVC instruction.

Example: MOVC A, @A+DPTR










LED (Light Emitting Diode):

• Light-emitting diodes are elements for light

signalization in electronics.

• They are manufactured in different shapes, colors and

sizes.• Low price, low consumption and simple use

• These LED’s are used for indication purpose i.e., ON

& OFF.




Symbol of LED:

http://commons.wikimedia.org/wiki/File:LED_symbol.svg




Some different colors of LED:

H i f LED i h

http://en.wikipedia.org/wiki/File:RBG-LED.jpg




How to interface LED with

microcontroller ?

• Anode is connected through a resistor to Vcc &

the Cathode is connected to the Microcontroller

pin.

• So when the Port Pin is HIGH the LED is OFF &

when the Port Pin is LOW the LED is turned ON.




Can we connect like this?




Can we connect like this?

• When the port Pin is HIGH the Anode is positive

http://knol.google.com/k/-/-/189gpauady45g/btt8fb/ledinterfacing1.jpg




• When the port Pin is HIGH the Anode is positivewith respect to the Cathode so the LED shouldturn ON right?

• But the internal pull-up resistor comes in serieswith the resistor thus limiting the current flowingthrough the LED. This current is not sufficientenough to Turn ON the LED.




A Simple Program to glow an LED:

ORG 0000H

CLR P1.0 //Turn ON LED

CLR P1.1

CLR P1.2END




A program using port to glow an LED :

ORG 0000H

MOV p1,#OOH //Copy P1 to A

END




A program to ON &OFF the LED:

CASE1:

ORG 0000H

MOV P1,#OFFH

MOV P1,#OOH

END




CASE 2:

ORG 0000H

MOV P1,#OFFH

MOV A,P1

CPL A //ComplimentEND




SWITCH INTERFACING




SWITCH INTERFACING

An electrical switch is any device used to interrupt

the flow of electrons in a circuit. Switches areessentially binary devices: they are eithercompletely on ("closed") or completely off ("open").

• CPU accesses the switches through ports.Therefore these switches are connected to amicrocontroller. This switch is connected between

the supply and ground terminals.

• These switches are connected to an input port.

• In 8051 PORT 1, PORT 2 & PORT 3 have




In 8051 PORT 1, PORT 2 & PORT 3 have

internal 10k Pull-up resistors whereas this Pull-up

resistor is absent in PORT 0. Hence PORT 1, 2

& 3 can be directly used to interface a switch

whereas we have to use an external 10k pull-up

resistor for PORT 0 to be used for switch

interfacing or for any other input.

• When no switch is pressed, reading the input port

will yield 1s since they are all connected to high

(Vcc). But if any switch is pressed, one of the input

port pins will have 0 since the switch pressedprovides the path to ground.




P2.1

Vcc

R

GND

Interfacing switch with the microcontroller

8

0

5

1

Thus now the two conditions are to be




remembered:

• When the switch is open, i.e., when not pressed thetotal supply i.e., Vcc appears at the port pin P2.0

P2.0 = 1

• When the switch is closed i.e., when it is pressed,

the total supply path is provided to ground. Thus

the voltage value at the port pin P2.0 will be zero.

P2.0 = 0




P2.1

Vcc

R

GND

Interfacing Led And Switch with the Microcontroller

8

0

5

1

Vcc

P1.0

Simple program to turn on led when




Simple program to turn on led when

switch is pressed:

ORG 0000H

SETB P1.0

LOOP:JB P2.1, LOOP

CLR P1.0

END




Liquid crystal display (LCD):




• A liquid crystal display (LCD) is a thin, flat panel

used for electronically displaying information suchas text, images, and moving pictures.

• Its uses include monitors for computers,

televisions, instrument panels, and other devices

ranging from aircraft cockpit displays, to every-day consumer devices such as gaming devices,

clocks, watches, calculators, and telephones.

• Among its major features are its lightweight




• Among its major features are its lightweight

construction, its portability, and its ability to be

produced in much larger screen sizes than arepractical for the construction of cathode ray tube

(CRT) display technology.

Why we are using LCD ?




• Its low electrical power consumption enables it to

be used in battery-powered electronic equipment.

It is an electronically-modulated optical device

made up of any number of pixels filled with liquid

crystals and arrayed in front of a light source

(backlight) or reflector to produce images in color

or monochrome.

Why we are using LCD ?




Liquid Crystal Display (LCD )is finding wide spread use

replacing LEDs (seven segment LEDs or other multi

segment LEDs) because of the following reasons:

The declining prices of LCD’s.

The ability to display numbers, characters ,graphics

and limited to numbers and a few characters

Ease of programming for characters and graphics.

Pin Description of LCD:




1. Ground

2. Vcc +5V

3. Contrast control

4. Register select (RS)5. Read/Write (RD/WR)

6. Enable (EN)

7 – 14 pins all are data pins D0 – D715. Vcc +5V }

16. Ground }

Pin Description of LCD:

For backlight purpose

RS (register select):

Th i t l t i i d f th l ti f




The register select pin is used for the selection of the required register either data or command

registerIf RS=0 ; command register is selected

If RS=1 ; data register is selected

R/W (read or write):

This pin is for the selection of read or write mode

If R/W=0 ; write mode is selected

If R/W=1 ; read mode is selected

EN (enable):• Enable pin is a active high to low pin used for

writing the data to the LCD.

LCD COMMAND CODES:




• 01 Clear display screen

• 06 Increment cursor

• 38 2lines and 5 by 7 matrix

• 80 Force cursor to beginning of 1st line

• 0E Display on, cursor blinking

• C0 Force cursor to beginning 0f 2nd line

LCD COMMAND CODES:

LCD INTERFACING WITH MICRO

CONTROLLER:




P0.0P0.1

P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

D0D1

D2

D3

D4

D5

D6

D7RS R/W E

P2.0

P2.1

P2.2

Vss

Vee

Vss

10k

POT

8

05

1

LCD

GND

CONTROLLER:




How To Send Commands To LCD:

COMMAND:

CLR RS

CLR R/W

SETB EN

CLR EN

C




How to send Data to LCD:

DATA:SETB RS

CLR R/W

SETB ENCLR EN

A Si l P Of LCD




A Simple Program Of LCD:

ORG OOH

MOV A,#38H

ACALL COMMAND

MOV A,#0EH

ACALL COMMANDMOV A,# ’H’

ACALL DATA

MOV A,# ‘I’

ACALL DATA

COMMAND : CLR RS

CLR R/W




CLR R/W

SETB EN

CLR ENRET

DATA:

SETB RSCLR R/W

SETB EN

CLR ENRET

END




Relay Interfacing With

Mi ll




Microcontroller

Relay: It can be defined as an electrical switch that opensand closes under the control of another electrical circuit.

The switch is operated by an electromagnet to open or

close one or more of contacts. A relay is able to control an

output circuit of higher power than the input circuit.Relays are devices which allow low power circuits to

switch a relatively high Current/Voltage ON/OFF.

For a relay to operate a suitable pull-in & holding currentshould be passed through its coil.

Generally relay coils are designed to operate from a

particular voltage often its 5V or 12V.

Types:

There are many types of relays which are as




There are many types of relays which are as

follows:

SPDTDPDT

Symbol Of Relay:

• The relay's switch connections are usually labelled

COM NC and NO:




COM, NC and NO:

• COM = Common, always connect to this, it is the

moving part of the switch.

• NC = Normally Closed, COM is connected to this

when the relay coil is off.

• NO = Normally Open, COM is connected to thiswhen the relay coil is on.

• Connect to COM and NO if you want the switched

circuit to be on when the relay coil is on.

• Connect to COM and NC if you want the switched

circuit to be on when the relay coil is off.

Advantages of relays:




g y

• Relays can switch AC and DC, transistors

can only switch DC.

• Relays can switch high voltages, transistors

cannot.

• Relays are a better choice for switching

large currents (> 5A).

• Relays can switch many contacts at once.

Di d Of R l




Disadvantages Of Relay:

• Relays are bulkier than transistors for

switching small currents.

• Relays cannot switch rapidly , transistorscan switch many times per second.

• Relays use more power due to the current

flowing through their coil.

SPDT Relay (Single Pole Double Throw) :




An electromagnetic switch, consist of a coil , 1

common terminal , 1 normally closed terminal ,and one normally open terminal.

When the coil of the relay is at rest (not

energized), the common terminal and thenormally closed terminal have continuity. When

the coil is energized, the common terminal and the

normally open terminal have continuity.

DPDT (Double Pole Double Throw):




• Can be used to isolate float switches from spiking

voltage or excessive current.

• Avoids risk that spiking pump voltage will hurt

float switches.

Specifications:

• Coil voltage: 12VDC

• Coil resistance: 160 Ohms

• Contact rating: 10A at 250VAC or 30VDC.

Why do I want to use a relay and do I really




need to?

• The coil of an SPDT relay that we most commonly

use draws very little current (less than 200

milliamps) and the amount of current that you can

pass through a relay's common, normally closed,and normally open contacts will handle up to 30 or

40 amps. This allows you to switch devices such as

headlights, parking lights, horns, etc.,

SPDT & DPDT:




SPDT & DPDT:

Relay Interfacing with the Microcontroller:




1 U 16

2 L 15

3 N 14

4 2 13

5 8 12

6 0 117 3 10

8 9

RELAY LOAD

Ground Vcc

AT 89S52

P1.0

ULN2003 CURRENT DRIVER:




• The ULN2003 current driver is a high voltage, high

current Darlington arrays each containing sevenopen collector Darlington pairs with common

emitters. Each channel is rated at 500mA and can

withstand peak currents of 600mA.

ULN DRIVER CIRCUIT




This ULN2003 driver can drive seven relays at a

time. The pins 8 and 9 provide ground and Vcc

respectively.

Working Of ULN Driver:




Working Of ULN Driver:

• It can accept seven inputs at a time and produces

seven corresponding outputs. If the input to any

one of the seven input pins is high, then the value

at its corresponding output pin will be low, forexample if the input at pin 6 is high, then the value

at the corresponding output i.e., output at pin 11

will be low. Similarly if the input at a particular

pin is low, then the corresponding output will be

high.

• Thus for the output to be low, the input applied at

that corresponding input pin should be high The




that corresponding input pin should be high. The

input to the ULN driver is provided by the

microcontroller. Thus the instruction required tooperate the relay through the microcontroller is

SETB PX.Y

• Where X is the port number (P0, P1, P2and P3).

• And Y is the pin number of Port X.

Applications:




Applications:

• To control a high-voltage circuit with a low-

voltage signal

• To control a high-current circuit with a low-

current signal,• To detect and isolate faults on transmission and

distribution lines by opening and closing circuit

breakers.




What is communication?




What is communication?

• Communication is nothing but sharing of data or

transferring the data from one system to another.

system1 system2

Types of communication:




In Serial communications means informationis transmitted from source to destination over a

single pathway.

In Parallel Communication, often 8 or more

lines are used to transfer data to a device that is

only a few feet.

COMPUTERS TRANSFER DATA IN

TWO WAYS:




TWO WAYS:

Sender Receiver Sender Receiver

Serial Transfer Parallel Transfer

D0-D7D0

Other control lines

Other control lines

Why we prefer serial transmission

ll l t i i ?




over parallel transmission?

• In Parallel data transfers, often 8 or more lines

are used to transfer data to a device that is only

a few feet.

• Where as serial transmission uses only single

line to transmit the same data over long

distances

• There are chances of loosing data in parallelcommunication rather than in serial

communication.

Simplex vs Duplex Transmission




Simplex vs. Duplex Transmission

• Simplex transmission: the data can sent in one

direction.

– Example: the computer only sends data to the

printer.

• Duplex transmission: the data can be transmitted

and received.

Transmitter Receiver

Transmitter

Receiver Receiver

Transmitter

Half vs Full Duplex




Half vs. Full Duplex

• Half duplex: if the data is transmitted one way at

a time.

• Full duplex: if the data can go both ways at the

same time. Two wire conductors for the data lines.

Transmitter

Receiver

Receiver

Transmitter

Transmitter

Receiver

Receiver

Transmitter

Registers Used in Serial Transfer Circuit




Registers Used in Serial Transfer Circuit

• SBUF (Serial data buffer)

• SCON (Serial control register)

• TMOD (Timer mode register)

SBUF




SBUF

• This is an 8-bit register used for serial

communication in 8051.For a byte of data to be

transferred it must be placed in sbuf register and

in similar way sbuf holds the data when it isreceived.

SCON Register (serial control)




SM0 SM1 SM2 REN TB8 RB8 TI RI

It used to program the start bit, stop bit and data

bits of data framing

SM0 , SM1:

These two bits determine the framing of data by

specifying the number of bits per character, and

the start and stop bits.

SM0 SM1




SM0 SM1

0 0 Serial Mode 0

0 1 Serial Mode 1, 8-bit data, 1 stop bit,

1 start bit

1 0 Serial Mode 2

1 1 Serial Mode 3

RECEIVE - Data receive through the RXD pin starts

upon the two following conditions are met: bit REN=1




and RI=0

(both of them are stored in the SCON register). When all8 bits have been received, the RI bit of the SCON register

is automatically set indicating that one byte receive is

complete.

TRANSMIT - Data transmit is initiated by writing data

to the SBUF register. In fact, this process starts after any

instruction being performed upon this register. When all

8 bits have been sent, the TI bit of the SCON register isautomatically set.

TMOD




TMOD

• TMOD is an 8 bit register in which the lower 4 bits

are set aside for Timer0 and the upper 4 bits for

Timer1.

GATE C/T M0 M1 GATE C/T M1 M0

TMOD -Timers




Bit Number Type Working Timer Type

7 GATE1

Gating Control when

set 1

6 C/T1

To decide whether

timer is used as a

delay generator or

as an event counter

1

5 M1 Timer mode bit 1


3 GATE0Gating Control

Purpose0

2 C/T0

To decide whether

timer is used as a

delay generator or as an event counter

0






M1 M0 Timer ModeDescription

of Mode

0 0 0 13-bit Timer.

0 1 1 16-bit Timer

1 0 28-bit auto-

reload

1 1 3Split timer

mode

RS232




RS232

To ensure fast and reliable data transmission

between two devices

In RS232 it consists of 9 pins but we generally

use only three pins 2,3 and 5 namely TXD RXD

GND respectively.

MAX232To convert TTL or CMOS voltages to RS232




g

voltages, and vice versa

Complementary metal – oxide – semiconductor

(CMOS)

CMOS uses complementary and symmetrical

pairs of p-type and n-type metal oxide

semiconductor field effect transistors (MOSFET’s)

for logic functions.

Two important characteristics of CMOS devicesare high noise immunity and low static power

consumption.

TTL (Transistor transistor logic)




( s s o s s o og c)

• TTL integrated circuits were a standard method

of construction for the processors of mini-

computer and mainframe processors

• Transistor – transistor logic (TTL) is a class of digital circuits built from bipolar junction

transistors (BJT) and resistors. It is called

transistor – transistor logic because both the logic

gating function (e.g., AND) and the amplifying

function are performed by transistors

Baud Rates in the 8051:




• Baud rate is the number of signal changes per

second

• The 8051 transfers and receives data serially atmany different baud rates by using UART.

• UART divides the machine cycle frequency by 32and sends it to Timer 1 to set the baud rate.

• Signal change for each roll over of timer 1.

XTAL

oscillator ÷ 12

÷ 32

By UART

Machine cycle frequency28800 Hz

To timer 1

To set the

Baud rate

921.6 kHz

11.0592 MHz

Timer 1

MAX 232 INTERFACING WITH MICRO

CONTROLLER




135

14TxD0(P3.1)

RxD0(P3.0)

11 11

10 12

2

3

8

0

5

1

M

A

X

2

3

2

D

B

9 GND

CONTROLLER




ANALOG TO DIGITAL CONVERTER




• Analog-to-digital converters are among the most

widely used devices for data acquisition. Digitalsystems use binary values, but in the physical world

everything is continuous i.e., analog values.

Temperature, pressure (wind or liquid), humidity

and velocity are the physical analog quantities.

• These physical quantities are to be converted into

digital values for further processing. Thus, an

analog-to-digital converter is needed to convertthese electrical signals into digital values so that the

microcontroller can read and process them.

ADC0804:




• The ADC chip that is used in this project is

ADC0804. The ADC0804 IC is an 8-bit parallelADC in the family of the ADC0800 series from

National Semiconductor. It works with +5 volts

and has a resolution of 8 bits. In the ADC0804, the

conversion time varies depending on the clocking

signals applied to the CLK IN pin, but it cannot be

faster than 110µs.

PIN Diagram of ADC




Pin description of ADC

CS (Chi l ti )




CS (Chip selection):

Chip select is a active low input used to activatethe ADC 0804.

RD (read):

This is also a active low pin used to get theconverted data out of the ADC 0804.

WR (write):

This is also active low used to inform the ADC tostart the conversion process.

CLK IN & CLK R:

CLK IN is connected to external clock when




external clock is used and if internal clock is used

both clocks are connected to capacitor and aresistor.

INTR (INTERRUPT):

It is an active low output pin using for stop theconversion.

Vin(+) & Vin(-):Vin(+) is used for the conversion of analog todigital by connecting Vin(-) to the ground.

Vcc:It is the +5v power supply to the chip.

Vref/2:




Vref/2:

Pin 9 is used for the reference voltage. If we needthe input range 0-4V, Vref/2 is connected to 2V.

D0-D7:

These are the digital data output pins.

D7 is the MSB.Analog ground & Digital ground:

Analog ground is connected to ground of analogVin while taking the inputs in the same way digital

ground is also used for the digital outputs.

ADC INTERFACE WITH MICROCONTROLLER




89C51

20P2.5P2.6

A P2.7D P1.7

C P1.60 P1.58 P1.40 P1.34 P1.2

P1.1

P1.0

Keypads are a part of HMI or Human Machine Interface and

KEYPAD INTERFACING




Keypads are a part of HMI or Human Machine Interface and

play really important role in a small embedded system where

human interaction or human input is needed. Matrix keypadsare well known for their simple architecture and ease of

interfacing with any microcontroller.

Interfacing the Keyboard to the 8051

At the lowest level, keypads are organized in a matrix of rows

and columns. The CPU accesses both rows and column

through ports; therefore, an 4*4 matrix of keys can be

connected to a microprocessor. When a key pressed, a row andcolumn make a connect; otherwise, there is no connection

between row and column.

Constructing a Matrix Keypad:

Construction of a keypad is really simple. As per the




yp y p p

outline shown in the figure below we have four rows and

four columns. In between each overlapping row andcolumn line there is a key.keeping this outline we can

construct a keypad using simple SPST Switches as

shown below:

Consider an example




Row4-row1 = 1110

Col4-col1 = 1011

That means the row 1 and the col 3 intersected i.e.

sw3 is pressed.



Date post:	03-Apr-2018
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Theory - Basic Electrical and Electronic Components

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