Report_car Parking System

8/9/2019 Report_car Parking System

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CAR PARKING SYSTEM

Introduction:

In the project Car Parking System we have shown the concept of an automatic car

parking system. As in the modern world everything is going automatic we have

built a system which will automatically sense the entry and exit of cars through

the gate and then display the number of cars in the parking lot. Even we can set a

maximum capacity of cars with the help of user interface given in the hardware in

the form of switches so that there is no congestion. We have deployed a

microcontroller which is used to sense the movement of cars and depending upon

whether there is a capacity of cars to enter, it either opens the gate or not. It is

also possible to open a gate when any car enters in the parking lot or close the

door when a car exits from the parking lot.

There are two sets of sensors: one on the first gate (entry gate) and one on the second

gate (exit gate). When a car arrives at the door the microcontroller receives the

signal from the entry sensors and then checks whether there is a capacity of cars

to be accommodated. Simultaneously it will also display the number of cars

present in the parking lot on a LCD screen and also opens the gate. When a car

moves out of the parking area the microcontroller reduces the count displayed

accordingly and also closes the gate. The user will have an option to set the

maximum count for the cars with the help of switches connected to the

microcontroller.

The sensing of entry and exit of cars is done with the help of Infrared transmitters and

receivers. Before the door the Infrared transmitter is mounted on one side and the

receiver is placed directly in front of the transmitter across the door. When a car

arrives the Infrared beam is blocked by the car and the receiver is devoid of

Infrared rays and its output changes. This change in output is sensed by the

microcontroller and accordingly it increments the count and opens the door if

there is some capacity. The procedure for the exit of the cars is similar as the

entry.


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Block Diagram of the Project:

Microcontroller unit:

Microcontroller used in the project is AT89s52. This part is the heart of the project. It

checks for the entry and exit of the car. It continuously polls the pins from where we

receive the signal from the intruder circuits.

MICROCONTROLLER

LCD ISOLATOR

CIRCUIT

KEY PAD

POWER

SUPPLY1

(+5V)

INTRUDER2

(FOR EXIT

GATE)

INTRUDER1

(FOR ENTRY

GATE)

AMPLIFIER

MOTOR

BUZZER


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When it detects the car from the entry gate then it checks whether there is any vacant

space in the parking lot. If there is vacant space then it opens the door and increases

the over all count in the parking lot by one. And after 3 seconds automatically closes

the door. And if it detects the car from the exit gate then it decreases the count by one.

Interfacing with switches (keypad):

Interfacing with keypad makes instrument menu driven user friendly. This will help to

the user to select the maximum capacity of the parking area.

Display unit (LCD)

LCD makes this instrument user friendly by displaying everything on the display. It is

an intelligent LCD module, as it has inbuilt controller which convert the alphabet anddigit into its ASCII code and then display it by its own i.e. we do not required to

specify which LCD combination must glow for a particular alphabet or digit.

Stepper Motor:

Stepper motor is used to open and close the door. It is interfaced with microcontroller

and takes command from the microcontroller to rotate some particular specified angle.

It can be interfaced with MCU as shown below:

The switching circuit is comprises of an optocoupler which will isolate the controller

from the outer spikes or fluctuations or from the external hardware and at the same

OPTOISOLATOR

IC (MCT- 2E)

POWER AMPLIFIER

USING BC369

TRANSISTOR

Motor Winding


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time it drives a power transistor i.e. make it on when a signal from the controller pin

is applied to it. Optocoupler actually comprises of a diode and a phototransistor. It

comes in a DIP IC package. Thus signal from the MCU is given to the LED part or

the driving part. When LED begins to glow then the phototransistor acts as on switch

or short circuit. This output is given to power transistor, which will amplify the

current of the signal and then use it to drive winding of the Motor. Ground is directly

given to the common of the Motor. And +vcc is provided to the motor winding

through the amplifier.

If user wants to switch ON the Motor winding, then the microcontroller is sending a

signal to the optocoupler then ultimately that supply to that winding is ON. Reverse is

the case when MCU does not send any signal and thus, supply to that winding is OFF.

Intruder:

The 555 timer is used in the Infrared transmitters and receivers. At the transmitter it is

used to produce a pulse of 38 kHz. This pulse is then fed to the Infrared LED so that it

produces bursts of Infrared energy at the rate of 38 kHz. The reason of transmitting

frequency being this much particular value is that the Infrared receiver (i.e. TSOP

1738) works at maximum efficiency when the Infrared rays falling on it, are of 38

kHz. At the receiver the 555 timer is used to pass the output of the Infrared receiver to

the microcontroller. We are using the 555 timer in monostable operation where one

external resistor and capacitor control the pulse width. The 555 timer has a number of

features. When there is a person between receiver and transmitter then the trigger pin

gets low due to which at the output pin of timer we get a high pulse. This high pulse is

applied to the pin of microcontroller which in turn senses this pin and activates the

next task.


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N C

< D o c > < R e v C

< T i t l e >

A

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T i t l e

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Q 1B C 5 4 7

1

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T O M I C R O C O N T R O L L E R G R O U N D

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T O M I C R O C O N T R O L L E R P O R T 2 . 1

8

R 1 - 1 0 0 K , R 2 - 1 K , R 3 - 4 7 0 E , R 4 - 4 7 K

6

R 1R

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C 1 - 2 2 M F / 2 5 V , C 2 - 1 0 4 P F

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2

Entrance or Exit Detector:

The entrance or the exit of a person in the room is detected by using two infrared

modules. Each module will contain an IR transmitter and an IR receiver. Before the

door the Infrared transmitter is mounted on one side and the receiver is placed directly

in front of the transmitter on the other side of door. Infrared transmitter will

continuously transmit IR waves and the receiver will continuously receive IR waves.

The IR transmitter will use an IR LED. This LED can transmit IR whenever it is

supplied from a 5-volt voltage source. The receiver can either be photodiode if the

width of the door is less or a special IR receiver known as the IR eye. Now whether a

person enters or exits, the beam of each module will be interrupted that is the output

from the two receivers which actually is the pulse output from two different

monostable multivibrator using 555 timers. Thus the outputs from the two receivers

are in the form of pulse.


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BLOCK DIAGRAM FOR IR RECEIVER

O/P TO MCU OUTPUT IR INPUT

At the receiver side the IR eye or the IR demodulator will demodulate the IR signal

and then give its output to the trigger of a 555 timer, which is mounted as a

monostable vibrator. Thus whenever there is an interrupt in the IR beam then

corresponding trigger will go from high to low thus the output from the 555 timer will

be a pulse which is then generated as in monostable mode by applying a ve voltage

at the trigger a pulse is generated.

Features of the Project:

Powered by +5V & +12V supply

Current consumption 0.45mA for Microcontroller circuit, 0.75mA for

switching circuit, 200mA for amplification circuit

Automatic detection of any incoming/outgoing car

Automatic opening and closing of entry gate

User interface using LCD and switches

Always display the number of cars present in the Parking Lot

Various Components used in various Modules of the Project along

with specifications and quantity:

Power Supply Unit1 (+5V):

S. No. Component Specification Qty.

1. PCB Designed 1

2. Transformer 9-0-9,

500mA

1

3. Diode 1N4007 4

4. Cap. 1000 F 1

5. Regulator 7805 1

POWER

SUPPLY

555 TIMERPHOTODIODE


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Power Supply Unit2 (+12V):


1. PCB Designed 1

2. Transformer 9-0-9,500mA

1

3. Diode 1N4007 4

4. Cap. 1000 F 1

5. Regulator 7812 1

Microcontroller Unit:


1. PCB Designed 1

2. Base 40 Pin 13. Crystal 11.0592MHZ 1

4. Cap. 33 PF 2

10F 1

5. MCU AT89s52 1

6. Micro switch 1

7. Resistance 10K 1

LCD Module:


1. LCD Connector 16 Pin 12. LCD 16 x 2 1

Keypad Module (For input to MCU):


1. PCB G.P.PCB 1

2. Micro Switches 2 Pin 3

Intruder Module1 (For Entry gate):


1. PCB Designed 1

2. Base 8 Pin 1

3. IC Timer 555 1

4. Resistance 10K 1

470 1

100K 1

5. IR Pair 1

6. Capacitor 10F 1

103 (0.01 F) 1


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Intruder Module2 (For Exit gate):


1. PCB Designed 1

2. Base 8 Pin 13. IC Timer 555 1

4. Resistance 10K 1

470 1

100K 1

5. IR Pair 1

6. Capacitor 10F 1

103 (0.01 F) 1

Motor Driver Card:


1. PCB Designed 1

General 1

2. Base 6 Pin 4

3. Opto coupler 817 4

4. Resistance 470 4

5. Transistor 369 4

6. Stepper Motor 12V 1

Detailed Hardware Description:

POWER SUPPLY

Power supplies are designed to convert high voltage AC mains to a suitable low

voltage supply for electronics circuits and other devices. A power supply can be

broken down into a series of blocks, each of which performs a particular function.

For example a 5V regulated supply:

Each of the block has its own function as described below

1. Transformer steps down high voltage AC mains to low voltage AC.

2. Rectifier converts AC to DC, but the DC output is varying.


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3. Smoothing smoothes the DC from varying greatly to a small ripple.

4. Regulator eliminates ripple by setting DC output to a fixed voltage.

TRANSFORMER

Transformers convert AC electricity from one voltage to another with little loss of

power. Transformers work only with AC and this is one of the reasons why

mains electricity is AC. The two types of transformers

Step-up transformers increase voltage,

Step-down transformers reduce voltage.

Transformer

Most power supplies use a step-down transformer to reduce the dangerously

high mains voltage (230V in UK) to a safer low voltage. The input coil is

called the primary and the output coil is called the secondary. There is no

electrical connection between the two coils, instead they are linked by an

alternating magnetic field created in the soft-iron core of the transformer. Thetwo lines in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power

in. Note that as voltage is stepped down current is stepped up. The ratio of the number

of turns on each coil, called the turn ratio, determines the ratio of the voltages. A step-

down transformer has a large number of turns on its primary (input) coil which is

connected to the high voltage mains supply, and a small number of turns on its

secondary (output) coil to give a low output voltage.


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Turns ratio = Vp = Np

Vs Ns

And Power Out = Power In

Vs Is = Vp Ip

Where

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

Ns = number of turns on secondary coil

Is = secondary (output) current

Vs = secondary (output) voltage

BRIDGE RECTIFIER

A bridge rectifier can be made using four individual diodes, but it is also available in

special packages containing the four diodes required. It is called a full-wave rectifier

because it uses all AC wave (both positive and negative sections). 1.4V is used up in

the bridge rectifier because each diode uses 0.7V when conducting and there are

always two diodes conducting, as shown in the diagram below. Bridge rectifiers are

rated by the maximum current they can pass and the maximum reverse voltage they

can withstand (this must be at least three times the supply RMS voltage so the

rectifier can withstand the peak voltages). In this alternate pairs of diodes conduct,

changing over the connections so the alternating directions of AC are converted to the

one direction of DC.


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OUTPUT Full-wave Varying DC

SMOOTHING

Smoothing is performed by a large value electrolytic capacitor connected across the

DC supply to act as a reservoir, supplying current to the output when the varying

DC voltage from the rectifier is falling. The diagram shows the unsmoothed

varying DC (dotted line) and the smoothed DC (solid line). The capacitor charges

quickly near the peak of the varying DC, and then discharges as it supplies current to

the output.

Note that smoothing significantly increases the average DC voltage to almost the peak

value (1.4 RMS value). For example 6V RMS AC is rectified to full wave DC of

about 4.6V RMS (1.4V is lost in the bridge rectifier), with smoothing this

increases to almost the peak value giving 1.4 4.6 = 6.4V smooth DC.


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Smoothing is not perfect due to the capacitor voltage falling a little as it discharges,

giving a small ripple voltage. For many circuits a ripple which is 10% of the supply

voltage is satisfactory and the equation below gives the required value for the

smoothing capacitor. A larger capacitor will give fewer ripples. The capacitor value

must be doubled when smoothing half-wave DC.

Smoothing capacitor for 10% ripple, C = 5 Io

Vs f

Where

C = smoothing capacitance in farads (F)

Io = output current from the supply in amps (A)

Vs = supply voltage in volts (V), this is the peak value of the unsmoothed

DC

f = frequency of the AC supply in hertz (Hz), 50Hz in the UK

REGULATOR

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable

output voltages. They are also rated by the maximum current they can pass. Negative

voltage regulators are available, mainly for use in dual supplies. Most regulators

include some automatic protection from excessive current (overload protection') and

overheating (thermal protection'). Many of the fixed voltage regulator ICs has 3 leads

and look like power transistors, such as the 7805 +5V 1A regulator shown on the

right. They include a hole for attaching a heat sink if necessary.


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Working of Power Supply

Transformer

The low voltage AC output is suitable for lamps, heaters and special AC motors. It is

not suitable for electronic circuits unless they include a rectifier and a smoothing

capacitor.

Transformer + Rectifier

The varying DC output is suitable for lamps, heaters and standard motors. It is not

suitable for electronic circuits unless they include a smoothing capacitor.

Transformer + Rectifier + Smoothing


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The smooth DC output has a small ripple. It is suitable for most electronic circuits.

Transformer + Rectifier + Smoothing + Regulator

D 2

C 1

1 0 0 0 u f

1 N 4 0 0 7 + 5

V

L M 7 8 0 5

1 2

3

V I N V O U T

G

N

D

J 1

1

2

3

D 3

g n d

D 4

D 1

The regulated DC output is very smooth with no ripple. It is suitable for all electronic

circuits.

The Microcontroller:

In our day to day life the role of micro-controllers has been immense. They are used

in a variety of applications ranging from home appliances, FAX machines, Video

games, Camera, Exercise equipment, Cellular phones musical Instruments to

Computers, engine control, aeronautics, security systems and the list goes on.

Microcontroller versus Microprocessors:


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What is the difference between a microprocessor and microcontroller? The

microprocessors (such as 8086, 80286, 68000 etc.) contain no RAM, no ROM and no

I/O ports on the chip itself. For this reason they are referred as general- purpose

microprocessors. A system designer using general- purpose microprocessor must add

external RAM, ROM, I/O ports and timers to make them functional. Although the

addition of external RAM, ROM, and I/O ports make the system bulkier and much

more expensive, they have the advantage of versatility such that the designer can

decide on the amount of RAM, ROM and I/o ports needed to fit the task at hand. This

is the not the case with microcontrollers. A microcontroller has a CPU (a

microprocessor) in addition to the fixed amount of RAM, ROM, I/O ports, and

timers are all embedded together on the chip: therefore, the designer cannot add any

external memory, I/O, or timer to it. The fixed amount of on chip RAM, ROM, and

number of I/O ports in microcontrollers make them ideal for many applications in

which cost and space are critical. In many applications, for example a TV remote

control, there is no need for the computing power of a 486 or even a 8086

microprocessor. In many applications, the space it takes, the power it consumes, and

the price per unit are much more critical considerations than the computing power.

These applications most often require some I/O operations to read signals and turn on

and off certain bits. It is interesting to know that some microcontrollers manufactures

have gone as far as integrating an ADC and other peripherals into the

microcontrollers.

Microcontrollers for Embedded Systems:

In the literature discussing microprocessors, we often see a term embedded system.

Microprocessors and microcontrollers are widely used in embedded system products.

An embedded product uses a microprocessor (or microcontroller) to do one task and

one task only. A printer is an example of embedded system since the processor inside

it performs one task only: namely, get data and print it. Contrasting this with a IBM

PC which can be used for a number of applications such as word processor, print

server, network server, video game player, or internet terminal. Software for a variety

of applications can be loaded and run. Of course the reason a PC can perform myriad

tasks is that it has RAM memory and an operating system that loads the application

software into RAM and lets the CPU run it. In an embedded system, there is only oneapplication software that is burned into ROM. A PC contains or is connected to


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various embedded products such as the keyboard, printer, modem, disk controller,

sound card, CD-ROM driver, mouse and so on. Each one of these peripherals has a

microcontroller inside it that performs only one task. For example, inside every mouse

there is a microcontroller to perform the task of finding the mouse position and

sending it to the PC.

Although microcontrollers are the preferred choice for many embedded systems,

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

many years the manufacturers for general-purpose microprocessors have targeted

their microprocessor for the high end of the embedded market.

Introduction to 8051:

In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051. This

microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one

serial port, and four ports (8-bit) all on a single chip. The 8051 is an 8-bit processor,

meaning the CPU can work on only 8- bit pieces to be processed by the CPU. The

8051 has a total of four I/O ports, each 8- bit wide. Although 8051 can have a

maximum of 64K bytes of on-chip ROM, many manufacturers put only 4K bytes on

the chip.

The 8051 became widely popular after Intel allowed other

manufacturers to make any flavor of the 8051 they please with the condition that they

remain code compatible with the 8051. This has led to many versions of the 8051 with

different speeds and amount of on-chip ROM marketed by more than half a dozen

manufacturers. It is important to know that although there are different flavors of the

8051, they are all compatible with the original 8051 as far as the instructions are

concerned. This means that if you write your program for one, it will run on any one

of them regardless of the manufacturer. The major 8051 manufacturers are Intel,

Atmel, Dallas Semiconductors, Philips Corporation, Infineon.

AT89C51 From ATMEL Corporation:

This popular 8051 chip has on-chip ROM in the form of flash memory. This is ideal

for fast development since flash memory can be erased in seconds compared to


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twenty minutes or more needed for the earlier versions of the 8051. To use the

AT89C51 to develop a microcontroller-based system requires a ROM burner that

supports flash memory: However, a ROM eraser is not needed. Notice that in flash

memory you must erase the entire contents of ROM in order to program it again. The

PROM burner does this erasing of flash itself and this is why a separate burner is not

needed. To eliminate the need for a PROM burner Atmel is working on a version of

the AT89C51 that can be programmed by the serial COM port of the PC.

Atmel Microcontroller AT89C51

Hardware features

40 pin Ic.

4 Kbytes of Flash.

128 Bytes of RAM.

32 I/O lines.

Two16-Bit Timer/Counters.

Five Vector.

Two-Level Interrupt Architecture.

Full Duplex Serial Port.

On Chip Oscillator and Clock Circuitry.

Software features

Bit Manipulations

Single Instruction Manipulation


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Separate Program And Data Memory

4 Bank Of Temporary Registers

Direct, Indirect, Register and Relative Addressing.

In addition, the AT89C51 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The Idle Mode

stops the CPU while allowing the RAM, timer/counters, serial port and interrupt

system to continue functioning. The Power Down Mode saves the RAM contents but

freezes the oscillator disabling all other chip functions until the next hardware reset.

The Atmel Flash devices are ideal for developing, since they can be reprogrammed

easy and fast. If we need more code space for our application, particularly for

developing 89Cxx projects with C language. Atmel offers a broad range of

microcontrollers based on the 8051 architecture, with on-chip Flash program memory.
http://www.atmel.com/atmel/products/prod71.htmhttp://www.atmel.com/atmel/products/prod71.htm


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Interal Architecture of AT89C51

Pin description:

The 89C51 have a total of 40 pins that are dedicated for various functions such as I/O,

RD, WR, address and interrupts. Out of 40 pins, a total of 32 pins are set aside for the


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four ports P0, P1, P2, and P3, where each port takes 8 pins. The rest of the pins are

designated as Vcc, GND, XTAL1, XTAL, RST, EA, and PSEN. All these pins except

PSEN and ALE are used by all members of the 8051 and 8031 families. In other

words, they must be connected in order for the system to work, regardless of whether

the microcontroller is of the 8051 or the 8031 family. The other two pins, PSEN and

ALE are used mainly in 8031 based systems.

Vcc

Pin 40 provides supply voltage to the chip. The voltage source is +5V.

GND

Pin 20 is the ground.

Oscillator Characteristics:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier

which can be configured for use as an on-chip oscillator, as shown in Figure. Either a

quartz crystal or ceramic resonator may be used. To drive the device from an external

clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in

Figure.


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Oscillator Connections

It must be noted that there are various speeds of the 8051 family. Speed refers to the

maximum oscillator frequency connected to the XTAL. For example, a 12 MHz chip

must be connected to a crystal with 12 MHz frequency or less. Likewise, a 20 MHz

microcontroller requires a crystal frequency of no more than 20 MHz. When the 8051

is connected to a crystal oscillator and is powered up, we can observe the frequency

on the XTAL2 pin using oscilloscope.

RST

Pin 9 is the reset pin. It is an input and is active high (normally low). Upon

applying a high pulse to this pin, the microcontroller will reset and terminate all

activities. This is often referred to as a power on reset. Activating a power-on reset

will cause all values in the registers to be lost. Notice that the value of Program

Counter is 0000 upon reset, forcing the CPU to fetch the first code from ROM

memory location 0000. This means that we must place the first line of source code in

ROM location 0000 that is where the CPU wakes up and expects to find the first

instruction. In order to RESET input to be effective, it must have a minimum duration

of 2 machine cycles. In other words, the high pulse must be high for a minimum of 2

machine cycles before it is allowed to go low.

EA

All the 8051 family members come with on-chip ROM to store programs. In such

cases, the EA pin is connected to the Vcc. For family members such as 8031 and 8032

in which there is no on-chip ROM, code is stored on an external ROM and is fetched

by the 8031/32. Therefore for the 8031 the EA pin must be connected to ground to

indicate that the code is stored externally. EA, which stands for external access, is


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pin number 31 in the DIP packages. It is input pin and must be connected to either Vcc

or GND. In other words, it cannot be left unconnected.

PSEN

This is an output pin. PSEN stands for program store enable. It is the read

strobe to external program memory. When the microcontroller is executing from

external memory, PSEN is activated twice each machine cycle.

ALE

ALE (Address latch enable) is an output pin and is active high. When

connecting a microcontroller to external memory, port 0 provides both address and

data. In other words the microcontroller multiplexes address and data through port 0

to save pins. The ALE pin is used for de-multiplexing the address and data by

connecting to the G pin of the 74LS373 chip.

I/O port pins and their functions

The four ports P0, P1, P2, and P3 each use 8 pins, making them 8-bit ports.

All the ports upon RESET are configured as output, ready to be used as output ports.

To use any of these as input port, it must be programmed.

Port 0

Port 0 occupies a total of 8 pins (pins 32 to 39). It can be used for input

or output. To use the pins of port 0 as both input and output ports, each pin

must be connected externally to a 10K-ohm pull-up resistor. This is due to fact

that port 0 is an open drain, unlike P1, P2 and P3. With external pull-up

resistors connected upon reset, port 0 is configured as output port. In order to

make port 0 an input port, the port must be programmed by writing 1 to all the

bits of it. Port 0 is also designated as AD0-AD7, allowing it to be used for

both data and address. When connecting a microcontroller to an external

memory, port 0 provides both address and data. The microcontroller

multiplexes address and data through port 0 to save pins. ALE indicates if P0

has address or data. When ALE=0, it provides data D0-D7, but when ALE=1

it has address A0-A7. Therefore, ALE is used for de-multiplexing address and

data with the help of latch 74LS373.

Port 1


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Port 1 occupies a total of 8 pins (pins 1 to 8). It can be used as input or

output. In contrast to port 0, this port does not require pull-up resistors since it

has already pull-up resistors internally. Upon reset, port 1 is configures as an

output port. Similar to port 0, port 1 can be used as an input port by writing 1

to all its bits.

Port 2

Port 2 occupies a total of 8 pins (pins 21 to 28). It can be used as input

or output. Just like P1, port 2 does not need any pull-up resistors since it has

pull-up resistors internally. Upon reset port 2 is configured as output port. To

make port 2 as input port, it must be programmed as such by writing 1s to it.

Port 3

Port 3 occupies a total of 8 pins (pins 10 to 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 output port upon reset, this is not the way

it is most commonly used. Port 3 has an additional function of providing some

extremely important signals such as interrupts. Some of the alternate functions

of P3 are listed below:

P3.0 RXD (Serial input)

P3.1 TXD (Serial output)

P3.2 INT0 (External interrupt 0)

P3.3 INT1 (External interrupt 1)

P3.4 T0 (Timer 0 external input)

P3.5 T1 (Timer 1 external input)

P3.6 WR (External memory write strobe)

P3.7 RD (External memory read strobe)

Memory Space Allocation

1. Internal ROM


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The 89C51 has 4K bytes of on-chip ROM. This 4K bytes ROM

memory has memory addresses of 0000 to 0FFFh. Program addresses higher

than 0FFFh, which exceed the internal ROM capacity, will cause the

microcontroller to automatically fetch code bytes from external memory.

Code bytes can also be fetched exclusively from an external memory,

addresses 0000h to FFFFh, by connecting the external access pin to ground.

The program counter doesnt care where the code is: the circuit designer

decides whether the code is found totally in internal ROM, totally in external

ROM or in a combination of internal and external ROM.

2. Internal RAM

The 1289 bytes of RAM inside the 8051 are assigned addresses 00 to7Fh. These 128 bytes can be divided into three different groups as follows:

1. A total of 32 bytes from locations 00 to 1Fh are set aside for register

banks and the stack.

2. A total of 16 bytes from locations 20h to 2Fh are set aside for bit

addressable read/write memory and instructions.

A total of 80 bytes from locations 30h to 7Fh are used for read and write storage, or

what is normally called a scratch pad. These 80 locations of RAM are widely used for

the purpose of storing data and parameters by 8051 programmers.

Interfacing of Microcontroller with LCD

The LCD, which is used as a display in the system, is LMB162A. The main features

of this LCD are: 16*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.

LCD pin description


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Liquid Crystal Display:

Liquid 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.

LCD pin description:

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.

Pin Symbol I/O Description

1 VSS - Ground

2 VCC - +5V power supply

3 VEE - Power supply to control contrast

4 RS I RS=0 to select command register, RS=1 to select data

register.

5 R/W I R/W=0 for write, R/W=1 for read

6 E I/O Enable

7 DB0 I/O The 8 bit data bus









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V c c

1 6

1 5

1 4

1 3

1 2

1 1

1 0

9

8

6

5

4

3

2

1

7

1 6

1 5

1 4

1 3

1 2

1 1

1 0

9

8

6

5

4

3

2

1

7

D 7

E

V c c

D 4

C o n t r a s tR S

G n d

R / W

G n d

D 0

D 3

D 6D 5

3

2

D 2D 1

LCD Pin Description Diagram

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.

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 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.

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.

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.

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 LCDs 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.


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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.

Interfacing of micro controller with LCD display:

In 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", 160s 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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Interfacing of Microcontroller with LCD

LCD Command Code

555Timer:

The 8-pin 555

timer must be

one of the most

useful ICs ever

made and it is

used in many projects. With

AT89C5

1

9181929

30

31

12345678

2122232425262728

1011121314151617

3938373635343332

RSTXTAL2XTAL1PSEN

ALE/PROG

EA/VPP

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7

P2.0/A8P2.1/A9P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15

P3.0/RXDP3.1/TXDP3.2/INTOP3.3/INT1P3.4/TOP3.5/T1P3.6/WRP3.7/RD

P0.0/AD0P0.1/AD1P0.2/AD2P0.3/AD3P0.4/AD4P0.5/AD5P0.6/AD6P0.7/AD7

123456789

101112131415

16

12345678910111213141516VCC

VCC

13

33pF

33pF

VCCVCC

22uF

VCC

8.

2

K

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 57 matrix


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just a few external components it can be used to build many circuits, not all of them

involve timing!

A popular version is the NE555 and this is suitable in most cases where a '555 timer'

is specified. The 556 is a dual version of the 555 housed in a 14-pin package, the two

timers (A and B) share the same power supply pins. The circuit diagrams on this page

show a 555, but they could all be adapted to use one half of a 556.

Low power versions of the 555 are made, such as the ICM7555, but these should only

be used when specified (to increase battery life) because their maximum output

current of about 20mA (with a 9V supply) is too low for many standard 555 circuits.

The ICM7555 has the same pin arrangement as a standard 555.

The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the

circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output

on the right. Usually just the pin numbers are used and they are not labeled with their

function.

The 555 and 556 can be used with a supply voltage (Vs) in the range 4.5 to 15V (18V

absolute maximum).


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Standard 555 and 556 ICs create a significant 'glitch' on the supply when their output

changes state. This is rarely a problem in simple circuits with no other ICs, but in

more complex circuits a smoothing capacitor (eg 100F) should be connected across

the +Vs and 0V supply near the 555 or 556.

The input and output pin functions are described briefly below and there are fuller

explanations covering the various circuits:

Astable - producing a square wave

Monostable - producing a single pulse when triggered

Bistable - a simple memory which can be set and reset

Buffer- an inverting buffer (Schmitt trigger)

Inputs of 555/556

Trigger input: when < 1/3 Vs ('active low') this makes the output high (+Vs). It

monitors the discharging of the timing capacitor in an astable circuit. It has a high

input impedance > 2M .

Threshold input: when >2

/3 Vs ('active high') this makes the output low (0V)*. Itmonitors the charging of the timing capacitor in astable and monostable circuits. It has

a high input impedance > 10M .

* providing the trigger input is > 1/3 Vs, otherwise the trigger input will override the

threshold input and hold the output high (+Vs).

Reset input: when less than about 0.7V ('active low') this makes the output low

(0V), overriding other inputs. When not required it should be connected to +Vs. It has

an input impedance of about 10k .
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Control input: this can be used to adjust the threshold voltage which is set internally

to be 2/3 Vs. Usually this function is not required and the control input is connected to

0V with a 0.01F capacitor to eliminate electrical noise. It can be left unconnected if

noise is not a problem.

The discharge pin is not an input, but it is listed here for convenience. It is connected

to 0V when the timer output is low and is used to discharge the timing capacitor in

astable and monostable circuits.

Output of 555/556

The output of a standard 555 or 556 can sink and sourceup to 200mA. This is more

than most ICs and it is sufficient to supply many output transducers directly, including

LEDs (with a resistor in series), low current lamps, piezo transducers, loudspeakers

(with a capacitor in series), relay coils (with diode protection) and some motors (with

diode protection). The output voltage does not quite reach 0V and +Vs, especially if a

large current is flowing.

To switch larger currents you can connect a transistor.

The ability to both sink and source current means that two devices can be connectedto the output so that one is on when the output is low and the other is on when the

output is high. The diagram shows two LEDs connected in this way. This

arrangement is used in the

Disco Lights project to

make the LEDs flash

alternately.
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555/556 Astable

An astable circuit produces a 'square

wave', this is a digital waveform with

sharp transitions between low (0V) and

high (+Vs). Note that the durations of

the low and high states may be different.

The circuit is called an astable because

it is not stable in any state: the output is

continually changing between 'low' and

'high'.

The time period (T) of the square wave is the time for one complete cycle, but it is

usually better to considerfrequency (f) which is the number of cycles per second.

T = 0.7 (R1 + 2R2) C1 and f =1.4

(R1 + 2R2) C1

T = time period in seconds (s)

f = frequency in hertz (Hz)

R1 = resistance in ohms ( )


C1 = capacitance in farads (F)

The time period can be split into two parts: T = Tm + Ts

Mark time (output high): Tm = 0.7 (R1 + R2) C1

Space time (output low): Ts = 0.7 R2 C1

Many circuits require Tm and Ts to be almost equal; this is achieved if R2 is much

larger than R1.

For a standard astable circuit Tm cannot be less than Ts, but this is not too restricting

because the output can both sink and source current. For example an LED can be

made to flash briefly with long gaps by connecting it (with its resistor) between +Vs

and the output. This way the LED is on during Ts, so brief flashes are achieved with

R1 larger than R2, making Ts short and Tm long. If Tm must be less than Ts a diode

can be added to the circuit as explained under duty cycle below.

555 astable output, a square wave

(Tm and Ts may be different)

555 astable circuit
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Choosing R1, R2 and C1

R1 and R2 should be in the range

1k to 1M . It is best to choose

C1 first because capacitors are

available in just a few values.

Choose C1 to suit the frequency range you require (use the table as a guide).

Choose R2 to give the frequency (f) you require. Assume that R1 is much

smaller than R2 (so that Tm and Ts are almost equal), then you can use:

R2 =0.7

f C1

Choose R1 to be about a tenth of R2 (1k min.) unless you want the mark

time Tm to be significantly longer than the space time Ts.

If you wish to use a variable resistor it is best to make it R2.

If R1 is variable it must have a fixed resistor of at least 1k in series

(this is not required for R2 if it is variable).

Astable operation

With the output high (+Vs) the capacitor C1 is charged by current flowing through R1

and R2. The threshold and trigger inputs monitor the capacitor voltage and when it

reaches 2/3Vs (threshold voltage) the output becomes low and the discharge pin is

connected to 0V.

555 astable frequencies

C1R2 = 10k

R1 = 1k

R2 = 100k

R1 = 10k

R2 = 1M

R1 = 100k

0.001F 68kHz 6.8kHz 680Hz

0.01F 6.8kHz 680Hz 68Hz

0.1F 680Hz 68Hz 6.8Hz

1F 68Hz 6.8Hz 0.68Hz

10F 6.8Hz0.68Hz

(41 per min.)

0.068Hz

(4 per min.)


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The capacitor now discharges with current flowing through R2 into the discharge pin.

When the voltage falls to 1/3Vs (trigger voltage) the output becomes high again and

the discharge pin is disconnected, allowing the capacitor to start charging again.

This cycle repeats continuously unless the reset input is connected to 0V which forces

the output low while reset is 0V.

An astable can be used to provide the clock signal for circuits such as counters.

A low frequency astable (< 10Hz) can be used to flash an LED on and off, higher

frequency flashes are too fast to be seen clearly. Driving a loudspeaker or piezo

transducer with a low frequency of less than 20Hz will produce a series of 'clicks'

(one for each low/high transition) and this can be used to make a simple metronome.

An audio frequency astable (20Hz to 20kHz) can be used to produce a sound from a

loudspeaker or piezo transducer. The sound is suitable for buzzes and beeps. The

natural (resonant) frequency of most piezo transducers is about 3kHz and this will

make them produce a particularly loud sound.

Duty cycle

The duty cycle of an astable circuit is the proportion of the complete cycle for which

the output is high (the mark time). It is usually given as a percentage.

For a standard 555/556 astable circuit the mark time (Tm) must be greater than the

space time (Ts), so the duty cycle must be at least 50%:

Duty cycle =Tm

=R1 + R2

Tm + Ts R1 + 2R2


35/65

555/556 Monostable

A monostable circuit produces a single output pulse when triggered. It is called a

monostable because it is stable in just one state: 'output low'. The 'output high' state is

temporary.

555 monostable out, a single pulse

555 monostable circuit with manual trigger

The duration of the pulse is called the time period (T) and this is determined by

resistor R1 and capacitor C1:

time period, T = 1.1 R1 C1

T = time period in seconds (s)


C1 = capacitance in farads (F)

The maximum reliable time period is about 10 minutes.


36/65

Why 1.1? The capacitor charges to 2/3 = 67% so it is a bit longer than the

time constant (R1 C1) which is the time taken to charge to 63%.

Choose C1 first (there are relatively few values available).

Choose R1 to give the time period you need. R1 should be in the range 1k to

1M , so use a fixed resistor of at least 1k in series if R1 is variable.

Beware that electrolytic capacitor values are not accurate, errors of at least

20% are common.

Beware that electrolytic capacitors leak charge which substantially increases

the time period if you are using a high value resistor - use the formula as only

a very rough guide!

Monostable operation

The timing period is triggered (started) when the trigger input (555 pin 2) is less than

1/3 Vs, this makes the output high (+Vs) and the capacitor C1 starts to charge through

resistor R1. Once the time period has started further trigger pulses are ignored.

The threshold input (555 pin 6) monitors the voltage across C1 and when this reaches

2

/3 Vs the time period is over and the output becomes low. At the same time

discharge (555 pin 7) is connected to 0V, discharging the capacitor ready for the next

trigger.

The reset input (555 pin 4) overrides all other inputs and the timing may be cancelled

at any time by connecting reset to 0V, this instantly makes the output low and
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37/65

discharges the capacitor. If the reset function is not required the reset pin should be

connected to +Vs.

IR Light Emitter

Principle of Operation

Because they emit at wavelengths which provide a close match to the peak spectral

response of silicon photo detectors, both GaAs and GaAlAs. There are many off-the-

shelf, commercially available, IR LED emitters that can be used for a discrete infrared

transceiver circuit design. It should be mentioned here that there are also a number of

integrated transceivers that the designer can choose as well. In general, there are four

characteristics of IR emitters that designers have to be wary of:

Rise and Fall Time

Emitter Wavelength

Emitter Power

Emitter Half-angle


38/65

Wavelength vs. Radiant Power

Description

In this system IR LED used is The QED233 / QED234 which is a 940 nm GaAs /

AlGaAs LED encapsulated in a clear untinted, plastic T-1 3/4 package.

QED234 Features

Wavelength=940nm

Chip material =GaAs with AlGaAs window

Package type: T-1 3/4 (5mm lens diameter)

Matched Photo sensor: QSD122/123/124, QSE 973.

Medium Emission Angle, 40

High Output Power

Package material and color: Clear, untinted, plastic

Ideal for remote control applications

Semiconductor Light Detectors

Energy entering a semiconductor crystal excites electrons to higher levels, leaving

behind "holes". These electrons and "holes" can recombine and emit photons, or they

can move away from one another and form a current. This is the basics of

semiconductor light detectors. The basic optical receiver converts the modulated light

coming from the space back in to a replica of the original signal applied to the

transmitter.

Types of optical detector

P-N photodiode


39/65

P-I-N photodiode

Avalanche photodiode

In P-N photodiode, electron hole pairs are created in the depletion region of a p-n

junction in proportion to the optical power. Electrons and holes are swept out by the

electric field, leading to a current. In P-I-N photodiode, electric field is concentrated

in a thin intrinsic layer. In avalanche photodiode, like P-I-N photodiodes, but have an

additional layer in which an average of M secondary electron hole pairs are

generated through impact ionization for each primary pair. Photodiodes usually have a

large sensitive detecting area that can be several hundreds microns in diameter.

IR Light Detector

The most common device used for detecting light energy in the standard data stream

is a photodiode, Photo transistors are not typically used in IrDA standard-compatible

systems because of their slow speed. Photo transistors typically have ton/toff of 2 s or

more. A photo transistor may be used, however, if the data rate is limited to 9.6 kb

with a pulse width of 19.5 s. A photodiode is packaged in such a way as to allow

light to strike the PN junction.

Characteristic Curve of a Reverse Biased Photodiode

In infrared applications, it is common practice to apply a reverse bias to the device.

Refer to Figure 3.17 for a characteristic curve of a reverse biased photodiode. Therewill be a reverse current that will vary with the light level. Like all diodes, there is an


40/65

intrinsic capacitance that varies with the reverse bias voltage. This capacitance is an

important factor in speed.

Description

The QSE973 is a silicon PIN photodiode encapsulated in an infrared transparent,black, plastic T092 package.

1 2

+_

QSE 973 Features

Daylight filter

T092 package

PIN photodiode

Receipting angle 90 Chip size = .1072 sq. inches (2.712 sq. mm)

Link Distance

To select an appropriate IR photo-detect diode, the designer must keep in mind the

distance of communication, the amount of light that may be expected at that distance

and the current that will be generated by the photodiode given a certain amount of

light energy. The amount of light energy, or irradiance that is present at the active-

input interface is typically given in W/cm2. This is a convenient scale of light flux.

Stepper Motor:

Introduction to Stepper Motor

The stepper motor is an electromagnetic device that converts digital pulses into

mechanical shaft rotation. The shaft or spindle of a stepper motor rotates in discrete

step increments when electrical command pulses are applied to it in the proper


41/65

sequence. The sequence of the applied pulses is directly related to the direction of

motor shafts rotation. The speed of the motor shafts rotation is directly related to the

frequency of the input pulses and the length of rotation is directly related to the

number of input pulses applied. Many advantages are achieved using this kind of

motors, such as higher simplicity, since no brushes or contacts are present, low cost,

high reliability, high torque at low speeds, and high accuracy of motion. Many

systems with stepper motors need to control the acceleration/ deceleration when

changing the speed.

Stepper Motor

Bipolar v/s. Unipolar Stepper Motors

The two common types of stepper motors are the bipolar motor and the unipolar

motor. The bipolar and unipolar motors are similar, except that the unipolar has a

center tap on each winding. The bipolar motor needs current to be driven in both

directions through the windings, and a full bridge driver is needed .The center tap onthe unipolar motor allows a simpler driving circuit, limiting the current flow to one

direction. The main drawback with the unipolar motor is the limited capability to

energize all windings at any time, resulting in a lower torque compared to the bipolar

motor. The unipolar stepper motor can be used as a bipolar motor by disconnecting

the center tap.

In unipolar there are 5 wires. One common wire and four wires to which power

supply has to be given in a serial order to make it drive. Bipolar can have 6 wires and

a pair of wires is given supply at a time to drive it in steps.


42/65

A 2- phase (winding) unipolar Stepper Schematic

A two phase (winding) bipolar stepper motor

Driving a Stepper Motor:

Identify the wire: Common and windings

Connection to identify the common winding


43/65

It has been seen that out of the five wires two are grouped as common. The other four

are the windings that have to give supply to. Major crux here is to identify the

common line. Just take the multimeter and check the resistance between the wires.

Hold one wire a common and it must bear a resistance of 75 ohms with all the other

wires then that is the common wire.

Connection of the Circuit:

Stepper Motor Advantages and Disadvantages

Advantages:

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors

have an accuracy of 3 5% of a step and this error is non cumulative from one

step to the next.

4. Excellent response to starting/ stopping/reversing.

5. Very reliable since there are no contact brushes in the motor. Therefore, the

life of the motor is simply dependant on the life of the bearing.

6. The motors response to digital input pulses provides open-loop control,

making the motor simpler and less costly to control.

7. It is possible to achieve very low speed synchronous rotation with a load that

is directly coupled to the shaft.

8. A wide range of rotational speeds can be realized as the speed is proportional

to the frequency of the input pulses.


44/65

Disadvantages:

1. Resonances can occur if not properly controlled.

2. Not easy to operate at extremely high speeds.

Stepper Motor Type

There are three basic stepper motor types. They are:

Variable-reluctance

Permanent-magnet

Hybrid

Variable-reluctance (VR)

This type of stepper motor has been around for a long time. It is probably the easiest

to understand from a structural point of view. This type of motor consists of a soft

iron multi-toothed rotor and a wound stator. When the stator windings are energized

with DC current the poles become magnetized. Rotation occurs when the rotor teeth

are attracted to the energized stator poles.

Cross section of a variable reluctance motor

Permanent Magnet (PM)

Often referred to as a tin can or canstock motor the permanent magnet step motor

is a low cost and low resolution type motor with typical step angles of 7.5 to 15. (48


45/65

24 steps/revolution) PM motors as the motor name implies have permanent magnets

added to the motor structure. The rotor no longer has teeth as with the VR motor.

Instead the rotor is magnetized with alternating north and south poles situated in a

straight line parallel to the rotor shaft. These magnetized rotor poles provide an

increased magnetic flux intensity and because of this the PM motor exhibits improved

torque characteristics when compared with the VR type.

Principle of a PM type stepper motor

Hybrid (HB)

The hybrid stepper motor is more expensive than the PM stepper motor but provides

better performance with respect to step resolution, torque and speed. Typical step

angles for the hybrid stepper motor, range from 3.6 to 0.9 (100 400 steps per

revolution). The hybrid stepper motor combines the best features of both the PM and

VR type stepper motors. The rotor is multi toothed like the VR motor and contains an

axially magnetized concentric magnet around its shaft. The teeth on the rotor provide

an even better path which helps guide the magnetic flux to preferred locations in the

air gap. This further increases the detent, holding and dynamic torque characteristics

of the motor when compared with both the VR and PM types.


46/65

Cross section of hybrid stepper motor

Applications of Stepper Motor

A stepper motor can be a good choice whenever controlled movement is required.

They can be used to advantage in applications where you need to control rotation

angle, speed, position and synchronism. Because of the inherent advantages listed

previously, stepper motors have found their place in many different applications.

Some of these include printers, plotters, high end office equipment, hard disk drives,

medical equipment, fax machines, automotive and many more.

Torque Generation

The torque produced by a stepper motor depends on several factors:

The step rate

The drive current in the windings

The drive design or type

In a stepper motor a torque is developed when the magnetic fluxes of the rotor and

stator are displaced from each other. The stator is made up of a high permeability

magnetic material. The presence of this high permeability material causes the

magnetic flux to be confined for the most part to the paths defined by the stator

structure in the same fashion that currents are confined to the conductors of an

electronic circuit. This serves to concentrate the flux at the stator poles. The torque

output produced by the motor is proportional to the intensity of the magnetic flux


47/65

generated when the winding is energized. The basic relationship which defines the

intensity of the magnetic flux is defined by:

H = (N * i) / l

Where:

N = Number of winding turns

i = Current

H = Magnetic field intensity

l =Magnetic flux path length

This relationship shows that the magnetic flux intensity and consequently the torque is

proportional to the number of winding turns and the current and inversely

proportional to the length of the magnetic flux path. It has been seen that the same

frame size stepper motor could have very different torque output capabilities simply

by changing the winding parameters.

Phases, Poles and Stepping Angles

Usually stepper motors have two phases, but three- and five-phase motors also exist.

A bipolar motor with two phases has one winding/phase and a unipolar motor has one

winding, with a center tap per phase. Sometimes the unipolar stepper motor is referred

to as a four phase motor, even though it has only two phases. Motors that have two

separate windings per phase also existthese can be driven in either bipolar or

unipolar mode. A pole can be defined as one of the regions in a magnetized body

where the magnetic flux density is concentrated. Both the rotor and the stator of a step

motor have poles.

In reality several more poles are added to both the rotor and stator structure in order to

increase the number of steps per revolution of the motor, or in other words to provide

a smaller basic (full step) stepping angle. The permanent magnet stepper motor

contains an equal number of rotor and stator pole pairs. Typically the PM motor has

12 pole pairs. The stator has 12 pole pairs per phase. The hybrid type stepper motor

has a rotor with teeth. The rotor is split into two parts, separated by a permanent

magnet making half of the teeth south poles and half north poles. The number of pole

pairs is equal to the number of teeth on one of the rotor halves. The stator of a hybrid

motor also has teeth to build up a higher number of equivalent poles (smaller pole

pitch, number of equivalent poles = 360/teeth pitch) compared to the main poles, on

which the winding coils are wound. It is the relationship between the number of rotor


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poles and the equivalent stator poles, and the number the number of phases that

determines the full-step angle of a stepper motor.

Step Angle: The angle with which the stepper motor turns for a single pulse if supply

to one wire or a pair is called step angle.

NPh = Number of equivalent poles per

Phase = number of rotor poles

Ph = Number of phasesN = Total number of poles for all phases together

If the rotor and stator tooth pitch is unequal, a more-complicated relationship exist

Optocoupler:

It has one IR LED and a phototransistor. One pin of the LED is connected to the

MCU to get a signal (0 or 1) and the pin is given ground. When the signal from theMCU is 0, then LED emits light. This light will turn on the NPN transistor. Emitter of

the transistor is grounded. Collector is connected to the PNP transistor whose emitter

is connected to Vcc and collector to the relay.

The purpose of using the optocouplers is to pass the supply from the PC/MCU to the

appliances & is for isolation of the port of the PC/MCU from an external hardware.

The voltage signal from the PC/MCU is being converted into light by the LED and

then further converted into voltage by the phototransistor. This ensures that there is no

physical connection between the PC and the appliances. The signal from the

PC/MCU is coupled only through light so that if in any case the external hardware

( in this case :appliances) produces an error voltage it will not be passed over to the

port of the PC/MCU and will not damage the internal circuitry of the PC/MCU.


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MCT-2E Pin Diagram

The MCT2XXX series opto isolators consist of a gallium arsenide infrared emitting

diode driving a silicon phototransistor in a 6-pin dual in-line package. There is noelectrical connection between the two, just a beam of light. The light emitter is nearly

always an LED. The light sensitive device may be a photodiode, phototransistor, or

more esoteric devices such as thyristors, triacs etc. To carry a signal across the

isolation barrier, optocouplers are operated in linear mode.

Pin Description of MCT2E

The IC package may also be called an IC or a chip. It is important to note that each

type of optocoupler may use different pin assignments. For carrying a linear signal

across isolation barrier there are two types of optocouplers. Both types use an infrared

light emitting diode (LED) to generate and send a light signal across an isolation

barrier. The difference is in the detection method. Some optocouplers use a

phototransistor detector while others use a photodiode detector which drives the base

of a transistor.

Pin no. Function

1 Anode

2 Cathode3 NC

4 Emitter

5 Collector

6 Base


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The phototransistor detector uses the transistors collector base junction to

detect the light signal. This necessitates that the base area be relatively large

compared to a standard transistor. The result is a large collector to base capacitance

which slows the collector rise time and limits the effective frequency response of the

device. In addition the amplified photocurrent flows in the collector base junction and

modulates the response of the transistor to the photons. This cause the transistor to

behave in a non-linear manner. Typical phototransistor gains range from 100 to 1000.

The photodiode/transistor detector combination on the other hand uses a diode

to detect the photons and convert them to a current to drive the transistor base. The

transistor no longer has a large base area. The response of this pair is not affected by

amplified photocurrent and the photodiode capacitance does not impair speed.

Optocoupler Operation:

Optocouplers are good devices for conveying analog information across a power

supply isolation barrier, they operate over a wide temperature range and are often

safety agency approved they do, however, have many unique operating

considerations.

Optocouplers are current input and current output devices. The input LED is

excited by changes in drive current and maintains a relatively constant forward

voltage. The output is a current which is proportional to the input current. The output

current can easily be converted to a voltage through a pull-up or load resistor.

Applications:

AC mains detection

Reed relay driving

Switch mode power supply feedback

Telephone ring detection

Logic ground isolation

Logic coupling with high frequency noise rejection.

Features:

Interfaces with common logic families


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Input-output coupling capacitance < 0.5 pF

Industry Standard Dual-in line 6-pin package

5300 VRMS isolation test voltage

Lead-free component

Optocoupler (817)

Description

The HCPL-817 contains a light emitting diode optically coupled to a phototransistor.

It is packaged in a 4-pin DIP package and available in wide-lead spacing option.

Input-output isolation voltage is 5000 Vrms. Response time (t r), is typically 4 ms and

minimum CTR (Current transfer ratio) is 50% at input current of 5 mA.

Power Transistor (BC 369):

High current gain

High collector current

Low collector-emitter saturation voltage

Complementary type: BC 368 (NPN)


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Various Hardware Tools used are:

Soldering Iron

Soldering Wire

Ribbon wire

Flux

Cutter

Tin wire

De-soldering pump

Multimeter

IC Programmer

PC

Software Tools used are:

Keil compiler

Sunroms software to Program the Microcontroller (AT89s52)

Embedded C Language


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Basic Tutorials for Keil Software:

1. Open Keil from the Start menu

2. The Figure below shows the basic names of the windows referred in this document

Starting a new Assembler Project

1. Select New Project from the Project Menu.


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2.Name the project Toggle.a51

3. Click on the Save Button.

4. The device window will be displayed.

5. Select the part you will be using to test with. For now we will use the Dallas

Semiconductor part DS89C420.


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6. Double Click on the Dallas Semiconductor.

7. Scroll down and select the DS89C420 Part

8. Click OK


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Creating Source File

1. Click File Menu and select New.

2. A new window will open up in the Keil IDE.


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3. Write any code on this file.

4. Click on File menu and select Save as


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5.Name the file with extension (.asm for assembly language code & .c for embedded

C language code).

6. Click the Save Button

Adding File to the Project

1. Expand Target 1 in the Tree Menu


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2. Click on Project and select Targets, Groups, Files

3. Click on Groups/Add Files tab

4. Under Available Groups select Source Group 1

5. Click Add Files to Group button


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6. Change file type to Asm Source file(*.a*; *.src)

7. Click on toggle.a51

8. Click Add button

9. Click Close Button

10. Click OK button when you return to Target, Groups, Files dialog box.


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11. Expand the Source Group 1 in the Tree menu to ensure that the file was added to

the project.

Creating HEX for the Part

1. Click on Target 1 in Tree menu

2. Click on Project Menu and select Options for Target 1


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3. Select Target Tab

4. Change Xtal (Mhz) from 50.0 to 11.0592


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5. Select Output Tab

6. Click on Create Hex File check box

7. Click OK Button

8. Click on Project Menu and select Rebuild all Target Files

9. In the Build Window it should report 0 Errors (s), 0 Warnings

10. You are now ready to Program your Part


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CONCLUSION

I would like to conclude this project as a very great and enriching experience.

During the project labs I familiarized myself with P.C.B designing, application of I.C.(its pin diagram), mounting of components using soldering process and interfacing of

the hardware circuit with the computer.

The circuit can be used at all places starting from domestic to the industrial sectors.

The simplicity in the usage of this circuit helps it to be used by a large number of

people as people with less knowledge of hardware can also use it without facing any

problem. The

I also learned about the engg. Responsibility and about their hard work. This project

was not only good for personality development but also great in terms of imparting

practical knowledge.

Thus I conclude our project with a very nice and wonderful experience

Documents

Report_car Parking System