automatic room light controller

8

BLOCK DIAGRAM

7-SEGMENT DISPLAY

ENTER

SENSOR

SIGNAL

CONDITIONING

EXIT

SENSOR

SIGNAL

CONDITIONING

A

T

8

9

S

5

2

RELAY

DRIVER

LIGHT

POWER

SUPPLY

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BLOCK DIAGRAM DESCRIPTION

The basic block diagram of the bidirectional visitor counter with automatic light

controller is shown in the above figure. Mainly this block diagram consists of the

following essential blocks.

1. Power Supply

2. Entry and Exit sensor circuit

3. AT89S52 micro-controller

4. Relay driver circuit

1. Power Supply:-

Here we used +12V and +5V dc power supply. The main function of this block

is to provide the required amount of voltage to essential circuits. +12V is given to

relay driver. To get the +5V dc power supply we have used here IC 7805, which

provides the +5V dc regulated power supply.

2. Enter and Exit Circuits:-

This is one of the main part of our project. The main intention of this block is to

sense the person. For sensing the person we are using a TSOP 1738 sensor. By

using this sensor and its related circuit diagram we can count the number of

persons.

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3. 89S52 Microcontroller:-

It is a low-power, high performance CMOS 8-bit microcontroller with 8KB of

Flash Programmable and Erasable Read Only Memory (PEROM). The device is

manufactured using Atmel’s high-density nonvolatile memory technology and is

compatible with the MCS-51TM

instruction set and pin out. The on-chip Flash

allows the program memory to be reprogrammed in-system or by a conventional

nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash

on a monolithic chip, the Atmel AT89S52 is a powerful Microcontroller, which

provides a highly flexible and cost effective solution for many embedded control

applications.

4. Relay Driver Circuit:-

This block has the potential to drive the various controlled devices. In this block

mainly we are using the transistor and the relays. One relay driver circuit we are

using to control the light. Output signal from AT89S52 is given to the base of the

transistor, which energizes the particular relay, because of this, appropriate device

is selected and which performs its allotted function.

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CIRCUIT DESCRIPTION

There are two main parts of the circuits.

1. Transmission Circuit (Infrared LEDs)

2. Receiver Circuit (Sensors)

1. Transmission Circuit:

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This circuit diagram shows how a 555 timer IC, configured to function as a basic

astable multivibrator. The astable multivibrator generates a square wave, the period

of which is determined by the circuit external to IC 555. The astable multivibrator

does not require any external trigger to change the state of the output. Hence the

name free running oscillator. The time during which the output is either high or

low is determined by the two resistors and a capacitor which are externally

connected to the 555 timer.

IR Transmission circuit is used to generate the modulated 36 kHz IR signal.

The IC555 in the transmitter side is to generate 36 kHz square wave. Adjust the

preset in the transmitter to get a 38 kHz signal at the o/p. Then you point it over the

sensor and its o/p will go low when it senses the IR signal of 38 kHz.

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2. Receiver Circuit:

The IR transmitter will emit modulated 38 kHz IR signal and at the receiver

we use TSOP1738 (Infrared Sensor). The output goes high when there is an

interruption and it return back to low after the time period determined by the

capacitor and resistor in the circuit i.e. around 1 second. CL100 is to trigger the

IC555 which is configured as monostable multivibrator. Input is given to the Port 1

of the microcontroller. Port 0 is used for the 7-Segment display purpose. Port 2 is

used for the Relay Turn On and Turn off Purpose.LTS 542 (Common Anode) is

used for 7-Segment display and that time Relay will get voltage and triggered, so

light will get voltage and it will turn on and when counter will be 00 and at that

time Relay will be turned off. Reset button will reset the microcontroller

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LIST OF COMPONENTS

Microcontroller – AT89S52

IC – 7805

Sensor – TSOP 1738 (Infrared Sensor)

Transformer – 12-0-12, 500 mA

Preset – 4.7K

Disc capacitor – 104,33pF

Reset button switch

Rectifier diode – IN4148

Transistor – BC 547, 2N2222

7-Segment Display

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DESCRIPTION OF THE COMPONENTS USED

1. Microcontroller AT89S52

The AT89S52 is a low-power, high-performance CMOS 8-bit

microcontroller with 8K bytes of in-system programmable Flash memory. The

device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the Industry-standard 80C51 instruction set and

pin out. The on-chip Flash allows the program memory to be reprogrammed in-

system or by a conventional nonvolatile memory pro-grammar. By combining a

versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the

Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible

and cost-effective solution to many embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash,

256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit

timer/counters, a six-vector two-level interrupt architecture, a full duplex serial

port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 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 interrupt or hardware reset.

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FEATURES:

8 KB Reprogrammable flash.

32 Programmable I/O lines.

16 bit Timer/Counter—3.

8 Interrupt sources.

Power range: 4V – 5.5V

Endurance : 1000 Writes / Erase cycles

Fully static operation: 0 Hz to 33 MHz

Three level program memory lock

Power off flag

Full duplex UART serial channel

Low power idle and power down modes

Interrupt recovery from power down modes

256 KB internal RAM

Dual data pointer

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2. TSOP1738 (INFRARED SENSOR)

Fig. Infrared Sensor

Description:

The TSOP17.. – Series are miniaturized receivers for infrared remote control

systems. PIN diode and preamplifier are assembled on lead frame, the epoxy

package is designed as IR filter. The demodulated output signal can directly be

decoded by a microprocessor. TSOP17.. is the standard IR remote control receiver

series, supporting all major transmission codes.

Features:

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance

TTL and CMOS compatibility

Output active low

Low power consumption

High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Suitable burst length .10 cycles/burst

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Block Diagram:

Fig. Block Diagram of TSOP 173

Application Circuit:

Fig. Application circuit

3. 555 (TIMER IC)

Fig. Timer IC (555)

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Description:

The LM555 is a highly stable device for generating accurate time delays

or oscillation. Additional terminals are provided for triggering or resetting if

desired. In the time delay mode of operation, the time is precisely controlled by

one external resistor and capacitor. For astable operation as an oscillator, the free

running frequency and duty cycle are accurately controlled with two external

resistors and one capacitor. The circuit may be triggered and reset on falling

waveforms, and the output circuit can source or sink up to 200mA or drive TTL

circuits.

Features:

Direct replacement for SE555/NE555

Timing from microseconds through hours

Operates in both astable and monostable modes

Adjustable duty cycle

Output can source or sink 200 mA

Output and supply TTL compatible

Temperature stability better than 0.005% per °C

Normally on and normally off output

Available in 8-pin MSOP package

Applications:

Precision timing

Pulse generation

Sequential timing

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Time delay generation

Pulse width modulation

Pulse position modulation

Linear ramp generator

4. LTS 542 (7-Segment Display)

Description:

The LTS 542 is a 0.52 inch digit height single digit seven-segment display.

This device utilizes Hi-eff. Red LED chips, which are made from GaAsP on GaP

substrate, and has a red face and red segment.

Fig. 7 Segment Display

Features:

Common Anode

0.52 Inch Digit Height

Continuous Uniform Segments

Low power Requirement

Excellent Characters Appearance

High Brightness & High Contrast

Wide Viewing Angle

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5. LM7805 (Voltage Regulator)

Fig. Voltage Regulator

Description:

The KA78XX/KA78XXA series of three-terminal positive regulator

are available in the TO-220/D-PAK package and with several fixed output

voltages, making them useful in a wide range of applications. Each type employs

internal current limiting, thermal shut down and safe operating area protection,

making it essentially indestructible. If adequate heat sinking is provided, they can

deliver over 1A output current. Although designed primarily as fixed voltage

regulators, these devices can be used with external components to obtain adjustable

voltages and currents.

Features:

Output Current up to 1A

Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V

Thermal Overload Protection

Short Circuit Protection

Output Transistor Safe Operating Area Protection

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6. RELAY CIRCUIT:

Fig. Relay

A single pole dabble throw (SPDT) relay is connected to port RB1 of the

microcontroller through a driver transistor. The relay requires 12 volts at a current

of around 100ma, which cannot be provided by the microcontroller. So the driver

transistor is added. The relay is used to operate the external solenoid forming part

of a locking device or for operating any other electrical devices. Normally the relay

remains off. As soon as pin of the microcontroller goes high, the relay operates and

releases. Diode D2 is the standard diode on a mechanical relay to prevent back

EMF from damaging Q3 when the relay releases.

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FLOW CHART

Fig. Flow Chart

If the sensor 1 is interrupted first then the microcontroller will look for

the sensor 2, and if it is interrupted then the microcontroller will

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increment the count and switch on the relay, if it is first time

interrupted.

If the sensor 2 is interrupted first then the microcontroller will look for

the sensor 1, and if it is interrupted then the microcontroller will

decrement the count.

When the last person leaves the room then counter goes to 0 and that

time the relay will turn off, and light will be turned off.

PROGRAM

// Program to make a bidirectional visitor counter using IR sensor

#include <reg51.h>

#define msec 1

unsigned int num=0;

sbit dig_ctrl_4=P2^6; //declare the control pins of seven segments

sbit dig_ctrl_3=P2^5;



sbit relay1 = P2^0;

sbit pin = P3^7;

unsigned char

digi_val[11]={0xFE,0x18,0x6D,0x3d,0x1B,0X37,0x77,0x1C,0xfF,0x3F};

unsigned int dig_1,dig_2,dig_3,dig_4,test=0;

unsigned char dig_disp=0;

sbit up=P1^0; //up pin to make counter count up

sbit down=P1^1; //down pin to make counter count down

void delay(int x)

{

char y = 200;

pin = !pin;

while((x--))

{

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while((y--));

}

}

void init() // to initialize the output pins and Timer0

{

up=down=1;

dig_ctrl_4 = 0;

dig_ctrl_3 = 0;

dig_ctrl_2 = 0;

dig_ctrl_1 = 0;

relay1 = 0;

TMOD=0x01;

TL0=0xf6;

TH0=0xFf;

IE=0x82;

TR0=1;

P0=0x00;

}

void delay1() //To provide a small time delay

{

TMOD=0x01;

TL0=0x36;

TH0=0xF6;

TR0=1;

while(TF0==0);

TR0=0;

TF0=0;

}

void display() interrupt 1 // Function to display the digits on seven segment. For

more details refer seven segment multiplexing.

{

TL0=0x36;

TH0=0xf6;

P0=0xFF;

dig_ctrl_1 = dig_ctrl_3 = dig_ctrl_2 = dig_ctrl_4 = 0;

dig_disp++;

dig_disp=dig_disp%2;

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switch(dig_disp)

{

case 0:

P0= ~digi_val[dig_1];

dig_ctrl_1 = 1;

break;

case 1:


dig_ctrl_2 = 1;

break;

case 2:


dig_ctrl_3 = 1;

break;

case 3:


dig_ctrl_4 = 1;

break;

}

}

void main()

{

unsigned int cnt=0;

init();

relay1 = 0;

dig_ctrl_2 = 0;

dig_ctrl_1 = 0;

cnt = 0;

relay1 = 1;

delay(100);

relay1 = 0;

delay(100);

while(1)

{

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if(up==1)

{

cnt=0;

delay(1000);

if(down==1)

{

if(test<99)test++;

dig_2=test%10;

dig_1=test/10;

relay1 = 1;

}

}

if(down==1)

{

cnt=0;

delay(1000);

if(up==1)

{

if(test>0)test--;

if(test == 0) { relay1 = 0; }

dig_2=test%10;

dig_1=test/10;

}

}

}

}

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PCB FABRICATION

Printed Circuit Board (PCB) is piece of art. The performance of an electronic

circuit depends on the layout and the design of PCB. A PCB mechanically supports

and connects components by conductive pathways, etched from copper sheets

laminated on to insulated substrate. PCB ape used to rotate electrical currents and

signals through copper tracts which are firmly bonded to an insulating base.

PCB Fabrication involves the following steps:

1. Drawing the layout of the PCB in the paper. The track layout of the

Electronic circuit should be made in such manner that the paths are in easy

routes. It is then transferred to a Mylar sheet. The sheet is then touched with

black ink.

2. The solder side of the Mylar sheet is placed on the shiny side of the five-

Star sheet and is placed in a frame. Then it is exposed to sunlight with Mylar

sheet facing the sunlight.

3. The exposed five- star sheet is put in Hydrogen Peroxide solution. Then it is

put in hot water and shook till unexposed region becomes transparent.

4. This is put in cold water and then the rough side is stuck on to the silk

screen. This is then pressed and dried well.

5. The plastic sheet of the five-star sheet is removed leaving the pattern on the

screen.

6. A copper clad sheet is cut to the size and cleaned. This is placed under

screen.

7. As it resistant ink if spread on the screen so that a pattern of tracks and a pad

is obtained on a copper clad sheet. It is then dried.

8. The dried sheet is then etched using Ferric chloride solution (32Baume) till

all the unwanted Copper is etched away. Swish the board to keep each fluid

moving. Lift up the PCB and check whether all the unwanted Copper is

removed. Etching is done by immersing the marked copper clad in Ferric

Chloride solution after that the etched sheet is dried.

9. The unwanted resist ink is removed using Sodium Hydroxide solution Holes

are them dried.

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PCB PARAMETERS

Copper thickness - 72mil (1mm=39.37 mils)

Track width - 60mil

Clearance - 60mil

Pad width - 86mil

Pad height - 86mil

Pad shape - Oval

Pad hole size - 25mil

On board - Through

Hole size - 0.9mm (36mil)

Base - Paper phenolic, Hylam

PCB Quality - FRC4

SOLDERING

Soldering is the process of joining metals by using lower melting point to

weld or alloy with joining surface.

SOLDER

Solder is the joining material that melts below 427 degree connections

between components. The popularly used solders are alloys of tin (Sn) and lead

(Pb) that melts below the melting point of tin.

Types:

1. Rosin core: - 60/40 Sn/Pb solders are the most common types used for

electronics assembly. These solders are available in various diameters and

are most appropriate for small electronics work (0.02’’-0.05‖ dia is recommended)

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2. Lead free: - lead free solders are used as more environmental-friendly

substitutes for leaded solder, but they are typically not as easy to use mainly

because of their higher melting point and poorer wetting properties.

3. Silver: - Silver solders are typically used for low resistance connections but

they have a higher melting point and are expensive than Sn/ Pb solders.

4. Acid –core: - Acid-core solders should not be used for electronics. They are

intended for plumbing or non-electronics assembly work. The acid-core flux

will cause corrosion of circuitry and can damage components.

5. Other special solders :-

Various melting point eutectics: These special solders are

typically used for non-electronic assembly of difficult to

construct mechanical items that must be assembled in a particular

sequence.

Paste solders: These solders are used in the field application or in

specialized manufacturing application.

FLUX

In order to make the surface accept the solder readily, the components

terminals should be free oxides and other obstructing films. The lead should be

cleaned chemically or by abrasion using blades or knives.

Small amount of lead coating can be done on the portion of the leads using

soldering iron. This process is called thinning. Zinc chloride or ammonium

chloride separately or in combination is mostly used as fluxes. These are available

in petroleum jelly as paste flux.

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Flux medium used to remove the degree of wetting. The desirable properties of

flux are:-

It should provide a liquid cover over the materials and exclude air

gap up to the soldering temperature.

It should dissolve any Oxide on the metal surface.

It should be easily replaced from the metal by the molten soldering

operation

Residue should be removable after completing soldering operation.

The most common flux used in hand soldering of electronic components is

rosin, a combination of mild organic acids extracted from pine tree.

SOLDERING IRON

It is a tool used to melt the solder and apply it at the joints in the circuit. It

operates in 230V supply. The iron at the tip gets heated while few minutes. The

50W and 25W soldering irons are commonly used for soldering of electronics

circuit.

SOLDERING STEPS

1. Make the layout of the component in the circuit. Plug in the chord of the

soldering iron the mains to get heated.

2. Straighten and clean the component leads using a blade or a knife.

3. Mount the components on the PCB by bending the leads of the

components. Use nose pliers.

4. Apply flux on the joints and solder the joints. Soldering must be in

minimum time to avoid dry soldering and heating up of the components.

5. Wash the residue using water and brush.

6. Solder joins should be inspected when completed to determine if they

have been properly made.

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CHARACTERISTICS OF A GOOD SOLDER JOINTS:

A. Shiny surface.

B. Good, smooth fillet.

CHARACTERISTICS OF A POOR SOLDER JOINTS:

1. Dull or crystallized surface: This is an indicator of a cold solder joint.

Cold solder joint result from moving the component after soldering has

been removed, but before the solder has hardened. Cold solder joints may

work at first, but will eventually fail.

2. Air pocket: Air pocket (voids) result from incomplete wetting of surface,

allowing air to be in contact with the connecting metals. This will cause

oxidation of the joints and eventual failure. Blow holes can occur due to

vaporization of the moisture on the surface of the board and existing

through the molten solder. Boards should be clean and dry. Prior to

soldering. Ethanol (100%) can be used as a moisture chaser if boards are

wet prior to soldering.

3. Dimples: Dimples in the surface do not always indicate a serious

problem, but they should be avoided since they are precursors to voids.

4. Floaters: Black spots ―floating‖ in the soldering fillet should be avoided

because they indicate contamination and a potential for failure as in the

case of voids. These black spots usually result from overheated (burnt)

Rosin or other contaminants such as burnt wire insulation. Maintaining a

clean tip will help to avoid these problems.

5. Balls: A solder balls, instead of a fillet can occur if the trace was heated

but the leads was not (vice versa). This prevents proper wetting of both

surfaces and result in solder being attached to only one surface

(component or trace)

6. Excess solder: Excess solder usage can cover up other potential problems

and should be avoided. It can lead to solder bridges. In addition, spherical

solder joints can result from the application of too much solder.

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CIRCUIT DIAGRAM IN PCB

automatic room light controller

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