Bidirectional Visitor Counter

1. Introduction

This project titled “Microcontroller based Bidirectional Visitor counter” is

designed and presented in order to count the visitors of an auditorium, hall, offices, malls,

sports venue, etc. The system counts both the entering and exiting visitor of the auditorium or

hall or other place, where it is placed. Depending upon the interrupt from the sensors, the

system identifies the entry and exit of the visitor. On the successful implementation of the

system, it displays the number of visitor present in the auditorium or hall. This system can be

economically implemented in all the places where the visitors have to be counted and

controlled. Since counting the visitors helps to maximize the efficiency and effectiveness of

employees, floor area and sales potential of an organization, etc.

[Type text]

Bidirectional Visitor Counter

2.1 Block Diagram

Sensor arrangement at the way

[Type text]

SensorsLogic

Control Circuit

Micro-controllerAT89C52

Display

PowerSupply +5V

Enter

Exit

IR TX1

IR TX2 RX2

RX1

Bidirectional Visitor Counter

2.2 Description

I. Sensors

The block shows the sensor arrangement at the entrance cum exit passage. Here a pair

of IR transmitter – receiver is used as sensor. Photo transistors are used as IR receiver, since it has

sensitivity to receive IR rays.

IR Transmitter:

Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of

visible light, but shorter than that of microwaves. The name means "below red" (from the Latin infra,

"below"), red being the color of visible light with the longest wavelength. Infrared radiation has

wavelengths between about 750 nm and 1 mm, spanning five orders of magnitude. A longer

wavelength means it has a lower frequency than red, hence "below". Objects generally emit infrared

radiation across a spectrum of wavelengths, but only a specific region of the spectrum is of interest

because sensors are usually designed only to collect radiation within a specific bandwidth.

Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit

infrared radiation which is focused by a plastic lens into a narrow beam. The receiver uses a silicon

photodiode to convert the infrared radiation to an electric current. It responds only to the rapidly

pulsing signal created by the transmitter, and filters out slowly changing infrared radiation from

ambient light. IR does not penetrate walls and so does not interfere with other devices in adjoining

rooms.

Photo-transistors:

Phototransistors are examples of photodiode-amplifier combinations integrated within a

single silicon ship. These combinations are put together in order to overcome the major fault of

photodiodes: unity gain. Many applications demand a greater output signal from photodiode can

always be amplified through use of an external op-amp or other circuitry, this approach is often not as

practical or as cost effective as the use of phototransistors.

[Type text]

Bidirectional Visitor Counter

The phototransistor can be viewed as a photodiode whose output photocurrent is fed into the base of a

conventional small signal transistor. While not required for operation of the device as a photo

detector, a base connection is often provided allowing the designer the option of using base current to

bias the transistor. The typical gain of a phototransistor can range from 100 to over 1500.

Symbol and typical view of photo-transistor:

Features:

Low-cost visible and near-IR photo detector.

Available with gains from 100 to over 1500.

Moderately fast response times.

Available in a wide range of packages including epoxy-coated, transfer-molded,

cast, hermetic, and in chip form.

Usable with almost any visible or near-infrared light source such as IREDs;

neon; fluorescent, incandescent bulbs; lasers; flame sources; sunlight; etc.

Same general electrical characteristics as familiar signal transistors.

[Type text]

Bidirectional Visitor Counter

II. Logic control circuit

Here the logic control circuit consists of two circuits, a op-amp comparator and a flip-flop circuit.

Comparators:

A comparator is a device which compares two voltages or currents and

switches its output to indicate which is larger. A standard op-amp operating without negative

feedback is used as a comparator. When the non-inverting input (V+) is at a higher voltage than the

inverting input (V-), the high gain of the op-amp causes it to output the most positive voltage it can.

When the non-inverting input (V+) drops below the inverting input (V-), the op-amp outputs the most

negative voltage it can. Since the output voltage is limited by the supply voltage. Here the operational

amplifier LM 324 is used as comparator.

Inputs Output

- > + Negative

+ > - Floating

Pin Diagram of LM324:

[Type text]

Bidirectional Visitor Counter

General description on LM324:

The LM324 consists of four independent, high-gain, internally frequency-compensated

operational amplifiers designed specially to operate from a single power supply over a wide range of

voltages.

In linear mode, the input common-mode voltage range includes ground and the output

voltage can also swing to ground, even though operated from only a single power supply voltage. The

unity gain crossover frequency and the input bias current are temperature-compensated.

Features:

Internally frequency-compensated for unity gain

Large DC voltage gain: 100 dB

Wide bandwidth (unity gain): 1 MHz (temperature-compensated)

Wide power supply range Single supply:

3VDC to 30VDC or dual supplies: +/-1.5VDC to +/-15VDC.

Very low supply current drain: essentially independent of supply voltage (1mW/op amp at +5

VDC )

Low input biasing current: 45nADC (temperature-compensated)

Low input offset voltage: 2 mVDC and offset current: 5nADC

Differential input voltage range equal to the power supply voltage

Large output voltage: 0VDC to VCC – 1.5 VDC swing

Typical Applications:

[Type text]

Bidirectional Visitor Counter

Flip-flop:

A flip-flop is a kind of bistable multivibrator, an electronic circuit which has

two stable states and thereby is capable of serving as one bit of memory. Today, the term flip-flop has

come to generally denote non-transparent (clocked or edge-triggered) devices, while the simpler

transparent ones are often referred to as latches. A flip-flop is controlled by (usually) one or two

control signals and/or a gate or clock signal. The output often includes the complement as well as the

normal output. As flip-flops are implemented electronically, they require power and ground

connections.

JK Flip-flop:

The JK flip-flop augments the behavior of the SR flip-flop by interpreting the S

= R = 1 condition as a "flip" or toggle command. Specifically, the combination J = 1, K = 0 is a

command to set the flip-flop; the combination J = 0, K = 1 is a command to reset the flip-flop; and the

combination J = K = 1 is a command to toggle the flip-flop, i.e., change its output to the logical

complement of its current value. Setting J = K = 0 does NOT result in a D flip-flop, but rather, will

hold the current state. To synthesize a D flip-flop, simply set K equal to the complement of J. The JK

flip-flop is therefore a universal flip-flop, because it can be configured to work as an SR flip-flop, a D

flip-flop or a T flip-flop.

Symbol for JK flip-flop:

A circuit symbol for a JK flip-flop, where > is the clock input, J and K are data

inputs, Q is the stored data output, and Q' is the inverse of Q.

[Type text]

Bidirectional Visitor Counter

Equation and Truth table:

The characteristic equation of the JK flip-flop is:

And the corresponding truth table is:

J K Qnext Comments

0 0 Hold State

0 1 0 Reset

1 0 1 Set

1 1 Toggle

[Type text]

Bidirectional Visitor Counter

Pin Diagram of Dual JK flip-flop IC 74LS76:

[Type text]

Bidirectional Visitor Counter

III. Microcontroller AT89C52

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer

with 8Kbytes 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

industry-standard 80C51 and 80C52 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 AT89C52 is a powerful

microcomputer which provides a highly-flexible and cost-effective solution to many embedded control

applications.

Features:

• Compatible with MCS-51™ Products

• 8K Bytes of In-System Reprogrammable Flash Memory

• Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-level Program Memory Lock

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 16-bit Timer/Counters

• Eight Interrupt Sources

• Programmable Serial Channel

• Low-power Idle and Power-down Modes

[Type text]

Bidirectional Visitor Counter

[Type text]

Bidirectional Visitor Counter

Pin configuration of Microcontroller AT89C52:

[Type text]

Bidirectional Visitor CounterBlock Diagram of Atmel 89C52 Microcontroller

[Type text]

Bidirectional Visitor Counter

Pin Description of Microcontroller AT89C52:

Port 0:

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink

eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs.

Port 0 can also be configured to be the multiplexed low order address/data bus during accesses to

external program and data memory. In this mode, P0 has internal pull-ups.

Port 0 also receives the code bytes during Flash programming and outputs the code bytes during

program verification. External pull-ups are required during program verification.

Port 1:

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by

the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input

(P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as

shown in the following table.

Port 1 also receives the low-order address bytes during Flash programming and verification.

Port 2:

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output

buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by

the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

[Type text]

Bidirectional Visitor Counter

low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte

during fetches from external program memory and during accesses to external data memory that uses

16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when

emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2

emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits

and some control signals during Flash programming and verification.

Port 3:

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output

buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by

the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled

low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various special

features of the AT89C51, as shown in the following table. Port 3 also receives some control signals for

Flash programming and verification.

RST:

Reset input. A high on this pin for two machine cycles while the oscillator is running

resets the device.

ALE/PROG:Address Latch Enable is an output pulse for latching the low byte of the address during

accesses to external memory. This pin is also the program pulse input (PROG) during Flash

programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency

[Type text]

Bidirectional Visitor Counter

and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is

skipped during each access to external data memory. If desired, ALE operation can be disabled by

setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC

instruction. Otherwise, the pin is

weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external

execution mode.

PSEN:

Program Store Enable is the read strobe to external program memory. When the AT89C52 is

executing code from external program memory, PSEN is activated twice each machine cycle, except

that two PSEN activations are skipped during each access to external data memory.

EA/VPP:

External Access Enable. EA must be strapped to GND in order to enable the device to fetch

code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if

lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for

internal program executions. This pin also receives the 12-volt programming enable voltage

(VPP) during Flash programming when 12-volt programming is selected.

XTAL1:

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2:

Output from the inverting oscillator amplifier.

[Type text]

Bidirectional Visitor Counter

Data Memory:

The AT89C52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a

parallel address space to the Special Function Registers. That means the upper 128 bytes have the

same addresses as the SFR space but are physically separate from SFR space. When an instruction

accesses an internal location above address 7FH, the address mode used in the instruction specifies

whether the CPU accesses the upper 128 bytes of RAM or the SFR space. Instructions that use direct

addressing access SFR space.

Interrupts:

The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0 and INT1),

three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all shown

in Figure below. Each of these interrupt sources can be individually enabled or disabled by setting or

clearing a bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables

all interrupts at once. Note that Table shows that bit position IE.6 is unimplemented.

Interrupt Enable (IE) Register

[Type text]

Bidirectional Visitor Counter

In the AT89C51, bit position IE.5 is also unimplemented. Timer 2 interrupt is generated

by the logical OR of bits TF2 and EXF2 in register T2CON. Neither of these flags is cleared by

hardware when the service routine is vectored to. In fact, the service routine may have to determine

whether it was TF2 or EXF2 that generated the interrupt, and that bit will have to be cleared in

software. The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the

timers overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2

flag, TF2, is set at S2P2 and is polled in the same cycle in which the timer overflows.

Interrupt Sources

Oscillator Characteristics:

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

that can be configured for use as an on-chip oscillator, as shown in Figure below. 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. There are no requirements on the duty cycle of

the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two

flip-flop, but minimum and maximum voltage high and low time specifications must be observed.

[Type text]

Bidirectional Visitor Counter

Oscillator Connections

Programming the Flash:

The AT89C52 is normally shipped with the on-chip Flash memory array in the erased

state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either

a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The Low-voltage

programming mode provides a convenient way to program the AT89C52 inside the user’s system,

while the high-voltage programming mode is compatible with conventional third party Flash or

EPROM programmers. The AT89C52 is shipped with either the high-voltage or low-voltage

programming mode enabled. The respective top-side marking and device signature codes are listed in

the following table.

The AT89C52 code memory array is programmed byte-by-byte in either programming

mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased

using the Chip Erase Mode.

Programming Algorithm:

Before programming the AT89C52, the address, data and control signals should be set

up according to the Flash programming mode. To program the AT89C52, take the following steps.

1. Input the desired memory location on the address lines.

2. Input the appropriate data byte on the data lines.

3. Activate the correct combination of control signals.

4. Raise EA/VPP to 12V for the high-voltage programming mode.

[Type text]

Bidirectional Visitor Counter

5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write

cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing

the address and data for the entire array or until the end of the object file is reached.

Data Polling:

The AT89C52 features Data Polling to indicate the end of a write cycle. During a write

cycle, an attempted read of the last byte written will result in the complement of the written data on

PO.7. Once the write cycle has been completed, true data is valid on all outputs, and the next cycle

may begin. Data Polling may begin any time after a write cycle has been initiated.

Ready/Busy:

The progress of byte programming can also be monitored by the RDY/BSY output

signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled

high again when programming is done to indicate READY.

Program Verify:

If lock bits LB1 and LB2 have not been programmed, the programmed code data can be

read back via the address and data lines for verification. The lock bits cannot be verified directly.

Verification of the lock bits is achieved by observing that their features are enabled.

Chip Erase:

The entire Flash array is erased electrically by using the proper combination of control

signals and by holding ALE/PROG low for 10 ms. The code array is written with all 1s. The chip erase

operation must be executed before the code memory can be reprogrammed.

Programming Interface:

Every code byte in the Flash array can be written, and the entire array can be erased, by

using the appropriate combination of control signals. The write operation cycle is self timed and once

initiated, will automatically time itself to completion.

[Type text]

Bidirectional Visitor Counter

IV. Display

The circuit comprises three seven segment displays to represent the number of visitors present.

Seven segment display:

A typical 7-segment LED display component, with decimal point.

A seven segment display, as its name indicates, is composed of seven elements. Individually on

or off, they can be combined to produce simplified representations of the Hindu-Arabic numerals.

Often the seven segments are arranged in an oblique, or italic, arrangement, which aids readability.

The individual segments of a seven-segment display.

In a simple LED package, each LED is typically connected with one terminal to its own pin on

the outside of the package and the other LED terminal connected in common with all other LEDs in

the device and brought out to a shared pin. This shared pin will then make up all of the cathodes

(negative terminals) OR all of the anodes (positive terminals) of the LEDs in the device; and so will be

either a "Common Cathode" or "Common Anode" device depending how it is constructed. Hence a 7

segment plus DP package will only require nine pins to be present and connected.

[Type text]

Bidirectional Visitor Counter

V. Power supply

The entire circuit is powered up by a power supply circuit, which is shown

above. The circuit comprises following components,

1. Step-down transformer of 9V/500mA

2. Bridge rectifier

3. A Positive 5 V regulator IC

4. Filter capacitors.

The AC supply of 220V is step-downed to 9V by the step-down transformer.

And the 9v is now given to bridge rectifier to convert the AC source to DC source. The bridge rectifier

consists of four diodes, which two of them comprises forward bias and other two of them reverse bias

during the positive half cycle of AC voltage. And vice versa during the negative half cycle of the AC

source. After rectification, the 9v DC is given to regulator IC 7805. The positive voltage regulator IC

7805, provides a constant 5v DC to the load. Since the output may be pulsated DC, the filters circuit

filters the AC components present in the output to provide a pure DC.

[Type text]

Bidirectional Visitor Counter3.1 Schematic Diagram of Bidirectional Visitor Counter

[Type text]

Bidirectional Visitor Counter

3.2 Circuit Operation

The circuit shows the microcontroller based bidirectional visitor counter, wherein the

transmitter and the receiver form the IR detection circuit. Control logic is built around transistors,

operational amplifier LM324 (IC1) and flip-flop (IC2).

The IR transmitter-receiver setup at the entrance-cum-exit of the passage is shown at

the block diagram. Two similar sections detect interruption of the IR beam and generate clock pulse

for the microcontroller. The microcontroller controls counting and displays the number of persons

present inside the hall. When nobody is passing through the entry/exit point, the IR beam

continuously falls on phototransistor T1. Phototransistor T1 conducts and the high voltage as its

emitter drives transistor T3 into saturation, which makes pin 3 of comparator N1 low and finally

output pin 1 of comparator N1 is high.

Now if someone inters the place, first the IR beam from IR TX1 is interrupted and then

the IR beam from IR TX1 is interrupted, phototransistor T1 and transistor T3 cut-off and pin 3 of

comparator N1 goes high. The low output (pin1) of comparator N1 provides negative trigger pulse to

pin 1 of J-K flip-flop IC(A). At this moment, the high input at ‘J’ and ‘K’ pins of flip-flop IC2(A)

toggles its output to low. On the other hand, the low input at ‘J’ and ‘K’ pins of IC2(B) due to clock

pin 1 of IC2(A) and ’J’ input (pin 9) and ‘K’ input (pin 12) of IC2(B) are connected to pin1 of

comparator N1. the negative-going pulse is applied to clock pin 6 of IC2(B) when the person

interrupts the IR beam from IR TX2. There is no change in the output of IC2(B) flip-flop. This

triggers the external interrupt INT0 (pin 12) of microcontroller AT89C52.

The AT89C52 us an 8-bit microcontroller with 8 kb of flash based program memory,

256 bytes of RAM, 32 input/output lines, three 16 bits timers/counters, on-chip oscillator and clock

circuitry. A 12MHz crystal is used fro providing clock. Ports 0, 1 and 2 are configured for 7-segment

displays. Port-0 pin is externally pulled up with 10-kilo-ohm resistor network RNW1 because port-0

is an 8-bit, open-drain, bidirectional, input/output (I/O) port. Port-1 and port-2 are 8-bit bidirectional

I/O ports with internal pull-ups (no need of external pull-ups).

[Type text]

Bidirectional Visitor Counter

Port pins 3.0 and 3.1 are configured to provide the set pulse to J-K flip-flops IC2(A)

and IC2(B), respectively. External interrupts INT0 and INT1 Receive the interrupt the IR beams.

Resistor R9 and capacitor C5 provide power-on-reset pulse to the microcontroller. Switch S1 is used

for manual reset.

When the microcontroller is reset, the flip-flops are brought in ‘set’ state through the

microcontroller at software run time by making their ‘set’ pin high for a moment. The value of the

counter increments by ‘1’ when the interrupt service routine for INT0 is executed. The output of the

corresponding J-K flip-flop is set to ‘high’ again by making its ‘set’ input pin low through the

microcontroller is configured as a negative-edge-triggered interrupt sensor.

Similarly, if somebody exits the place, first the IR beam from IR TX2 is interrupted and

then the IR beam from IR TX1. When the beam from IR Tx2 is interrupted, output pin 7 of

comparator N2 goes low. This provides clock pulse to pin 6 of J-K flip-flop IC2(B).

At this moment, the high input at ‘J’ and ‘K’ pins of flip-flop IC2(B) toggles its output

to low. ON the other hand, the low input at ‘J’ and ‘K’ pins of IC2(A) flip-flop. This triggers the

external interrupt INT1 (pin 13) of microcontroller AT89C52. The value of the counter decrements by

‘1’ when interrupt service routing for INT1 is executed. The output of the corresponding J-K flip-flop

is set to ‘high’ again by making its ‘set’ input pin low through the microcontroller.

[Type text]

Bidirectional Visitor Counter

4.1 Algorithm

Algorithm:

Step 1 : Start the process

Step 2 : Select ports 0, 1, 2 as output ports for displaying the count value in

7-segment display

Step 3 : Select port 3 also as output port for providing set pulse to flip-flop

Step 4 : When external interrupt INT0 occurred, increment the count by 1.

Step 5 : When external interrupt INT1 occurred, decrement the count by 1.

Step 6 : Continue the process, whenever the interruption occurs.

[Type text]

Bidirectional Visitor Counter

4.2 Flow chart

Flow chart:

[Type text]

START

Ext-interrupt occurred!INT0 or INT1

Send data to display the count in 7-segment via the ports 0, 1, 2

Select Ports 0, 1, 2 as output ports for 7-segment display

Select Port 3 as output port for providing set- pulse to

flip-flop

Increment the count by 1

Decrement the count by 1

Bidirectional Visitor Counter

4.3 Program Coding

The program coding for this bidirectional visitor counter circuit is written in ‘C’

language and is compiled using C51 Keil compiler.

Program:

#include <AT89x52.h>int i=0,j,k,l,m,a[ ]=[63,6,91,79,102,109,125,7,127,111];void enter (void) interrupt 0{i++;if(i>999) i=999;P3_1=0;for(m=0;m<=1000;m++);P3_1=1;}void exit (void) interrupt 2{i--;if(i<0) i=0;P3_0=0;for(m=0;m<=1000;m++);P3_0=1;}void main(){IE = 1333;TCON = 5;P3_0=1;P3_1=1;i=0;while(1){j=i%10;k=i/10;l=i/100;k=k-l*10;P2=a[j];P0=a[k];P1=a[l];}}

[Type text]

Bidirectional Visitor Counter

5.1 PCB Design and Fabrication

PCB Design:

Using the Protel schematics software, designed this PCB.

Protel for windows PCB 1.5 capabilities:

Protel for windows PCB is a complete PCB layout environment with many attractive

features for productive design work. You can use Protel for windows PCB as a stand-alone manual

board layout. When combined with the schematics capture package, Protel for windows PCB

becomes the backbone of fully automated, end to end design system that features a high degree of

design automation and integration. However you use Protel for windows PCB, you will appreciate its

helps of use and the high degree of flexibility built into this proven PCB design system.

PCB generates through hole and design and SND design of up to sixteen signal layers,

plus four mid layer power planes and four mechanical drawing layers. Board size can be as big as 100

inches (or 81 cm) square. Placement accuracy is to 1/1,000,000 inch (.001 mil or .00025 mm).

Metric/imperial grid system allows you to work accurately in both measurement system and the gird

can be “toggled” Between metric and imperial modes as you design by pressing Q.

A PCB design is a series of layers which correspond to the individual “tools” used to

create the board such as the top and bottom signal layers independently and some operations, such as

track placement and layers dependent – you must first select the layers and then place the track. PCB

print/plot options also reflect this requirement for “layered” design.

PCB design differs from other drawing tasks in its requirements for extreme precision.

As a result, PCB is more of a “placing” environment than a freehand “drawing” environment. Another

fundamental difference is connectivity – PCB’s ability to recognize connection between track

segments, tracks and component pads, etc. for example, PCB allows you to move a component without

breaking its track to pad connections. You will be using connectivity on several levels as you design

with PCB.

[Type text]

Bidirectional Visitor Counter

PCB fabrication :

The proposed PCB has been carefully designed by considering all the aspects

such as the overall circuit functionality, size requirements, electromagnetic interface, etc. once the

PCB pattern is photographed and reproduce on clear plastic sheet. The plastic sheet is placed over a

copper glass epoxy or phenolic board, the assembly is injected to undergo a photochemical process

and the resulting copper coated board consists of printed tracks which interconnect the components as

per the schematic design. The basic material used for making printed circuit board is copper clad

phenolic resin laminate. For general use, fuse boards are single sided.

The procedure for making PCB is as follows,

The board has to be cut to the required size and the copper surface has to be

cleaned.

The drawing of the circuit through which conduction takes place is made on the

copper surface using resist inks.

Then the uncovered copper areas are etched away in chemical bath.

The resist ink is removed to expose copper conducting areas.

Degreasing and cleaning the board are necessary to ensure that the areas take solder

readily.

Layout starts with an experimental design of components position and connections

are required.

Connections on a PCB should cross and sketching is usually done when

components positions are to be altered. Tracking of the PCB plane has to be made

after having arrived at a suitable layout.

The copper surface should be cleaned and dried before sketching the circuit in the

board.

After tracking the pattern on the copper surface, this pattern then painted with resist

marker pen. It is allowed to dry for about 15 minutes.

The board is then transferred to an etching bath. This consists of a solution of ferric

chloride kept in a plastic tray.

[Type text]

Bidirectional Visitor Counter

The board is placed in the path such that the copper surface is kept facing upwards.

This process is to be continued until all the tracks of copper have disappeared from

the surface.

After etching, the board is removed and washed under running water to remove

traces of chemicals.

Finally it is dried with soft cloth. The rest should be done is drilling.

The points to be considered while drilling are,

Drilling should carryout such that the copper side is upper most. The use of a sharp

drill is a must.

A hard material under the board prevents the points of the drill from tearing up a

lump out of the back of the board, when the drill breaks through.

To prevent the drill running of its correct position while drilling, the point to be

drilled has to be spotted with the center punch.

Vertical drill stand is best suited for drilling PCB’s. This should ensure square

holes. Due to small size drill is used breakage rate can be high.

The original tracking will be helpful for making the components positions on the

plan side of the board, which acts a guide for components assembly.

[Type text]

Bidirectional Visitor Counter

5.2 PCB Layout

PCB Layout for Bidirectional Visitor Counting Circuit:

[Type text]

Bidirectional Visitor Counter

[Type text]

Bidirectional Visitor Counter

6. Conclusion

Thus the project entitled “Bidirectional Visitor Counter” helps to measure the

visitor entering and exiting a particular passage or way. The circuit counts both entering and

exiting visitors and displays the number of visitors present inside the hall. Visitor counting is

not limited to the entry/exit point of a company but has a wide range of applications that

provide information to management on the volume and flow of people throughout a location.

the visitor helps to maximize the efficiency and effectiveness of employees, floor area and

sales potential of an organization.

The circuit may also be enhanced with a wide counting range of above three

digits by modifying software section of the system. It can also be enhanced for long and

accurate sensing range using a laser torch instead of IR transmission circuit. Thus the circuit

can be used to monitor visitor flow in effective manner, where the visitors have to counted and

controlled.

[Type text]