DIGITAL VISITOR

COUNTERby Spandana &

Sharmistha

WHY DO WE NEED ONE ?Visitors counting is simply a

measurement of the visitor traffic entering and exiting

Offices Malls Sports venues Metro stations Industries Lift Car parking

WHAT IS IT ?

Reliable circuit that takes over the task of counting number of persons/ visitors in the room very accurately

When anybody enters into the Room then

the counter is Incremented by one and when any one leaves the room then the counter is decremented by one. The total number of persons inside the room is displayed on the seven segment displays.

PRINCIPLE OF DIGITAL COUNTER

The sensor pairs are placed face to face so that an IR radiations from IR LED are continuously received by phototransistor which makes its emitter base junction forward and collector current Ic equals to emitter current Ie (i.e, Ic=Ie) assuming base current to be negligible.

Hence the voltage at collector node becomes zero (logic 0) which is fed to microcontroller port pin P3.2 and P3.3, if any object is placed in between the sensor pair blocks the IR radiation which in turns put the phototransistor in cut-off mode and Ic!=Ie, this makes collector voltage to +5V (logic 1)

If sensor pair one is been obstructed (P3.2 becomes one) first, implies persons entry and second pair is obstructed (P3.3 becomes one) first shows exit.

COMPONENTS Resistors Capacitors Transistors Integrated Circuits-555 Timers Sensors AT89C2051 processor 7 segment display units Power Supply

RESISTOR Resistor is a passive component that

resists the flow of direct or alternating electric circuit.

The resistance of the resistor can be estimated by their colour codes.

There are some non linear resistors whose resistance changes with temperature or light.

CAPACITORS:

Capacitor is a passive component used to store charge.

capacitors are used for smoothing power supply variations , coupling the various stages of audio system, tuning in radio circuits, store energy like in a camera flash.

TRANSISTORS:

Transistor SL100: It is a medium power NPN Transistor. Commonly used as switch in common emitter

configuration. Transistor BC547: NPN transistor. Low voltage(max 65v) Low current(max 100mA) Used for general purpose switching and amplification.

555 TIMER:

It is an 8pin timer IC. It has mainly two modes of operation:

monostable and astable. In monostable mode time delay of the

pulses can be precisely controlled by an external resistor and a capacitor.

In astable mode the frequency & duty cycle are controlled by two external resistors and a capacitor

SENSORS

A sensor is a device which receives and responds to a signal.

Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base

FEATURES OF THE AT89C2051 PROCESSOR

Compatible with Intel 8051 2kB of internal FLASH program memory

(1000 write cycles) Voltage range from 2.7 to 6 V Fully statical operation Clock 0 Hz to 24 MHz Two-level data protection

128 bytes of internal RAM 15 programmable I/O pins Two 16-bit counters/timers Analog comparator 6 interrupt sources Programmable UART - (RS232) 2 power-saving modes Small and non-expandable program

memory

PIN DIAGRAM OF AT89C2051

CIRCUIT DIAGRAM

According to the previous diagram, we see that

Pin 1 is also known as the reset input. All the i/o are rested to 1 as soon as the RST goes high. Here, each machine cycle has 16 clock cycles

Pin 2 and 3 are connected to the 555 timers which act as serial input and output ports.

Pin 4 and 5 are XTAL2 and XTAL1 respectively which means that input to the internal inverting amplifier and output from the inverting amplifier.

Pin 6 is left open. Pin 7,8 and 9 are connected to the resistor

and then connected to the transistors BC 547

These pins are bidirectional i/o pins with internal pull ups.The Port 3 outputs buffers can sink 20 mA which is done so that the base of the transistor is in the forward biased even if the logic high is written on port 3 pins, they are pulled high by the internal pull ups and can used as inputs. As inputs, port 3 will source currents due to pull ups.

Pin 10 will be grounded as per the pin configuration

Pin 13,14,15,16,17,18 and 19 are connected to three seven segment display units. The Port 1 out-put buffers can sink 20 mA and can drive LED displays directly . Here they are used as output ports.

PROCEDURE

The IR transmitter will emit modulated 38 kHz IR signal and at the receiver we use TSOP1738 (Infrared Sensor).

The output goes high when the 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.

SL100 is to trigger the IC555 which is configured as monostable multivibrator.

Input is given to the microprocessor. Microprocessor gives output to the 7-

Segment display. LTS542 (Common Anode) is used for 7-

Segment display. Reset button will reset the microprocessor.

555 timer IC is configured to function as a basic monostable multivibrator. A monostable multivibrator is a timing circuit that changes state once triggered, but returns to its original state after a certain time delay. It got its name from the fact that only one of its output states is stable. It is also known as a ‘one-shot’.

In this circuit, a negative pulse applied at pin 2 triggers an internal flip-flop that turns off pin 7′s discharge transistor, allowing C1 to charge up through R1. At the same time, the flip-flop brings the output (pin 3) level to ‘high’. When capacitor C1 as charged up to about 2/3 Vcc, the flip-flop is triggered once again, this time making the pin 3 output ‘low’ and turning on pin 7′s discharge transistor, which discharges C1 to ground. This circuit, in effect, produces a pulse at pin 3 whose width t is just the product of R1 and C1, i.e., t=R1C1.

ADVANTAGES Provide information to management on

the volume and flow of people throughout a location

Human-based data collection comes at great expense.

Counting the visitors helps to maximise the efficiency and effectiveness of employees, floor area and sales potential of an organisation

Low-cost microprocessor based visitor counter is easy to build

Thank you