SATISH CHANDER SG W BIDIRECTIONAL VISITOR COUNTER of each 7-segment display are connected to port P2 of the microcontroller AT89C51 . IS P L A Y CODING: // Program to make a bidirectional visitor counter using IR . Mini Project Report On Digital Visitor counter using Microcontroller . ROOM APPLIANCE CONTROL WITH BIDIRECTIONAL VISITOR COUNTER. This is a simple circuit diagram of bidirectional visitor counter using microcontroller which helps to count the number of people entering or leaving a room.

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Skip to main content. Log In Sign Up. The report embodies result of original work and studies carried out by student himself 80551 the contents of the thesis do not form the basis for the awrd of any other degree or diploma to the candidate or to anybody else.

Signature of the project guide MR. I also give special thanks to my colleagues for that endless flow of ideas and all those who helped in this project in some way or the other.

The circuit given here can count numbers from 0 to in up and down modes depending upon the state of the selector. It can be used to count the number of persons entering a hall in the up mode at entrance gate. In the down mode, it can count the number of persons leaving the hall by decrementing the count at exit gate. It can also be used at gates of parking areas and other public places. This circuit divided in three parts: The same count is displayed on a set of 7-segment displays through the controller.

Microcontroller (AT89C51) based Digital Visitor Counter Project

From the block diagram it is clear that the sensor pairs are placed face to face so that an IR radiations viitor IR LED are continuously received by phototransistor which makes its emitter base junction forward and collector current Ic equals to bidirecional current Usng i.

Hence the voltage at collector node becomes zero logic 0 which is feed to microcontroller port pin P3. In this circuit, two infrared IR bidirecitonal modules are used each for up and down counting, respectively. Whenever an interruption is observed by the first IR sensor, it increments the counter value.

Similarly, when the second sensor detects an obstacle, the count is decremented. The sensor inputs are defined as up and down selector modes for the counter in the code. At each step, the value of the counter is sent to be displayed on the segments. For more details refer seven segment multiplexing. It is often required to produce a signal whose frequency or pulse rate is very stable and exactly known. This is important in any application where anything to do with time or exact measurement is crucial.

It is relatively simple to make an oscillator that produces some sort of a signal, but another matter to produce one of relatively precise frequency and stability. An ordinary quartz watch must have an oscillator bidirectoonal to better than a few parts per million. One part per million will result in an error of slightly less than one half second a day, which would be about 3 minutes a year.

This might not sound like much, but an error of 10 parts per million would result in an error of about a half an hour per year. A clock such as this would need resetting about once a month, and more often if you are the punctual type. This frequency is commonly used to keep track of time as in quartz wristwatchesto provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers.

The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around them were called “crystal oscillators”. Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of megahertz. Most are small devices for consumer devices such as wristwatches, clocks, radios, computers, and cellphones. Quartz crystals are also found inside test and measurement equipment, such as counters, signal generators, and oscilloscopes. A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions.


Almost any object made of an elastic material could be used like a crystal, with appropriate transducers, since all objects have natural resonant frequencies of vibration. For example, steel is very elastic and has a high speed of sound.

It was often used in mechanical filters before quartz. The resonant frequency depends on size, shape, elasticity, and the speed of sound in the material. High-frequency crystals are typically cut in the shape of a simple, rectangular plate. For applications not needing very precise timing, a low-cost ceramic resonator is often used in place of a quartz crystal.

Automatic bidirectional visitor counter using 8051 microcontroller (AT89C51)

When a crystal of quartz bidirectoinal properly cut and mounted, it can be made to distort in an electric field by applying a voltage to an electrode near or on the crystal. This property is known as piezoelectricity. When the field is removed, the quartz will generate an electric field as it returns to its previous shape, and this can generate a voltage. The result is that a quartz crystal behaves like a circuit composed of an inductor, capacitor and resistor, with a precise resonant frequency.

Quartz has the further advantage that its elastic constants and its size change in such a way that the frequency dependence visiotr temperature hsing be very low. The specific characteristics will depend on the mode of vibration and the angle at which the quartz is cut relative to its crystallographic axes. This means that a quartz clock, filter or oscillator will remain accurate.

For critical applications the quartz oscillator is mounted in a temperature-controlled container, called a crystal oven, and can also be mounted on shock absorbers to prevent perturbation by external mechanical vibrations. The connections on the PCB should be identical to the circuit diagram, but while the circuit diagram is arranged to be readable, the PCB layout is arranged to be functional, so there is rarely any visible correlation between the circuit diagram and the layout. The best results are usually still achieved using atleast some manual routing Sometimes abbreviated PCB, a thin plate on which bidirectiojal and other electronic components are placed.

A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. It may use an electromechanical bkdirectional, or passive or active electronic components.

Depending on the design, it may be used to regulate one or more AC or DC voltages. With the exception of passive shunt regulators, all modern electronic visitof regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element in such a way as to reduce the voltage error. If the output voltage is too low perhaps due to input voltage reducing or load current increasingthe regulation element is commanded, up to a point, to produce a higher output voltage – by dropping less of the input voltage for linear series regulators and buck switching regulatorsor to draw input current for longer periods boost-type switching regulators ; if the output voltage is too high, the regulation element will normally be commanded to produce a lower voltage.

Fig Regulator ICs The 78xx also sometimes known as LM78xx series of devices is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is a very popular choice for many electronic circuits which require a regulated power supply, due to their ease of use and relative cheapness.

When specifying individual ICs within this family, the xx is replaced with a two-digit number, which indicates the output voltage the particular device is designed to provide for example, the has a 5 volt output, while the produces 9 volts. There is a related line of 79xx devices which are complementary negative voltage regulators. The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the bifirectional rating. Other characteristics include temperature coefficient, noise, and inductance.

Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it’s determined by design. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads or terminals are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.


During manufacture, at in film of carbon is deposited onto a small ceramic rod. The resistive coating is spiraled away in an automatic machine until the resistance between there two ends of the rods is as close as possible to the correct value.

A wire wound resistor is made of metal resistance wire, and because of this, they can be manufactured to precise values. Also, high wattage resistors can be made by using a thick wire material. Wire wound resistors cannot be used for high frequency circuits. Coils are used in high frequency circuit. Wire wound resistors in a ceramic case, strengthened with special cement.

They have very high power rating, bidirectiona, 1 or 2 watts to dozens of watts. These resistors can become extremely hot when used for high power application, and this must be taken into account when ueing the circuit. This field stores energy and produces a mechanical force between the conductors.

The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates. An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current.

The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage. Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.

Inside the capacitor, vvisitor terminals connect to two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or anything else that does not conduct electricity and keeps the plates from touching each other. It won’t be a particularly good capacitor in terms of its storage capacity, but it will work. In an electronic circuit, a capacitor is shown like this: They are often referred to in electronics usage simply as “electrolytics”.

They are valuable in relatively high-current and low-frequency electrical circuits. This is especially the case in power-supply filters, where they store charge needed to moderate output voltage and current fluctuations in rectifier output. They are also widely used as coupling capacitors in circuits where AC should be conducted but DC should not.

Electrolytic capacitors can have a very high capacitance, allowing filters made with them to have very low corner frequencies. They are available in small values, and are mostly used at high frequencies. C0G and NP0 negative-positive-zero, i.

Ceramic capacitors tend to have low inductance because of their small size. NP0 refers to the shape of the capacitor’s temperature coefficient graph how much the capacitance changes with temperature.

NP0 means that the graph is flat and the device is not affected by temperature changes. Typically values range from 5 pF to 60 pF. The negative terminal is fashioned into a snap fitting which mechanically and electrically connects to a mating terminal on the power connector. The power connector has a similar snap fitting on its positive terminal which mates to the battery. This makes battery polarization obvious since mechanical connection is only possible in one configuration.