Visitor Counter Seminar Report

Explanation of the Circuit
Microcontroller PIC16F873
The Microcontroller receives input from three external circuits: the sensors, the Light dependent resistor, and the LM35 temperature sensor. It then sends output to the Liquid Crystal Display, the light bulb and to the fans. It is the heart of the circuit that controls the actual automation processes.
Light Dependent Resistor
LDR is a passive device whose resistivity is a function of the incident electromagnetic radiation (light). The resistance decreases drastically when light falls on it and increases when the light is moved away from it. They are made up of semiconductor materials (usually cadmium sulphide), having no p-n junction but with a high resistance.
The input from the LDR goes

The Visitor Counter
A visitor counter is a system that can read the number of people coming in or going out of a place through particular space at the boundary of the place. The bidirectional counter system gives the number of people entering a room subtracted from the number of people exiting the room. The micro controller does the subtraction. The bidirectional counter consists of two IR transmitter and two IR receiver.
An IR transmitter is simply a LED diode that emits lights in the infrared region (700nm – 1mm) of the electromagnetic spectrum due to recombination of electrons into holes in the semiconductor as current flows through. Such diodes are usually made of gallium arsenic, gallium Antimony or Indium phosphide.
The IR receiver is simply a phototransistor. A phototransistor is a transistor, without a base lead, that uses light (in this case infrared light) rather than electricity to cause an electric current to flow from one side to the other, hence they are used to convert light signals into electric signals. They are usually made of silicon or Germanium (Ambroziak, 2010). A resistor placed in series with the phototransistor controls the sensitivity of the phototransistor to light. A higher resistance makes the phototransistor circuit more sensitive to