20-12-2012, 03:16 PM
Automatic room light controller with visitor counder
Automatic room light controller with visitor counder.docx (Size: 245.89 KB / Downloads: 270)
Introduction
In our busy life we used to forget to switch off the lights or appliance while going out. This causes the wastage of energy. Automatic room light controller will solve these problems.
The project Automatic room light controller is a reliable circuit that takes over the task of controlling the room lights as well as counting the number of persons in the room very accurately. When somebody enters into the room then counter is incremented by one and the light in the room will be switched ON and when any one leaves the room then the counter is decremented by one. The light will be switched off when all the persons in the room go out of the room. The total number of persons inside the room is also displayed on the LCD.
The microcontroller does the job of counting. It receives the signals from the sensors, and operates under the control of software which is stored in the ROM.
Power supply:
230v line voltage is step-down, rectified, filtered and regulated using regulators to obtain desired voltages. The regulator circuit will give +5V output.
Sensing unit:
Sensing unit consists of IR transmitter and IR Receiver. It is used to sense the number of persons entering and leaving the room.
Controlling unit:
Controlling unit consists of microcontroller AT89S52.It is used to control the system. It counts the number of persons entering and leaving the room using sensor. It sends the signal to turn on Light Emitting Diode (LED) and sends data to be displayed on Liquid Crystal display (LCD).
Display unit:
Display unit consist of liquid crystal display (LCD).It is 16*2 type. It is used to display the number of persons in the room.
Transformer
Transformers convert AC electricity from one voltage to another with little loss of power. Step up transformer increase voltage, step down transformer reduce the voltage. Most power supply use a step down transformers to reduce the dangerously high mains voltage to a safer low voltage.
The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the 2 coils; instead they are linked by an alternating magnetic field created in the soft iron core of the transformer. Transformer waste very little power so the power out is almost equal to the power in. note that as voltage is stepped down current is stepped up. The ratio of number of currents turns on each coil called the turns ratio, determines the ratio of the voltages. A step down transformer as a large number of turns on its primary coil which is connected to the high voltage mains supply and a small number of turns on its secondary coil to give a low output voltage.
In our project we are using 12-0-12 step down transformer.
Bridge rectifier
A bridge rectifier can be made using 4 individual diodes as shown in figure 3.2 , but it is also available in special packages containing the 4 diodes required. It is called a full wave rectifier because it uses the entire AC wave.1.4V is used up in the bridge rectifier because each diode uses 0.7V when conducting and there are always 2 diodes conducting during each half cycle. Bridge rectifiers are rated by the maximum current they can pass and the maximum reverse voltage they can withstand. This must be at least 3 times the supply RMS voltage so the rectifier can withstand the Peak voltage.