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When we are furnishing a home, light is everything. The light level in a room dictates what we can and cannot do and it has a huge effect on how we feel.
The problem is that people need to use some rooms for multiple purposes and these different functions call for varying amounts of light. The dimmer switch is a handy electrical component that allows the user to adjust light levels from nearly dark to fully lit by simply turning a knob or sliding a lever.
Early dimmer switches were very efficient but the problem with them is using a lot of energy to heat the resistor, which does not help to light up the room but still costs a lot. In addition to be being inefficient, these switches tend to be cumbersome and potentially dangerous, since the variable resistor releases a substantial amount of heat.
Thus the only solution to vary the intensity of light even in small steps or vary the speed of an AC motor is by using a TRIAC. The dimmer switch rapidly turns the circuit on and off to reduce the energy flowing to the circuit. The central element in this switching circuit is a triode alternating current switch or TRIAC.
The speed of AC motor can be varied rapidly on and off by TRIAC. The main advantage of using a TRIAC to vary the speed of an AC motor is the TRIAC reduces the energy flow to the motor and TRIAC works very well for alternating current
POWER SUPPLY:
Whenever the 230v ac supply is connected to the step down transformer the transformer steps down the voltage to the 12v ac. This is converted into pulsating dc by the bridge rectifier formed by connecting the 1n4007 diodes. The output of diodes is connected across the 1000uf 35v capacitor to filter the ripples in the pulsating dc. This pure dc is connected to the 7805 and 7818 voltage regulator IC’s. The 7805 voltage regulator IC gives the regulated 5v output and 7812 voltage regulator IC gives 12v output. This pure regulated dc is used in the circuit.
SWITCH POSITION:
The switch position section will enable the microcontroller to know whether we have pressed the switch or not. This design will give the logic one when the switch is not pressed and will give the logic zero when the switch is pressed. This will enable us to construct the software according to it. Total three push to on switches are used in this section. Each switch will have special function.
CRYSTAL OSCILLATORS:
The circuit is connected to 18th and 19th pin of the microcontroller. This crystal oscillator circuit generates the frequency which is used by the internal oscillator of the microcontroller to generate the clock pulse. This clock pulse is used by microcontroller to control all the section of the controller synchronously with clock pulse. This crystal is used in the circuit generates a sinusoidal voltage at a frequency of 11.0529MHZ the crystal frequency will also determine the speed of the controller.
RESET SWITCH:
The reset switch is used to reset the microcontroller. When ever switch is pressed logic one is given to the 9th pin of microcontroller. This will make the microcontroller to again start executing the program from starting
LCD DISPLAY:
In this project we have used a 16*2 alpha numerical LCD to display the status of the controller. Thus LCD is connected to microcontroller through port1. This LCD contains a port named “RS” which make the LCD known whether the code send by microcontroller is data or the instruction .and the port ”RW” of the LCD will make the LCD known whether we are writing the data to the LCD or reading the date. As in the circuit we are only writing the data to the LCD we connected to pin directly to ground.
89S52 MICRO CONTROLLER
89S52 chips are used in a wide variety of control systems, telecom applications robotics applications as well as in the automotive industry. By some Estimations 89S52 family chips make up over 50% of the embedded chip market.
Pin diagram of the 89S52 DIP:
PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller`s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)
PINS 18 & 19: 89S52 has a built-in oscillator amplifier hence we need to only connect a crystal at these pins to provide clock pulses to the circuit.
PIN 40 & 20: Pins 40 and 20 are VCC and ground respectively. The 89S52 chip needs +5V 500 MA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 89S52which runs on +3v.
TRAIC:
TRAIC, from Triode for alternating current, is a generisized trade name for an electronic component that can conduct current in either direction when it is triggered (turned on), and is formally called a bidirectional triode thyristor or bilateral triode thyristor
TRIACs belong to the thyristor family and are closely related to silicon-controlled rectifiers (SCR). However, unlike SCRs, which are unidirectional devices (i.e, can conduct current only in one direction), TRAICs are bidirectional and so current can flow through in either direction. Another difference from SCRs is that TRAICs can be triggered by either a positive or a negative current applied to its gate electrode, where as SCRs can be triggered only by currents going in to the gate. In order to create a triggering current, a positive or negative voltage has to be applied to the gate with the respect to the MT1 terminal (otherwise known as A1)
Once triggered, the device continues to conduct until the current below a certain threshold, called the holding current
The bi directionality makes TRAICs very convenient switches for AC circuits, also allowing them to control very large power flows with milli ampere-scale gate currents. In additions, applying a trigger pulse at a controlled phase angle in an AC cycle allows one to control the percentage of current that flows through the TRAIC to the load (phase control), which is commonly used, for example, in controlling the speed of low-power induction motors, in dimming lamps and in controlling AC heating resistors.
STEP DOWN TRANSFORMER:
A transformer is a device which is use to high alternating voltage to a low alternating voltage and vice versa.
WORKING PRINCIPLE:
Transformer works on the principle of mutual induction of two coils. When current in the primary coil is changed the flux linked to the secondary coil also changes. Consequently an EMF is induced in the secondary coil.
CONSTRUCTION:
A transformer consists of a rectangular core of soft iron in the form of sheets insulated from one another. Two separate coils of insulated wires, a primary coil and a secondary coils are wound on the core. These coils are well insulated from one another and form the core. The coil on the input side is called primary coil and the coil on the output side of the coil is called secondary coil.
WORKING:
Suppose an alternating voltage source Vp is connected to primary coil. Current in the primary will produce a magnetic flux in the secondary also changes which results an EMF Vs in secondary. According to faradays low EMF induced in a coil depends upon the rate of change of magnetic flux in the coil. If resistance of the coil is small then the EMF will be equal to voltage applied.
Vp/Vs =Np/Ns
This expression shows the magnitude of EMF depends upon the number of turns in the coil.
AC MOTOR WORKING PRINCIPLE
AC motors are widely used to drive machinery for a wide variety of applications. To understand how these motors operate, a knowledge of the basic theory of operation of AC motors is necessary
Principles of Operations
The principle of operation for all AC motors relies on the interaction of a revolving magnetic field created in the stator by AC current, with an opposing magnetic field either induced on the rotor or provided by separate DC current source.
The resulting interaction produces usable torque, which can be coupled to desired loads throughout the facility in a convenient manner. Prior to the discussion of specific types of AC motors, some common terms and principles must be introduced.
Rotating field
Before discussing how to a rotating magnetic field will cause a motor rotor to turn, we must first find out how a rotating magnetic field is produced. Figure1 illustrates a three phase stator to which a three phase AC current supplied.
The windings are connected in wave. The two windings in each phase are wound in the same direction. At any instant in time, the magnetic field generated by one particular phase will depend on the current through that phase.
If the current through that phase is zero, the resulting magnetic field is zero .if the Current is at a maximum values, the resulting field is at a maximum value.
Since the currents in the three windings are 120 out of phase, the magneticfields
Produced will also be 120 out of phase. The three magnetic fields will combine to produce one field, which will act upon the rotor.
In an AC induction motor, a magnetic field is induced in the rotor opposite in
polarity of the magnetic field in the stator. Therefore, as the magnetic field rotates in the stator, the rotor also rotates to maintain its alignment with the stators magnetic field. The remainder of this chapter’s discussion deals with AC induction motors.
C REGULATOR:
7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs . The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage .It is designed to provide. 7805 provides+5V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.
CONCLUSION:
The final prototype of our project is constructed which works with minimum supply of 6 volts. During the project we learned many electrical and electronics components as well as to work in groups. We now able to understand the need for proper planning and organized actions and we hope that this project will help us in our future.
By this project we are able to know how the microcontroller is programmed practically and how the hardware is designed based on the software