21-07-2014, 12:25 PM
TRANSFORMER LESS AUTOMATION HOME APPLIANCE CONTROL SYSTEM
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ABSTRACT
Transformer less automation home appliance control system is a very useful project. Generally house supply 230V. 50Hz AC. Every electronics circuits needed small quantity DC .So All are use step-down transformer but we are discovered in this project without use transformer that is specialize for our project. This is sensor based project. This project is operated in DC +12volt. It can control to electrical device (fans, lights, Freeze and air-conditions etc).This project is not just for demonstration, it is practically possible. This project is related to Basic electronics experiment. Our project is completely based on Basic electronics. This project is discovered by our guide Er…………. This project is a very interesting and new one for all. This project can be used in Govt. sector, Private sector, Public sector and Domestic purpose. This project is meant for light sensitivity switch, Water tank levels Indicator, temperature sensitive FAN cooling1. This can be used for energy conservation system . It can be used every where any machine operates, i.e. when sunlight falls morning, as night falls, or in dark room, lighted room etc. The present project is sensing agent which senses the light and then operates accordingly. For example we can connect it to the street light . It senses the daylight. When sun sets, it will be dark. This helps in triggering the street light to switch ON. Fan speed is depend on room temperature. We are set in a particular temperature. When room temperature either fall or rise fan will ON/OFF. It helps the manpower for making switch ON and OFF. Automatic controlling of water level while filling the container of level . As the water layer crosses the particular level which is predefined. The corresponding LEDs glow. Thus this circuit can be use as indication of knowing the current content of water in the container . The electrodes connected in the output should be dropped in the container. The input of each electrodes is connected to each switch of the transistor. There is one common electrode switch continuously emits 5v D. C. power, as water is conductor of electricity, the respective electrodes captures this power voltage while filling the container with water. This causes the control inputs of each switch to go high as water fills which in terns switches particular LEDs to ground. This allows corresponding LEDs to glow indicating the level of water. As the water reaches its top most position the transistor switches, the motor rotating will be stop. That is indicating water container is full. This project also helps to reducing energy consumption due to our forgetfulness to switch off the switch as sunlight comes in the morning. It also helps in switching ON the light as soon as night falls. Therefore it maintains a routine to switch ON and OFF.
POWER SUPPLY
Power supply is essential for circuit operation and to provide the reference voltage. Therefore it should be regulated. A 220V AC to 2- 0-12 v transformer is used and for rectification four diodes IN4007are connected for Bridge type fashion wave rectification of the reduced AC SUPPLY. Filter capacitor of 1000uF is used. Then it is regulated to +12V & +05 using positive regulator 7812 &7805.
Circuit Explanations
When 230V.50Hz ac signal is given to the circuit through the resistor this resistor can be reduced to the power. Then diodes are connected in a bridge fashion for rectification purposes. The regulator 7812 &7805 positive regulator offer contained fixed – voltage capability up to 1.0 ampere of load current and input voltage up to 35 volts This unit provides a unique on chip trimming system to set the out put voltages to within +/- 1.5% of nominal on the IC . It provide a line as well as load regulation. All protective feature like thermal shutdown current limiting, and safe area control have been design into these units and since these regulator requires only a small out put capacitor for satisfactory performance ease of application is assured. Although the voltage fixed the output voltage can be increased by voltage divider method.
AUTOMATIC LIGHT
Automatic light system is part of this project. Automatic light system meant for light sensitivity switch. This can be used for energy conservation system . It can be used every where any machine operates, i.e. when sunlight falls morning, as night falls, or in dark room, lighted room etc. The present project is sensing agent which senses the light and then operates accordingly. For example we can connect it to the room light. It senses the day light. When sun sets, it will be dark. This helps in triggering the room light to switch ON. It helps the manpower for making switch ON and OFF. It also helps in reducing energy consumption due to our forgetfulness to switch off the switch as sunlight comes in the morning. It also helps in switching ON the light as soon as night falls. Therefore it maintains a routine to switch ON and OFF.
Light Dependent Resistor
Sensor (LDR) has two terminal this section to be work in +12 volt DC need. When light fall on light depending resistor (LDR) , LDR resistance will be increases and absent of the light from sensor resistance will be decreases. So we are know LDR is work as a variable resistor. When light fall on the sensor sensor (LDR) resistance is decrease and absent of light from sensor (LDR), sensor resistance increase. This sensor is connected with pin 2 to pin no. 7through 1M resistance and sensor and one capacitor 1 mF/50V is connected for timer. When light fall on LDR out put is high and absent of the light out put is low. Relay will be on and light is glow
Function
The main purpose of a light dependent resistor is to change the brightness of a light in different weather conditions. This can easily be explained with the use of a watch. Some watches start to glow in the dark so that it is possible to see the time without having to press any buttons. It is the light dependent resistor that allows the watch to know when it has gotten dark, and change the emissions level of the light at that time. Traffic lights use this principle as well but their lights have to be brighter in the day time
CAPACITOR
In the 60BC static electricity was discovered in Greece, But this electricity exists for every short time. So it was felt necessary to store it. Although till the 18th century capacitor was not invented but in the year 1746 Dutch scientist van Mussenbrock invented it. Firstly capacitor was termed as Leyder Jar. It was used to charge with static electricity. It had the capacity to charge the electricity in low space. That’s why scientist Volta named it condenser in 1782.Popular English Scientist Michael Faraday decided the nature of capacitance and electricity after 18th century. After this the unit of capacitance was named as Farad.Now a days, condenser is known as capacitor. Its function is to store the electrical energy and give this energy again to the circuit when necessary. In other words, it charges and discharges the electricity
TRANSISTOR
Invention of transistor was done by great American scientist Mr. Vardon and Mr. Bradone in 1947. After the invention of transistor there is a treat revolution in electronics field. It (Transistor ) is totally an electronics device which is generally made of semiconductor materials germanium or silicon. In pure condition semiconductor. is generally non conductor . By adding two types of impurities we make two types of semiconductor.
1) N – Type semiconductor.
2) P – Type semiconductor.
By adding the P and N type semiconductor make a junction and the device called a diode. There are two junction in a transistor, so it is called a unijunction or Bipolar transistor. In a transistor there are two junctions one provide a very low resistance for current flow and the other provide a very high resistance. One transistor transfers the current from low resistance towards high resistance due to this reason it called a transfer of resistor or transistor. On the Basis of construction, there are two types there are there terminals , namely emitter, base and collector. The terminal which emits the charge, called a emitter and that which collect charge is called collector. The middle layer between the emitter and collector is called base, which makes two junction one with emitter and other with collector, the junction between base and emitter is called emitter junction and that between base and collector is called collector junction. The function of base is to control the collector current. In symbolic representation of P – N – P transistor the direction of arrow is towards inside but N- P –N transistor the direction of arrow is towards outside
TRANSISTOR AS A SWITCH
Electronic circuits inevitably involve reactive elements, in some cases intentionally but always at least as parasitic elements. Although their influence on circuit performance may be subordinate for a particular circuit reactive elements introduce an ultimate limitation on frequency response/switching speed. Energy storage in reactive elements introduces consideration ‘past history’ into the analysis of a circuit. This note examines switching delays associated with circuit capacitance and inductance. There are related delays associated with device internal phenomena, generally significant only for very fast changes. These device-specific contributions are considered elsewhere,; ordinarily they are of little import other than for significant time intervals less than (roughly) 10 to 100 nanoseconds. Switching is examined here in the context of a bipolar junction transistor circuit. Switching a Capacitative Load The circuit on the right is a simplified CE amplifier with an external capacitor load; the capacitor may represent an inevitable circuit parasitic or it might approximate the capacitance that would be added by an additional stage of amplification. A voltage pulse is applied, increasing the base input voltage from an initial zero level for which the transistor is cut-off, to a level at which the emitter junction is turned ON. The junction becomes cut-off again on the trailing edge of the pulse. The pulse width is assumed to be wide enough so that turn-on and turn-off transients are disjoint. The basic question considered is the locus of the operating point on the IC-VCE plane. Qualitative Evaluation
Consider the circuit performance qualitatively at first; this is done with reference to the figure to the right. A representative constant base-current characteristic is shown, and superimposed on the graph is the load line for the circuit. Initially (base voltage zero) the transistor is cut-off and there is no collector current; the collector voltage then is VCC. This is the abscissa point labeled 'cutoff' on the figure, and is the quiescent point so long as no base voltage is applied. Note particularly that energy is stored in the capacitor, i.e., the capacitor is charged so that the voltage across it is VCC. Now suppose an abrupt base voltage change occurs corresponding to the leading edge of the base voltage pulse. (As a practical matter ‘abrupt’ means the change occurs within a time interval much shorter that that within which the circuit can respond; the analysis will indicate how small this interval need be.) Base current rises abruptly to a finite value, approximately equal to (pulse-height - 0.7 volt)/ RB. The collector voltage however remains at VCC initially, since the capacitor charge cannot change instantaneously. Hence the operating point jumps abruptly, as shown, to the collector characteristic corresponding to the base current. Note that the transistor is not saturated initially whatever the base current because the collector voltage is constrained by the capacitor. Note also that initially there is no current through and so no voltage drop across the collector resistor. It is the capacitor that supplies the BJT collector current (so that to the extent that the collector current remains constant the collector voltage drops linearly). As the capacitor discharges, lowering the collector voltage, current through the collector resistor increases and current from the capacitor decreases. Roughly equal magnitudes of change are involved, at least to the extent that the transistor collector current for a fixed base current remains constant. As the collector voltage decreases the operating point moves down the constant base current characteristic until the intersection with the load line is reached. At this point the collector current is provided entirely through the collector resistor. There is no current drawn from the capacitor, and so no further decrease in collector voltage. This is the steady-state condition that persists until the amplitude of the base-voltage pulse changes. The transistor may or may not be saturated in steady state; this depends on the circuit element values fixing the intersection of the load line and the collector characteristic. In general the turn-on will be fairly rapid, because the transistor provides a relatively high-current discharge path for the capacitor. Assume now the steady state has been reached, and then after that the base voltage is brought back to zero voltage, once again cutting off the transistor; this is at the trailing edge of the base pulse. The collector current drops immediately (ideally) to zero. However the capacitor again does not permit the collector voltage to change abruptly. Hence the operating point drops abruptly to intersect the axis; zero current, same voltage. Current now flows through the collector resistor to charge the capacitor, and the operating point moves along the abscissa to return to steady state at VCC. Quantitative Evaluation A PSpice analysis of the switching circuit considered was performed, using the BC 547 PSpice model and circuit element values as shown to the left. The computed currents as a function of time are shown in the figure below. The transistor collector current (which should be distinguished from the current provided by the power supply) jumps immediately on turn-on to a magnitude determined by the collector characteristic corresponding to the base current; the transistor is not saturated at this point and there is no current-limiting because of saturation. A turn-on current spike of this sort (see plot below) can cause damage if the current is not limited to a safe value by one means or another. In this example that the base resistor provides limiting, but the point really is that the matter should not be left to chance. The supply current, on the other hand, initially is zero; the capacitor holds the voltage drop across the collector resister to zero. As the supply current increases (the capacitor is discharging through the transistor and consequently the collector voltage is decaying) the collector current decreases in this illustration. As is not uncommon in such switching the base current magnitude used generally is intended to saturate the transistor. Because the capacitor at first prevents the transistor from saturating an initially larger current speeds the capacitor discharge. Eventually steady state is reached; there is no current contributed by the capacitor, and the power supply provides the collector current. When the transistor is cutoff on the trailing edge of the base voltage pulse the collector current drops to zero immediately. The supply current, however, continues to flow, recharging the capacitor. A plot of the computed collector and power supply current is shown below. Switching an Inductive Load Because of a fundamental conflict between the physical laws associated with the inductive effect and the practical and economic constraints of monolithic construction the phrase integrated circuit inductor is by and large an oxymoron. On the other hand discrete inductors are important in a number of applications; high-current mechanical relay switches are a specific example. A simplified transistor-actuated switch circuit is shown to the left; the dotted rectangle represents a relay coil having a winding resistance RL and an inductance L; associated mechanical switch contacts are not shown explicitly since they are not involved in the present discussion. As was done in the capacitor switching illustration a pulse is applied which temporarily switches the transistor from a cutoff state to a conducting state. Also, as in that earlier illustration, we first examine the circuit behavior during the pulse qualitatively. Qualitative Evaluation The inductance is a more sinister circuit element than a capacitor in the sense that it stores energy dynamically, i.e., via a current flow through the inductor. For capacitor loading turning off a power supply is a relatively benign operation, although there are some hazards. Capacitors discharge their stored energy if there is a current path, but if not they remain effectively dormant in an energized state. An inductor, on the other hand, stores its energy in a current flow, and in general turning off the power supply means turning off current flow.