ACKNOWLEDGEMENT:-
The completion completion of our mini project project successfu successfully lly was possible only because of the people who guided us and encouraged us whom we would like to acknowledgement. We than thanks ks to ou ourr belo belove ved d prin princi cipa pall S.M.JAMEEL BHASHA For providing providing all facilit facilities ies to to complete complete our project project successfully. We express our gratitude and sincere thanks of our head of the department ………..……… for his encouragement and moral support sundered and facilities provided towards completion of our project work. We express of sincere thanks to our project guide …………………for their Guidance suggestions, suggestions, encouragement
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CONTENTS:-
Introduction. Circuit diagram. Block diagram explanation. Component description. Principle of operation. Working principle. Advantages. Disadvantages. Application. Conclusion. Bibliography. Appendix.
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CONTENTS:-
Introduction. Circuit diagram. Block diagram explanation. Component description. Principle of operation. Working principle. Advantages. Disadvantages. Application. Conclusion. Bibliography. Appendix.
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DESCRIPTION:-
The circuit diagram present here is that of a street light that automatically automatically switches ON when the night falls falls and turns turns OFF when the sun rises. rises. In fact fact you can this circuit circuit for for implementing any type of automatic night light. When the resistance of LDR increases to make the voltage across the POT R2 to decrease below 0.6.This makes transistor Q1 OFF which in turn makes Q2 ON.
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ABSTRACT
STREET LIGHT CONTRLOL SYSTEM USING LDR. Automatic street light control using LDR system is simple yet powerful concept, which uses transistor as a switch to switch ON and OFF the street light automatically. By using this system manual works are 100% removed. It automatically switches ON lights when the sunlight goes below the visible region of our eyes. By using this system energy consumption is also reduced because now a days the manually operated street light are not switched off properly even the sun light comes and also not switched on earlier before sunset. In sunny and rainy days, ON time and OFF time differ significantly which is one of the major disadvantages of using timer circuits or manual operation. This project exploits the working of a transistor in saturation region and cut -off region to switch ON and switch OFF the lights at appropriate time with the help of an electromagnetically operated switch. LDR are the main component of this project. The resistance of light dependent resistor (LDR) varies according to the light falling on it. The LDR is connected as biasing resistor of the transistor. According to the light falls on the LDR, the transistor is operated in saturation and cut off region. By makes use of the transistor switching condition controller operates the light through relay. In this project LED has placed in place of relay, by placing relay we can control the ON and OFF of AC light. Moreover, the circuit is carefully designed to avoid common problems like overload, relay and inductive kick back in relay.
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INTRODUCTION
Automatically street light needs no manual operation of switching ON and OFF. The system itself detect whether there is need for light or not. When darkness rises to a certain value then automatically street light is switched ON and when there is other source of light i.e. day time, the street light gets OFF. The sensitive of the street light can also be adjusted. In our project we have used Two L.E.Ds for indication of bulb but for high power switching one can connect relay (electromagnetic switch) at the output.
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CIRCIUT DIAGRAM:-
Fig: Automatic street light control system.
Explanation of block diagram:The circuit diagram of automatic street light control system using LDR are as follows, LDR senses the illumination level and gives the input signal as voltage drop. Amplifier: Darlington circuit amplifies the input current to get maximum current gain. Switch: Relay switch closes or opens electrically and automatically, which is energized or de energized by the Darlington pair. Street light: Street light is the output of the circuit. In this circuit, it has been replaced by LED
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COMPONENTS:-
LDR 100 k preset Resistors 9 v Regulated DC supply LEDs Diode Variableresistance (potentiometer) PCB (printed circuit board) Transistors (n-p-n type)..
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LDR:-
LDR-light dependent Resistor
Fig: light dependent resistor
Fig : connection of LDR
LDR is also called photoresist or a cadmium supplied (Cds) cell. It is also called a photo conductor.it is basically a photocell that works on principle of photoconductivity .the passive component is basically a resistor whose resistance value decreases when the intensity of light decreases. This is photo electronic device is mostly used in light varying sensor circuit, and light and dark activated switching circuits. Some of its applications include camera light meters, street lights, clock radios, light beam alarms, reflective smoke alarms, and outdoor clocks.
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STRUCTURE & WORKING OF LDR:-
The snake like track shown below is the cadmium supplied film which also passes through the side’s .on the top and bottom are metal films which are connected to the terminals leads. It is designed in such a way as to provide maximum possible contact area with the two metal films. The structure is housed in clear plastic or resin case, to provide free access to external light. As explained above, the main component for the construction of LDR is Cds (cadmium supplied), which is used as the photo conductor and contains no or very few electrons when not illuminated. In the absence of light it is designed to have a high resistance in the range of mega ohms. As soon as light falls on the sensor, the electrons are liberated and the conductivity of the materials increases. When the light intensity exceeds a certain frequency.
The photons absorbed by the semiconductor give the band electrons the energy required to jump into the conduction band. This causes the free electrons or holes to conduct electricity and thus dropping the resistance dramatically (< 1 kilo ohms). The equation to show the relation between resistance and illumination can be written as R=A.E^a Where …E-illumination (flux) R –Resistance (ohms) A, a-constant The value of “a” depends on the Cds used and on the manufacturing process. Values usually range between 0.7 and 0.9. ADVANTAGES:1. LDR’s are cheap and are readily available in many sizes and shapes. 2. Practical LDRs are available in a variety of sizes and package styles, the most popular size having face diameter of roughly 10mm. 3. They need very small power and voltage for its operation. : DISADVANTAGES:Highly inaccurate with a response time of about tens or hundreds of milliseconds.
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DIODE:-
A diode is a two-terminal electronic component that conducts electric current in only one direction. A semiconductor diode is a crystalline piece of semi –conductor material connected to two electrical terminals. A vacuum tube diode is a vacuum tube with two electrodes a plate and a cathode. The most common function of a diode is to allow an electric current to pass in one direction while blocking current in the opposite direction. Thus, the diode can be thought of an electronic version of a check value. This unidirectional behavior is extract modulation from radio signal in radio receivers. When p-type and n-type materials are placed in contact with each other, the junction is depleted of charge carries and behaviors very differently than either type of materials.
LED:-[light emitting diode]
Fig : light emitting diode Schematic diagram of working of an LED Light emitting Diode and its circuit symbol the main advantage of Light emitting diode over other light sources is its increased efficiency. LEDs are available in red, orange, amber, yellow, green, and blue and white. Blue and white LEDs are much more expensive than the other colors. We have employed low cost Red LED in our electronic circuit. LEDs are elements for light signalization in electronics. The basic Principle behind the working of LED is electro luminescence. The light emitting diode should be forward biased to get light.
In LEDs, electrons are injected from low work function cathode to the conduction band of the n-type semiconducting material and holes are injected from high work function anode to the valence band of the p-type semiconducting material.When the electrons in the conduction band combines with the hole in the valence band, energy is released. In case of indirect band gap semiconductors. Photon will be released to conserve of both energy and momentum. But in case of direct band gap semiconductors, light will be emitted whose wave length depends on the band gap of the semiconductors. LED has two connections, an anode and cathode. The cathode is the end of the schematic line. In other words, the triangle points to words that cathode. The anode is, of course, the opposite end. Current flows from the anode to the point of the triangle pointing towards a cathode light emitting diodes.
PCB :-( PRINTED CIRCUIT BOARD) With the help of P.C.B it is very easy to assemble circuit with neat and clean end products. P.C.B is made of Bakelite with surface pasted with copper track layout. For each components pin is passed through the hole and is soldered.
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TRANSISTORS:-
(A) Fig: Schematic diagram of transistor
(B) Fig: Types of transistors NPN and PNP, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. A transistor is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. Bipolar Junction basic construction consists of two PN-junctions producing three connecting terminals with each terminal being given a name to identify it from the other two. These three terminals are known and labeled as the Emitter (E), the Base (B) and the Collector (C) respectively. Bipolar Transistors are current regulating devices that control the amount of current flowing through them in proportion to the amount of biasing voltage applied to their base terminal acting like a current-controlled switch.
PRINCIPLE OF OPERATION:The principle of operation of the two transistors types NPN and PNP, is exactly the same the only difference being in their biasing and the polarity of the power supply for each type. Bipolar Junction Transistor Configurations since Bipolar Junction Transistor is a three terminal device, there are basically three possible ways to connect it within an electronic circuit with one terminal being common to both the input and output. Each method of connection responding differently to its input signal within a circuit as the static characteristics of the transistor varies with each circuit arrangement. Common Base Configuration – has Voltage Gain but no Current Gain. Common Emitter Configuration - has both Current and Voltage Gain. Common Collector Configuration - has Current Gain but no Voltage Gain. NPN transistor configuration the construction and terminal voltages for an NPN transistor are shown above. The voltage between the Base and Emitter (VBE) is positive at the Base and negative at the Emitter because for an NPN transistor, the Base terminal is always positive with respect to the Emitter. Also the Collector supply voltage is positive with respect to the Emitter (VCE). For an NPN transistor to conduct, the Collector is always more positive with respect to both the Base and the Emitter. The voltage sources will be connected to an NPN transistor as shown above. The Collector is connected to the Supply voltage VCC via the load resistor, RL which also acts to limit the maximum current flowing through the device. In this project we will discussed about the transistor BC 107 & SL100 type of N-P-N transistors are used. These transistors are explained are as follow,
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BC 107 TYPE OF N-P-N TRANSISTOR:-
SL 100 TYPE OF N-P-N TRANSISTOR:-
FIXED RESIST0RS:1K ohm, this resistor provides fixed resistance we cannot vary the resistance, we can get any range of resistances. Typically 1K ohm, ¼ watt resistor that can be used with various circuits. The color band on the resistor is Brown, Black, Red and Gold.
VARIABLE RESISTANCE:Resistors are one of the most common electronic components. A resistor is a device that limits, or resists current. The current limiting ability or resistance is measured in ohms, represented by the Greek symbol measured
FEATURES:
1K ohm resistance ¼ watt, Flexible leads
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RESISTORS:-
9-VOLTS BATTERY:-
Fig: - 9-volts battery The most common form of nine-volt battery is commonly called the transistor battery which was introduced for the early transistor radios. It has a rectangular prism shape with rounded edges and a polarized snap connector at the top.
This type is commonly used in pocket radios and other small electronic devices. They are also used as backup power to keep the time in certain electronic clocks. This format is commonly available in primary carbon-zinc and alkaline 9-volt batteries power our smoke alarms, household items and toys. They can be found in most homes. But these batteries can be a fire hazard if not stored safely or disposed of with care. The positive and negative posts are close together. If a metal object touches the two posts of a 9-volt battery, it can cause a short circuit. This can make enough heat to start a fire. Weak batteries may have enough charge to cause a fire. 9-volt batteries should not be stored loose in a drawer. Do not store them in containers with other batteries.
Disposal:9-volt batteries should not be thrown away with trash. They can come in contact with other batteries or pieces Of metal.
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PRNCIPLE OF OPERATION:The automatic streetlight control system operates on 12 V DC supply. The automatic streetlight controller has a photoconductive device whose resistance changes proportional to the extent of illumination, which switches ON or OFF the LED with the use of transistor as a switch. Light dependent resistor, a photoconductive device has been used as the transducer to convert light energy into electrical energy. The central dogma of the circuit is that the change in voltage drop across the light dependent resistor on illumination or darkness switches the transistor between cut-off region or saturation region and switches OFF or ON the LED.
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WORKING OF STREET LIGHT:This is a design for circuit diagram of a street light that automatically switches ON when the night falls and turns OFF when the sun rise. In fact you can this circuit for implementing any type of automatic night light. This circuit is based on the operation of an LDR system. This is the figure of the circuit. For operation this circuit, it is use an LDR to sense the light. The LDR offers Very low Resistance in brightness. In this case the voltage drop across the LDR is less than 0.7V. This voltage is more sufficient to drive the transistor into saturation region. In saturation region, IC (Collector current) is very high. Because of this IC, The relay gets energized, and switches ON the lamp. LDR offers Very high Resistance in darkness. In this case the voltage drop across the LDR is more than 0.7V.When there is light the resistance of LDR will be low. So, the voltage drop across POT R2 will be high. This keeps the transistors Q1 ON. The collector of Q1 (BC 107) is coupled to base of Q2 (SL 100). So Q2 will be OFF and so do the relay. The bulb will remains OFF. When night falls the resistance of LDR increases to make the voltage across the POT R2 to decrease below 0.6V. This makes transistor Q1OFF which in turn ON Q2. The L.E.D will glow. The high collector current flowing through the relay, diode, LED and resistor makes the LED glow. When a light of suitable intensity is incident on the light dependent resistor, the resistance decreases and the voltage drop across the light dependent resistor is low In POT R2 can be used to adjust the sensitivity of the circuit. In this project we have used one L.E.D for indication bulb but for high switching one can connect relay(electromagnetic switch) at the output.
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We Can use bulb of any wattage, provided with relay should have the sufficient rating. The circuit can be powered from a regulated 9V DC power supply. The resistance of LDR will be low. So, the voltage drop across POT R2 will be high. This keeps the transistor Q1 ON. The collector of Q1 (BC 107) is coupled to base of Q2 (SL100). So Q2 will be OFF. The bulb will remain OFF.
NOTE: POY R2 can be used to adjust the sensitivity of the circuit. You can use bulb any wattage, provided that relay should have the sufficient rating. The circuit can be powered from a regulated 9V DC power supply. The relay K1 can be a9V SPDT relay.
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ADVANTAGES:1. LDRs are highly sensitivity. 2. It works accordingly to the light intensity. 3. Fit and forget system. 4. Low cost and reliable circuit. 5. To complete elimination of man power. 6. It can handle heavy loads up to 7A. 7. This system can be switched into manual mode whenever required. 8. Good power and voltage handling capabilities with high accuracy. DISADVANTAGES:-
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APPLICATIONS:1. In this project photo sensors are used which have wide range of applications in real life for detecting day. 2. Photo sensors (LDR) are used in camera design for auto detecting light and adjusting automatically for better image quality. 3. Other applications are smoke detection, auto light control system, watches, electronics equipment’s. 4. Balcony / stair case/ parking lightings. 5. Street lights and garden light
USES OF THIS PROJECT:By employing this circuit, energy consumption can be reduced considerably as the light switches ON or OFF automatically in appropriate time. Moreover, errors which occur due to manual operation also can be eliminated completely. The Automatic street light controller unit fabrication is costeffective with good sensitivity and high reproducibility. Moreover, the construction of the circuit is also simple so that it can be done easily as it involves locally available components. The circuit is designed in such a way that the extent of darkness at which the light has to switch ON or OFF also can be tailored whenever it is needed. It can be used for other purposes like garden lighting, balcony lighting etc.
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CONCLUSION:The uses of automatic street light control using LDR have many advantages. Since we are using LDR it consumes low power, we don’t to turn off the street light, and automatically it will turn off by depending on day and night. By this we can save the power and no need of ON/OFF the switches without man power.
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APPENDIX:-
S/NO. 1
2
COMPONENTS
RANGE
LDR
-
QUANTITY 1
BC 107
1
SL 100
1
100K
1
TRANSISTORS
3
PRESET
4
RESISTORS
1K
5
BATTERY
9V
1
6
LED
2mA
1
ohms
2
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