Automatic Street Light Control System is a simple and powerful construct. which uses transistor as a switch to exchange ON and OFF the street light automatically. By utilizing this system manual plants are removed. It automatically switches ON visible radiations when the sunshine goes below the seeable part of our eyes. It automatically switches OFF visible radiations under light by sunshine. This is done by a detector called Light Dependant Resistor ( LDR ) which senses the light really like our eyes. By utilizing this system energy ingestion is besides reduced because now-a-days the manually operated street visible radiations are non switched off decently even the sunshine comes and besides non switched on earlier before sundown. In cheery and showery yearss. On clip and OFF clip differ significantly which is one of the major disadvantage of utilizing timer circuits or manual operation.
This undertaking exploits the working of a transistor in impregnation part and cut-off part to exchange ON and exchange OFF the visible radiations at appropriate clip with the aid of an electromagnetically operated switch. Automatic Streetlight needs no manual operation of exchanging ON and OFF. The system itself detects whether there is demand for visible radiation or non. When darkness rises to a certain value so automatically streetlight is switched ON and when there is other beginning of visible radiation. the street light gets OFF. The extent of darkness at which the street light to be switched on can besides be tailored utilizing the potentiometer provided in the circuit. Furthermore. the circuit is carefully designed to avoid common jobs like overload. relay clicking and inductive boot back in relay.
The automatic street lamp control system operates on 12 V DC supply. The automatic street lamp accountant has a photoconductive device whose opposition changes relative to the extent of light. which switches ON or OFF the LED with the usage of transistor as a switch.
Light dependent resistance. a photoconductive device has been used as the transducer to change over light energy into electrical energy. The cardinal tenet of the circuit is that the alteration in electromotive force bead across the light dependent resistance on light or darkness switches the transistor between cut-off part or impregnation part and switches OFF or ON the LED.
3. Block Diagram & A ; Circuit Diagram
3. 1 Block Diagram
3. 1. 1 Individual Block Explanation
Power supply: AC power supply is stepped down. rectified and filtered to acquire about ripple-free DC end product for the operation of the circuit.
Light dependent resistance: LDR senses the light degree and gives the input signal as electromotive force bead. Amplifier: Darlington circuit amplifies the input current to acquire maximal current addition. Switch: Relay exchange stopping points or opens electrically and automatically. which is energized or de energized by the Darlington brace.
Street visible radiation: Street visible radiation is the end product of the circuit. In this circuit. it has been replaced by LED
3. 1. 2 Amplification Unit
In the Darlington constellation. the emitter current of one transistor becomes the basal current of the 2nd. so that the amplified current from the first is amplified farther by the 2nd transistor. This gives the Darlington brace a really high current addition such as 10000. since the Darlington constellation Acts of the Apostless like one transistor with a beta which is the merchandise of the betas of the two transistors. Darlington constellation can be used where high end product currents are needed. The Darlington constellation has rather high input electric resistance. A Darlington brace can be sensitive plenty to react to the current passed by tegument contact even at safe electromotive forces. Thus it can organize the input phase of a touch-sensitive switch. Darlington Configuration
DC Current addition hFE = hFE1 X hFE2
3. 1. 3 ON OFF control
The circuit is switched ON or OFF by the transistor in impregnation part or cut off part severally. which is controlled by the signal from LDR. The aggregator current from the transistor toggle between ON or OFF manners. 3. 2 Circuit Diagram
The circuit diagram of automatic street light accountant is given below:
The description of all the constituents used in this circuit is given in chapter 5.
4. Component Description
4. 1 Diode
A rectifying tube is a two-terminal electronic constituent that conducts electric current in merely one way. A semiconducting material rectifying tube is a crystalline piece of semiconducting material stuff connected to two electrical terminuss. A vacuity tubing rectifying tube is a vacuity tubing with two electrodes: a home base and a cathode. The most common map of a rectifying tube is to let an electric current to go through in one way while barricading current in the opposite way. Therefore. the rectifying tube can be thought of as an electronic version of a cheque valve. This unidirectional behaviour is called rectification. and is used to change over jumping current to direct current and to pull out transition from wireless signals in wireless receiving systems. When p-type and n-type stuffs are placed in contact with each other. the junction is depleted of charge bearers and behaves really otherwise than either type of stuff. The negatrons in n-type stuff diffuse across the junction and combines with holes in p-type stuff.
The part of the p-type stuff near the junction takes on a net negative charge because of the negatrons attracted. Since negatrons departed the N-type part. it takes on a localised positive charge. The thin bed of the crystal lattice between these charges has been depleted of bulk bearers. therefore. is known as the depletion part. It becomes nonconducting intrinsic semiconducting material stuff. This separation of charges at the p-n junction constitutes a possible barrier. which must be overcome by an external electromotive force beginning to do the junction behavior. The electric field created by the infinite charge part opposes the diffusion procedure for both negatrons and holes. There are two coincident phenomena: the diffusion procedure that tends to bring forth more infinite charge and the electric field generated by the infinite charge that tends to antagonize the diffusion p-n junction in thermic equilibrium with nothing prejudice electromotive force applied Equilibrium. forward and contrary biased conditions in a p-n junction
When the rectifying tube is frontward biased. the positive charge applied to the P-type stuff repels the holes. while the negative charge applied to the N-type stuff repels the negatrons. As negatrons and holes are pushed towards the junction. the breadth of depletion zone decreases. This lowers the barrier in possible. With increasing forward-bias electromotive force. the depletion zone finally becomes thin plenty that the electric field of the zone can’t counteract charge bearer gesture across the p–n junction. accordingly cut downing electrical opposition. The negatrons which cross the p–n junction into the P-type stuff will spread in the near-neutral part. Therefore. the sum of minority diffusion in the near-neutral zones determines the sum of current that may flux through the rectifying tube.
p-n junction in thermic equilibrium with nothing prejudice electromotive force applied. Under the junction. secret plans for the charge denseness. the electric field and the electromotive force When the rectifying tube is frontward biased. the positive charge applied to the P-type stuff repels the holes. while the negative charge applied to the N-type stuff repels the negatrons. As negatrons and holes are pushed towards the junction. the breadth of depletion zone decreases. This lowers the barrier in possible. With increasing forward-bias electromotive force. the depletion zone finally becomes thin plenty that
the electric field of the zone can’t counteract charge bearer gesture across the p–n junction. accordingly cut downing electrical opposition. The negatrons which cross the p–n junction into the P-type stuff will spread in the near-neutral part. Therefore. the sum of minority diffusion in the near-neutral zones determines the sum of current that may flux through the rectifying tube.
p-n junction under forward and contrary prejudice When the rectifying tube is rearward biased. the holes in the p-type stuff and the negatrons in the n-type stuff are pulled off from the junction. doing the breadth of the depletion zone to increase with addition in rearward prejudice electromotive force. This increases the electromotive force barrier doing a high opposition to the flow of charge bearers therefore leting minimum electric current to traverse the p–n junction. The addition in opposition of the p-n junction consequences in the junction to act as an dielectric. The strength of the depletion zone electric field additions as the reverse-bias electromotive force additions. Once the electric field strength increases beyond a critical degree. the p-n junction depletion zone breaks down and current Begins to flux.
Forward and change by reversal bias features of a rectifying tube a nd it’s circuit symbol A Zener rectifying tube is a type of p-n junction rectifying tube that permits current non merely in the forward way like a normal rectifying tube. but besides in the rearward way if the electromotive force is larger than the breakdown electromotive force known as Zener knee electromotive force. By contrast with the conventional device. a reverse-biased Zener rectifying tube will exhibit a controlled dislocation and let the current to maintain the electromotive force across the Zener rectifying tube near to the Zener electromotive force. The Zener diode’s operation depends on the heavy doping of its p-n junction leting negatrons to burrow from the valency set of the p-type stuff to the conductivity set of the n-type stuff.
In the atomic graduated table. this burrowing corresponds to the conveyance of valency set negatrons into the empty conductivity set provinces as a consequence of the reduced barrier between these sets and high electric Fieldss that are induced due to the comparatively high degrees of doping on both sides. The breakdown electromotive force can be controlled rather accurately in the doping procedure. In this undertaking. rectifying tube has been as a rectifier in full-wave rectifier circuit. Furthermore. it has besides been used a safety constituent to forestall inductive boot back in the contrary prejudice manner. 4. 2 Light breathing Diode
Light-emitting rectifying tubes are elements for light signalisation in electronics. The basic rule behind the working of LED is electroluminescence. The Light breathing rectifying tube should be frontward biased to acquire the visible radiation. In Light breathing rectifying tubes. negatrons are injected from low work map cathode to the conductivity set of the n-type semiconducting stuff and holes are injected from high work map anode to the valency set ot the p-type semiconducting stuff. When the negatron in the conductivity set combines with the hole in the valency set. energy is released. In instance of indirect set spread semicondutors. phonon will be released to conserve of both energy and impulse. But in instance of direct set spread semiconducting material. visible radiation will be emitted whose wavelength depends on the set spread of the semiconducting material.
Different parts of a Light breathing rectifying tube
Radiative recombination in direct and indirect bandgap semiconducting material
Cartoon demoing radiative recombination in a direct band-gap semiconducting material
Conventional diagram of working of an LED Light breathing Diode and its circuit symbol The chief advantage of Light breathing rectifying tube over other light beginnings is its increased efficiency. LEDs are available in ruddy. orange. gold. yellow. green. blue and white. Blue and white LEDs are much more expensive than the other colorss. We have employed low cost Red LED in our electronic circuit. 4. 3 Light Dependent resistance
A light dependent resisitor is a resisitor whose opposition alterations with the strength of incident visible radiation. The working rule of light dependent resistance is photoelectric consequence. A light dependent resisitor is made of a high opposition semiconducting material. If the energy of the incident visible radiation is greater than the set spread of the semiconducting material. electron -hole braces are generated. The photogenerated electron-hole brace transits the device giving rise to photoconduction. The indispensable elements of a photoconductive cell are the ceramic substrate. a bed of photoconductive stuff. metallic electrodes to link the device into a circuit and a wet immune enclosure. Light sensitive stuff is arranged in the signifier of a long strip. zig-zagged across a phonograph record shaped base with protective sides. For extra protection. a glass or plastic screen may be included. The two terminals of the strip are brought out to linking pins below the base as shown below. Side position
Top position and side position of Light Dependent Resisitor The commercial photoconductive stuffs include cadmium sulfide ( CdS ) . Cd selenide ( CdSe ) . Lead sulphide ( PbS ) and Indium antimonide ( InSb ) etc. . There is big alteration in the opposition of a Cd selenide cell with alterations in ambient temperature. but the opposition of Cd sulfide remains comparatively stable. Furthermore. the spectral response of a Cd sulfide cell closely matches to that of a human oculus. Hence. LDR is used in applications where human vision is a factor such as street light control or automatic flags control for cameras. The above mentioned characteristics drive us to choose for CdS based LDR in our electronic circuit for Automatic street light accountant.
Light Dependent Resistor and its circuit symbol 4. 4 Full-wave rectifier:
The full moving ridge rectifier circuit consists of two rectifying tubes connected to a individual burden opposition ( RL ) with each rectifying tube taking it in bend to provide current to the burden. When point A of the transformer is positive with regard to indicate C. rectifying tube D1 will be frontward biased and it conducts in the forward way as indicated by the pointers. When point B is positive ( in the negative half of the rhythm ) with regard to indicate C. rectifying tube D2 will be change by reversal biased and behaviors in the forward way and the current flowing through resistance R is in the same way for both half-cycles. As the end product electromotive force across the resistance R is the phasor amount of the two wave forms combined. this type of full moving ridge rectifier circuit is besides known as a bi-phase circuit which is shown below.
Full-wave rectifier end product
4. 5 Capacitor Filter:
The end product of the full-wave rectifier will be a crinkled DC electromotive force. In order to obtain a changeless DC end product electromotive force. a capacitance is connected across the end product of the full-wave rectifier. We have employed an Aluminium Electrolytic type capacitance ( 100 ?F ) for our intent. The belongings of a capacitance is that it allows ac constituent and blocks dc constituent. The capacitance will acquire charged to the peak electromotive force during each half-cycle and so will acquire discharged exponentially through the burden while the rectified electromotive force drops back to nothing. Therefore. the capacitance helps to make full in the spreads between the extremums. As a consequence. the existent electromotive force end product from this combination ne’er drops to zero. but instead takes the form as shown in the figure given below. Full-wave rectifier end product after go throughing through filter
Full-wave rectifier end product before go throughing through filter
Eventhough the end product electromotive force is a non pure District of Columbia. but has much less fluctuation in electromotive force than the unfiltered end product of the full-wave rectifier. The extent to which the capacitance electromotive force drops depends on the electrical capacity of the capacitance and the sum of current drawn by the burden ( RC clip invariable ) . The two of import parametric quantities to see when taking a suited smoothing capacitance are its Working Voltage. which must be higher than the burden end product value of the rectifier and it’s Capacitance Value. which determines the sum of rippling that will look superimposed on top of the DC electromotive force. Furthermore. the extent of smoothing is limited by the frequence of the AC electromotive force and the burden current. 4. 6 Relaies:
A relay is an electrically operated switch. Most of the relays use an electromagnet to run a shift mechanism automatically. Relaies are used where it is necessary to command a circuit by a low-power signal with complete electrical isolation between control and controlled circuits or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits. reiterating the signal coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early computing machines to execute logical operations. Relaies can besides be used to protect electrical circuits from overload. In modern electric power systems these maps are performed by digital instruments still called protective relay. which designed to cipher operating conditions on an electrical circuit and trip circuit surfs when a mistake is detected.
When an electric current is passed through the spiral it generates a magnetic field that attracts the armature and the attendant motion of the movable contact either makes or interrupt a connexion with a fixed contact. If the set of contacts was closed when the relay was de-energized. so the motion opens the contacts and breaks the connexion. and frailty versa if the contacts were unfastened. When the current to the spiral is switched away. the armature is returned by a force. about half every bit strong as the magnetic force. to its relaxed place. Normally this force is provided by a spring. but gravitation is besides used normally in industrial motor starting motors. Most relays are manufactured to run rapidly. In a low-tension application this reduces noise ; in a high electromotive force or current application it reduces curving. 4. 6. 1 Single pole individual throw Relay:
In Single Pole Single Throw relay. current will merely flux through the contacts when the relay spiral is energized.
Single pole individual throw Relay and its circuit symbol 4. 7 Transistors
Transistors are three terminal active devices made from different semiconducting material stuffs that can move as either an dielectric or a music director by the application of a little signal electromotive force. The transistor’s ability to alter between these two provinces enables it to hold two basic maps: shift or elaboration. Then bipolar transistors have the ability to run within three different parts: * Active Region – the transistor operates as an amplifier and IC = ? IB * Saturation – the transistor is fully-ON operating as a switch and IC = Isaturation * Cut-off – the transistor is “fully-OFF” operating as a switch and IC = 0 The word Transistor is an acronym. and is a combination of the words Transfer Varistor used to depict their manner of operation manner back in their early yearss of development. There are two basic types of bipolar transistor building. NPN and PNP. which fundamentally describes the physical agreement of the P-type and N-type semiconducting material stuffs from which they are made.
A transistor is made of a solid piece of semiconducting material stuff. with at least three terminuss for connexion to an external circuit. The Bipolar Junction Transistor basic building consists of two PN-junctions bring forthing three linking terminuss with each terminus being given a name to place it from the other two. These three terminuss are known and labeled as the Emitter ( E ) . the Base ( B ) and the Collector ( C ) severally. Bipolar Transistors are current modulating devices that control the sum of current fluxing through them in proportion to the sum of biasing electromotive force applied to their base terminus moving like a current-controlled switch. The rule of operation of the two transistor types NPN and PNP. is precisely the same the lone difference being in their biasing and the mutual opposition of the power supply for each type.
Bipolar Junction Transistor Configurations Since Bipolar Junction Transistor is a three terminal device. there are fundamentally three possible ways to link it within an electronic circuit with one terminus being common to both the input and end product. Each method of connexion reacting otherwise to its input signal within a circuit as the inactive features of the transistor varies with each circuit agreement.
* 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. 4. 7. 1 NPN transistor constellation
NPN transistor constellation The building and terminal electromotive forces for an NPN transistor are shown above. The electromotive force between the Base and Emitter ( VBE ) is positive at the Base and negative at the Emitter because for an NPN transistor. the Base terminus is ever positive with regard to the Emitter. Besides the Collector supply electromotive force is positive with regard to the Emitter ( VCE ) . For an NPN transistor to carry on. the Collector is ever more positive with regard to both the Base and the Emitter.
The electromotive force beginnings will be connected to an NPN transistor as shown above. The Collector is connected to the supply electromotive force VCC via the burden resistance. RL which besides acts to restrict the maximal current fluxing through the device. The Base supply electromotive force VB is connected to the Base resistance RB. which once more is used to restrict the maximal Base current. It is good known that the transistor is a current controlled device since the base current controls the aggregator current. The transistor current in an NPN transistor is the ratio of these two currents ( IC/IB ) . called the DC Current Gain of the device and is given the symbol ? of hFE.
The value of ? or hFE can be big up to 200 for standard transistors and this big ratio between IC and IB that makes the NPN transistor a utile amplifying device when used in its active part. Besides. the current addition of the transistor from the aggregator terminus to the emitter terminus. IC/IE. is called Alpha ( ? ) . and is a map of the transistor. As the emitter current IE is the merchandise of a really little base current plus a really big aggregator current. the value of alpha ?. is really close to integrity. and for a typical low-power signal transistor this value ranges from about 0. 950 to 0. 999.
NPN Bipolar Junction transistor
All the transistors have three province of operation:
OFF province: in this province there is no basal current applied or IB = 0. ON ACTIVE province: In this province any alterations in IB will do alterations in IC since IC = IB x hFE. This type of province is suited when we use transistor as a signal amplifier because transistor is said is in the additive province. ON SATURATION province: In this province any alterations in IB will non do alterations in IC any longer ( non linear ) and IC will be about changeless. This province can non be used to run the transistor as a signal amplifier since the end product signal will be clamped when the transistor becomes saturate.
Transistor in operating province
When transistor is in OFF province. the electromotive force across aggregator and emitter terminus is equal to the supplied electromotive force. which is tantamount to the unfastened circuit. When transistor is in the SATURATION province. the aggregator to emitter electromotive force is equal or less than 0. 2 V. which is tantamount to the closed circuit. Here. the OFF province is tantamount to the logical “0” and the SATURATION province is tantamount to the logical “1“ . 4. 7. 2 Transistor as an Amplifier
A electromotive force or current applied to one brace of the transistor’s terminuss changes the current flowing through another brace of terminuss. To be more specific. the current applied to the basal terminus will be multiplied by the current addition factor of the transistor which known as hFE. Therefore transistor can be used as amplifier. Any little signal applied to the basal terminus will be amplified by the factor of hFE and reflected as a aggregator current on the aggregator terminal side.
When we operate transistor as an amplifier. we choose the prejudice electromotive force VBE and VCE in such a manner that the end product IC and VCE will swing to maximum value ( saturation part ) or minimal value ( cut-off part ) without any deformation when the input IB swing to its upper limit or minimal value.
Typical NPN transistor characteristic curves for CE Amplifier 4. 7. 3 Transistor as a switch
As mentioned above. bipolar transistor has three parts of operation: the cut-off part. the additive or active part. and the impregnation part. When utilizing the bipolar transistor as a switch they must be either fully-OFF or fully-ON. When used as a switch. the bipolar transistor is operated in the cut-off part. the part wherein the transistor is non carry oning which makes the circuit unfastened so that the applied electromotive force will be same as the end product to do the transistor OFF and impregnation part. the part wherein the transistor is in full conducting. thereby shuting the circuit so as to acquire the lowest possible VCE ( i. e. about 0. 2 V ) to do the transistor ON. Transistors that are to the full ON are said to be in their Impregnation part and transistors that are to the full OFF are said to be in their Cut-off part. When utilizing the transistor as a switch. a little base current controls a much larger aggregator burden current.
When utilizing transistors to exchange inductive tonss such as relays and solenoids. a Flywheel Diode is used. When big currents or electromotive forces need to be controlled. Darlington constellation can be used. Transistor switches can be used to exchange and command lamps. relays or even motors. NPN transistor as a switch Here. RB resistance is used to command the current on base terminus that make transistor OFF and ON ( saturate ) and RC resistance is the current clipper for the burden. if the burden operate with the same electromotive force as the supplied power ( Vcc ) . the resistance RC can be omitted. In the inductive burden circuit. a rectifying tube ( clamp rectifying tube ) is connected across the inductive burden to protect the transistor once more the EMF electromotive force generated by the inductance constituent when the transistor is switched on and off quickly. which is an opposing electromotive force to the beginning electromotive force. Here. the rectifying tube will move as a short circuit to the high electromotive force generated by the inductance constituent. Any rectifying tube which is capable of managing minimal 1 A of current can be used.
The jumping current electromotive force ( 220 V ) is stepped down to ( 12 V ) utilizing a suited measure down transformer. The stepped down AC electromotive force is rectified to direct current Voltage utilizing a full moving ridge rectifier. To obtain a changeless ripple-free DC electromotive force. a capacitance filter is used across the circuit. In dark. the opposition of light dependent resistance is high. So. the electromotive force bead across the light dependent resistance is besides high. Now the end product of the NAND gate N1 is low since both the input signals are high. which makes the switch SW1 to stay unfastened. And now the end product from NAND gate N2 becomes high since both the input signals are low. The high end product signal from the N2 terminus thrusts transistor to the impregnation part. which makes the aggregator current IC really high. Finally. the high aggregator current fluxing through the relay. rectifying tube. LED and resistance makes the LED freshness. When a visible radiation of suited strength is incident on the light dependent resistance. the opposition lessenings and the electromotive force bead across the light dependent resistance is low.
Now the end product of the NAND gate N1 is high since one of the input signal is low and the other one is high. which makes the switch SW1 to shut. And now the end product from NAND gate N2 becomes low since both the input signals are high. The low end product signal from the N2 terminus thrusts transistor to the cut-off part. In this instance. the aggregator current is non high plenty to do the LED freshness. since other circuit elements such as relay. rectifying tube. LED and resistance are connected in analogue to each other. Therefore. by toggling the transistor between cut-off part and impregnation part it is possible to exchange OFF or exchange ON the LED. In this circuit. Darlington brace is employed to increase the aggregator current. Relay switch is connected in analogue to the LED to protect electrical circuits from overload. The extent of darkness or the strength of visible radiation at which the visible radiation should exchange ON or OFF can besides be tuned by seting the potentiometer PR1. The capacitance C3 has been connected parallel to relay to avoid the relay from clicking during dusky threshold degrees.
7. Uses of this undertaking
By using this circuit. energy ingestion can be reduced well as the light switches ON or OFF automatically in appropriate clip. Furthermore. mistakes which occur due to manual operation besides can be eliminated wholly. The Automatic street light accountant unit fiction is cost-efficient with good sensitiveness and high duplicability. Furthermore. the building of the circuit is besides simple so that it can be done easy as it involves locally available constituents. The circuit is designed in such a manner that the extent of darkness at which the visible radiation has to exchange ON or OFF besides can be tailored whenever it is needed. It can be used for other intents like garden lighting. balcony illuming etc. .
8. Conclusion & A ; Scope
The above circuit can be powered from a battery. which can be charged during twenty-four hours clip by reaping the solar energy through a solar cell as shown below:
The solar energy harvested from sunshine can be stored. inverted from DC electromotive force to AC electromotive force utilizing sun tie convertor. The AC electromotive force can be stepped up and given to the electric grid. Photovoltaic array
The AC electromotive force from the electric grid can be stepped down. rectified and used for powering the circuit. Meanwhile. the street visible radiation can besides be powered by the A. C. electromotive force. which is controlled by a relay switch connected to the exchanging portion of the circuit. The above mentioned scheme will enable us to reap solar energy in an effectual manner for the operation of the circuit and for powering the street visible radiation besides.
Solar Street visible radiation system with Automatic street light accountant A Future position
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