AUTOMATIC STREET LIGHTING DURING FESTIVALS TO PREVENT UNNECESSARY POWER WASTAGE

AUTOMATIC STREET LIGHTING DURING FESTIVALS TO PREVENT UNNECESSARY POWERWASTAGE

By Reetam Sen Biswas, Sanket Basu, Rajarshi Dutta

INTRODUCTION

During festivals like Durga puja and the Diwalis decorative streetlighting is used. Many a times it is observed that once the lights areswitched on, they continue to glow throughout the night and even onearly morning the next day, people forget to switch off those lights. Asit is electrical load on the power system is very high during thefestivals, we should try to minimize the power wastage. This can beeasily achieved, if by some mechanism the street lights can beswitched on and off automatically;- when sunlight is not present thelighting will automatically be switched on and when the sun rises duringthe next morning the lights will automatically be turned off.

Approximate power wastage estimation during Durga Puja festival inKolkata.

Assumptions :

Total no. of puja committees in Kolkata (N)= 100

No. of lighting boards in each committee (n)= 50

Power consumed by each lighting board (P)= 100 W

Duration of power wastage(5 a.m to 7 a.m)(T)= 2 hr

Power wastage calculation :

Total energy wastage in each committee= n×P×T = 50×100×2=10000 Wh=10 kWh

Energy wastage all over Kolkata= 100X10 kWh=1000 kWh

Considering Durga puja, let us assume that the energy wastagecontinues for 6 days

Hence, the total energy wastage in Kolkata = 1000X6 kWh= 6000kWh

Let, the cost of electricity = Rs. 8 per unit

So, cost of electricity that is wasted= Rs. 6000X8=Rs. 48000

So, we see that CESC has to waste near about Rs. 50000 during the DurgaPuja. Our aim of this project is to completely reduce the unnecessarywastage of power

MODELLING OF THE CIRCUIT:-Circuit consisting of 3 major parts-

1) Power Supply Circuit :

For the setup we will require a power supply of 9 volt. Previously we used DCbattery to meet the purpose but it created problems as the battery discharges.So we replaced it by a voltage stabilizer or voltage regulator circuit. For thispurpose we used a 7809 voltage regulator chip and fed it from 230 Volt ac supplyby means of a 36 volt peak to peak transformer and a full wave bridge rectifiercircuit. So by using this we get a stabilized supply of 9 Volt DC. As shown infig 2 we observe that capacitors C1, C2 and C3 are connected in parallel so asto filter out the unnecessary voltages in the voltage waveform.

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Fig 1 : Pin configuration of 7809 Fig 2 : Circuit Diagram of Voltage Stabilizer Circuit

2) Dark detector Circuit :-

DARK detector circuit components :

1) Bread board

2) LM324 OPAMP IC

3) LDR (Light dependent resistor)

4) LED

5)220 ohm and 10 kilo ohm resistor

6)10 kilo ohm potentiometer pot

7)9 Volt supply

8) Jumper wires

General explaining of the dark detector circuit:-

The main components of the dark detector circuits are:-

1. Op-amp LM-324 as comparator2. Light dependent resistor(LDR)3. Potentiometer for adjusting reference voltage.

1. Opamp as comparator:-

A comparator is an electronic circuit which can compare an input voltage signal(Vin) with a known reference voltage(Vref). It is basically an open-loopoperational amplifier. The input voltage is applied to one of the inputterminals of an opamp and the reference voltage is applied at the otherterminal. When the input voltage Vin >Vref output voltage is Vsat(9V) and ifVin<Vref output voltage is –Vsat(-9V). In this project we have used LM-324 asan opamp I.C for our comparator circuit. We have used the comparator circuit innon-inverting mode.

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Fig 3: Transfer characteristics of an ideal op-am Fig 4: Comparator circuit

Fig 5: Pin configuration of LM-324

2. LDR (Light Dependent Resistor) :

A photo-resistor or light-dependent resistor (LDR) or photocell is alight-controlled variable resistor. The resistance of a photo resistordecreases with increasing incident light intensity; in other words, itexhibits photoconductivity. A photo resistor can be applied in light-sensitive detector circuit, and light- and dark-activated switchingcircuits. A photo-resistor is made of a high resistance semiconductor. Inthe dark, a photo resistor can have a resistance as high as a few mega

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ohms (MΩ), while in the light, a photo resistor can have a resistance aslow as a few hundred ohms. If incident light on a photo-resistor exceeds acertain frequency, photons absorbed by the semiconductor give boundelectrons enough energy to jump into the conduction band. The resultingfree electrons (and their hole partners) conduct electricity, therebylowering resistance. The resistance range and sensitivity of a photo-resistor can substantially differ among dissimilar devices. Moreover,unique photo-resistors may react substantially differently to photonswithin certain wavelength bands.

Fig-6: A schematic diagram of a LDR

3. Potentiometer :

A potentiometer, informally a pot, is a three-terminal resistor witha sliding or rotating contact that forms an adjustable voltage divider. Ifonly two terminals are used, one end and the wiper, it acts as a variableresistor or rheostat.

Fig-7: A pot type potentiometer

Working of the dark detector circuit : 5

Fig 8: Circuit diagram of the Dark-detector circuit

We have to connect the components as shown in Fig 8.The centre tap ofthe 10 K pot is connected to the non inverting terminal of the Op-Amp.The knob of the pot is to be adjusted so that the LED stops glowing atnormal surrounding light intensity. We have designed a voltage dividerusing the LDR and 10 K resistor given in the diagram. The junction pointof the LDR and the resistor id being tapped and given to the invertingterminal of the opamp. Now when the light intensity is high ( during theday time) the resistance of the LDR is very low and so the voltage atthe inverting terminal of the opamp is higher compared to the noninverting terminal. Thus the output of the opamp will have –V(sat) whichis equal to zero volt. Thus the LED will not glow. When night falls theresistance of the LDR becomes very high and thus the voltage of the noninverting terminal becomes lesser than the voltage of the non invertingterminal and thus the output of the Op-Amp goes to +V(sat) which isequal to 9 volt and thus the LED glows brightly.

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3) Designing circuit:-

Components used in this circuit are :

I. N555 timerII. Light emitting diodeIII. 2 capacitors(0.1 and 10 microfarad)IV. 2 resistors(50 k-ohm each)

Fig 9: Circuit diagram of the designing circuit

The connection of the pins for a DIP package is as follows:

Pin Name Purpose

1 GND Ground reference voltage, low level (0 V)

2 TRIGThe OUT pin goes high and a timing interval starts when thisinput falls below 1/2 of CTRL voltage (hence TRIG is typically1/3 VCC, CTRL being 2/3 VCC by default, if CTRL is left open).

3 OUT This output is driven to approximately 1.7 V below + V CC or GND.4 RESET A timing interval may be reset by driving this input to GND, but

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the timing does not begin again until RESET rises aboveapproximately 0.7 volts. Overrides TRIG which overrides THR.

5 CTRL Provides "control" access to the internal voltage divider (bydefault, 2/3 VCC).

6 THR The timing (OUT high) interval ends when the voltage at THR isgreater than that at CTRL (2/3 VCC if CTRL is open).

7 DIS Open collector output which may discharge a capacitor betweenintervals. In phase with output.

8 VCCPositive supply voltage, which is usually between 3 and 15 Vdepending on the variation.

Pin 5 is also sometimes called the CONTROL VOLTAGE pin. By applying avoltage to the CONTROL VOLTAGE input one can alter the timingcharacteristics of the device. In most applications, the CONTROL VOLTAGEinput is not used. It is usual to connect a 10 nF capacitor between pin5 and 0 V to prevent interference. The CONTROL VOLTAGE input can be usedto build an astable multivibrator with a frequency modulated output.

ASTABLE MODE OF OPERATION OF 555-timer:- Astable multivibrator is free runningmultivibrator, i.e with the addition of an external capacitor and two externalresistors, to that of the monostable mode the 555 can be configured to producea periodic pulsating waveform at the output, without any external triggerpulses. The key difference between the monostable and the astable operation isthat the TRIGGER input is connected together with the THRESHOLD input so that thetimer triggers itself during operation.Let the voltage across the capacitance C be Vc.

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NE555 figure

Pin configuration of555 timer

Fig 10: Pin connection for the astable operation

A) Charging:- (At t=0,Vc<Vcc/3):-

1. When the power is turned on, capacitor C1 is not charged and pin2(TRIGGER) and pin 6 (THRESHOLD) voltage (VIN) is at 0 V.2. The output of lower comparator 2 (inverting) is therefore HIGH(VIN <1/3 VCC) and the output of the upper comparator 1(noninverting) is LOW(VIN < 2/3 VCC).3. Comparator 2 serves as input S (Set) and comparator 1 serves as the Rinput (Reset) for the SR flip flop (also called a RS flip-flop). SoS=1,R=0,Q =1,Q’=0 therefore the output Q of the SR flip-flop is high andthe 555 timer OUTPUT is HIGH due to the inverting buffer stage.4. Since Q is LOW, the discharge transistor is turned off and C1 beginscharging through R1 and R2, with charging time constant (R1+R2)C

B) Intermediate period (Vcc/3<Vc<2Vcc/3):-

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1. When the voltage across C (VIN)(threshold voltage=capacitor’s voltageincreases) reaches 1/3 VCC, the output of lower comparator 2 changes toLOW; comparator1 remain unchanged(low).So,s=0,R=0,Q=1,Q’=0,O/P of SR flip-flop and 555 timer remains high.

C) Discharging(Vc>Vcc/3):-

1. C1 continues to charge until it reaches 2/3 VCC. At this point, the uppercomparator1 changes to a HIGH state.R=1,s=0,Q=0,Q’=1the output Q of the SR flip-flop and 555 timer goes low.

2. The high O/P Q’, drives the transistor in active mode, and thus it discharges through R2 with discharging time constant R2C occurs till the Vc<Vcc/3.

The 555 timer repeats the charge/discharge cycle between1/3 VCC and 2/3 VCC producing an output periodic square wave.

Implementation of astable multivibrators in this project:- 10

Astable multivibrator

As shown above the designing circuit helps us to generate a rectangularpulse at its output, which is essential to create a sample streetlightening pattern. Now we need to couple the Dark Detector Circuit withthe designing circuit so that the designing circuit switches on when theoutput of the Dark Detector Circuit is high. For that reason we haveused an AND gate (14081BP). One input for the AND gate is fed from 9volt supply and the other input is fed from the output of the DARKDetector Circuit. The output of the AND gate goes to the Pin 8 of theMultivibrator. Thus the output of the Dark Detector Circuit is latchedto the triggering input of the Multivibartor. Thus when detector circuitdetects the darkness the designing circuit get triggered and themultivibrator starts generating a rectangular pulse which “on and off”the Led at the output. Simultaneously when the light intensity increasesthe detector circuit output dies down and with it the designing circuitstops as well.

LINKING of the 3 circuits:-

For the realization of the project we need to inter link the three majorcircuits:-

1. Power Supply Circuit2. The Dark Detector Circuit3. The Designing Circuit (described above).

The power supply circuit drives power to the Dark Detector circuit and the designing circuit which are linked together by an And gate (IC -14081BP).

Fig 10: The Complete Circuit Diagram

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PRECAUTIONS TO BE TAKEN:-

1) There should be no loose connections.

2) There should be no dry soldering.

3) The current rating of the transformer used in the voltage stabilizer circuitshould be checked.

4) Internal short circuit conditions or connectivity between the pins of the respective ICs should be verified using multimeter prior to their implementation in the circuit.

5) Supply to all the IC chips should be given properly, otherwise it will result in burning out of the IC chips.

Practical Implementation of this Circuit: Here we are driving the designing circuit by the output of the detectorcircuit. But here the load is just one LED;- so its very low. In practicalcases the load will be very high and it won’t be possible for this circuit todrive such bulk loads. In that case we have to think about an alternative.

Relay can be a very economical way for such cases. The circuit configurationwill be a bit different. In that case the output of the Dark Detector Circuitwill be used to activate the contacts of the relay on the basis of intensitylevel set by the reference voltage level. As the relay get energized, itscontacts will switch on the designing circuit capable of driving a high load.If the light intensity is above reference level then the detector circuit willgive a zero voltage at output and thus the relay won’t be energized andconsequently designing circuit will remain “off”.

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Fig : Modified Circuit for practical implementation in real life where we have to drive high loads

CONCLUSION:-

In this project we have successfully designed a model which mightbe effectively used to reduce unnecessary power wastage during festivalslike Durga Puja and the Diwalis. Automatic street lighting techniquesare being used in some places these days;- however this technique israrely used in the decorative street lights of festivals. So we havedesigned this model which demonstrates the automatic glowing ofdecorative street lighting when darkness falls and vice-versa.

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