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Apr 03, 2018

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Areeba Shujaat
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    A PROJECT REPORT ON

    AUTOMATIC LED EMERGENCY LIGHT

    SIR SYED UNIVERSITY OF ENGINEERING AND TECHNOLOGY

    EE211 - ELECTRONIC DEVICES AND CIRCUIT

    3RD SEMESTER

    SUBMITTED TO:

    SIR WASEEM

    SUBMITTED BY:

    AREEBA SHUJAAT

    2012_TE_

    ERUM NAZ RASHID

    2012_TE_

    HINA KHAN

    2012_TE_

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    TABLE OF CONTENTS

    CHAPTERS:

    Acknowledgement

    Introduction

    Block diagram & description

    Circuit diagram and description

    Graphical representation of documents

    Uses, Advantages and disadvantages

    Implementation and results

    References

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    ACKNOWLEDGEMENT:

    We take this opportunity to express our profound gratitude and deep regards to our

    guide Sir Waseem for his exemplary guidance, monitoring and constant

    encouragement throughout the course of this project. The blessing, help and

    guidance given by him time to time shall carry us a long way in the journey of life.

    We are obliged to staff members for the valuable information provided by them in

    their respective fields. We are grateful for their cooperation during the period of

    our assignment.

    Lastly, We thank The Almighty, our parents, brother, sisters and friends for their

    constant encouragement without which this assignment would not be possible.

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    INTRODUCTION:

    There was a time when emergency lighting was a source of light backed by abattery or a generator system, which would go on automatically in case of a power

    failure or a fire.

    This is automatic emergency light used in night at emergency time when the power

    cut or off by some region. This emergency light takes 230V AC and it converts it

    in 9V DC and charge the battery which is used in this circuit. The power of the

    battery is used that time when the power is cut off or we need to use it. This light is

    used mostly in villages because there is the lack of electricity is provided.In this circuit we use BD 140 transistor the advantage of this emergency light is

    that if we use this emergency light in a room no other light source is required but in

    other emergency light we use another light source when the power is available.

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    BLOCK DIAGRAM:

    BLOCK DESCRIPTION

    First the power supply is given 230 through the step down transformer, the

    transformer convert it into 9V 500mA but it is not gives dc so rectifier is used in it

    to convert it into dc. For filter the signals in the circuit a capacitor is used on it

    which filter the signals and convert it into pure DC. It also charged the battery

    when the power is given in the circuit. A transistor is used to maintain the power

    supply regularly and the control units (Zener diode) it maintain the zener voltage

    and also used it as a switch in reverse biased condition after that battery is the

    second power supplier which charged first and give backup power when the main

    power is cut off.

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    CIRCUIT DIAGRAM:

    COMPONENTS REQUIRED:

    DEVICE DESCRIPTION QUANTITY

    Step down transformer 230 V to 9V, 500mA 1

    Diodes 1N4007 5

    Adjustable voltage regulator LM317 1

    Potentiometer 2.2K 1

    Darlington transistor BD140, PNP 1

    Transistor 2 BC548, NPN 1

    Zener diode 6.8V 1

    Resistors 100 12

    1K 1

    16 1

    1.2K 1

    Capacitor 1000F 25V 1

    Battery 6V, 4.5 Ah 1

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    DESCRIPTION:

    Here is a white-LED-based emergency light that offers the following advantages:

    1. It is highly bright due to the use of white LEDs.

    2. The light turns on automatically when mains supply fails, and turns off whenmains power resumes.

    3. It has its own battery charger. When the battery is fully charged, charging stopsautomatically.

    The circuit comprises two sections: charger power supply and LED driver.Thecharger power supply section is

    built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver

    section is built around transistor BD140(T2). In the charger power supply section,

    input AC mains is stepped down by transformer to deliver 9V, 500mA to thebridge rectifier, which comprises diodes (IN4007x4). Filter capacitor

    (25v/1000uf)eliminates ripples. Unregulated DC voltage is fed to input pin 3 ofIC1 and provides charging current through diode IN4007(D5) and limiting resistor

    (16ohm)R16. By adjusting preset 2.2K(VR1), the output voltage can be adjusted to

    deliver the required charging current. When the battery gets charged to 6.8V, zener

    diode conducts and charging current from regulator (IC1) finds a path through

    transistor BC547(T1) to ground and it stops charging of the battery. The LEDdriver section uses a total of twelve 10mm white LEDs. All the LEDs areconnected in parallel with a 100-ohm resistor in series with each. The common-

    anode junction of all the twelve LEDs is connected to the collector of pnptransistor T2 and the emitter of transistor T2 is directly connected to the positive

    terminal of 6V battery. The unregulated DC voltage, produced at the cathodejunction of Bridge(Diodes), is fed to the base of transistor T2 through a 1k resistor.

    When mains power is available, the base of transistor T2 remains high and T2 doesnot conduct. Thus LEDs are off. On the other hand, when mains fails, the base of

    transistor T2 becomes low and it conducts. This makes all the LEDs (LED1through LED12) glow. The mains power supply, when available, charges the

    battery and keeps the LEDs off as transistor T2 remains cut-off. During mainsfailure, the charging section stops working and the battery supply makes the LEDs

    glow. Assemble the circuit on a general-purpose PCB and enclose in a cabinet withenough space for battery and switches. Mount the LEDs on the cabinet such that

    they light up the room. A hole in the cabinet should be drilled to connect 230V AC

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    input for the primary of the transformer. I have tested the circuit with twelve 10mm

    white LEDs.You can use more LEDs provided the total current consumption doesnot exceed 1.5A. Driver transistor T2 can deliver up to 1.5A with proper heat-sinkarrangement.

    FROM CALCULATED & MEASYRED ASPECT

    LED LAMP CIRCUIT:

    1.All are white hi bright LEDs rated for 3Volt @ 25mA

    2. The total current requirement is 12 X 25 = 300mA3. This current has to flow through T2 BD140 PNP transistor

    4. The minimum current gain (hfe) of this transistor @ 500mA is 50

    5. Hence the base current Ib requirement is Ic / hfe, 300 / 50 = 6mA

    6. Base emitter drop of T2 at 500mA is 0.77 volt

    7. With the fully charged battery at 6.9volt terminal voltage (for cycle

    operation use) the voltage available across the new bias resistance is (6.9

    0.77)

    8. Hence the bias resistance is = 6.13 / 6 = 1000ohms9. As the battery drains the final terminal voltage will be 5.4volt

    10. The bias resistance will be (5.4 0.77) / 6 = 770 ohms Hence a 680

    ohms was preferred for bias resistance with drained battery also it will

    give enough brightness.

    11. The very important information about BD140 is, as you view the

    pins, metal portion of the transistor facing down left is emitter centre

    collector and right is base. Most of the constructors make this mistake,

    relying on the convention that left base and right emitter. If you have

    made this mistake please correct it.

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    THE BATTERY CHARGER CIRCUIT

    1.The battery requires a full terminal voltage of 6.9V at this point charger

    should cut off.

    2. That is the voltage across the chain ZD1, R2 and T1 be should be 6.9 volt3. T1 be voltage of 0.7 volt plus drop across R2 and zener voltage should be

    6.9V

    4.T1 be current = Ic / hfe

    5. Ic is 1.25 / 180 = 7mA

    6. Ibe = Ic / hfe of T1 i.e = 7 / 70 = 100uA

    7. Drop across R2 =1.2 X .1 mA = 0.12volt

    8. Hence Zener voltage = 6.9(0.7 + 0.12) = 6.08 the near by preferred

    zener voltage is 6.2 volt

    9. Say the battery voltage at full charge will be 7 volt with 6.2 volt zener

    diode

    10. To calculate R16 value for charging at 1 /10 th of the rated current of the

    battery 4.5AH / 10 = 450mAH

    11. Transformer 9volt AC the voltage across C1 will be 9 X 1.414 = 12.6

    volt

    12. The drop across LM317 at 450mA current for good regulation is 3volt

    13. The drop across protective diode D5 is 0.7 volt.

    14. The voltage available at cathode of D5 is 12.6(3+0.7) = 8.9volt

    15. The battery after fair discharge will be at 6 volt

    16. Hence R16 = (8.97) / 0.45 = 6 ohms17. The nearby standard value for operation is 5 ohms.

    18. At the end point of battery 5.4 volt the maximum charging current can be

    of (8.95.4) / 5 = 0.7 amps well within the higher charging limit of the

    battery.

    19. With this circuit over night the battery will get charged fully.

    20. Over charging is taken care and protected by T1.

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    GRAPHICAL REPRESENTATION OF COMPONENTS:

    LM317

    BD140

    BC548

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    USES

    1. Convert 120V-230V Ac into 12V Dc and charge the battery.2. Use in that places where the power doesnt supply properly.

    ADVANTAGES

    Saves fuel.

    Pollution free.

    Easy to use. Very low cost under Rs(200-300)

    Easy to install anywhere.

    DISADVANTAGES

    It can be used only for short period.

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    IMPLEMENTATION AND RESULTS:

    This project is useful to us. It is used in emergency.

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    REFERENCES:

    1-[online], Available:http://seminarprojects.com/Thread-automatic-emergency-light-

    full- report#ixzz2S6L1vudK

    2- [online], Available:http://www.circuitstoday.com/automatic-led-emergency-light

    http://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudKhttp://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudKhttp://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudKhttp://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudKhttp://www.circuitstoday.com/automatic-led-emergency-lighthttp://www.circuitstoday.com/automatic-led-emergency-lighthttp://www.circuitstoday.com/automatic-led-emergency-lighthttp://www.circuitstoday.com/automatic-led-emergency-lighthttp://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudKhttp://seminarprojects.com/Thread-automatic-emergency-light-full-%20%20%20%20report#ixzz2S6L1vudK