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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
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