The design of an LED emergency light that switches on automatically when main power fails. Power to the LED is supplied by a battery that keeps charging when the main power is present. The circuit of the automatic LED light is designed, simulated and built with hardware. The simulation results and design details are provided. Complete circuit diagram, which is tested successfully, is given.

1. Automatic LED emergency Light
Mini Project
By
Darshil shah (IU1241090051)
Vatsal shah (IU1241090055)
Under the guidance
Of
Prof. Omkar Pabbati
Electronics & Communication Department
5th Semester
Indus Institute of Technology and Engineering
INDUS UNIVERSITY

2. Index
S No. Details P. No.
List of Figure 3
List of Table 3
1 Abstract 5
Chapter 1
Block Diagram With Explanation Of Each Block
1.1 Introduction 6
1.2 Block Diagram 6
1.2.1 Functional Block Diagram 7
1.2.2 Flow Diagram 8
1.3 Explanation Of Each Block 8
1.3.1 Power Supply 8
1.3.2 Relay 9
1.3.3 Rechargeable Battery 9
1.3.4 LEDS
Chapter 2
Design Details
2.1 Transformer 10
2.2 Relay Circuit 10
2.3 Zener Diode 11
2.4 Capacitor 11
2.5 Diode 12
2.6 LEDS 12
2.7 Rechargeable Battery 12
2.8 Bridge Circuit 13
Chapter 3
Circuit Diagram With Explanation Of Each Block
3.1 Circuit Diagram 14
3.2 Operational Of Circuit Diagram 14
3.3 Circuit Diagram With Operational Details 15
3.3.1 Transformer 15
3.3.2 Bridge Circuit 15
3.3.3 Relay 15
3.3.4 Rechargeable Battery 15
3.4 Simulated Circuit 16
Chapter 4
Features
4.1 Scope 17
4.2 Advantages 17
4.3 Disadvantages 17
4.4 Application 17
4.5 Comparison of LED Lamps with other Lighting Technologies 18
Chapter 5
Simulation
5.1 Eagle PCB Layout 19
5.2 Part List 20
Chapter 6
Result, Future-Scope, References
6.1 Result 21
6,2 Future Scope 21
6.3 Conclusion 21

3. List of Figures
Figure No. Figure Title Page No.
1.2.1 Functional Block Diagram 7
1.2.2 Flow Diagram 8
2.2 Relay 10
2.2.1 Relay Simulated Circuit 10
2.3 Zener Diode 11
2.4 Capacitor 11
2.5 Diode 12
2.6 LED 12
2.7 Rechargeable Battery 12
2.8 Bridge Circuit 13
3.1 Circuit Diagram 14
3.3.1 Bridge Circuit 15
3.3.2 Relay 15
3.4 Simulated Circuit 16
4.5 Comparison of LED with other Technologies 18
5.1 PCB Layout 19
6.1 Circuit diagram in working condition 21
List of Table
Table No. Table Title Page No.
5.2 Part List 20

4. 4
Acknowledgement
It is our privilege to express our sincerest regards to our project coordinator, Mr. Omkar
Pabbati, for their valuable inputs, able guidance, encouragement, whole-hearted cooperation
throughout the duration of our project.
I also express my sincere thanks to Mr. Subhash Patel for his help.
We deeply express our sincere thanks to our Head of Department Prof. R N Mutagi for
encouraging and allowing us to present the project on the topic “Automatic LED Emergency
Light “.
We take this opportunity to thank all our lecturers who contributed their valuable advice and
helped to complete the project successfully.

5. Abstract
This report describes the design of an LED emergency light that switches on automatically
when main power fails. Power to the LED is supplied by a battery that keeps charging when
the main power is present. The circuit of the automatic LED light is designed, simulated and
built with hardware. The simulation results and design details are provided. Complete circuit
diagram, which is tested successfully, is given.

6. 6
Ch. – 1 Block Diagram with Explanation of Each Block
1.1 Introduction
Growing demand for the saving of electricity. It is based on the principle of providing light when
the power is cut off. This is accomplished by the use of automatic charger which gets charged
when power supply exists. When the battery is fully charged it stops charging. In case of power
failure, the LED glows automatically with the supply provided by the charged battery.
This project is working on two major processes:
1. It turns on automatically when the mains power fails, so you need not search it in the
dark.
2. Its battery starts charging as soon as mains resumes.
This Emergency light is used mostly in village because there is the lack of electricity which is
very required. In industries and as well as in household applications an emergency light is
employed where there is frequent non uniform voltage distribution occurs. Many types of
emergency lights from rechargeable torches to systems like generators are available in
market. All of them require a switch to operate them when frequent power failure occurs.
The present one deals with a model which senses the mains as well as daylight to switch on
the emergency light. There is no need to search the switch in the dark as it switches on/off
automatically. This present one has one on/off switch on operating which the emergency light
glows. In most of the emergency light there exists a drawback. The discharge level of the
battery is not being controlled to a safe level. The batteries get discharged completely and
lose their life rapidly. This is a very serious aspect in order to overcome this cut-off is provided
and there exists a minimum discharge level which ensures the long life of batter.

7. 7
1.2 Block Diagram
Functional block diagram and flow diagram are explained below:
1.2.1 Functional Block Diagram
Power supply block is connected with relay and if the supply is off it will turn of LEDs.
When supply is on it charge the battery continuously. Functional Block diagram
describe as below.
FIG. 1.2.1 FUNCTIONAL BLOCK DIAGRAM
Power
Supply
Design
(AC -> DC)
Relay Turn On
LEDs
Battery
Charge
Supply ON
Supply OFF

8. 8
1.2.2 Flow Diagram:
When AC is on the flow shows that battery will be charge. When AC is off it turn on
the LEDs as shown in the flow diagram.
FIG. 1.2.2 FLOW DIAGRAM
1.3 Explanation Of Each Block:
1.3.1 Power Supply:
For converting 230V AC to 12V AC, 12-0-12V Transformer is used. It steps down the
voltage from 230V to 12V AC. Now, to convert 12V AC to 12V DC we use Bridge
Circuit. There are four 1N4007 Diode is used to get 12V DC output. This is the function
of Power Supply to convert AC to DC.
1.3.2 Relay:
Relay is working as a Switch. There are three terminal NC (Normally Close) and NO
(Normally Open) and Common. Here we connect. NC terminal to the rechargeable
battery and Common terminal is Connects with the LEDs. Now if Power supply is on it
connects with NO terminal and charge the battery and when there is no power supply
NC terminal is connected with the battery and LEDs will be ON.
Battery
Charge
Turn On Lights
NO
YES
NO
YESAC
On
AC
Off

9. 9
1.3.3 Rechargeable Battery:
Li-ION battery is used to give 3.7V as Output and Maximum Voltage of the battery is
4.7 voltage Zener Diode of 4.5V is used to get 4.5V as an input. So that it can be
measured how much time it will take to charge battery.
1.3.4 LEDs:
10 LEDs are connected in parallel to get charge from rechargeable battery when power
supply is cut off. It is on automatically when power supply is off.

10. 10
Ch. – 2 Design Details
2.1 Transformer:
In this circuit the transformer used is of step down type which consumes 230 volts
as input (primary side) and produces output of 12volts. This can be termed as
230votls primary, 12v secondary step down transformer.
2.2 Relay circuit:
Relay is working as a Switch. In the input of Relay 9V DC supply can be given and
at the output if we connect bulb so relay is working as switch and bulb will turn
On/Off so, we can verify the working of Relay.
FIG.2.2 Relay
(Source: http://i.stack.imgur.com/AujXg.png)
Simulated circuit for relay as shown below:
FIG. 2.2.1 Relay Simulation Circuit

11. 11
2.3 Zener Diode:
It permits current to flow in the forward direction as normal, but will also allow it to
flow in the reverse direction when the voltage is above a certain value - the
breakdown voltage known as the Zener voltage. The Zener diode specially made
to have a reverse voltage breakdown at a specific voltage.
For example, a diode with a Zener breakdown voltage of 4.2 V exhibits a voltage
drop of very nearly 4.2 V across a wide range of reverse currents.
FIG. 2.3 ZENER DIODE
(Source: http://www.completepowerelectronics.com/wp-content/uploads/2013/01/zener-diode.jpg)
2.4 Capacitor:
A capacitor is a passive two-terminal electrical component used to store energy
electro statically in an electric field. The forms of practical capacitors vary widely,
but all contain at least two electrical conductors (plates) separated by a dielectric
(I.e. insulator). An ideal capacitor is characterized by a single constant value for
its capacitance. Capacitance is expressed as the ratio of the electric charge Q on
each conductor to the potential difference V between them. The SI unit of
capacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical
capacitance values range from about 1 pF (10−12
F) to about 1 mF (10−3
F)
FIG.2.4 Capacitor
(Source: http://www.diyguitarmods.com/images/electrolyticcap.gif)

12. 12
2.5 Diode:
Diode is a two-terminal electronic component with asymmetric conductance; it has
low (ideally zero) resistance to current in one direction, and high (ideally infinite)
resistance in the other.
FIG. 2.5 Diode
(Source: http://www.electronix.com/images/diode.jpg?osCsid=6tiv9u6bg2re7slavbljhqqpo6)
2.6 LED:
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a
basic PN-junction diode, which emits light when activated. When a fitting voltage is
applied to the leads, electrons are able to recombine with electron holes within the
device, releasing energy in the form of photons
Here 10 LEDs are connected in parallel to get charge from rechargeable battery
when power supply is cut off. And it will on automatically when power supply is off.
FIG. 2.6 LED
(Source: http://www.lumenstarled.com/media/catalog/category/single_5mm_LEDS.jpg)
2.7 Rechargeable Battery:
Li-ION battery is used to give 3.7V as Output and Maximum Voltage of the battery
is 4.7 voltages. Zener Diode of 4.5V is used to get 4.5V as an input. So that it can
be measured how much time it will take to charge battery.
FIG. 2.7 Rechargeable Battery
(Source: http://ecx.images-amazon.com/images/I/41u7Hh78sLL._SY300_.jpg)

13. 13
2.8 Bridge Circuit:
A bridge circuit is a type of electrical circuit in which two circuit branches (usually
in parallel with each other) are "bridged" by a third branch connected between the
first two branches at some intermediate point along them.
In the circuit of automatic emergency light the bridge circuit is used for convert
12VAC to 12VDC voltage.
FIG. 2.8 Bridge Simulation

14. 14
Ch. – 3 Circuit Diagram with Explanation of Each Block
3.1 Circuit Diagram
Circuit diagram of Automatic LED Emergency light is as below:
FIG. 3.1 Circuit Diagram
3.2 Operation of circuit Diagram
 The step down transformer and the diode bridge rectifier steps down and convert
the high AC (in the range of 110V or 230V) voltage to low (12V) DC voltage.
 The diode D5 prevents the battery charge from flowing back, it acts as a
freewheeling diode too.
 In the presence of electricity, the relay contact connects the NO (Normally Open)
terminal to battery. Thus battery charges during this time.
 Use Green LED as the charging indicator which glows when the emergency light
battery is charging.
 When supply failure occurs, relay connects the NC (Normally Closed) terminal to
the battery.
 The LED arrays are connected to NC terminal, thus they glow by using the charge
stored in the battery.

15. 15
3.3 Circuit Diagram With Operational Details
3.3.1 Transformer:
For Converting High AC voltage to Low AC voltage we used 12-0-12V
Transformer.
3.3.2 Bridge Circuit:
To convert 12V AC to 12 V DC, we use 4 Diode 1N4007. It has High Current
Capability and Low Forward Voltage Drop. The value of capacitor is 470µF. So
we get rectified output.
FIG. 3.3.2 Bridge Circuit
(Source: http://www.radio-electronics.com/info/circuits/diode-rectifier/diode-rectifier-full-wave-
bridge-03.gif)
3.3.3 Relay:
Relay is working as a Switch. To operate relay we needs 12V DC supply so
that we are using 12V Transformer.
FIG. 3.3.3 Relay
(Source: http://electronicsclub.info/images/swabc.gif)
3.3.4 Rechargeable Battery:
For Rechargeable battery, Nominal Voltage of Li-Ion battery is 3.7 Voltage.
Standard capacity is 1950mAh. Charging voltage is 4.2V.Constant current
0.2C5A.

16. 16
3.4 Simulated Circuit
At the time of simulation, circuit is simulated and diagram is as shown below:
FIG. 3.4 Simulated Circuit

17. 17
Ch. – 4 Features
 Simple:
Simple circuit. Components are easily available and low cost.
 Automatic:
Automatically switches ON when the mains fails and turns OFF when mains power
resumes. Also has its own battery charger which when fully charged stops charging
automatically.
 Convenient :
Makes our lives simpler, convenient to use.
 Economical:
Energy consumption is very less, proves to be more economic for the consumer.
4.1 Scope
Scopes of the Automatic LED Emergency Light are:
 Longer Lasting battery that works approx. 8 hours
 Power is available; it senses and switches off the LEDs (lamp) instantly.
 Easy to use.
 Uses at office, conference room, exhibition hall lighting
 Uses at Direction Arrow Board for Bathroom
4.2 Advantages
The advantage are; it is easy to use, very low cost, save energy more and easy to
install anywhere.
 Efficiency: more light per watt than incandescent bulbs.
 Color: can emit of an intended color without use of color filters.
 Size: very small.
 On/off time: light up very quickly.
 Life time: long useful life time.
4.3 Disadvantages
 Cost: currently more expensive.
 Health hazard: cool white LEDs can cause problems to eyes.
4.4 Application
 Used as an alternative source at the time of power failure.
 It is suitable for domestic applications.
 Used in remote residential areas.

18. 4.5 Comparison of LED Lamps with other Lighting Technologies:
The comparison between LED, Florescent Lamp and incandescent lamp is shown:
(Source: https://www.scribd.com/doc/161102521/Automatic-Led-Emergency-Light-Ppt)
FIG 4.5 Comparison of LED with other Technologies

19. 19
Ch. – 5 Simulation
5.1 Eagle PCB Layout
With the use of circuit diagram PCB layout is as below:
FIG. 5.1 PCB Layout

20. 20
5.2 Part list
Part Value Package Library Position (inch)
Orientation
C1 470u E3, 5-8 rcl (0.3 1.1) R0
D1 1N4007 DO41-10 diode (0.45 0.45)
R270
D2 1N4007 DO41-10 diode (0.7 0.45) R90
D3 1N4007 DO41-10 diode (0.9 0.45) R90
D4 1N4007 DO41-10 diode (1.05 0.45)
R270
D5 1N4004 DO41-10 diode (0.9 1.05) R90
D6 1N4007 DO41-10 diode (1.3 0.8)
R180
D7 1N5333 C1702-15 diode (1.6 0.25) R0
JP1 3.7V JP1 jumper (1.9 0.55) R0
JP2 230V JP1 jumper (0.25 0.35) R18
K2 G5L G5LE relay (2.2 1.05) R0
L1 Green LED5MM led (0.65 1.05) R90
L2 Red LED5MM led (0.25 1.45) R90
L3 Red LED5MM led (0.55 1.45) R90
L4 Red LED5MM led (0.85 1.45) R90
L5 Red LED5MM led (1.15 1.45) R90
L6 Red LED5MM led (1.45 1.45) R90
R1 1k 0207/10 resistor (0.45 0.8) R0
R2 1k 0207/10 resistor (1.25 1.1)
R180
R3 330 0207/10 resistor (2.05 1.5)
R180
R4 330 0207/10 resistor (1.5 0.65)
R180
Table 5.2 Part List

21. 21
Ch. – 6 Result, Future-Scope, References
6.1 Result
The output of the LEDs is measured and tested battery backup is approx. 8 Hours. At
the input of the battery the measured voltage is 4.5V through Zener Diode. Across
Capacitor measured voltage is 12.15V DC and from calculated current is 12.15mA.
Across Diode D2 voltage is 13.7V. This circuit can also be extended to a higher output
voltage for which the charging voltage and the load are to be chosen accordingly. All
the other components involved in the circuit are of same value.
6.1 Circuit Diagram in Working Condition
6.2 Future Scope
The emergency light which uses IC is a reliable one comparing to other on IC
emergency lights and there is an automatic feature by which itself get glows.
This project can be adopted for mass production as cheap and efficient method.
6.3 Conclusion
 The project was concluded to be innovative for the improvement of day today life.
 Device also adds a new look to the traditional lamps.
 The cost of implementing this circuit is also very less - an added advantage in using
this circuit.
 Thus the implementation of automatic LED emergency light proves to be a cost
effective and compact application in today’s world of technological miniaturization.
As of there has been an increase in the use of LEDs for the development of new
applications, its promotion would lead to the enhancement of future innovations!

22. 22
References
 Jacob Millman & Christos C. Halkias, Electronic Devices & Circuits, McGraw-Hill,
1967 – Textbook
 http://www.fmlink.com/article.cgi?type=Magazine&pub=Premises%20&%20Facilit
ies%20Management&id=30856&mode=source
 http://www.circuitstoday.com/automatic-led-emergency-light
 http://www.ucl.ac.uk/estates/maintenance/fire/documents/UCLFire_TN_022.pdf
 http://en.wikipedia.org/wiki/Emergency_light
 http://electrotech99.blogspot.in/2012/11/led-based-automatic-rechargeable.html
 http://www.connectingindustry.com/electricalengineering/the-benefits-of-
automatic-emergency-lighting-testing.aspx
 https://www.scribd.com/doc/161102521/Automatic-Led-Emergency-Light-Ppt
 http://www.tridonic.com/pl/download/Emergency_Lighting_Overview_EN.pdf
 http://www.8051projects.net/files/public/1259220442_20766_FT0_7380969-line-
follower-using-at89c51.pdf