This is our 3rd semester project of electronics-1 which is a mobile battery charger with night switch as load circuit, it will work as a ups the night switch works on input 220 volt supply and when we cut off the supply it continues it working on battery power and vice virsa.

1. 5/26/2014 Electronics Project Report
Instructors:
Mam Saira Latif
Mam Nihala Khalid
COMSATS INSTITUTE OF INFORMATION TEC. ISLAMABAD
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2. A SIMPLE MOBILE CHARGER WITH INVERTER 1
1. Course information:......................................................................................... 3
2. Project title:..................................................................................................... 4
3. Abstract:........................................................................................................ 5
4. Introduction: ................................................................................................. 5
5. Parts of project:............................................................................................. 5
5.1. Dc Power supply:............................................................................. 6
5.1.1. Compnents required:............................................................... 6
5.1.2. Transformer:............................................................................ 6
5.1.3. Voltage Regulators:.................................................................. 7
5.1.4. Diode Bridge............................................................................. 7
5.1.5 Filter Circuit ............................................................................. 8
5.1.6. Circuit diagram:........................................................................ 9
5.1.7. How it works:.......................................................................... 9
5.1.8. Circuit layout:.......................................................................... 9
5.2. Night switch: ................................................................................. 10
5.2.1. Component used :.................................................................. 10
5.2.2. Principle:............................................................................... 10
5.2.3. L.D.R: (Light Depending Resistance):..................................... 11
5.2.4. L.E.D: (Light Emitting Diode):................................................. 12
5.2.5. Circuit diagram:..................................................................... 12
5.2.6. Vero board layout: ................................................................ 13
5.3. Battery charger:............................................................................ 13
5.3.1. Components needed: ........................................................... 14

3. A SIMPLE MOBILE CHARGER WITH INVERTER 2
5.3.2. Circuit diagram:.................................................................... 14
5.3.3. Working: .............................................................................. 15
5.3.4. Drawback: ............................................................................ 15
5.4. Inverter:...................................................................................... 15
5.4.1. Relay:...................................................................................... 15
5.4.2. Working:................................................................................. 16
6. Bibliography.……………………………….………………………………………………………..……16
7. Conclusion ……………………………………........……………………………………………..……16
8. Whole Schematic …………………………………………..…………………………………........17

4. A SIMPLE MOBILE CHARGER WITH INVERTER 3
1. Course information:
Electronics-1
Instructors:
Lab:
Mam Saira Latif
Theory :
Mam Nihala Khalid

5. A SIMPLE MOBILE CHARGER WITH INVERTER 4
2. Project title:
A simple mobile battery charger with inverter

6. A SIMPLE MOBILE CHARGER WITH INVERTER 5
3. Abstract:
In this report, the design and implementation processes of a simple battery charger is
documented. The initial design criteria for the project were:
1. To design a circuit which will charge the mobile battery.
2. To introduce a night switch circuit.
3. To implement the inverter schematic.
Research was conducted into similar analogue electronic circuits and a suitable starting point
was identified. Using this starting point, the idea was implemented. The proposed circuit was
modelled using Proteus, showing that the concepts used in the design were sound. The circuit
was then implemented and tested on breadboard. Then the same circuit was implemented on
vero board.
4. Introduction:
In this section we will discuss our idea of project, which thing encourage us to choose that
project.
In our country load shedding is serious problem, the government is taking measures to
complete the need of electricity. As an engineering student we think that why should not, we
will make some alternative to that problem, so that’s the point which encourage us to make a
inverter.
Our circuit will run a night switch circuit as a load just to show the running of inverter. The
main source power supply of 220v is connected to our inverter it will charge the battery and at
the same time the load circuit will also runs on that input source, but as soon as the main
source is cut off the inverter will immediately change over the source and load (night switch)
will continue its running on battery power, and again when main 220v supply is again
connected the inverter will change the source and starts the charging.
5. Parts of project:

7. A SIMPLE MOBILE CHARGER WITH INVERTER 6
Basically our project consists of three different circuits, that will perform its working. The list is
as follow:
 12v power supply
 Battery charger+inverter
 Night switch
The basic construction & working of each is given below;
5.1. Dc Power supply:
In this section the construction and working of a 12v power supply is documented.
A power supply is a device which delivers an exact voltage to another device as per its needs. Power
supplies, often called power adapters, or simply adapters, are available in various voltages, with varying
current capacities.
5.1.1. Compnents required:
1. Copper wires
2. Step Down Transformer
3. 1N4007 Silica Diodes (×4)
4. 470µF Capacitors
5. 10µF Capacitors
6. Voltage regulator (78XX) (XX is the output voltage req).
7. Soldering iron
8. Solder
9. Vero board
10. Adapter jack (to provide the output voltage to a device with a particular socket)
11. 2 Pin plug
12. LED (for indication)
13. Resistor (Value explained later)
5.1.2. Transformer:
A transformer is an electrical device that transfers energy between two circuits through electr
omagnetic induction. A transformer may be used as a safe and efficient voltage converter to change the
AC voltage at its input to a higher or lower voltage at its output without changing the frequency. A
transformer most commonly consists of two windings of wire that are wound around a

8. A SIMPLE MOBILE CHARGER WITH INVERTER 7
common core to provide tight electromagnetic coupling between the windings. The core
material is often a laminated iron core. The coil that receives the electrical input energy is
referred to as the primary winding, the output coil is the secondary winding.
5.1.3. Voltage Regulators:
The 78XX series of voltage regulators is a widely used range of regulators all over the world. The
XX denotes the voltage that the regulator will regulate as output, from the input voltage. For
instance, 7805, will regulate the voltage to 5V. Similarly, 7812 will regulate the voltage to 12V
5.1.4. Diode Bridge
A bridge rectifier consists of an assembly of four ordinary diodes, by means of which we can
convert AC Voltage into DC Voltage. It is found to be the best model for AC to DC conversion,
over Full wave and Half wave rectifiers.

9. A SIMPLE MOBILE CHARGER WITH INVERTER 8
5.1.5. Filter Circuit
We filter, both the input and output of the voltage regulator in order to get the smoothest DC
Voltage as possible, from our adapter, for which we use capacitors. Capacitors are the simplest
current filters available, they let AC current pass through and block DC, so they are used in
parallel to the output. Furthermore, if there is a ripple in the input or output, a capacitor
rectifies it by discharging the charge stored in it.

10. A SIMPLE MOBILE CHARGER WITH INVERTER 9
5.1.6. Circuit diagram:
5.1.7. How it works:
The AC mains are fed to the transformer, which steps down the 230 Volts to the desired
voltage. The bridge rectifier follows the transformer thus converting AC voltage into a DC
output and through a filtering capacitor feeds it directly into the input (Pin 1) of the voltage
regulator. The common pin (Pin 2) of the voltage regulator is grounded. The output (Pin 3) of
the voltage regulator is first filtered by a capacitor, and then the output is taken.
5.1.8. Circuit layout:

11. A SIMPLE MOBILE CHARGER WITH INVERTER 10
5.2. Night switch:
When there is need of light it automatically switches ON. When darkness rises to a certain value
then sensor circuit gets activated and switches ON and when there is other source of light i.e.
day time, light gets OFF.
5.2.1. Component used :
1. 9v Battery with strip
2. Switch
3. L.D.R (Light Depending Resistance)
4. I.C NE555 with Base
5. L.E.D (Light Emitting Diode) 3 to 6 pieces.
6. Variable Resistance of 47 KΩ
7. P.C.B (Printed Circuit Board of 555 or Vero board.
5.2.2. Principle:
This circuit uses a popular timer I.C 555. I.C 555 is connected as comparator with pin-6 connected
with positive rail, the output goes high(1) when the trigger pin 2 is at lower then 1/3rd level of
the supply voltage. Conversely the output goes low (0) when it is above 1/3rd level. So small
change in the voltage of pin-2 is enough to change the level of output (pin-3) from 1 to 0 and 0
to 1. The output has only two states high and low and can not remain in any intermediate stage.

12. A SIMPLE MOBILE CHARGER WITH INVERTER 11
It is powered by a 6V battery for portable use. The circuit is economic in power consumption. Pin
4, 6 and 8 is connected to the positive supply and pin 1 is grounded. To detect the present of an
object we have used LDR and a source of light.
Sensitiveness can be adjusted by this variable resistance. As soon as LDR gets dark the voltage
of pin 2 drops 1/3rd of the supply voltage and pin 3 gets high and LED or buzzer which is
connected to the output gets activated.
5.2.3. L.D.R: (Light Depending Resistance):
It is a special type of resistance whose value depends on the brightness of light which is falling
on it. It has resistance of about 1mega ohm when in total darkness, but a resistance of only
about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.

13. A SIMPLE MOBILE CHARGER WITH INVERTER 12
5.2.4. L.E.D: (Light Emitting Diode):
A diode is a component that only allows electricity to flow one way. It can be thought as a sort
of one way street for electrons. Because of this characteristic, diode are used to transform or
rectify AC voltage into a DC voltage. Diodes have two connections, an anode and a cathode. The
cathode is the end on the schematic with the point of the triangle pointing towards a line. In
other words, the triangle points toward that cathode. The anode is, of course, the opposite
end. Current flows from the anode to the cathode.
5.2.5. Circuit diagram:

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5.2.6. Vero board layout:
5.3. Battery charger:
charging of the cellphone battery is a big problem while travelling as power supply source is
not generally accessible. If you keep your cellphone switched on continuously, its battery will go
flat within five to six hours, making the cellphone useless. A fully charged battery becomes
necessary especially when your distance from the nearest relay station increases. Here’s a
simple charger that replenishes the cellphone battery within two to three hours.:

15. A SIMPLE MOBILE CHARGER WITH INVERTER 14
5.3.1. Components needed:
 Diodes
 Resistors
 Wires
 Led
 6 volt dc source
5.3.2. Circuit diagram:

16. A SIMPLE MOBILE CHARGER WITH INVERTER 15
5.3.3. Working:
The positive DC supply is directly connected to the charger’s output contact, while the
negative terminal is connected through current limiting resistor R2. LED2 works as a power
indicator with resistor R1 serving as the current limiter and LED3 indicates the charging
status. During the charging period, about 3 volts drop occurs across resistor R2, which turns on
LED3 through resistor R3. The diode D1 is used to stop the back flow of current, so that when
we disconnect the input source the power of battery remain save & not flow back.
5.3.4. Drawback:
There is one drawback of our this charger circuit that is it does not cut off the charging process
when battery is full, in other words we say that this circuit is not able to guess the condition
when battery is fully charged ,so we have to make little care that after charging the battery for
3-4 hours we manual have to take it off .
Due to time restriction we don’t go in to more complication otherwise this logic to turn off the
the charging can also be implemented by using a 555 ic.
5.4. Inverter:
Now in this section the main and important action of the circuit is discussed:
The principle of our inverter is same as used in UPS(unbreakable power source) used in our
homes.
The main component used for purpose is relay. We used two relays in our circuit.
5.4.1. Relay:
A relay circuit is typically a smaller switch or device which drives (opens/closes) an electric
switch that is capable of carrying much larger current amounts. Or a circuit which operates the
coil or electronic actuator from one source and uses a separate power source to drive an
isolated device. Generally speaking, a relay circuit is a circuit that uses a small mechanical
switch or a semiconductor device (with associated circuitry) to energize a relay, which will then
close a contact set to complete another circuit.

17. A SIMPLE MOBILE CHARGER WITH INVERTER 16
5.4.2. Working:
We connect the input terminals of load (night switch) circuit to the outputs of relays.The circuit is
designed in such way that when the main input supply for transformer is on the relay is on and it allows
the current to flow through the load (night switch) from the main, and battery power is off.
But when we turn off the main power source the relay becomes off and inverts the connection so now
current also flows in the load(night switch) but in this condition the current flows from the battery, and
our load circuit runs on battery power.
6. Bibliography:
 http://wiki.answers.com/Q/What_does_a_reed_relay_do_in_a_circuit#slide=3
 http://www.engineersgarage.com/electronic-circuits/electronic-letter-box
 https://www.google.co.uk/search?q=battery+charger&es_sm=93&source=lnms&tbm=isch&sa=
X&ei=9Ft3U57INK7o7Ab20IGYDw&ved=0CAkQ_AUoAg&biw=1366&bih=564
 http://www.instructables.com/id/Make-a-simple-12-volt-power-supply/
7. Conclusion:
All of the circuits were implemented on vero board , then all of them are interlinked to each
other through wiring. . Different methods were analysed to determine the best technique for
creating an efficient result until one was chosen and the circuit was designed. The chosen
circuit was verified through simulation using Proteus. This design was then implemented and
modified to suit the needs of the project. Problems were analysed and repaired where
necessary until it was concluded that the circuit had met the design criteria of the project.

18. A SIMPLE MOBILE CHARGER WITH INVERTER 17
We have to work hard will keen devotion to complete this project. Many problems will arise
during the preparation of this project, such conditions also arise during working on project that
we are totally disappointed , but will not lose hope so then by the collaboration of mates and
Blessings of Almighty Allah we got the +ve result.
8. Whole schematic: