The document describes the design of a multiple output battery charger circuit. It includes: 1) An introduction outlining the need for a single charger with multiple outputs to charge many devices simultaneously. 2) Details of the circuit design including a transformer to step down 220V AC to 12V AC, a bridge rectifier to convert to DC, and four voltage regulators to provide stable 5V outputs for charging. 3) Descriptions of testing the circuit which provided the expected output voltage and ability to simultaneously charge multiple batteries.

1. Multiple output
charger
1St : 37103008

2. Table of contents
1. Introduction
2. Batteries
3. User requirement specification
4. Circuit design
5. Practical work
6. Problems encountered
7. Time spent on the project
8. Work done
9. Subject theory applied
10. Photos and videos
2St : 37103008

3. INTRODUCTION
 To meet the need of charging a lot of devices at once in a workshop
,and to avoid crowding workstations with single chargers that also
requires multiple sources ,we have design a single charger that will
utilize one source supply and make multiple outputs available for
charging purposes .this will be simple and more efficient .
3St : 37103008

4. Batteries
An electric battery is a device consisting of one or more electrochemical
cells that convert stored chemical energy into electrical energy. Each
cell contains a positive terminal, or cathode, and a negative terminal, or
anode. Electrolytes allow ions to move between the electrodes and
terminals, which allows current to flow out of the battery to perform
work.
We use batteries to power electronic devices specially in this case
batteries are used for powering communication devices.
4St : 37103008

5. A battery need to be recharged frequently to keep the voltage on its
terminals at it nominal value for a good operation of the device it
supplies .and that is the role of chargers to bring back the battery
voltage to it nominal value.
Internal view External view
5St : 37103008

6. User requirement specification
 The user require A device that will provide multiple 5v DC output to
charge many mobile device at a same time
 The device must be simple and not very heavy
 Capable of charging not less than 10 battery at a time
 It should be utilising a normal input source of 220v.
 It must be of an acceptable size not to take a lot of spaces.
 Must provider connecter which are universal (USB)
 If using cables their size should not exceed 5mm.
 The charging time should not be longer than the normal single
charger.
6St : 37103008

7. Concept 1:Using multiple different hall chargers
Advantage Disadvantage
No cost involve They crowd the area because you need a number of
them to charge many batteries same time.
A battery can be utilised while
charging.
Requires cell phones for each battery to be charged
so if you want to charge 20 batteries you will need
20 working phone devices or it will cost you a lot of
time to charge many batteries with one device...
Batteries cant kept fully charged at anytime.
Concept for multiple output charger
7St : 37103008

8. Concept 2:Multi output charger
Advantage Disadvantage
Clean and neat not
crowding the area
Cost of building high.
It can charge more than
10batteries at once.
Batteries can’t be used
while charging.
It is simple to understand
Easy to manipulate.
8St : 37103008

9. Criterion Weight of Out
Of 100
Concept 1 Concept 2
Score (%) weighted Score (%) weighted
Expectation 100 50 20 90 80
Reliability 100 25 10 80 75
Investment .Cap 80 10 10 70 20
Implementation 70 5 5 50 30
Total 50 70.68
9St : 37103008

10. It is obvious that concept 2 is much more efficient and can meet the expectations
set in the introduction of our project.
Technical specification
The technical specifications for this project are as follow:
Supply side or input voltage specification: 220V a.c. ±10% 50Hz
Output specification: Nominal Voltage: 4.2V dc ±0.5%
current: 1500mAh
Temperature: 5 to 50˚C
The input should be made of a female connector of tree pins (a phase, a neutral and
a ground pin) a transformer 220V to 5V, a full wave ac to dc converter.
10St : 37103008

11. Circuit Design
Sub-systems representation
Source: Is responsible of reducing the alternative 220V unto a low alternative
voltage ranging between 12 and 20V for supplying our circuit .
Circuit rectifier: This circuit convert the supply voltage from AC to DC.
Circuit regulator :This receive the DC voltage for the rectifier on it inputs and
releases on it output a stable none variant voltage .
Load: Is the device of which the battery require charging power.
Source
Circuit
rectifier
Circuit
regulator
Load
11St : 37103008

12. Initial design circuit
NB: It must be noted that this circuit can be modifier according to the
performance to get the best result components may be replaced by
others or replaced differently in the circuit.
D6
DIODE
+ V1
3.7V
T1
10TO1CT
D5
DIODE
D4
DIODE
D3
DIODE
Q1
NPN1
D2
ZENER
D1
DIODE
R2
1k
R1
1k
12St : 37103008

13.  Power source
A charging circuit require power to be able the generate 3.7V nominal voltage permanently
for the charging of a battery. The power could be supplied by any standard power generator.
It could be a diesel generator, or solar panel, a DC generator...
The circuit application is what determines the type of source to be utilised according to the
type of power sources available on the application site. And in this case the power supplied
in our workshop is simply an AC power 220V rms voltage .But we can see that the voltage
required for charging is a Dc voltage and is way to small compare to 220V therefore the first
thing will be to reduce the Ac voltage to a value closer to the charging voltage . To obtain a
low voltage out of 220 we have need of a transformer.
13St : 37103008

14. Brief on transformers
A transformer is made of a ferromagnetic core which is slices of metal sheets
stuck together with insulating material. The insulation between sheets is to
reduce Eddy current loses .the ferromagnetic core is graded with Primary and
secondary windings. When an alternative voltage is applied on the primary
winding it circulate a alternating current which produces an alternating flux
in the ferromagnetic core and the alternating flux will induce an e.m.f in the
secondary winding ,the e.m.f is proportional to the number of turns on the
winding .
𝑉2
𝑉1
≅
𝑁2
𝑁1
This formula gives way to step up or step down transformers. In this project
we need to low the voltage therefore our transformer is a step down transformer. Our
step down transformer takes an input voltage of 220V AC gives out 12V AC.
14St : 37103008

15. This formula gives way to step up or step down transformers. In this
project we need to low the voltage therefore our transformer is a step
down transformer. Our step down transformer takes an input voltage
of 220V AC gives out 12V AC.
15St : 37103008

16. Ideal transformer equations
By Faraday's law of induction
(1)
(2)
Combining ratio of (1) & (2)
Turns ratio =
𝑉𝑝
𝑉𝑠
=
𝑁 𝑝
𝑁 𝑆
Consequently
𝑉𝑠 =
𝑁𝑠
𝑁 𝑝
× 𝑉𝑝
16St : 37103008

17. Circuit Rectifier
The voltage on the secondary of the transformer is alternative
therefore there is need of rectifying that voltage since batteries are DC
components. The rectifier is made of four diode which makes it a full
wave rectifier.
17St : 37103008

18. Brief on Diode
Diodes allow electricity to flow in only one direction. Diodes are the
electrical version of a valve and early Diodes were actually called
valves. Diode rectifier gives a unipolar voltage, but pulsating with
time. If a negative voltage is applied to the cathode and a positive
voltage to the anode, the diode is forward biased and conducts. The
diode acts nearly as a short circuit. If the polarity of the applied
voltage is changed, the diode is reverse biased and does not conduct.
The diode acts very much as an open circuit. Finally, if the voltage
VD is more negative than the Reverse Breakdown voltage (also called
the Zener voltage,
VZ), the diode conducts again, but in a reverse direction. The voltage
versus current characteristics of silicon
18St : 37103008

19. Diode characteristics
19St : 37103008

20. Bridge rectifier
In many power supply circuits, the bridge rectifier is used. The bridge
rectifier produces almost double the output voltage as a full wave
centre-tapped transformer rectifier using the same secondary voltage.
The advantage of using this circuit is that no centre-tapped
transformer is required.
Observe that the current in the load on the two below figures doesn’t
change directions for both positive and negative cycle.
20St : 37103008

21. 21St : 37103008

22. Resistance R1
R1 limits the current flow from the source through the diode when
the transistor Darlington pair is switched off. This is the trickle
current which is designed to replace the losses in a lead acid battery
which is > 50 mA for a single battery charging. We using a colour
coded resistor of 560 ohm
That will be: Green, Blue, run and Gold (tolerance 5%)
Colour code Resistor.
22St : 37103008

23. 23St : 37103008

24. Regulator circuit
A voltage regulator generates a fixed output voltage of a pre-set
magnitude that remains constant regardless of changes to its input
voltage or load conditions. There are two types of voltage regulators:
linear and switching.
24St : 37103008

25. A linear regulator employs an active (BJT or MOSFET) pass device
(series or shunt) controlled by a high gain differential amplifier. It
compares the output voltage with a precise reference voltage and adjusts
the pass device to maintain a constant output voltage.
25St : 37103008

26. Functionality
The Zener diode D2 and diode D6 keep the base of transistor Q1 at
13.7 V. The sum of the two base-emitter volt drops of the transistor
equals 1.4 V. Thus, when the battery voltage falls below 12.3 V the
Darlington pair starts to conduct adding to the trickle current via R1.
The more discharged the battery becomes, the harder the transistor is
switched on. The lower battery voltage causes the charging current to
increase dramatically to bring the battery voltage back above 12 V.
26St : 37103008

27. The Darlington pair consists of two transistors connected as the
drawing. This connection has the characteristic of very high current
gain. Actually, the overall gain is:
hFE = hFE1 X hFE2
These results to gain more than 10000 it require only a tiny base current
change on the input of the Darlington pair in order to switch a load. A
Darlington pair will act exactly as a single transistor only with very high
current gain. Also, because there must be at least 0.7volts in both base-
emitter junctions, to switch on a pair like that will need at least 1.4volts.
27St : 37103008

28. Name Part number Function Maker Price
S.P. transformer D3687 Reduces 220VAC voltage to 12V
AC
Wurth Elektronik R250
Bridge rectifier KBU4J-E4/51 Convert The 12V AC voltage to
7 V DC(AV)
Vishay R52
Zener diode MM3Z11VT1G Stabilises voltage at the Bjt base
transistor
ON Semiconductor R10
Resistance Limit the current when the Bjt is
off
R3
Transistor. KSC945YTA Regulator the charging voltage Fairchild
Semiconductor
R0.64
Regulator
Module
L7805CV Regulator the charging voltage Texas Instruments R0.84
Capacitor ECOS1JP332CA Smooth the variations in the DC
voltage
Panasonic R64.7
28St : 37103008

29. Practical works
Lab:
29St : 37103008

30. Rectified signal
Before bridge rectifier
30St : 37103008

31. Our project is built in the ARC Electronic Lab .The place is mostly
utilised for Technical trainings of employees. It is equipped with
different electronic Equipment’s necessary for diverse manipulations.
Few that can be enumerate.
 Soldering Equipment
 Measuring Equipment
 Fault finding Equipment
 Calibration Equipment
 Signal tracing Equipment
 Power control Equipment
In our project Equipment’s that we be necessary are measuring, Signal
tracing and power control equipment.
31St : 37103008

32. MEASURING INSTRUMENTS
The basic measuring instrument is the multimeter. We find in the
categories of meters the analogue meters and digital maters .An
analogue meter has a large screen processing different scales and a
pointer.
Figure 4 an analogue multimeter
32St : 37103008

33. Digital meter has an electronic digital screen to display digit digital
meters have a much small screens compare to analogues meters.
33St : 37103008

34. It have been proven that digital meters are more accurate than analogue meters
because the accuracy of digital meters is based on the amount of digits that can be
displayed on the screen.
Signal tracing Equipment
Dual Trace OscilloscopeSpectrum Analyser
34St : 37103008

35. Measures the magnitude of an input signal versus frequency within the full
frequency range of the instrument. The primary use is to measure the power of the
spectrum of known and unknown signals.
Oscilloscope
Is a test instrument which allows you to look at the 'shape' of electrical signals by
displaying a graph of voltage against time on its screen?
The graph, usually called the trace, is drawn by a beam of electrons striking the
phosphor coating of the screen making it emit light, usually green or blue.
Oscilloscopes contain a vacuum tube with a cathode (negative electrode) at one
end to emit electrons and an anode (positive electrode) to accelerate them so they
move rapidly down the tube to the screen. This arrangement is called an electron
gun. The tube also contains electrodes to deflect the electron beam up/down and
left/right.
The electrons are called cathode rays because they are emitted by the cathode and
this gives the oscilloscope its full name of cathode ray oscilloscope or CRO.
35St : 37103008

36. Power control Equipment
Power supplies are used to provide low voltage range.
36St : 37103008

37. They cover up to 120V depending on the demand. But the most utilised range is form 0 to 12 V.
Circuit building
After Test and trial of our initial circuit we came across some challenges using the 2 transistors as
Darlington pair .The output was low and the transistors over heat with time and the output was to
low far from expected values.
Solution advised
Due to difficulties mentioned in the previous paragraph we had to redesign the circuit.
Therefore we opted for a LM587CV regulator and build a circuit slightly different from the initial
circuit.
37St : 37103008

38. T2
10TO1
P1
R1
1k
C2
420uF
C1
420uF
D2
ZENER
D1
BRIDGE
IN
COM
OUT
U1
LM317
38St : 37103008

39. Circuit with 4 Diode Bridge, resistance, L780CV, 2
capacitors.
39St : 37103008

40. This is our first acceptable output with this circuit with an input voltage of about 7V.
40St : 37103008

41. 41
T1
10TO1CT
1234
USB4
1234
USB3
1234
USB2
1234
USB1
C8
470uF
IN
COM
OUT
U4
78L05
C7
470uF
C5
470uF
IN
COM
OUT
U3
78L05
C6
470uF
C3
470uF
IN
COM
OUT
U1
78L05
C4
470uF
C2
470uF
IN
COM
OUT
U2
78L05
C1
470uF
D1
BRIDGE
R20
RESISTOR
R19
RESISTOR
R18
RESISTOR
R17
RESISTOR
R16
RESISTOR
R11
RESISTOR
R12
RESISTOR
R13
RESISTOR
R14
RESISTOR
R15
RESISTOR
R4
RESISTOR
R7
RESISTOR
R8
RESISTOR
R9
RESISTOR
R10
RESISTOR
R6
RESISTOR
R5
RESISTOR
R3
RESISTOR
R2
RESISTOR
R1
RESISTOR
Final design
St : 37103008

42. Due to the size of our transformer it can’t be fitted on the breadboard it just on the
side.
We managed to get approximately 7 V ac voltage from the transformer, which is
the source of our circuit directly connected to the bridge rectifier input .
The output of the bridge gives an average DC voltage of about 5.7V which goes
through the 560 ohm resistance then to the input of the L780CV regulator, 2
capacitors mounted one between the input and the base of the regulator and the
other between the base and the output of the regulator. The charging voltage can
be measured between the output pin of the LM7805CV and the ground which gave
5V after many tests.
42St : 37103008

43. Problem encountered
 The first difficulty encountered was time issue, to switch between work and school project . I was expected to
reach my target as usual and still had to make time for going in the laboratory for the practical project work
,and time for writing the project.
 Difficulty getting spares due finance limitations rely on scrap Pcb’s I eventually sponsored my self .
 The output voltage was low after the first trial and couldn’t charge .so I switched to a different transformer to
generate an input voltage above 9V and I got one who’s output was 17V so I used it with a trimmer to divide
de voltage.
 Even though we get the 5V output the device could not charge via the USB port .The circuit was not proper for
USB usage.so I have to redesign the circuit to have the device charging through USB.
Time spent on the project
I spent at more less 6hours every week since march which is & month makes a total of 168hours.
At least for 4 hours every week I would be in the lab, and 2 hours on my computer writing .
43St : 37103008

44. Work done
 Design conception and drawings.
 Spares purchase.
 Circuit building.
 Testing and Assessing the effectiveness of the circuit.
 Adjustment
 Photos and video shooting
 Final building
 Project closure
44St : 37103008

45. Subjects theory applied
 Industrial Electronics
 Mathematics
 Electronics 1and 2
 Electrical
 Machine 2
 English for academicals purpose
 Instrumentation and Measurement
45St : 37103008

46. 46St : 37103008
Photos and Videos

47. 47St : 37103008

48. 48St : 37103008

49. 49St : 37103008

50. 50St : 37103008

51. St : 37103008 51

52. 52St : 37103008