Mya Hnin Aye
1
, Ohmar Aung
2
, Mya Aye
3
, Khin Tint
4
Abstract
A Fixed Regulated Power Supply, a Variable Regulated Power Supply and a Dual
Regulated Power Supply are constructed by using transformers ( INPUT 220V AC,
OUTPUT 12V AC, OUTPUT 24V AC), 1N 4001 Diodes, Capacitors, ICs (7805 IC, LM
337 IC, LM 317 IC) and Variable resistors. The regulated power supply can be used with circuits containing linear integrated circuit elements . The DC voltage produced by a power supply is used to power all types of electronic circuits, such as television receivers, stereo systems, VCRs, CD players and laboratory equipment. A dual-polarity power supply is to be used for FM receiver. Two regulators, one positive and the other negative, provide the positive voltage required for the receiver circuits and dual-polarity voltages from the op-amp circuits .
Key words: Power Supply, Transformers, Diodes, Capacitors, Variable resistors
Introduction
Power supplies are used in all types of digital displays and cathode ray tube (CRT) colour display. Any equipment that has electronic circuits in it must have a DC supply voltage available. Since all power in the factory originates as an AC voltage, converters must be used in the power supplies to convert an AC to DC power. The regulated power supplies are typically used with circuits containing linear integrated with circuit elements.
It is necessary to supply DC at various voltages to the whole or a part of electronic equipment. The power source is usually the main electricity supply of 220V AC.
POWER-SUPPLY CIRCUITS
There are many types of power supply. Most are designed to convert high voltage
AC mains electricity to a suitable low voltage supply for electronics circuits and other devices. A power supply can be broken down into a series of blocks, and each of which performs a particular function.
The elements of a DC power supply
1.
Protection devices at the input, including fuses, transient suppressors and line filters
2.
A transformer to produce the desired voltage from the 220V supply
3.
A bridge rectifier and smoothing capacitor to produce unregulated DC with 10% ripple
4.
A voltage regulator to keep the voltage down to the specified value without ripple
1. Assistant Lecturer, Dr., Department of Geography, Yangon Institute of Education
2. Assistant Lecturer, Dr., Department of Geography, Yangon Institute of Education

Needed Apparatus
1. Transformer (INPUT 220V AC, OUTPUT 12V AC, 24V AC)
2. Rectifier, Capacitors (1000  F, 1.0
 F , 0.1
 F)
3. Filter
4. Regulator
5. Resistors
6. ICs ( 1N 4007, 7805 IC, LM 337 IC, LM 317 IC )
Design and construction of power supplies
1. Design and construction of a fixed regulated power supply
+ 6V
Input
220V
AC
+ 6V
1N 4001× 4
1000 µF
50V
+
_
1
7805
2
3 output
5V
DC
Figure1. Design and construction of a fixed regulated power supply
Result and Discussion
Minimum DC output voltage = 5V
Maximum DC output voltage = 5V
The regulated power supply can be used with circuits containing linear integrated circuit elements. It is constructed to get necessary voltage of 5V to supply DC at electronic equipment. The power source is usually the main electricity supply of 220V AC.
The photo of a Fixed Regulated Power Supply constructed in the Department of
Physics, Yangon Institute of Education is shown here.
Fixed regulated power supply

2. Design and Construction of a Variable Regulated Power Supply
+12V
1N 4001× 4
X
1
D
2
D
3
INPUT
220V
AC
D
1
D
4
IN
3
LM317
1
ADJ
OUT
2
R
1
220
+12V
C
1
1000 F
C
2
0.1 F
VR
1
5K
+24V
:
+2V
C
3
1 F
V
OUT
Figure 2. Design and Construction of a Variable Regulated Power Supply
Result and Discussion
Minimum DC output voltage = 2V
Maximum DC output voltage = 24V
The power source is usually the main electricity supply 220V AC
The photo of a Variable Regulated Power Supply constructed in the Department of Physics, Yangon Institute of Education is shown here.
Variable Regulated Power Supply

3. Design and Construction of a Dual Regulated Power Supply
INPUT
220V
AC
6V
3
317
2
1000  F
+
25V
-
+
0.1
 F
1 220 
6V
100  F
25V
+
-
0.1
 F
-
+
2
- 1
337
100 
3
5k 
+ 5V output
+
1  F
-
50V
5k 
GND
1  F
+
-
- 50V
- 5V output
Figure 3. Design and Construction of a Dual Regulated Power Supply
Result and Discussion
Maximum DC output voltage 6.8 V
Minimum DC voltage 1.2V, for FM receiver
Two regulators: one positive and the other negative, the positive voltage is required for the receiver circuits the dual-polarity voltage for the operational –amplifier.
The photo of a Dual Regulated Power Supply constructed in the Department of
Physics, Yangon Institute of Education is shown here.
Dual Regulated Power Supply

Overall Discussion
The regulated power supply can be used with circuits containing linear integrated circuit elements. It is constructed to get necessary voltage of 5V to supply DC at electronic equipment. The power source is usually the main electricity supply 220V AC. The variable regulated power supply can be easily constructed with an adjustable positive linear voltage regulator (LM 317 IC). The output voltage can be varied from 2V (DC) to
24V (DC) depending on the resistor values. This dual regulated power supply produces the maximum DC output voltage 6.8 V and the minimum DC voltage 1.2V. Modern electronic equipment needs a wide variety of DC voltage for its operation. The purpose of a power supply is to provide the primary source. The basic element of this power supply is the AC to DC converter, which consists of a transformer that converts the standard 220V,
50Hz AC. It is suitable for using in any low power electronic circuits, especially the most of the circuit using op-amp ICs. A dual polarity power supply is used for FM receiver.
Two regulators, one positive and the other negative, provide the positive voltage required for the receiver circuits and the dual-polarity voltage for the operational – amplifier
(op-amp) circuits.
Application
This paper can be applied to get basic idea of electronic circuit design and construction.
And also it is used as a teaching aid for 4 th
year B.Ed students.
Acknowledgements
We would like to express our sincere gratitude to Dr. Lwin Lwin Soe and Dr. Pye Thein (Prorectors, Yangon Institute of Education), for their kind provision of opportunity to prepare this paper. Thanks are also to Professor U Kyaw Myint (Rtd) and all the staff, Department of Physics , Yangon Institute of
Education, for their help and valuable advice for this project.
References
Duncan, T. (1992) "Adventures with Microelectronics" (London: John Murray)
Duncan, T. (1999) "Success In Electronics" (London: John Murray)
Floyd, T. L. (1997) "Digital Fundamentals"(New Jersey: Prentice – Hall)
Kamichik, S. (1998) "IC Design Projects" (Indianapolis: Howard W Sams)
Pasil, Y. (2002) "Electronics Projects 16" (New Delhi: EFY)

Page
Enhancing Students' Mathematical Problem Solving Performance by Using a Cooperative Learning Model
Nu Nu Nyunt and Aye Aye Myint
1
A Study of the Quality Characteristics of Tube-well Water from the
9
17
27
35
Environment of Yangon Institute of Education (YIOE)
Mya Thu Zar, Nu Nu Khin, May Kyi Win and Thein Thein Win
Monopolistic Competition and Effects of Advertising
Kharttar Soe
Motivating Learners of English
Nwe Nwe Hlaing and Htay Htay Win
41
47
51 Development of Pottery Industry and Solving for Woodfuel in Ywatharyar
Village, Minbu Township
Kyaw Khiang Win and Khin Khin Htay
The Conditions of Myanmar Workers during the Colonial Period, (1886-1920)
Khin Yi
Statistical Estimation of Parameters Associated with the Probability
Distribution of Random Variable X
Hla Hla Win
59
65
Design and Construction of a Fixed Regulated Power Supply, a Variable
Regulated Power Supply and a Dual Regulated Power Supply
Mya Hnin Aye, Ohmar Aung, Mya Aye and Khin Tint
71
77