PHINMA-University of Pangasinan
College of Engineering and Architecture
Electrical Engineering Department
Electronic Circuits: Devices and Analysis
The Variable Dc Power Supply
Andaya, Mike Jerome S.
Alejano, Mark Oliver C.
Bonilla, Eunice Angela A.
Abrigo, Rizalyn T.
Amansec, Kyle Justin
Engr. Jayson M. Vinluan
Instructor
March 24, 2023
Laboratory Report No.01
The Variable DC Power Supply
TABLE OF CONTENTS
I.
Objectives
II. Introduction
III. Equipment and Circuit Component
IV. Set-Up/Schematic Drawings
i.
Figure 1.1
ii. Figure 1.2
iii. Figure 1.3
iv. Figure 1.4
V. Data and Results
VI. Analysis and Discussion
VII. Conclusion
VIII.
Appendix
IX. References
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The Variable DC Power Supply
I. Objectives
The purpose of this paper is to guide readers to a process of designing, structure
and testing of a DC power supply for an introductory engineering course. All the factors
of the circuit are explained along with the design approaches and computations.
II. Introduction
This document provides an overview of the introductory design and operation
behind a nearly universal in the world, a power supply. The power supply can simply
comprise four particular electronic factors the motor, the rectifier, the filter, and the
voltage regulator. While the first three factors are responsible for stepping down the
AC voltage, converting AC voltage to DC voltage, and maintaining the ripple of DC
voltage in a asked range; the voltage controller can play an important part in
furnishing a constant DC affair voltage, which isn't affected by changes in the cargo
currents, the input voltage or the temperature.
Electronic devices or circuits are highly sensitive. An excessive flow of 220
volts of electricity or alternating current (AC) could harm the circuitry, whereas a
steady direct current (DC) at a low voltage is harmless to the electronic components.
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The Variable DC Power Supply
III. Equipment and Circuit Component
A. Equipments
Breadboard
Soldering lead/iron
Cutter/ Scissor
Pliers
Driller
Enclose Box/ Case
Ferric Chloride (Pure)
Angle Grinder
B. Circuit Components
T1 - 12.6 Volt Center tapped transformer
D1-D4 - 1N4001 Rectifier Diode
C1 - 1000 microfarad 25 volt Capacitor
C2-C3 - 0.1 microfarad 200 volt Ceramic Capacitor
R1 - 510 ohm, ± 5%, 0.5 watt
R2 - 680 ohm, ± 5%, 0.5 watt
5 k ohm trimpot, 10 turn ± 5%, 0.5 watt
Red Standard Emitting Diode (LED)
U1 - LM317T Voltage Regulator
Heat Sink
Jumper Wires
C. Components of the Power Supply
Printed Circuit Board
Plug
Rocker Switch
Fasteners (bolts, screws)
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The Variable DC Power Supply
IV. Set-Up/Schematic Drawings
'
Figure 1.1 [DC Power Supply Schematic]
Figure 1.1 is the circuit diagram used for the construction of the power supply.
Analysis of the different stages that make up a power supply, makes one understand the
device. Therefore, a transformer is utilized to decrease the AC input to the required
value and provide the necessary AC voltage value. To convert an AC signal to a DC
signal, a rectifier is employed. At the load end connection, the rectifier transforms the
alternating current supply to direct current. There are several kinds of rectifiers,
including half-wave, full-wave, and bridge rectifiers. A full bridge rectifier is made up
of four diodes coupled in the shape of a bridge. At forward bias, the diode only conducts
in one direction. In the opposite direction, i.e. during reverse bias, it remains in an off
state. However, the output from the rectifier is not a pure DC output, but rather contains
numerous ripples, making it highly uneven. To smooth out the DC output and eliminate
the AC content of the rectifier, a filter circuit is implemented. This filter can be either
an inductor-capacitor filter or a resistive-capacitive filter, depending on the specified
circuit design and the type of power supply. The output now becomes a complete DC
signal with constant voltage, but it is still unregulated voltage, meaning that the design
is receiving a voltage higher than necessary. To obtain a variable or a constant output
of 5, 12, or 24V, a voltage regulator is employed. This power supply provides a variable
or constant voltage output at a constant current or an independent current output.
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The Variable DC Power Supply
Figure 1.2 [Hardwired implementation in the Breadboard of DC Power Supply]
A bread board is employed to construct provisional circuits. It proves
advantageous to developers as it facilitates the effortless removal and replacement of
components.
The prototype area is located in the center of the breadboard. This region is
made up of 5 hole rows that are joined together. Between the two sets of rows, there is
a channel for putting chips with pins on both sides, which prevents pins from being
joined together. There are also power busses (typically one or two) along the
breadboard's sides for running power and ground throughout the board.
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The Variable DC Power Supply
Figure 1.3 [ DC Power Supply PCB Artwork]
Figure 1.4 DC Power Supply PCB Artwork 3D
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The Variable DC Power Supply
The relationship may seem somewhat altered following the transfer of the
elements from the breadboard to the power circuit board (PCB), but it remains
unchanged. The PCB includes an input terminal for the transformer connection. Next,
the four diodes were linked with the capacitor in accordance with their polarity. The
positive connection of the filter capacitors is subsequently joined to the voltage
regulator's input connector. The voltage regulator's adjustable connection is connected
to the potentiometer to modify the voltage input. The voltage regulator's output is
attached to the positive side of the third ceramic capacitor. The LED is then connected
after the resistor to safeguard it from harm. To conclude, there are the output terminals
where the output voltage can be measured.
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The Variable DC Power Supply
V. Data and Results
1.
Output Voltage and LED Test: LED operational YES (As voltage increases, the
brightness also increases)
Output Voltage Range of Adjustment 2.08 V to 14.5 V
2.
Adjust output to 5 VDC with 20 ohm load resistor attached to the output
Calculated Load Current 0.25 A
Measured Load Current 0.25 A
Calculate the power being dissipated by the 20 ohm resistor? 1.25 Watts
3.
Calculate the expected turns ratio of the transformer from the transformer data
listed on the Bill of Material. Calculate and measure VsecRMS.
Calculated n = 18.33 turns
Measured Vrpp RMS = 236 V
4.
Calculate the expected DC Voltage (VDC) and Peak to Peak Ripple (Vrpp) out of
the filter circuit using the formula: Vrpp = ILoad/fc where f = frequency and C is the
value of the filter capacitor. Use a load current of 70 milliamps.
Calculated VDC = 16.82 V
5.
Calculated Vrpp = 0.583 V
Measure the DC Voltage (VDC) and Peak to Peak Ripple (Vrpp) out of the filter
circuit values with the 20 ohm resistor in place:
Measured VDC = 16.82 V
6.
Calculated Vsec RMS = 12 V
Measured Vsec RMS = 13.30 V
Measured Vrpp = 0.583 V
Measure VDC and Vrpp of the output voltage of the power supply with the 20 ohm
load resistor in place.
VDC of the Power Supply Output = 5 V
Vrpp of the Power Supply Output = 0 V
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The Variable DC Power Supply
Computations for Part V:
2. Calculated Load Current
Power dissipated
I=
P = VI
I=
P = (5)(0.25)
I = 0.25 A
P = 1.25 W
3. Calculated n
𝑁𝑝𝑟𝑖 𝑉𝑝𝑟𝑖
=
𝑁𝑠𝑒𝑐 𝑉𝑠𝑒𝑐
𝑁𝑝𝑟𝑖 220
=
1
12
N = 18.33 turns ≈ 18 turns
4. Calculated VDC
Calculated Vrpp
Vsec = 13.30 Vrms
Vrpp =
Vm = (13.30)(√2) = 18.81 V
Vrpp =
Vdc =
Vrpp = 583.33 mV
Vdc =
(
.
(
)(
)
)
Vdc = 11.97 V ≈ 𝟏𝟐 𝑽
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The Variable DC Power Supply
VI. Analysis and Discussion
VII. Conclusion
A variable direct current (DC) power supply is an electronic circuit that converts
aternating voltage (AC) to direct voltage (DC). The circuit is housed in a case or
protective enclosure. An example use of a power source is a backup power source, such
as a battery.
The group learns that the main purpose of the power supply is delivery of the
voltage required for operation. It is also useful for students if the course is designed
using DC machines and electronics for labs and experiments. The group also learned to
use a diode acting as a rectifier to convert an alternating current (AC) voltage that
fluctuates in two directions into a type of direct current (DC) voltage that pulsates in
one direction. A filter that adjusts the voltage to smooth the pulse and a voltage
regulator that adjusts the voltage to remove ripple.
While conducting the laboratory activity, the group observed that the overall
expected output was not accurate, but the output voltage was close to the target output
using simulations and real experiments. tested various output voltages, and when the
group switched to other outlets, the group concluded that the current in the various
outlets changed the resulting output voltage.
After conducting all the experiments, the team collected data and information
on the output voltage. And comparing the results obtained, the team concluded that the
output voltage of the power supply that produced the expected output voltage was
solved by applying theories and formulas.
After working in the laboratory activity, the group managed to get the right
amount of output voltage with only a slight margin of error, which is the effect of
tolerances in the resistor. Therefore, the group concluded that this power source is
reliable and can be used for other projects and lab experiments in the future.
Since this project involves a voltage regulated output power supply, many
improvements are possible. First, build the power supply to get more output voltage
than the band experience. Secondly, this type of power supply can add an extra feature
of converting 220V to 110V, which is very useful for devices requiring low
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The Variable DC Power Supply
voltage. Third, add more light-emitting diodes (LEDs) to the power supply as an
indicator of the output voltage.
For application, this type of power supply can be used in many ways as a charger,
batteries and as a reference to other research to discover new high-tech tunable power
supplies.
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The Variable DC Power Supply
VIII. Appendix
'
Figure 1.1 [DC Power Supply Schematic]
Figure 1.2 [Hardwired implementation in the Breadboard of DC Power Supply]
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Laboratory Report No.01
The Variable DC Power Supply
Figure 1.3 [ DC Power Supply PCB Artwork]
Figure 1.4 DC Power Supply PCB Artwork 3D
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Laboratory Report No.01
The Variable DC Power Supply
Initial breadboard simulation
Testing the PCB
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Laboratory Report No.01
The Variable DC Power Supply
Sketch of the PCB
Measuring the voltage output
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Laboratory Report No.01
The Variable DC Power Supply
Building the casing of the Power Supply
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Laboratory Report No.01
The Variable DC Power Supply
Testing the maximum and minimum brightness of the LED
Final PCB
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Laboratory Report No.01
The Variable DC Power Supply
IX. References
[1] Marvell-Maxim-Micrel-and-more (2011, December). Retrieved March 22,2023http://more.componentsdirect.com/blog/bid/260173/Product-EdVoltage-Regulators
[2] Adjustable Voltage Regulator Retrieved from: http://www.circuitstoday.com/25-vadjustable-regulator-using-lm117-ic
[3] Wavelength Electronics (2018). Power Supply Basics Retrieved March 22, 2023
from https://www.teamwavelength.com/power-supply-basics/
[4] M. H. Rashid, “Power Electronics”, 3rd ed, Burlington, MA: Elsevier Inc., 2007,
pp. 600-610.
[5] S. Salvivahanan, “Linear Integrated Circuits”, New Delhi: Tata
McGraw-Hill, 2008, pp. 375-385
[6] ITP Physical Computing. Understanding Power Supplies (2019). Retrieved from
https://itp.nyu.edu/physcomp/lessons/electronics/understanding-dc-power-supplies/
[7] How to Electronics. Pragya Chauhan (August 20, 2022) AC to DC Converters:
Features, Design & Applications. Retrieved March 22, 2023 from
https://how2electronics.com/ac-to-dc-converters-features-design-applications/
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