Download Multiple-Output, Variable-Output DC Power Supply

Multiple-Output, Variable-Output DC Power Supply
Project Plan
May03-22
Team Members:
Peter Holm
Erik Johnson
Joel Jorgensen
Philip Schulz
Clients – Dr. Patterson, Dr. Lamont
Faculty Advisor – Dr. Allan Potter
11/19/2002
i
1.2. Table of Contents
1.2.
Table of Contents .................................................................................... ii
1.4. List of Figures ................................................................................................ iv
1.5. List of Tables ................................................................................................... v
2.1. Abstract .............................................................................................................. 1
3.1. Introduction ..................................................................................................... 1
General Background ....................................................................................................... 1
Technical Problem .......................................................................................................... 2
Operating Environment ................................................................................................... 2
Intended User and Use .................................................................................................... 3
Assumptions.................................................................................................................... 3
Limitations ...................................................................................................................... 3
3.2.
Design Requirements ............................................................................ 3
Design Objectives ........................................................................................................... 3
Functional Requirements ................................................................................................ 4
Design Constraints .......................................................................................................... 5
Measurable Milestones ................................................................................................... 5
3.3.
End-Product Description ................................................................... 5
3.4. Approach and Design ................................................................................ 6
Technical Approaches ..................................................................................................... 6
Technical Design ............................................................................................................ 7
Testing Description ......................................................................................................... 8
Risks and Risk Management ........................................................................................... 8
Recommendation for Continued Work ........................................................................... 8
3.5. Financial Budget ........................................................................................... 8
3.6. Personal Effort Budget ............................................................................. 9
3.7. Project Schedule ........................................................................................... 9
4.1. Project Team Information .................................................................... 12
Clients ........................................................................................................................... 12
ii
John Lamont.............................................................................................................. 12
Ralph Patterson III .................................................................................................... 12
Faculty Advisor ............................................................................................................. 13
Al Potter .................................................................................................................... 13
Team Members ............................................................................................................. 13
Erik Johnson.............................................................................................................. 13
Joel Jorgensen ........................................................................................................... 13
Peter Holm ................................................................................................................ 13
Philip Schulz ............................................................................................................. 13
4.2.
Summary .................................................................................................... 14
4.3. References ....................................................................................................... 14
4.4. Appendices ..................................................................................................... 14
iii
1.4. List of Figures
Multiple-Output, Variable-Output DC Power Supply.......................................................12
Voltage Regulator and Surrounding Circuitry...................................................................13
Gantt Chart Part 1 …………………………………………………………………..…...16
Gantt Chart Part 2 ……………………………………………………………………….17
iv
1.5. List of Tables
Total Number of Terminals on the Power Supply……………………………………......7
Financial Budget ………………………………………………………………………...11
Personal Effort Budget ………………………………………………………………….11
v
vi
2.1. Abstract
A large number of devices require battery power of a wide variety of voltages.
These voltages include 1.5V, 3.0V, 4.5V, 5.0V, 6V, 9V, 12V, 15V, 18V, and 24V.
Although AC-to-DC converters can be found in these voltages, making use of eight or
more separate converters to cover the desired voltage range is expensive and
cumbersome. A single power supply is needed which can output a large number of
voltages simultaneously and at unique voltage potentials, at a relatively low cost.
The variable output, multiple output DC power supply described here will have
eight separate voltage terminals, each of which is capable of functioning simultaneously.
This power supply is intended to be suitable for use in design and research labs, and thus
will be small, rugged, low-cost, and simple. Efficiency and cost are two important goals
for this project.
This power supply will provide design and research oriented individuals with a
low-cost device which can be used for a variety of applications.
3.1. Introduction
General Background
A power supply will be developed with terminals for supplying the following: +1.5V,
3.0V, +3.2V, +4.5V, 5.0V, +6.0V, +7.5V, +9.0V, 12.0V, +15.0V, +18.0V, and
+24.0V. These voltages will be precise within 1% of their intended values. The goal of
this project is build the best possible power supply for as cheap as possible.
The voltages supplied will be split up into two separate groups: positive-only and plusminus voltages. There will be four rotary voltage-selector switches used to output four
separate voltages, two positive-only and two plus-minus. At any given time, all four of
the outputs can be used simultaneously.
One of the grounds for the positive-only voltages will be separated from the grounds for
the plus-minus voltages and the other positive-only voltage, allowing it to become
floating (not connected to earth ground, at a potential other than 0V DC).
For each selectable voltage output there will be two terminals capable of supplying that
specific voltage. The total number of output terminals can be found in Table X.
Switch
PositiveOnly #1
Positive-
No. of Positive
Voltage Outputs
1
No. of Negative
Voltage Outputs
0
Total No. of
Terminals
2
1
0
2
1
Only #2
PlusMinus #1
PlusMinus #2
1
1
4
1
1
4
Table 1: Total Number of Terminals on the Power Supply, Excluding Ground Terminals
Each output will be limited to 1 amp of current, or approximately 100 watts of total
power output from the supply. This should ensure that overloading of the exterior circuit
would not occur.
Included in the power supply will be a voltmeter and an ammeter that can be switched
between the four voltage outputs. A wattmeter is also being looked into in order to
monitor the power output.
Technical Problem
The power supply will be built with a circuit board and basic circuit components,
including transformers, resistors, inductors, capacitors, and diodes. Complicated
components, such as the LM317T adjustable output, positive voltage regulator, will be
purchased separately. The basic technical problem faced in this project is determining
how to implement a circuit within the design parameters that will fulfill our objectives.
Each non-structural design requirement will be realized by some combination of
electronic circuitry. This will involve extensive use of CAD software in testing several
different implementations. After a rigorous design has been decided upon and tested, the
components will be purchased and attached to the board.
In order to make the face of the power supply attractive, yet easy to navigate, a dimension
of approximately sixty square-inches will be utilized. This has been found to be more
than enough area to include all switches, displays, and terminals.
There will be basically two separate circuits included in the power supply design. One
will drive the positive-only voltages and the other will drive the plus-minus voltages.
Operating Environment
The power supply is designed for use in standard laboratory conditions: indoor at
approximately 24 C room temperature. Also, the power supply is designed for use in the
United States where the wall voltage is 120V at 60Hz.
A metal casing will surround the power supply’s inner circuitry to protect it from light
liquid us spills, short drops, and slight impact.
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Intended User and Use
The power supply is intended for use by research and design students. Its primary
function is to stably produce a small amount of current at a wide variety of voltages so
that the user can provide several electronic devices simultaneously with voltage output
from the power supply.
Assumptions
The following is a list of the known assumptions:



All four outputs can be used simultaneously via a maximum of 12 voltage
terminals.
The power supply will be used indoors at room temperature away from liquid of
any kind
The power supply will be powered by 120V at 60Hz
Limitations
The following is a list of the power supply’s limitations:



Current will be limited to one amp max from any output, with a tolerance of 1%.
Total cost of the design is to be minimal, so precision will be affected.
The power supply will be useless outside of the United States.
3.2. Design Requirements
Design Objectives
The following is a list of the design objectives for this project. These objectives
will be referenced while designing the supply and building our implementation. They
will also be used in evaluating success after the project is finished.



Power will be provided by a plug to a standard wall outlet, providing an input
voltage of 120 volts RMS at 60HZ.
The following voltages will be available: +1.5, 3.0, +3.2, +4.5, 5.0, +6.0, +7.5,
+9.0, 12.0, +15.0, +18.0, +24.0. These will be DC voltages and will operate
within 1% of their stated potential.
The power supply will provide four unique voltages and a common ground at any
given time. Two of these will be selected from 3.0, 5.0, or 12.0; these will
subsequently be referred to as plus/minus voltages. The other two voltages will
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




be selected from +1.5, +3.2, +4.5, +6.0, +7.5, +9.0, +15.0, +18.0, or +24.0; these
will subsequently be referred to as positive voltages.
The power supply will have twenty-one output terminals. Each of the plus/minus
voltages will have three pairs of terminals (positive, negative, and ground). Each
of the positive voltages will have two pairs of terminals (positive and ground).
One terminal will be provided for the common ground.
A current limiting feature will prevent the current from exceeding 1 Amp at any
voltage level. This feature will function in the background and be provided by
internal circuitry.
Will provide current, voltage, and power meters. These meters will monitor one
terminal pair at a time, as selected by the user.
Fuses will be included for the protection of the power supply. There will be one
two fuses each for the plus/minus sets of terminals (one for the positive and one
for the negative), one fuse each for the two sets of positive terminals, and one
main fuse for the entire supply.
The power supply will be small enough to be convenient in a design or research
lab. The size of this power supply is expected to be less than one cubic foot.
Standard power supplies will be examined for general size guidelines.
Functional Requirements
The following is a list of the functional requirements for this project. These
requirements will be referenced while designing and constructing the power supply.
They will also be used in evaluating success after the project is finished.



There will be a power switch with an on and off position.
There will be a rotary selector switch for each of the four main sets of terminals.
The voltage switches will allow the user to select between the available voltages
for that terminal.
There will be a rotary selector switch to allow the user to determine which of the
terminals to monitor with the current, voltage, and power meters.
4
Design Constraints
The following is a list of the design constraints for this project. These constraints
will be referenced while designing and constructing the power supply. They will also be
used in evaluating success after the project is finished.




The cost should be around $25 and should not exceed $50.
The power supply must be easy to use. Drawing power from it should be as
simple as connecting the wires to the terminals of the desired voltages.
The power supply must be reliable and rugged. It should be able to withstand
somewhat severe operating conditions (such as having the terminals accidentally
shorted or being dropped short distances) without sustaining permanent damage.
It must also be able to provide its outputs to within the specified tolerances.
The power supply will have a maximum power consumption of 100W.
Measurable Milestones
The following is a list of the measureable milestones for this project. These
milestones will be used to evalutate project success.



Percent ratio of final cost to cost of retail power supply with similar
characteristics. Final cost only includes the cost of individual components, to be
compared about what could have been purchased for that price. Success here
indicates that contracting a senior design group to design and build this supply
was more economical to Dr. Lamont and Dr. Patterson than purchasing one on the
market.
Percent ratio of final weight and size to average power supply weight and size.
One of the goals of this project is to develop a power supply which is portable in a
lab environment. Comparing the final product’s weight and size to existing
power supplies provides a moderately accurate quantitative estimate of success in
this area.
Percent ratio of actual power consumption to maximum power consumption of
100W. Power consumption over 100W would excede design constraints. Each
percent under 100W indicates a measureable degree of success.
3.3. End-Product Description
The MOVO (Multiple-Output, Variable-Output) DC Power Supply is designed
for use in research and development labs. It provides several common battery voltages
(+1.5, 3.0, +3.2, +4.5, 5.0, +6.0, +7.5, +9.0, 12.0, +15.0, +18.0, +24.0) for testing
products. The user will be able to choose the desired voltage by rotary knobs on the front
face of the power supply. It contains a current limiting feature that prevents it from
drawing more than 1 Amp for any given voltage. The user will be able to see the voltage,
current, and wattage use by a digital readout on the front of the power supply. It is low
cost, easy to use, and its rugged design enables it to endure the hazards of a development
environment. Finally, the MOVO DC Power Supply meets UL safety standards.
5
Figure 1: Multiple-Output, Variable-Output DC Power Supply
3.4. Approach and Design
Technical Approaches
The most difficult constraint to work around will be the target price of twenty-five
to fifty dollars. After some research it was found that most DC power supplies sell for
more than $100. Because of our lower cost, many of the design parameters will be
focused around cost-effectiveness.
There are four key requirements given by Dr. Lamont and Dr. Patterson: fifteen
separate voltage levels, short circuit protection, variable current (from 0A to 1A), and the
aforementioned target cost. Safety will be emphasized in the project design. Short
circuit protection will be incoporated. Following safety, the design will focus on
providing the voltages reliably. Having variable current is a very convenient option and
will also be included if time and resources allow.
There were three main approaches considered. The first was to use one main
transformer to step the voltage down, and then use voltage regulators to obtain the
desired voltages from the stepped-down voltage. After that, the outputs would be
directed through the selector switches for the output and monitoring.
The next approach was to use one main transformer with several taps to obtain the
desired voltages. The largest voltage was to be monitored, and a feedback loop set up to
ensure that this voltage was held to a very tight tolerance (within 1%). The outputs of the
taps would then be directed through the switches for the output and monitoring selection.
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The third approach was to use one main transformer and then several smaller
transformers to get the voltages down to approximately the desired levels. The outputs of
these transformers would then be sent through voltage regulators to obtain exactly the
desired voltages, which would then be connected to the switches to select the actual
output and monitoring.
Several approaches were considered for the outputs as well, such as having a pair
of terminals for each voltage or having a smaller number of terminals and then allowing
the user to switch between the voltages for each set of terminals.
Technical Design
After extensive searching, voltage regulators were found which could be used to
achieve our wide range of voltage outputs at the extremely low cost of $.30 each. This is
the LM317T voltage regulator in Figure 2. However, these voltage regulators dissipate
large amounts of power, so cooling will be an important consideration.
To help reduce the power dissipation in the voltage regulators, it was decided to
use a series of transformers to bring the input voltage down to the approximate output
levels. These stepped down voltages will then be passed into the voltage regulator and
rectification circuitry.
With this information at hand, the third approach was determined to be the most
feasible. Figure 2 below is a schematic of the circuitry surrounding the voltage regulators
for each of the voltages. Not shown is the input transformer to step down the wall
voltage, and the additional transformers to step it down further and reduce the power
dissipation in each regulator.
D5
D3
in_1
D1
LM317T
Vreg
IN
C1
C2
D6
D2
2200uF
in_2
D4
out
OUT
0.1uF
R1
240Ohm_5%
C4
1uF
C3
Key = a R2a
5K_LIN
50%
10uF
R2b
 R 2a // R 2b 
VOUT 1.25V  1 

240 

Figure 2: Voltage Regulator and Surrounding Circuitry
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Testing Description
Testing on the circuit will be conducted regularly as well as when a component is
constructed. First, the component alone will be tested. Next, the component will be
tested in the power supply circuit to eliminate wasted time spent analyzing the entire
circuit for errors.
The final testing process will ensure the converter will be rugged, as well as meet
UL (or equivalent) safety standards. Each output will be tested to make sure that its
output is within one percent of its intended value. To do this, each output will be tested
by stepping through the voltages and using a variable resistor to simulate a wide range of
possible loads from almost open (very high resistance) to completely short circuited
(almost no resistance). A pair of meters will be connected to the terminals to monitor the
output for each of these loads. The power supply meters will be tested by connecting
another set of meters at the terminals and observing whether the values agree as the
voltages are switched through. The fuses will be tested by deliberately overloading the
power supply and observing whether they break the circuit before the current gets too
high.
Risks and Risk Management
It is no longer possible to drop EE491, so the risk of losing a partner is very
minimal. However, several new risks have been identified.
This design is dependent upon acquiring and successfully installing a very
specific part, the LM317 voltage regulator. If this part is unavailable or does not work as
expected, the entire design will need to be modified. Additionally, this part will be
dissipating large amounts of heat. Adequete heat sinking will be required, and if that is
determined to be unfeasible the design will again need to be modified. The functionality
this part provides was very hard to find at a reasonable price.
It is entirely possible that keeping the design within safety and performance and
price specifications will be impossible. If this is the case, major changes will have to be
made, which will incur large penalties in cost and time.
Recommendation for Continued Work
There are many possibilities for continued work with this power supply. One
option would be to increase the power supply’s ability to handle large amounts of power.
This would enable each of the terminals to supply current independently of the terminal
that it is paired with. On a similar note, the power supply could be modified or
redesigned to handle a higher maximum current. Another feature that could be added
would be to make the voltage selectable from a continuous range of voltages instead of
from a discrete list of choices. This would greatly improve the power supply’s
versatility. Power factor correction could also be added to increase the power supply’s
efficiency.
3.5. Financial Budget
The following table summarizes the expenses which shall be incurred during the
development process.
8
Item
Poster
Case
Transformer
Resistors/capacitors/diodes
Cooling fan
Switches, dials, and terminals
Meters ($10.25 each)
Variable voltage regulator
Total
Table 2: Financial Budget
Original
Estimated Cost
$50.00
$14.99
$35.53
$26.80
$9.99
$25.00
$30.75
$4.00
$197.07
Cost to Date
$50.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$50.00
3.6. Personal Effort Budget
Person
Paper Research
work
Erik Johnson
8
21
Joel Jorgensen 5
25
Peter Holm
9
15
Philip Schulz
7
18
Total
29
79
Actual to date 27
45
Table 3: Personal Effort Budget
Design
Construction Total
32
34
25
28
119
12
12
13
14
12
51
0
73
77
63
65
278
84
Actual
to date
19
22
23
20
84
3.7. Project Schedule
The diagram below is a Gantt chart, which shows the projected schedule for this
project.
9
Figure 3: Gantt chart part 1
10
Figure 4: Gantt chart part 2
11
4.1. Project Team Information
Clients
John Lamont
Office Address:
324 Town Engr.
Ames, IA 50011
Office Phone #: (515) 294-3600
Email: jwlamont@iastate.edu
Department: Electrical and Computer Engineering
Ralph Patterson III
Office Address:
326 Town Engr.
Ames, IA 50011
Office Phone #: (515) 294-2428
Email: repiii@iastate.edu
Department: Electrical and Computer Engineering
12
Faculty Advisor
Al Potter
Address:
2019 Taylor Cir.
Ames, IA 50010
Phone #: (515) 233-4688
Email: agpotter@yahoo.com
Department: Electrical and Computer Engineering
Team Members
Erik Johnson
Address:
125 Campus Ave. #14
Ames, IA 50010
Phone #: (515) 292-8314
Email: erikj@iastate.edu
Department: Electrical Engineering
Joel Jorgensen
Address:
5132 Frederiksen Ct.
Ames, IA 50010
Phone #: (515) 572-7914
Email: jmjorgen@iatstate.edu
Department: Electrical Engineering
Peter Holm
Address:
3233 Frederiksen Ct.
Ames, IA 50010
Phone #: (515) 572-8024
Email: pholm@iastate.edu
Department: Computer Engineering
Philip Schulz
Address:
1316 S. Duff Ave.
Trailer #11
Ames, IA 50010
Phone #: (319) 850-0263
Email: pschulz@iastate.edu
Department: Electrical Engineering
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4.2. Summary
This is an ambitious project, but the research done indicates that it should be
successful. With relatively low cost voltage regulators, the rest of the components should
be cheap enough to fall within a reasonable range of the specified price.
This power supply will be an asset to the senior design lab. With a wide variety of
voltages which are unavailable through other power supplies, this project should allow
students to test other projects much more conveniently. If the project fits within the
budget, these feature will have been provided to the design lab at an excellent price.
4.3. References
4.4. Appendices
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