University of Portland
School of Engineering
5000 N. Willamette Blvd.
Portland, OR 97203-5798
Phone 503 943 7314
Fax 503 943 7316
Final Report
Project Molalla: MicroprocessorBased Charge Controller
Contributors:
Andrew Melton
Antoinette Realica
John Turner
Approvals
Name
Dr. Lu
Date
Name
Date
Dr. Lillevik
Insert checkmark (√) next to name when approved.
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Revision History
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Rev.
Date.
0.9
04/12/2006.
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0.95
1.0
04/18/2006
04/19/2006
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Author
A. Melton
A. Melton
A. Melton
Reason for Changes
Initial draft
Suggestions from advisor
Suggestions from approval mtg
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Acknowledgements
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We would like.to express our gratitude to:
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- Dr. Lu,
. our Faculty Advisor, and Mr. Hui, our Industry Representative, for the
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guidance and support they have given us through this project.
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Ms. Sandy Ressel, our Electronics Technician, for providing us with parts and
soldering services
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Mr. Gary Carlson for helping us formulate the idea for the project
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The University of Portland Multnomah School of Engineering for funding the
project
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The Electrical Engineering faculty for lending to us their wisdom through the
advice and insight they gave us
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Family and friends for the encouragement and patience they showed us during
the Senior Design process
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Table of Contents
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Summary.......................................................................................................................
1
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Introduction ..................................................................................................................
2
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Background .................................................................................................................. 3
Methodology ................................................................................................................ 4
Results .......................................................................................................................... 5
Technical..................................................................................................................................................5
Intermediate Battery .........................................................................................................................5
Vehicle Battery Pack ........................................................................................................................5
PIC Microprocessor .........................................................................................................................6
Voltage Sensors ...............................................................................................................................6
Boost Converter ...............................................................................................................................6
Relay .................................................................................................................................................7
Process ....................................................................................................................................................8
Assumptions .....................................................................................................................................8
Milestones.........................................................................................................................................8
Risks .................................................................................................................................................8
Resources ........................................................................................................................................9
Contingencies ................................................................................................................................ 10
Change Control Board (CCB) ...................................................................................................... 11
Final Outcome ............................................................................................................................... 11
Conclusions ...............................................................................................................12
Appendices.................................................................................................................13
Appendix A .................................................................................................................14
Appendix B .................................................................................................................15
Appendix C .................................................................................................................17
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Appendix D .................................................................................................................
18
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List of Figures.
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Figure 1 Molalla Product ................................................................................................................................3
Figure 2 Molalla System Block Diagram .......................................................................................................5
Figure 3 Boost converter and LM3488..........................................................................................................7
Figure 4 Molalla Schedule .......................................................................................................................... 18
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Summary
Project Molalla is a microprocessor based charge controller that will supplement the preexisting charging power control unit of a hybrid vehicle with an additional solar charging
source. In designing our project we followed standard engineering procedures in a top
down design method with bottom up implementation. We specified major inputs and
outputs, divided one main block into several small functional units, then researched and
designed each block.
There are two key components that comprise Project Molalla: the boost converter and the
microprocessor. The boost converter steps the voltage from the intermediate battery
(24V) to the desired level (150V) to charge the vehicle battery. The microprocessor
monitors whether or not the vehicle battery needs charging and selects an available
charging source, where the pre-existing power control unit is the default source.
After assessing our resources, we went forth with the design that was the best solution
given our budget and time constraints. Other boosting methods would have required
transformers or specific inductors, the production of which would need special design and
manufacturing. This would have called for more time and money than we were available
to us.
At the time of our prototype release, we were able to demonstrate a successful product.
Our boost converter block was capable of boosting from 24V to 150V and has
successfully charged batteries with 0.5A constant current, and our microprocessor block
was able to monitor input voltages and control relays accordingly. In encasing our
product, we encountered problems that we did not predict or expect and remedied them
as best we could. Thus incorporating the product into a single case would lend itself well to
future development.
The remainder of this document will further introduce our project, give greater detail about
our design and implementation methodology, and finally explain the results of our work.
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Introduction
This document describes how product Molalla, the microprocessor-based charge
controller, was constructed and the end results of the product. The methodology section
provides a description of design and build process. The results detail the performance of
the product, and the conclusions include future developments and improvement
suggestions to the product.
The rest of the document is laid out as followed:

Methodology

Results
o
Technical
o
Process

Conclusions

Appendices
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Background
As prices for crude oil continue to rise to historic levels, it is evident that reliance on fossil
fuels will be an unaffordable peril to future generations. Scarcity and cost of these fuels
combined with their emission of greenhouse gases make a powerful case for the
development of non-fossil fuel based methods of transportation. Project Molalla seeks to
increase the technology base for alternative energy based cars by providing an
upgradeable power mediator that will increase fuel efficiency.
There exist several categories and schemes of battery chargers. In general, our scheme
falls under “opportunity charging” as it incorporates power whenever it is available. This is
an apt description for an onboard charger in a hybrid vehicle as power sources (such as
regenerative braking, alternators, and solar panels) are not constant. Project Molalla must
choose from available power sources. The first available source is the pre-existing power
control system in the hybrid that mediates charging between regenerative braking and a
gasoline powered generator. The second source will be an intermediate battery charged
by a solar panel (see Figure 1). Project Molalla will act as a smart switch between these
sources, allowing the intermediate battery to charge the vehicle batteries when the existing
power unit is not available.
Molalla Product
Figure 1 Molalla Product
It is important to note that actual sources and loads such as working car alternators,
regenerative braking systems, multiple car batteries, and solar panels are costly and
difficult to obtain. This introduces a possible limitation on the ability to test the device,
requiring accurate source and load modeling.
A final limitation on Project Molalla’s design is in its ruggedness. Adequate research and
implementation of a rugged device capable of extreme operation over hundreds of
thousands of miles and several years is a project in itself. For this reason, the product will
be theoretical rather than actually mounted inside of a vehicle.
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Methodology
In designing our overall product, we began with a hierarchical approach. Our goal was top
down design and bottom up implementation. We defined how we wanted our project to
function, and then divided it into several functional blocks. Each block was then
independently designed and finally integrated. Before doing any design however, we had
to perform significant research to resolve various problems unique to our project.
Before performing any design work, we also made assumptions, assessed various risks,
created contingency plans, and created a detailed schedule with important milestones. In
addition, we listed all resources that we would need, assigned necessary tasks to specific
group members, and created a budget that encompassed the entire project.
After design began, our work was organized as follows:
-
Drew schematics
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Selected and ordered parts
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Building
-
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o
Boost converter – first on bread board, then designed PCB
o
Programmed PIC using MPLAB ICD2
Unit testing
o
PIC monitoring – completely debugged PIC control and relay switching
separate from boost circuit
o
Operated boost converter and analyzed various waveforms. Replaced key
parts to achieve stability.
Integration
o
Made all appropriate connections to use PIC to monitor and control the boost
converter and relays.
o
Encased finished product.
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Results
Technical
As shown in Figure 2, the Molalla Product consists of a PIC microprocessor, a boost
converter, voltage sensors, and relays. The PIC microprocessor monitors the output of
the pre-existing power unit of the hybrid vehicle and the intermediate battery through the
voltage sensors. When there is no output from the pre-existing power unit, the PIC checks
if there is enough charge in the intermediate battery to charge the vehicle battery, and if
there is a sufficient amount of charge, it switches the relays so that the intermediate
battery is charging the vehicle battery. The intermediate battery is able to provide the
necessary voltage/current needed for charging through the boost converter. Whenever
output appears from the pre-existing power unit, the PIC switches the relays so that the
pre-existing power unit is charging the vehicle battery (default mode). The overall Molalla
schematic can be found in Appendix A.
Figure 2 Molalla System Block Diagram
Intermediate Battery
- Modeled as two 12V Yuasa lead acid batteries
Vehicle Battery Pack
- Modeled as eleven 12V Yuasa lead acid batteries
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PIC Microprocessor .
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- PIC18F452
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- Enables/disables boost converter based on the status of the voltage sensors.
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-
Contains an A/D Converter used to verify charge from the pre-existing power unit and
from the intermediate battery
-
Output pins send out a logic 1 (approximately 5V) or 0 (0V)
-
o
Controls relays.
o
MOSFETS for voltage sampling
PIC Program Flow Diagram – see Appendix C
Voltage Sensors
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Sense the battery voltages and provide inputs to the PIC as feedback.
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Consists of two resistors that provide a voltage divider scheme
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Chosen to output a small current (μA range) for small i2R loss
o
For intermediate battery: 43.5 kΩ and 5.1 kΩ resistor combination
o
For vehicle battery: 1.5 MΩ and 27 kΩ resistor combination
Boost Converter
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Steps the intermediate battery voltage from 24V to 150V and charges the vehicle
battery pack with a constant 0.5A of current.
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Consists of n-channel MOSFET, N-Channel IC Controller (LM3488) which maintains
constant current for battery charging, an inductor, capacitors, and a diode rectifier as
shown in Figure 3. Refer to Appendix A and Appendix B for actual part values.
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Figure 3 Boost converter and LM3488
Relay
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Acts like a DC transfer switch, switching between two power sources: the intermediate
battery and the pre-existing power unit of the hybrid vehicle
o
o
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Consists of one normally open relay connecting the intermediate battery to
the vehicle battery and one normally closed relay connecting the pre-existing
power unit of the hybrid vehicle to the vehicle battery

Magnecraft 199BX-11 Power Relay

Crydom Solid State Relay D2D07
In case the product fails, the normal operation of the hybrid vehicle is not
hindered (connection between pre-existing power unit of the hybrid vehicle
and the vehicle battery remains intact)
Controlled by the PIC.
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Process
Assumptions
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In this project we assumed that:

Batteries can provide at least 12.5 amps continuous current.

Parts needed are available and affordable.
Our assumptions were adequate. We were able to draw enough current from the batteries
and found and acquired the parts needed.
Milestones
Our milestones were:
Number
1
2
3
4
Description
Product Approval
Plan Approval
Design Release
Boost Converter Built (added
Original
Previous
Present
10/28/05
03/02/06
04/13/06
10/07/05
11/11/05
12/09/05
N/A
10/07/05
11/11/05
12/09/05
12/15/05
10/05/05
11/11/05
12/09/05
12/15/05
01/27/06
02/24/06
03/03/06
04/07/06
04/11/06
04/13/06
03/24/06
02/24/06
03/30/05
04/03/06
04/11/06
04/13/06
03/24/06
02/24/06
03/30/06
04/05/06
04/11/06
04/13/06
12/08)
5
6
7
8
9
10
Parts Received
TOP’s Approval
PIC Program 0.95
Prototype Release
Founder’s Day
Final Report
Dropped Milestones
Boost Converter Stage 1 Built
Voltage and Current Sensor
Built
Boost Converter Stage 2 Built
12/15/05
02/10/06
N/A
N/A
N/A
N/A
03/03/05
N/A
N/A
We were able to meet most of our milestones on time. Some we accomplished before the
expected deadline. A few we had to postpone, but we adjusted the schedule accordingly.
Risks
We assessed and experienced the following risks:
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Boost converter failure – high risk.
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o Since the boost converter is an important component to Project Molalla. It
. the core functionality of the product by creating the boosted voltage
provides
. used to charge the vehicle batteries. Hence its failure will affect our project
signal
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severely.
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We experienced:
o
Stability issues – bread board vs. PCB
o
Extensive debugging
o
High voltages and current resulting in high parts fatality. We had to reorder
parts and use overnight shipping on several occasions.
Part availability – medium risk.
o
Special parts required for the completion of the product may not be available to
the typical consumer. This will restrict the choices available when designing the
product.
o
We experienced:
o
Difficulty in finding DC relay to fit the task.
o
Difficulty in finding the proper gate driver to drive the MOSFET that would
provide the proper on-voltage
Late arrival of parts – medium risk.
o
Delays the progress of Project Molalla.
Resources
These resources were available to us:

Personnel
o
Andrew Melton. Team leader for Spring 2006. Design, implement, and test PIC
program.
o
Antoinette Realica. Recording Secretary. Design, implement, and test relays and
voltage sensing portion. Webmaster.
o
John Turner. Team leader for Fall 2005. Design, implement, and test boost
converter.
o
Dr. Wayne Lu: Project advisor.
o
Mr. Andrew Hui: Industry representative.
o
Sandy Ressel: Electronics technician
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o Mr. Gary Carlson. Independent contributor
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Equipment
.
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o Oscilloscope
.
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Bread board
o
DC Power Supply
o
Ammeter
o
Voltmeter
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Facilities
o
EH 2007 (Electrical Circuits Laboratory)
o
EGR 312 (Microprocessor Lab)
o
EH 2001 (Senior Design Laboratory)
Time – see Appendix D for schedule
We created a schedule, met weekly, and prepared a budget to ensure successful completion
of our project. However, we spent more time and money on the project than originally
predicted due to unexpected problems that we encountered. Debugging the boost converter
and the PIC code took more time than expected. As for our budget, while we were able to
incur free samples from companies, our high parts fatality caused us to reorder parts with
overnight shipping to keep on schedule.
Contingencies
Our contingency plans were:


Boost Converter Failure:
o
Increase intermediate battery voltage
o
Purchase off the shelf 12V DC to 220V AC inverter, then rectify and buck to 150V
o
Use PIC for PWM in a cascaded boost converter topology
Part availability
o

Find an alternate part or redesign to match parts available
Late arrival of parts
o
Be patient
o
Order from another supplier
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Our final product used our main plan, thus no contingencies were fully developed. However,
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initial testing of the IC based boost converter gave mixed results so we began developing our
.
contingency plans. We were able to successfully use the PIC to provide PWM and control in a
single stage boost. converter and built a two stage boost converter on a PCB. Unfortunately,
we were not able .to successfully debug the circuit due to time constraints. We also purchased
. DC to 220V AC inverter and other required parts for our third contingency.
an off the shelf 12V
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We did not, however, afford time to developing this contingency because we felt that our time
would be spread too thin. Fortunately, continued debugging efforts on the IC based boost
proved successful.
Change Control Board (CCB)
We performed a CCB request on December 6, 2005 to use an IC instead of the PIC to provide
PWM and control for the boost converter. We had originally planned to use the PIC for the
PWM signal in a dual stage, cascaded boost but later found an IC that simplified the converter
significantly by requiring only one stage and eliminating the need for the PIC control. In
addition, after talking to professionals in industry, we were informed that it was somewhat
unconventional to take a cascaded boost approach. The impact of this CCB was that the role
of the PIC in providing PWM and providing current sensing for stability were eliminated since
the IC would be able to provide these, but the PIC was still necessary for voltage
sensing/source selection.
Final Outcome
We succeeded in producing all of the individual functions required for a microprocessor based
charge controller. At the time of our prototype release, we had a complete, functional system.
This included a successful boost circuit and monitoring circuit that was controlled by the
microprocessor. Upon integrating the entire product into a single enclosure, we encountered
complex problems as a result of mixing high and low power systems. We narrowed them
down to ground bouncing, EMI, and a sudden voltage change on the intermediate battery due
to large current draw. These problems are worth exploring and would be great for future
development of the product.
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Conclusions
Project Molalla is a step towards enhancing the current technology for alternative energy
based cars by including solar energy to the pre-existing charging scheme. With the rising
costs of fuel, it is our hope that the implementation of harnessing solar energy to power
hybrid vehicles will increase fuel efficiency in a vehicle.
Our boost converter is functional and is based on the LM3488 controller from National
Semiconductor. It outputs a constant 0.5A of current to charge the vehicle battery pack in
a single stage boost from 24V to 150V. The microprocessor can enable and disable the
two relays based on the input and output voltages read from the voltage sensing blocks.
We were successful in implementing the individual functional blocks of our design and in
integrating them into a final product outside of an enclosure. Full integration of the product
into an enclosure was not achieved at the time of this document. Should further
development of the Molalla product be undertaken, we would like to recommend analyzing
EMI issues, observing ground bounce issues, and finally realizing full integration into an
enclosure. Should more time and money become available, we would recommend a fly
back or forward converter approach instead of using a boost converter.
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Appendices
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Appendix A
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Appendix B
Int_Batt - 2 * Yuasa 12V, 7.0Ah lead-acid batteries
Veh_Batt - 11 * Yuasa 12V, 7.0Ah lead-acid batteries
R1 - 45.3kohm, 1/2W resistor
R2 - 5.1kohm, 1/2W resistor
R3 - 1.5Mohm, 1/2W resistor
R4 - 27kohm, 1/4W resistor
R5 - 10kohm, 1/4W resistor
R6 - 220ohm, 1/4W resistor
R7 - 220ohm, 1/4W resistor
R8 - 220ohm, 1/4W resistor
Rfb1 - 180kohm, 1/4W resistor
Rfb2 - 1.5kohm, 1/4W resistor
Rc - 4.7kohm, 1/4W resistor
Rfa - 43kohm, 1/4W resistor
Rsn - 0.015ohm, 5W resistor
C2 - 0.1uF, mylar capacitor
C3 - 1uF, mylar capacitor
C4 - 0.1uF, mylar capacitor
C5 - 1uF, mylar capacitor
C6 - 0.1uF, mylar capacitor
C7 - 1uF, mylar capacitor
Cin - 200uF, 50V electrolytic capacitor
Cbyp - 0.01uF, 30V ceramic capacitor
Csn - 0.01uF, 30V ceramic capacitor
Cc - 22nF, 25V mylar capacitor
Cout - 470uF, 200V electrolytic capacitor
L1 - 470uH, torroid inductor
D1 - PDS3200, Schottky diode, 3A, 200V
D2 - NTE580, 6A, 200V rectifier
D3 - T1-3/4, LED
D4 - T1-3/4, LED
D5 - T1-3/4, LED
Q1 - NTE2382, 100V MOSFET
Q3 - NTE2382, 100V MOSFET
Q4 - IRF510, 100V MOSFET
U1 - LM3488 analog boost converter controller
U2 - PIC18F452 microprocessor
U3 - 5V LDO voltage regulator
U4 - 10V LDO voltage regulator
U5 - 6V LDO voltage regulator
U6 - TC4427a dual 1.5A gate driver
S1 - Crydom D2D07 Solid State Relay
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S2 - Magnecraft 199BX-11 Power Relay
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Appendix C
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Appendix D
Figure 4 Molalla Schedule
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