Optical Encoder for a Game Steering Wheel
Final Report: May05-26
Client:
Thomas Enterprises
David Thomas Sr., President
David Thomas Jr., Vice President
Faculty Advisors:
Dr. James Davis
Dr. Douglas Jacobson
Team Members:
Samuel Dahlke
CprE
Peter Fecteau
CprE
Daniel Pates
EE
Lorenzo Subido
EE
DISCLAIMER: This document was developed as a part of the requirements of an
electrical and computer engineering course at Iowa State University, Ames, Iowa. This
document does not constitute a professional engineering design or a professional land
surveying document. Although the information is intended to be accurate, the
associated students, faculty, and Iowa State University make no claims, promises, or
guarantees about the accuracy, completeness, quality, or adequacy of the information.
The user of this document shall ensure that any such use does not violate any laws with
regard to professional licensing and certification requirements. This use includes any
work resulting from this student-prepared document that is required to be under the
responsible charge of a licensed engineer or surveyor. This document is copyrighted by
the students who produced this document and the associated faculty advisors. No part
may be reproduced without the written permission of the senior design course
coordinator.
Monday, March 07, 2016
1 Table of Contents
1 Table of Contents
i
1.1 List of Figures
iii
1.2 List of Tables
iv
1.3 List of Definitions
v
2 Introductory Material
1
2.1 Executive Summary
1
2.2 Acknowledgement
1
2.3 Background Information
2
2.4 Problem Statement
2
2.5 Solution Approach
3
2.6 Operating Environment
3
2.7 Intended Users
3
2.8 Intended Uses
3
2.9 Assumptions
4
2.10 Limitations
4
2.11 Expected End-Product and Other Deliverables
4
3 Project Approach and Results
5
3.1 Functional Requirements
5
3.2 Resultant Design Constraints
5
3.3 Approaches Considered and One Used
3.3.1 Electrical Design Approach
5
5
3.3.1.1
3.3.1.2
Optical Encoders
Power Supply
6
6
3.3.2 Microcontroller Design Approach
3.3.2.3
3.3.2.4
Microcontroller
Microcontroller Program
6
7
3.4 Detailed Design
3.4.1 Detailed Electrical Design
3.4.1.5
3.4.1.6
3.4.1.7
3.4.1.8
8
8
Optical Encoders
Encoder Background Information
Optical Encoder Operation
Encoder Selection and Installation
3.4.2 Power Supply
3.4.3 Circuit Board Design
3.4.3.1
3.4.3.2
6
8
8
8
10
11
14
Schematic layout
Component placement
14
16
3.4.4 Microcontroller Program Design
i
16
3.5 Implementation Process Description
3.5.1 Electrical Design Implementation
3.5.1.3
3.5.1.4
3.5.1.5
Optical Encoder Implementation
Power Supply Implementation
Board fabrication
3.5.2 Microcontroller Implementation
3.5.2.6
3.5.2.7
Microcontroller
Microcontroller Program
18
18
18
18
18
19
19
19
3.6 End-Product Testing Description
19
3.7 Project End Results
20
4 Resources and Schedules
20
4.1 Resource Requirements
4.1.1 Personnel Effort Requirements
4.1.2 Other Resource Requirements
4.1.3 Financial Resource Requirements
20
20
26
30
4.2 Schedules
35
5 Closing Material
38
5.1 Project Evaluation
38
5.2 Commercialization
39
5.3 Recommendations for Additional Work
39
5.4 Lessons Learned
39
5.5 Risk and Risk Management
5.5.1 Anticipated Potential Risks and Planned Management
5.5.2 Anticipated Risks Encountered
5.5.3 Resultant Changes in Risk Management
40
40
40
41
5.6 Project Team Information
5.6.1 Client Information
5.6.2 Faculty Advisors Information
5.6.3 May05-26 Team Members Information
41
41
41
42
5.7 Summary
42
ii
1.1 List of Figures
Figure 1 - Pin diagram of the PIC18F4455
7
Figure 2 - Timing diagram of optical encoder quadrature output
9
Figure 3 – Optical encoder
10
Figure 4 - Mechanical drawing of the optical encoder
10
Figure 5 – Steering wheel components
11
Figure 6 – Mechanical drawing of the power supply
12
Figure 7 - Schematic of the power jack
13
Figure 8 - Photo of the power jack
14
Figure 9 - A view of Eagle's schematic editor
15
Figure 10 - Board layout
16
Figure 11 – Data flow for microcontroller
17
Figure 12 – Original personnel efforts requirement estimate
21
Figure 13 - Revised personnel effort requirements estimate
23
Figure 14 - Final personnel effort requirements
25
Figure 15 – Original other resource requirements estimate
26
Figure 16 - Revised other resource requirements estimate
28
Figure 17 - Final other resource requirements
30
Figure 18 – Gantt chart for project tasks
36
Figure 19 – Gantt chart for deliverables
37
iii
1.2 List of Tables
Table 1 - Transitions of the encoder output and how they are interpreted
9
Table 2 – Original personnel effort requirements estimate
20
Table 3 – Revised personnel effort requirements estimate
22
Table 4 – Final personnel effort requirements
24
Table 5 – Original other resource requirements estimate
26
Table 6 - Revised other resource requirements estimate
27
Table 7 - Final other resource requirements
29
Table 8 – Original financial requirements estimate
31
Table 9 - Revised financial requirements estimate
32
Table 10 - Revised financial requirements estimate (continued)
33
Table 11 - Final financial requirements
34
Table 12 - Final financial requirements (continued)
35
iv
1.3 List of Definitions
The following terms are used throughout this report and may not be widely known or
understood.
American wire gauge (AWG): A standard system for measuring and classifying the
thickness of wire conductors.
Analog to digital conversion (ADC): The process of converting a signal from analog
to digital form.
Assembly language: Programming language one level above binary machine code.
C: Programming language used for many hardware systems.
Cycles per revolution (CPR): The maximum rate at which voltage pulses come out of
an optical encoder.
Breadboard: Structure used for the quick assembly/destruction of small circuits for the
purpose of testing.
Hardware interface driver (HID): Software that converts hardware output into a
standard from that can be used by computers.
Integrated circuit (IC): Small electrical single-function or multi-function device that is
assembled into one convenient package.
Microcontroller: Processing device responsible for receiving and handling electrical
signals or data from the various input sources.
Optical encoder: Small device used to detect rotational movement. Its resolution is
determined by the number of ticks that it can detect through one full rotation.
Printed circuit board (PCB): Structure that holds small electrical components and their
respective connections.
Potentiometer: Variable resistor. Potentiometers are commonly used in speaker
devices to change the volume.
Special function register (SFR): Register that is designated a specific address in
memory and function by the microcontroller’s manufacturer.
SPICE: Software used primarily for circuit simulation.
Universal serial bus (USB): Standard port that allows connection to external devices
(such as digital cameras, scanners, and mice) to computers.
v
2 Introductory Material
This section will introduce the project and specifically define the problem statement.
Topics discussed are the problem statement, operating environment, intended users and
uses, assumptions and limitations, and the expected end product and deliverables.
2.1 Executive Summary
This Iowa State University computer/electrical engineering senior design team has been
invited to upgrade a video game steering wheel for Thomas Enterprises’ product line.
Specifically, they would like an updated steering wheel design with optical encoders.
Currently potentiometers are responsible for the encoding of the steering wheel and
pedal input. The optical encoder offers greater resolution and better performance from
the steering wheel.
The new solution meets the following specifications:

Optical encoder: Thomas Enterprises has provided our team with the S1-512
optical encoder from US Digital. It provides a resolution of 2048 positions, but also
draws significantly more power than the currently used potentiometers.

Compatibility: The new design uses standard HID compliant drivers that are
similar to the previous design. This provides compatibility with the connecting
computer and software.

Cost: The design solution costs less than the $150 per board for parts and
fabrication. This is within the budget set at the beginning of the project.
In order to make the steering wheel work with the optical encoders, several components
needed to be added to the current design, and several components needed to be
modified. These components include an external power supply and a new
microcontroller.

Power supply: Currently, the entire steering wheel circuitry runs on power received
from the USB port, into which the steering wheel connects. However, the optical
encoders draw significantly more power than the currently used potentiometers, so
it was necessary to add a power supply to the system in order to run the steering
wheel properly.

Microcontroller: A 16-bit microcontroller was selected to handle the resolution of
the optical encoders.
The team has designed a solution that costs approximately $14 to produce in volumes of
about 100 circuit boards (not including optical encoders). The development of the code
was independent of the circuit. All code compilation was carried out with MPLAB
software and all circuit development was carried out in Eagle software. The solution has
been implemented as of March 2005 with testing through April 2005. The project is still
on schedule to deliver a working prototype by late April 2005.
2.2 Acknowledgement
Special thanks go to Thomas Enterprises of Anamosa, Iowa. Thomas Enterprises, the
client of this project, has provided the video game controller hardware and racing
simulation software for the team to use in researching the team’s design.
1
Appreciation is also expressed to Andrew Bice of Iowa State University’s Center for
Industrial Research and Service. Mr. Bice designed the original USB interface PCB and
has provided the team with the technical documentation generated during the original
design.
Faculty advisors Dr. Doug Jacobson and Dr. Jim Davis have also provided guidance and
advice for this project. Gratitude is expressed for their efforts.
2.3 Background Information
The overall purpose of this project is to upgrade an existing video game controller that is
produced by Thomas Enterprises of Anamosa, Iowa.
The video game controller consists of a steering wheel assembly, including several
pushbuttons, and a gear shifter control. In a separate module is the foot pedal
assembly, which includes a gas, brake, and clutch pedal.
The controller is to be used on a personal computer, connected via a USB cable. The
most common application of the controller is for racing video games and driving
simulations. Many users participate in online racing tournaments, simulating an entire
NASCAR season for example. Thomas Enterprises manufactures very high end
controllers for gaming enthusiasts who demand a high level of precision and
performance from their steering wheel controller.
The previous design on the controller used potentiometers to sense the angular position
of the steering wheel and pedals. The potentiometer is part of a voltage divider circuit,
and as the wheel turns the voltage across the potentiometer changes. A microcontroller,
with integrated USB communications, converts the analog voltage of the potentiometer
into a digital value and keeps track of the position of the wheel, pedals, and the state of
the pushbuttons. The electronics are located inside the housing of the steering wheel
assembly and connect to the foot pedal assembly via a cat-5 cable. The previous design
uses an 8-bit microcontroller, which makes it only capable of tracking 256 positions.
The main goal of this project was to increase the resolution of the controller by
incorporating optical encoders and a new microcontroller capable of handling more bits
of data. The client wanted to achieve a resolution of at least 1024 positions. The client
also wished to maintain the ability to use at least 16 pushbutton inputs
2.4 Problem Statement
Thomas’ current products are capable of sensing 256 positions on the steering wheel
and pedals and they also accept 16 pushbutton inputs. The output of the PCB connects
to a personal computer through a USB cable. The desired upgrade is a direct
replacement for the current sensors and PCB. The ideal solution would be capable of
sensing at least 1024 positions and retaining all 16 pushbutton inputs. The end-product
should cost on the order of $30 - $50 but no more than $150, not including the price of
the encoders.
2
2.5 Solution Approach
The solution for this project requires using optical encoders to replace the
potentiometers that were previously being used to sense the position of the steering
wheel and pedals. The encoders have the desired resolution to provide the precision
control that is required for this application. The encoders are mounted in the same
position as the current potentiometers.
The microcontroller senses the input from the wheel, pedals, pushbuttons, and sends
output to the computer through a USB cable. The previous microcontroller has been
replaced by a newer model that is capable of tracking the higher resolution input and all
the pushbutton functions. Assembly code has been written to interpret the input from the
steering wheel and pedals.
2.6 Operating Environment
The video game controllers are used with personal computers. In most instances the
controllers will be used indoors, or in similar conditions where temperature, moisture,
and other environmental factors will be controlled.
The typical conditions for use are:

Temperature of approximately 70°F

No moisture

Mostly dust-free conditions
Thomas Enterprises operates a scaled race car simulator that is taken to local
community events. The controller must operate in an outdoor environment under this
circumstance, although the simulator would not be operated under adverse weather
conditions.
The product is relatively robust and strong mechanically, such that it will last a long time
under normal use. Even though it is durable and strong it is not intended to be dropped
or thrown, but could withstand a drop from approximately 2 - 3 feet. The steering wheel
assembly is attached to a desk or table for use by a bracket similar to a C-clamp. The
pedals sit on the floor and are heavy so that they will stay in place when the pedals are
pushed.
2.7 Intended Users
The intended users of this product are serious video gamers, race car drivers, and
others who would play racing games on a personal computer and demand a high quality
product with high sensitivity from the controller input. The typical description of a person
who fits into the category of the intended users is age 12–30 with a familiarity with
computers. Described above is the typical user, but many other people can use and
enjoy the product.
2.8 Intended Uses
It is intended that a person would use this product in their home at a table or desk on
video games that are played on a personal computer. The controller is interfaced to the
computer via the standard hardware interface drivers (HIDs) that are currently being
used. The most common games used with the controller are racing simulation games.
3
Thomas Enterprises also has customers who are interested in controllers for other
simulations, such as semi truck driving. It is assumed that this controller will not be used
on video game consoles such as Sony Playstation® or Nintendo Gamecube®. It cannot
be used to with every video game; it only controls games that accept input from the
steering wheel device.
2.9 Assumptions
The team assumes the following statements in the design of the project solution:

The team should be able to modify and use some of the existing assembly code so
that the code can be written in a much shorter amount of time.

All the original schematics, documentation, part numbers, computer code, and other
relevant data from the design of the original PCB still exist and are available for the
team’s use.

Any additional power that is needed will be supplied by a secondary power source,
instead of solely operating from the USB power.
2.10 Limitations
The project solution must operate under the following limitations:

A replacement PCB should be of the same dimensions as the original so that it can
be replaced in existing products.

Optical encoders should be able to be placed in the same location as the current
potentiometers so that existing products can be easily upgraded.

Cost should be kept within the $150 budget; further funding will have to be requested
from Thomas Enterprises

The PCB should have all the same connections, inputs, and outputs as the existing
PCB.

Optical encoders should provide a resolution of at least 1024 positions.
2.11 Expected End-Product and Other Deliverables
The end-product includes:

Optical encoders that will be used to provide much greater input sensitivity. The
optical encoders will be direct replacements for the analog potentiometers that are
currently being used.

A PCB which receives input from the encoders and pushbuttons and sends output to
the computer through a USB cable. The USB interface PCB should be able to
discern at least 1024 positions of the steering wheel and foot pedals. The PCB
should be of the same external dimensions of the original board so that it may be
directly replaced in existing products.
4
The minimum required quality of the end-product is at least of prototype quality, although
the higher quality and reliability that the team has time to design and test, the better. If a
suitable outside vendor can be found to manufacture the PCBs in high volume for
Thomas Enterprises, then it should be fairly simple to implement the circuit design in a
way that is robust enough for high volume manufacturing.
Thomas Enterprises may also wish to have technical documentation, specifications, and
instructions that will fully explain the operation of the encoders and USB interface PCB.
3 Project Approach and Results
The approach used to complete the project and the teams results are discussed in this
section.
3.1 Functional Requirements
The project solution must meet the following functional requirements.

Longevity of the product: The new steering wheel controller design with optical
encoders should last longer than the potentiometer design and require little or no
replacement.

Higher resolution: The optical encoders should recognize at least 1024 positions for
the steering wheel. This will, in turn, provide a more realistic gaming experience to
the end user.

16 function buttons: The controller should maintain the 16 button layout that the
current PCB has.
3.2 Resultant Design Constraints
The project solution must adhere to the following constraints:

Dimensions: The dimensions of the finished PCB should be no larger than the
current design of 13.5 cm x 6 cm.

Wear and tear: The product should be sturdy and be able to handle racing
simulations, which can include long usage periods for the steering wheel and pedals.
With the replacement optical encoders, it will no longer be necessary to maintain the
internal workings of the controller.

USB power requirements: The USB connection will only provide a limited amount of
power. An external power supply is needed to provide the current drive for the
optical encoders.
3.3 Approaches Considered and One Used
This section discusses the approaches considered and used for the various aspects of
the video game controller system.
3.3.1 Electrical Design Approach
This section describes the approach which was used in considering the design of the
electrical components.
5
3.3.1.1 Optical Encoders
The optical encoders were provided by the client. The resolution of the encoders is 512
cycles per revolution (CPR). The quadrature encoding scheme provided by the operation
of the encoders actually provides a resolution of 2048 positions of the wheel and pedals
(explained in design section). This is twice as much resolution compared to the client’s
specifications, thus achieves the design goal very well.
There was no need to consider another type of encoder for this project. The encoders
that were provided exceeded the client’s specifications. The provided encoders also
offered a substantial cost savings to the group.
The design that was implemented will work with any optical encoder with a two-channel
quadrature output. If the client finds a cheaper encoder in the future, it can be installed
with no modifications to the hardware or software.
3.3.1.2 Power Supply
A 5V DC source was needed to power the optical encoders and also the microcontroller.
The previous design used the voltage that came from the USB cable connected to the
computer. Due to the additional load of the encoders, the power from the USB cable is
not sufficient.
A common wall transformer was the best solution in this case because they are cheap,
readily available, and most people are familiar with using them in everyday life. A model
that can supply 300 mA, at 5% voltage regulation, was chosen because it was the
smallest one available and provided more than enough current capability for this
application.
It would be possible to power the components with battery power. But the controller is
meant to be used at a home computer, which assumes a person would have a power
outlet nearby. A user would not be capable of moving the controller around while using it
anyway, so battery power was not a practical option.
The components could also be powered by a DC power supply, but most people don’t
own a DC power supply. This was also not considered to be a practical option.
3.3.2 Microcontroller Design Approach
This section describes the approaches considered when choosing the microcontroller
and designing the program for it.
3.3.2.3 Microcontroller
A microcontroller capable of handling at least 10 bit values was needed to handle the
higher resolution of the optical encoders. The previous microcontroller was only an 8-bit
microcontroller, but was otherwise capable of all functions required.
The chip chosen was an updated version of the previous chip. It includes the on-chip
USB functionality, not requiring a separate IC for communication with the PC. It also has
on-chip flash memory, not requiring a separate IC for storing the controller code. This
chip is 16-bit, providing the needed precision for the steering wheel data. It is made by
the same company and pin-for-pin compatible with the previous chip, which allowed
much of the code to be ported instead of newly written.
Other chips provided the functionality needed in terms of precision and features.
However, the ability to reuse a large part of the code from the previous chip was a great
advantage to the IC which was used, easily being the deciding factor.
6
The previous microcontroller was Microchip’s PIC16C765. This chip is an 8-bit
microcontroller with on-chip USB functionality and flash memory for storing microcode. It
operates at 6 MHz using an external oscillator.
The microcontroller the team decided to use is Microchip’s PIC18F4455. This chip is a
16-bit microcontroller with the same USB functionality and flash memory as the previous
one. It is operated at 24 MHz using an external oscillator. This model is available in 40pin PDIP or 44-pin TQFP form factors. The plastic dual-inline-package (PDIP) was
chosen because it is pin-for-pin compatible with the previous chip, requiring fewer
changes to the board layout.
The pin layout of this chip is shown in Figure 1, below. This diagram was taken from the
manufacturer's data sheet.
Figure 1 - Pin diagram of the PIC18F4455
3.3.2.4 Microcontroller Program
The team addressed two major design concerns for the microcontroller program: how to
handle the optical encoder input and what language to write the program in.
The decoding of the optical encoders and counting could be done using an extra IC or
by implementing the functionality into the microcontroller program. Potentially, the
decoder/counter IC would make for an easier design and a faster way of decoding and
counting. Implementing such functionality in the microcontroller program would require
more processing by the microcontroller and extra design time to write the code required.
The software approach was used because the PCB would need to be expanded to fit the
required ICs. Also, the team felt that the extra processing required by the processor to
run the software implementation was small enough that it would not affect the
functionality of the design.
The program could be written using C or assembly. Normally, the amount of time spent
designing, implementing, and testing a program written in C would be significantly less
than the time spent doing the same for a program written in assembly. However,
7
assembly was chosen for the team’s design because the microcontroller chosen was so
similar to the microcontroller used in the previous design. Only minor adjustments would
need to be made to the code used in the previous design.
3.4 Detailed Design
This section will detail the design of the electrical components of the video game
controller. The necessary components and their interconnection will be explained.
3.4.1 Detailed Electrical Design
This section details the design of the electrical components of the video game controller.
The necessary components and their interconnection will be explained.
3.4.1.5 Optical Encoders
This section explains how the encoders are used to sense the position of the steering
wheel and pedals and how the encoders interface with the rest of the components.
3.4.1 Encoder Background Information
The purpose of this project is to increase the resolution and sensitivity of the video game
steering wheel controller. To achieve this goal the potentiometers that were being used
were replaced with optical encoders.
The previous design used potentiometers connected to the steering wheel and foot
pedals. The potentiometer was used in a voltage divider circuit. The analog voltage
across the potentiometer is sampled by the microcontroller. The microcontroller used in
the original design has 8 channels of 8-bit analog-to-digital conversion (ADC). The
analog voltage is converted to an 8-bit binary word. The microcontroller uses the digital
word to keep track of where the steering wheel and foot pedals are, and which way they
are moving. The output is eventually sent to the computer through a USB connection
that is built into the microcontroller.
The previous system was limited by the 8-bit wide channels on the ADC. This only
provides, at most, 256 possible positions of the wheel and pedals. The sensitivity was
also limited by the analog potentiometers. The output voltage across the potentiometer
was not sensitive enough to changes in the angular position of the input shaft.
Optical encoders can be purchased in many different levels of resolution. Generally the
higher the resolution, the more expensive they are. The type of output generated by the
encoder also determines the level of resolution. The client requested that the team
implement a resolution of at least 1024 positions per revolution of the steering wheel.
3.4.2 Optical Encoder Operation
The most popular type of encoder for applications is an encoder with quadrature output.
Quadrature refers to the fact that the signals produced by the encoder are 90° out of
phase with each other. The encoder has two channels, A and B, and some models also
have an index output. As the input shaft of the rotary encoder is rotated square waves
are produced on channels A and B. The rate at which the square waves are produced by
the encoder depends on how fast the input shaft is rotated. The direction the input shaft
of the encoder is being rotated can be determined by looking at which voltage waveform
is leading, channel A or channel B. The index output goes high when both channels A
and B are low. The index output will not be used in the design.
8
The most attractive feature of the encoder with quadrature output is that the two square
waves give four transitions per cycle, high-to-low and low-to-high on each channel. This
effectively increases the resolution by four times the maximum CPR. For the design, an
encoder with a maximum cycles per revolution (CPR) of 512 was be used, so that the
overall resolution will be 4 x 512 = 2048. The encoder with a CPR rating of 512 was
used because it was provided by the client, which provided a significant cost savings to
the group.
The diagram shown below in Figure 2 illustrates the timing of the output waveforms of
the optical encoder. As can be seen, channels A and B are 90° out of phase and the
index goes high when both inputs are low. The timing diagram is from US Digital’s data
sheet.
Figure 2 - Timing diagram of optical encoder quadrature output
As mentioned above, monitoring the output channels of the encoder provides
information about how fast the input shaft is being rotated and which direction it is being
rotated. The most recent state of the encoder’s output channels can be stored in
memory and when the channels are sampled the next time, the current state is
compared to the previous state. It is necessary that the microcontroller is able to sample
the encoders faster than they are capable of changing, or else some transitions will be
lost. In general, the clock speed of the microcontroller will be much faster than the speed
at which a human would be capable of turning the wheel or moving the pedals.
Forward Travel
From
To
0,1
1,1
1,1
1,0
1,0
0,0
0,0
0,1
Reverse Travel
From
To
0,1
0,0
1,1
0,1
1,0
1,1
0,0
1,0
Table 1 - Transitions of the encoder output and how they are interpreted
9
The transitions of the encoder output shown above in Table 1 are the desired transitions.
There are also unwanted transitions that may occur. The unwanted transitions are: 0,0 to
1,1; 1,1 to 0,0; 0,1 to 1,0; and 1,0 to 0,1. When these transitions occur, it means that at
least one state was lost. The microcontroller code must contain instructions to handle
these situations.
3.4.2.6 Encoder Selection and Installation
This section explains the encoder that was chosen for this project and the issues related
to installing it in the video game controller.
The optical encoders for this project were provided by the client. The encoder provided
is manufactured by US Digital and is the manufacturer’s part number S1-512. The S1 is
an incremental rotary shaft encoder with a sleeve bushing and ball bearing. The price for
one encoder is $49 and the price for 100 encoders is $39 each. The S1-512 optical
encoder is shown below in Figure 3. A mechanical drawing of the encoder is shown in
Figure 4, and the dimensions are shown in inches. The following drawings are from the
US Digital data sheet.
Figure 3 – Optical encoder
Figure 4 - Mechanical drawing of the optical encoder
10
The encoders require a 5 V DC supply voltage. The typical supply current for this model
and CPR specification is 27 mA, and the maximum input supply current is 30 mA. The
encoders require an external DC power supply which will be discussed in Section 3.4.3.
Two of the most important characteristics of the optical encoders are the diameter of the
input shaft and the CPR of the output. The diameter of the input shaft must be correct so
that it can be properly coupled to the steering wheel and foot pedals. Figure 5 shows
how the encoder and the steering wheel connect using a rubber sleeve. The output
waveforms from the encoder must have a CPR of 256 so that a total resolution of 1024
can be achieved. The encoders that were provided for this design have a CPR of 512,
which is more than enough resolution.
One encoder will be installed onto the output shaft of the steering wheel. Three encoders
will be installed in the foot pedal housing, one for the gas, brake, and clutch. The
encoders are installed at the same location of the potentiometers that are currently being
used. In Figure 5, the potentiometer can be seen at the top, connected to the steering
wheel.
Potentiometer
Microcontroller
USB
PCB
Figure 5 – Steering wheel components
3.4.3 Power Supply
This section discusses the power supply that is needed for the operation of the optical
encoders.
The previous design did not use an external power supply to the video game controller.
The voltage supplied to the circuit came from the USB cable. The encoders require a
power input for the LED and circuitry that generates the output signals. The required
input is 5 V DC and a maximum current of 30 mA. With a total of four encoders a total
maximum of 120 mA needs to be supplied. The USB cable is not be capable of
supplying this load, so an external power supply is necessary.
11
The power supply chosen for this design converts 120 V AC, 60 Hz, from the wall outlet
into 5 V DC. It has a maximum output current of 300 mA and the output voltage is
regulated to within 5%. The manufacturer is CUI Inc. and it can be ordered from DigiKey. The price is $8.10 for one or $5.38 each for one hundred. The manufacturer’s part
number is DPR050030-P6P and the Digi-Key part number is T309-P6P-ND.
The dimensions of the wall transformer and the plug are shown below in Figure 6. The
drawing of the transformer is from the manufacturer’s data sheet and the dimensions are
given in millimeters. The drawing of the plug is from Digi-Key and the dimensions are
given in inches and millimeters are in parentheses.
Figure 6 – Mechanical drawing of the power supply
A power jack was installed on the case of the video game controller to accept power
from the output plug of the wall transformer. The jack could be installed on the steering
wheel assembly or the pedal assembly because both require power. It is more
convenient to install the jack on the steering wheel assembly because it is easier to
access for the user. A technical drawing and a photo of the jack are shown below in
Figure 7 and Figure 8. The drawing and photo are from Digi-Key.
12
Figure 7 - Schematic of the power jack
13
Figure 8 - Photo of the power jack
The power jack can also be ordered from Digi-Key. The price is $0.38 for one or $0.26
each for one hundred. The manufacturer is CUI Inc. The manufacturer’s part number is
PJ-002B and the Digi-Key part number is CP-002B-ND.
Once the power is connected to the video game controller, it must be routed to the
encoders. The power from the jack was wired to the encoder connected to the steering
wheel. Power also needs to be routed to the pedal assembly and distributed to each of
the three encoders for the pedals. The previous design uses a cat 5 cable with RJ-45
connections to connect the steering wheel and pedal assemblies. A standard cat 5 cable
consists of 8, 24 American wire gauge (AWG) wires. Of the 8 total wires, 6 carry the
output of the encoders to the microcontroller. The remaining two wires can be used to
carry power and ground for the power supply to the encoders. According to the
Handbook of Electronic Tables and Formulas, the current carrying capacity of 24 AWG
wire is 577 mA. Only 90 mA is supplied through these wires, so the cat 5 cable works
fine for connecting power between the steering wheel assembly and the pedal assembly.
3.4.4 Circuit Board Design
The circuit design was implemented in the Eagle software package. The circuit layout
includes three phases: schematic layout, component placement, and board fabrication.
3.4.4.1 Schematic layout
All required circuit libraries were included in the software. Andrew Bice has provided
CIRAS libraries for some of the specific headers used in the original design, which were
adapted to the new circuit layout. The Eagle software uses a graphical interface to place
circuit elements, such as resistors, capacitors, and wires. For the schematic portion of
the circuit, the layout was not the primary; it only exists to generate a board for the
component placement. The schematic was used to check the fabricated PCBs and for
reference when testing electrical connectivity.
14
In the Eagle convention, “nets” are used to connect the circuit elements, not to be
confused with “wires.” Components were added by clicking on the circuit symbol within
Eagle. The team’s hand-drawn circuit was transplanted into Eagle by adding all the
circuit elements, reasonably spacing each component, and connecting the appropriate
elements to a ground connection. The resistors and capacitors were labeled with
incrementing values. Eagle also includes the dimensions of each element for use in the
board layout.
The new model of Microchip microcontroller was not available in the standard Eagle
libraries, so the older model microcontroller was used in the schematic. The previous
version is pin for pin compatible with the model in the current design. Since the circuit is
not being simulated in Eagle, it was only necessary to model the physical dimensions of
a 40 pin DIP socket with the pins labeled accordingly.
Lastly, an electrical design rule check was performed within the software. This option
checks for any faults and inconsistencies within the schematic. To accommodate for
more functionality and for the optical encoders, the resistor count was nearly doubled in
the new design. Once the design was verified, the schematic was exported to the board
layout component of Eagle. The Eagle schematic editor is shown below in figure 9.
Figure 9 - A view of Eagle's schematic editor
15
3.4.4.2 Component placement
With a valid schematic, Eagle is able to generate a board design. The schematic was
imported into the board function of Eagle. The design constraints were applied to the
board area; the original specifications called for a similar sized PCB with the same
mounting holes.
The component placement is similar to the schematic placement, but with careful
attention to the distance between elements and wire dimensions. The ultimate goal of
the component placement was to have as little wire between elements as possible, for a
cleaner design. This meant putting the appropriate resistors in close proximity to the
connections on the microcontroller or headers.
Once the components were in place, the wires were routed by the auto routing function;
this generates the routing data used for the board fabrication. The mounting holes were
placed and the Gerber data was generated, using the CAM processor function. The
Gerber data contains the information of board dimensions and component placement.
The CAM processor also generates drill-hole locations, routed wires, and any labels on
the board.
Figure 10 - Board layout
3.4.5 Microcontroller Program Design
As is shown in Figure 11, the microcontroller receives input from the four optical
encoders and the 16 buttons. Two pins are required for each optical encoder to monitor
the A and B channels on the encoders. One pin is required for each of the sixteen
buttons. The main program for the microcontroller runs a loop that checks the input,
does some computing, and sends data to the USB encoder.
The I/O pins used for the encoders and buttons are memory mapped, so reading input
only requires reading a predefined memory location. During each iteration of the
program’s loop, the I/O pins are read and stored into temporary memory locations.
The state of the sixteen push buttons requires no processing, so the data is sent directly
to the USB encoder. The processing of the optical encoder input requires just a few
steps during each iteration. The current state that was read in the previous step is
16
compared with the previous state to determine if the direction is positive or negative. In
this design every change in direction is only one step, so there is no need to calculate
the magnitude of change. The stored position is then updated and sent to the USB
encoder along with the data from the sixteen push buttons.
The USB encoder packages the necessary information and handles the communication
between the microcontroller and the driver software on the host that it is connected to.
Optical
Encoder
1
Optical
Encoder
2
Current
State
Optical
Encoder
3
Optical
Encoder
4
Buttons
1-16
Previous
State
Determine
Direction
Update
Position
Update
State
USB Encoder
Microcontroller
Driver Software
Figure 11 – Data flow for microcontroller
17
3.5 Implementation Process Description
The implementation process for the various aspects of the system is discussed in this
section.
3.5.1 Electrical Design Implementation
This section describes the implementation procedure used for the electrical components
when assembling the prototype model.
3.5.1.3 Optical Encoder Implementation
The encoders were connected with Molex wiring harnesses and wire. An ohm meter was
used to verify connectivity between the buttons, wires, and pins and traces on the circuit
board. Once connectivity was verified, the wires were soldered into place.
The encoder for the steering wheel was connected directly to the circuit board through a
Molex connector that connects to the header pins on the periphery of the circuit board.
The encoders for the foot pedals connect through a cat-5 cable between the pedal and
wheel assemblies. Again, an ohm meter was used to verify connectivity between the cat5 cable and the jumper pins on the circuit board and the socket for the microcontroller
pins.
For the initial prototype, the encoders were not installed into the brackets that the
previous potentiometers were installed into. The encoders were connected electrically,
but not to the assemblies mechanically. This allows it to be easier to make changes to
the components as prototyping and testing progress. The encoders can be rotated by
hand, rather than by the steering wheel or foot pedals.
3.5.1.4 Power Supply Implementation
External electrical power coming from the wall transformer plugs into a power plug
socket that will be installed on the case of the steering wheel assembly. From the power
socket, power is wired to a Molex connector which plugs onto header pins on the
periphery of the circuit board. Power is also connected via wire and a Molex connector to
the steering wheel encoder. Traces on the circuit board carry power to the RJ-45 socket.
The cat-5 cable plugs into the RJ-45 socket, which then carries power to the encoders
on the foot pedal assembly. The traces of the circuit board also connect power to the
microcontroller.
3.5.1.5 Board fabrication
Using the contained files generated from Eagle, the board was fabricated by Advanced
Circuits (http://www.4pcb.com). This was a suggested board house from Andrew Bice,
as they do not require a minimum order for student projects. The Gerber data was
submitted electronically and run through another design check for compatibility with their
systems and if the data is consistent. The total cost per board was $33 plus shipping
and handling fees.
18
3.5.2 Microcontroller Implementation
This section describes how the microcontroller and its program is implemented in the
prototype.
3.5.2.6 Microcontroller
The board uses a 40-pin DIP socket soldered to the board. This allows the
microcontroller to be programmed and inserted after board fabrication. The chip may be
removed and reprogrammed easily if future firmware updates are required.
3.5.2.7 Microcontroller Program
The microcontroller program was written using Microchip’s PIC18 assembly instruction
set. Tasks included converting the program used in the previous design to work on the
new processor and implementing the optical encoder decoding and counting.
Converting the code was only a matter of updating the names of a few of the SFRs and
updating the USB buffers. Also, the new microcontroller has a slightly different method
for bank switching and the program was updated to reflect that difference. Implementing
the decoding and counting code required the insertion of a small block of assembly code
into the programs main function.
The completed program was compiled and linked using Microchip’s MPLAB program to
create the necessary files required by the boot loader to install the program onto the
microcontroller.
3.6 End-Product Testing Description
After the circuit board, encoders and all wiring were installed, connectivity was verified
with an ohm meter. Connectivity was verified at each connection point, including the
header pins on the periphery of the circuit board, and the pin sockets for the
microcontroller. After proper connectivity was verified, the various components could be
tested.
In initial testing, each optical encoder was turned through its full range of motion and
tested for proper response across this range. Each of the push-buttons was tested to
respond with its appropriate input, when pressed. Success in this test was each
component responding with correct values across its operating range for the optical
encoders and its activation when pressed for the buttons.
In the second phase of testing, the optical encoders were connected to the wheel and
pedals. The assembled prototype was tested for integration with the physical devices
and continued correct functioning while being used as a game controller, by each of the
team members. Success in this test was the prototype effectively serving as the game
input device in normal use.
In the third and final phase of testing, the prototype was used by non-team members for
game input under normal and stressful usage. The testers of this phase attempted to
cause the device to malfunction during use through physical strain and unusual input.
Damage or errant functioning of the physical components of the prototype outside the
scope of the project were not attempted nor tested here. Success in this test was the
prototype functioning correctly despite abnormal use.
19
3.7 Project End Results
The group has implemented an initial prototype and verified functionality of the software
and circuitry. Testing has been performed on common computing platforms, to ensure
compatibility. Within the parameters of the provided racing simulation, the steering
wheel controller appears to work as expected.
4 Resources and Schedules
The resource requirements and schedules are discussed in this section. This section
compares the original estimates for financial forecasting and total number of hours for
the project.
4.1 Resource Requirements
The following sub-section covers the time and money required for the project to be
completed successfully.
4.1.1 Personnel Effort Requirements
Problem Definition
Technology Consideration
and Selection
End-Product Design
End-Product Prototype
Implementation
End-Product Testing
End-Product
Documentation
End-Product
Demonstration
Project Reporting
Totals
The team members have estimated the required effort needed to complete the project
tasks successfully.
8
15
60
50
25
15
20
20
213
Fecteau, Peter
10
20
40
40
20
30
20
20
200
Pates, Daniel
8
20
60
40
30
50
10
20
238
Subido, Lorenzo
10
15
50
40
15
40
10
20
200
Combined Effort
36
70
210
170
90
135
60
80
851
Team Member
Dahlke, Samuel
Table 2 displays the original estimates that were made at the start of the project in terms
of the number of hours of work expected to complete each project task successfully in
addition to the total time expected to complete the entire project successfully. Figure 12
displays the information graphically.
20
Problem Definition
Technology Consideration
and Selection
End-Product Design
End-Product Prototype
Implementation
End-Product Testing
End-Product Documentation
End-Product Demonstration
Project Reporting
Totals
Team Member
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Combined Effort
8
10
8
10
36
15
20
20
15
70
60
40
60
50
210
50
40
40
40
170
25
20
30
20
95
15
30
50
40
135
20
20
10
10
60
30
20
40
20
110
223
200
258
205
886
Technology Consideration
and Selection
End-Product Design
End-Product Prototype
Implementation
End-Product Testing
End-Product
Documentation
End-Product
Demonstration
Project Reporting
Totals
Team Member
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Combined Effort
Problem Definition
Table 3 and Figure 13 show the revised estimates and Figure and
8
5
8
10
31
15
10
15
10
50
12
5
8
20
45
15
16
11
15
57
0
35
25
25
85
2
2
2
2
8
1
1
1
1
4
30
30
26
12
98
83
104
96
95
378
Problem Definition
Technology Consideration
and Selection
End-Product Design
End-Product Prototype
Implementation
End-Product Testing
End-Product
Documentation
End-Product
Demonstration
Project Reporting
Totals
Table 4 show the final requirements.
8
15
60
50
25
15
20
20
213
Fecteau, Peter
10
20
40
40
20
30
20
20
200
Pates, Daniel
8
20
60
40
30
50
10
20
238
Subido, Lorenzo
10
15
50
40
15
40
10
20
200
80
851
Team Member
Dahlke, Samuel
Combined Effort
36
70
210
170
90
135
60
Table 2 – Original personnel effort requirements estimate
21
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Project Reporting
End-Product Demonstration
End-Product Documentation
End-Product Testing
End-Product Prototype
Implementation
End-Product Design
Technology Consideration
and Selection
Problem Definition
0
50
100
150
Figure 12 – Original personnel efforts requirement estimate
22
200
250
23
Project Reporting
Totals
End-Product Demonstration
End-Product Documentation
End-Product Testing
End-Product Prototype
Implementation
End-Product Design
Technology Consideration
and Selection
Problem Definition
Team Member
Dahlke, Samuel
8
15
60
50
25
15
20
Fecteau, Peter
10
20
40
40
20
30
20
Pates, Daniel
8
20
60
40
30
50
10
Subido, Lorenzo
10
15
50
40
20
40
10
Combined Effort
36
70
210
170
95
135
60
Table 3 – Revised personnel effort requirements estimate
30
20
40
20
110
223
200
258
205
886
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Project Reporting
End-Product Demonstration
End-Product Documentation
End-Product Testing
End-Product Prototype
Implementation
End-Product Design
Technology Consideration
and Selection
Problem Definition
0
50
100
150
Figure 13 - Revised personnel effort requirements estimate
24
200
250
Problem Definition
Technology Consideration
and Selection
End-Product Design
End-Product Prototype
Implementation
End-Product Testing
End-Product Documentation
End-Product Demonstration
Project Reporting
Totals
Team Member
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Combined Effort
8
5
8
10
31
15
10
15
10
50
12
5
8
20
45
15
16
11
15
57
0
35
25
25
85
2
2
2
2
8
1
1
1
1
4
30
30
26
12
98
83
104
96
95
378
Table 4 – Final personnel effort requirements
25
Project Reporting
End-Product Demonstration
End-Product Documentation
End-Product Testing
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
End-Product Prototype
Implementation
End-Product Design
Technology Consideration and
Selection
Problem Definition
0
20
40
60
80
Figure 14 - Final personnel effort requirements
26
100
120
4.1.2 Other Resource Requirements
The team has estimated the cost of the required resources needed in order to complete the
Materials:
Cost
Microprocessor
$10.00
Optical Encoder
$50.00
Miscellaneous Parts
$10.00
(Donated)
Miscellaneous Resources:
Poster
$50.00
Total
project successfully.
$120.00
Table 5 displays the original estimated required resources required and their respective costs.
Figure 15 displays the information as percentages of the total projected cost. Table 6 and Figure
27
16
show
the
Item
Catalog
16-bit Microcontroller
Microchip
40-Pin DIP PIC Socket
Digi-Key
revised
Manuf.
Manuf. Part #
estimates
and
Required
Quantities
Offered
PIC18F4455
1
2
$13.00
ED3740-ND
1
100
$0.91
Catalog Part #
Price/Unit To
Wires and Connectors
$
$
24MHz Crystal Oscillator
Digi-Key
CTX026-ND
1
100
$0.57
20pF 500V Capacitor
Digi-Key
338-1051-ND
2
100
$0.65
0.1uF 50V Capacitor
Digi-Key
399-2054-ND
3
100
$0.11
0.22uF 50V Capacitor
Digi-Key
399-2056-ND
1
100
$0.28
1k Resistor
Mouser
Xicon
291-1k
16
1000
$0.01
1.5k Resistor
Mouser
Xicon
291-1.5k
1
200
$0.01
100 resistor
Mouser
Xicon
291-100
20
200
$0.01
RJ-12 Connector
Mouser
154-7623PCB
1
100
$0.55
RJ-45 Connector
Mouser
154-7641PCB
1
100
$0.65
USB Connector
Digi-Key
787780-1-ND
1
100
$0.72
3 Position Header
Digi-Key
22-23-2031
WM4201-ND
2
100
$0.23
9 Position Header
Digi-Key
22-23-2091
WM4207-ND
2
100
$0.51
6 Position Header
Digi-Key
22-23-2061
WM4204-ND
1
100
$0.35
Optical Encoder
US Digital S1-512
4
100
$39.00
Power Supply
Digi-Key
CUI Inc.
DPR050030-P6P T309-P6P-ND
1
100
$5.38
Power Jack
Digi-Key
CUI Inc.
PJ-002B
1
100
$0.26
CP-002B-ND
Circuit Board Fabrication
$
$
Subtotal
$
Miscellaneous Resources
Poster
$
Project Plan Binding
$
Design Document Binding
$
Final Report Binding
$
Subtotal
Total
Table 7 and Figure 17
28
$
$
Materials:
Cost
Microprocessor
$10.00
Optical Encoder
$50.00
Miscellaneous Parts
$10.00
(Donated)
Miscellaneous Resources:
Poster
Total
$50.00
$120.00
Table 5 – Original other resource requirements estimate
5%
Microprocessor
Optical Encoder
Miscellaneous Parts
Poster
26%
64%
5%
Figure 15 – Original other resource requirements estimate
29
Required
Quantities
Offered
PIC18F4455
1
100
$1.20
$1.20
Digi-Key
ED3740-ND
1
100
$0.91
$0.91
Digi-Key
CTX026-ND
1
100
$0.57
$0.57
20pF 500V Capacitor
Digi-Key
338-1051-ND
2
100
$0.65
$1.29
0.1uF 50V Capacitor
Digi-Key
399-2054-ND
3
100
$0.11
$0.34
0.22uF 50V Capacitor
Digi-Key
399-2056-ND
1
100
$0.28
$0.28
1k Resistor
Mouser
Xicon
291-1k
16
1000
$0.01
$0.10
1.5k Resistor
Mouser
Xicon
291-1.5k
1
200
$0.01
$0.01
100 resistor
Mouser
Xicon
291-100
20
200
$0.01
$0.18
RJ-12 Connector
Mouser
154-7623PCB
1
100
$0.55
$0.55
RJ-45 Connector
Mouser
154-7641PCB
1
100
$0.65
$0.65
USB Connector
Digi-Key
787780-1-ND
1
100
$0.72
$0.72
3 Position Header
Digi-Key
22-23-2031
WM4201-ND
2
100
$0.23
$0.46
9 Position Header
Digi-Key
22-23-2091
WM4207-ND
2
100
$0.51
$1.02
6 Position Header
Digi-Key
22-23-2061
WM4204-ND
1
100
$0.35
$0.35
4
100
$39.00
$156.00
Item
Catalog
11-bit Microcontroller
Microchip
40-Pin DIP PIC Socket
6MHz Crystal Oscillator
Optical Encoder
Manuf.
Manuf. Part #
Catalog Part #
US Digital S1-512
Price/Unit Total Price
Power Supply
Digi-Key
CUI Inc.
DPR050030-P6P T309-P6P-ND
1
100
$5.38
$5.38
Power Jack
Digi-Key
CUI Inc.
PJ-002B
1
100
$0.26
$0.26
Subtotal
$170.27
CP-002B-ND
Miscellaneous Resources
Poster
$60.00
Project Plan Binding
$10.00
Design Document Binding
$10.00
Final Report Binding
$10.00
Subtotal
Total
Table 6 - Revised other resource requirements estimate
30
$90.00
$260.27
3.8%
Optical Enco der
3.8%
11-bit M icro co ntro ller
P o wer Supply
3.8%
M iscellaneo us P arts
P o ster
P ro ject P lan B inding
Design Do cument B inding
Final Repo rt B inding
23.1%
59.9%
3.0%
2.1%
0.5%
Figure 16 - Revised other resource requirements estimate
31
Item
Catalog
16-bit Microcontroller
Microchip
40-Pin DIP PIC Socket
Digi-Key
Manuf.
Manuf. Part #
Required
Quantities
Offered
PIC18F4455
1
2
$13.00
$13.00
ED3740-ND
1
100
$0.91
$0.91
Catalog Part #
Price/Unit Total Price
Wires and Connectors
$12.00
24MHz Crystal Oscillator
Digi-Key
CTX026-ND
1
100
$0.57
$0.57
20pF 500V Capacitor
Digi-Key
338-1051-ND
2
100
$0.65
$1.29
0.1uF 50V Capacitor
Digi-Key
399-2054-ND
3
100
$0.11
$0.34
0.22uF 50V Capacitor
Digi-Key
399-2056-ND
1
100
$0.28
$0.28
1k Resistor
Mouser
Xicon
291-1k
16
1000
$0.01
$0.10
1.5k Resistor
Mouser
Xicon
291-1.5k
1
200
$0.01
$0.01
100 resistor
Mouser
Xicon
291-100
20
200
$0.01
$0.18
RJ-12 Connector
Mouser
154-7623PCB
1
100
$0.55
$0.55
RJ-45 Connector
Mouser
154-7641PCB
1
100
$0.65
$0.65
USB Connector
Digi-Key
787780-1-ND
1
100
$0.72
$0.72
3 Position Header
Digi-Key
22-23-2031
WM4201-ND
2
100
$0.23
$0.46
9 Position Header
Digi-Key
22-23-2091
WM4207-ND
2
100
$0.51
$1.02
6 Position Header
Digi-Key
22-23-2061
WM4204-ND
Optical Encoder
1
100
$0.35
$0.35
US Digital S1-512
4
100
$39.00
$156.00
Power Supply
Digi-Key
CUI Inc.
DPR050030-P6P T309-P6P-ND
1
100
$5.38
$5.38
Power Jack
Digi-Key
CUI Inc.
PJ-002B
1
100
$0.26
$0.26
Subtotal
$294.07
CP-002B-ND
Circuit Board Fabrication
$100.00
Miscellaneous Resources
Poster
$60.00
Project Plan Binding
$12.00
Design Document Binding
$12.00
Final Report Binding
$12.00
Subtotal
Total
Table 7 - Final other resource requirements
32
$96.00
$390.07
16-bit Microcontroller
Optical Encoder
3%
3%
3%
Power Supply
3%
Circuit Board Fabrication
Miscellaneous Parts
Poster
Project Plan Binding
15%
Design Document Binding
Final Report Binding
41%
5%
26%
1%
Figure 17 - Final other resource requirements
4.1.3 Financial Resource Requirements
The team has estimated the cost of labor for each team member over the course of the
project. Although the team members will be working without pay, for the purposes of the
project, adding labor costs adds context to the potential expenses of this project in a real-
33
real-world sense.
Materials:
Without Labor
With Labor
Microprocessor
$10.00
$10.00
Optical Encoder
$50.00
$50.00
Miscellaneous Parts
$10.00
$10.00
$70.00
$70.00
$50.00
$50.00
Subtotal
Miscellaneous
Resources:
Poster
Labor at $10.50 per hour:
Dahlke, Samuel
$2,236.50
Fecteau, Peter
$2,100.00
Pates, Daniel
$2,499.00
Subido, Lorenzo
$2,100.00
Subtotal
Total
$120.00
$8,935.50
$9,055.50
Table 8 displays the original estimated cost of the project with and without labor costs and
34
Table
9
Miscellaneous Resources
Poster
Project Plan Binding
Design Document Binding
Final Report Binding
Subtotal
Labor at $10.50/hour
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Table
10
Item
16-bit Microcontroller
40-Pin DIP PIC Socket
Wires and Connectors
24MHz Crystal Oscillator
20pF 500V Capacitor
0.1uF 50V Capacitor
0.22uF 50V Capacitor
1k Resistor
1.5k Resistor
100 resistor
RJ-12 Connector
RJ-45 Connector
USB Connector
3 Position Header
9 Position Header
6 Position Header
Optical Encoder
Power Supply
Power Jack
Circuit Board Fabrication
Subtotal
Total
the
show
Catalog
Microchip
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Mouser
Mouser
Mouser
Mouser
Mouser
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Manuf.
Total Price w/o
Labor
$60.00
$10.00
$10.00
$10.00
$90.00
and
Total Price
with Labor
$60.00
$10.00
$10.00
$10.00
$90.00
$0.00
$0.00
$0.00
$0.00
$0.00
$260.27
revised
$2,341.50
$2,100.00
$2,709.00
$2,152.50
$9,303.00
$9,563.27
estimates.
Manuf. Part #
Quantities
Catalog Part # Required
Offered
Price/U
PIC18F4455
1
2
13
ED3740-ND
1
100
0.91
CTX026-ND
338-1051-ND
399-2054-ND
399-2056-ND
291-1k
291-1.5k
291-100
154-7623PCB
154-7641PCB
787780-1-ND
WM4201-ND
WM4207-ND
WM4204-ND
Xicon
Xicon
Xicon
22-23-2031
22-23-2091
22-23-2061
US Digital S1-512
CUI Inc.
DPR050030-P6P T309-P6P-ND
CUI Inc.
PJ-002B
CP-002B-ND
1
2
3
1
16
1
20
1
1
1
2
2
1
4
1
1
100
100
100
100
1000
200
200
100
100
100
100
100
100
100
100
100
0.57
0.65
0.11
0.28
0.01
0.01
0.01
0.55
0.65
0.72
0.23
0.51
0.35
39
5.38
0.26
Subtota
Table
11
35
and
Miscellaneous Resources
Poster
Project Plan Binding
Design Document Binding
Final Report Binding
Subtotal
Labor at $10.50/hour
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Subtotal
Total
Table 12 show the final requirements.
36
Total Price w/o
Labor
$60.00
$12.00
$12.00
$12.00
$96.00
Total Price
with Labor
$60.00
$12.00
$12.00
$12.00
$96.00
$0.00
$0.00
$0.00
$0.00
$0.00
$390.07
$871.50
$1,092.00
$1,008.00
$997.50
$3,969.00
$4,359.07
Materials:
Without Labor
With Labor
Microprocessor
$10.00
$10.00
Optical Encoder
$50.00
$50.00
Miscellaneous Parts
$10.00
$10.00
$70.00
$70.00
$50.00
$50.00
Subtotal
Miscellaneous
Resources:
Poster
Labor at $10.50 per hour:
Dahlke, Samuel
$2,236.50
Fecteau, Peter
$2,100.00
Pates, Daniel
$2,499.00
Subido, Lorenzo
$2,100.00
Subtotal
Total
$120.00
Table 8 – Original financial requirements estimate
37
$8,935.50
$9,055.50
Required
Quantities
Offered
PIC18F4455
1
100
$1.20
$1.20
Digi-Key
ED3740-ND
1
100
$0.91
$0.91
24MHz Crystal Oscillator
Digi-Key
CTX026-ND
1
100
$0.57
$0.57
20pF 500V Capacitor
Digi-Key
338-1051-ND
2
100
$0.65
$1.29
0.1uF 50V Capacitor
Digi-Key
399-2054-ND
3
100
$0.11
$0.34
0.22uF 50V Capacitor
Digi-Key
399-2056-ND
1
100
$0.28
$0.28
1k Resistor
Mouser
Xicon
291-1k
16
1000
$0.01
$0.10
1.5k Resistor
Mouser
Xicon
291-1.5k
1
200
$0.01
$0.01
100 resistor
Mouser
Xicon
291-100
20
200
$0.01
$0.18
RJ-12 Connector
Mouser
154-7623PCB
1
100
$0.55
$0.55
RJ-45 Connector
Mouser
154-7641PCB
1
100
$0.65
$0.65
USB Connector
Digi-Key
787780-1-ND
1
100
$0.72
$0.72
3 Position Header
Digi-Key
22-23-2031
WM4201-ND
2
100
$0.23
$0.46
9 Position Header
Digi-Key
22-23-2091
WM4207-ND
2
100
$0.51
$1.02
6 Position Header
Digi-Key
22-23-2061
WM4204-ND
1
100
$0.35
$0.35
4
100
$39.00
$156.00
Item
Catalog
16-bit Microcontroller
Microchip
40-Pin DIP PIC Socket
Optical Encoder
Manuf.
Manuf. Part #
Catalog Part #
US Digital S1-512
Price/Unit Total Price
Power Supply
Digi-Key
CUI Inc.
DPR050030-P6P T309-P6P-ND
1
100
$5.38
$5.38
Power Jack
Digi-Key
CUI Inc.
PJ-002B
1
100
$0.26
$0.26
Subtotal
$170.27
CP-002B-ND
Table 9 - Revised financial requirements estimate
38
Miscellaneous Resources
Poster
Project Plan Binding
Design Document Binding
Final Report Binding
Subtotal
Labor at $10.50/hour
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Subtotal
Total
Total Price w/o
Labor
$60.00
$10.00
$10.00
$10.00
$90.00
Total Price
with Labor
$60.00
$10.00
$10.00
$10.00
$90.00
$0.00
$0.00
$0.00
$0.00
$0.00
$260.27
$2,341.50
$2,100.00
$2,709.00
$2,152.50
$9,303.00
$9,563.27
Table 10 - Revised financial requirements estimate (continued)
39
Item
16-bit Microcontroller
40-Pin DIP PIC Socket
Wires and Connectors
24MHz Crystal Oscillator
20pF 500V Capacitor
0.1uF 50V Capacitor
0.22uF 50V Capacitor
1k Resistor
1.5k Resistor
100 resistor
RJ-12 Connector
RJ-45 Connector
USB Connector
3 Position Header
9 Position Header
6 Position Header
Optical Encoder
Power Supply
Power Jack
Circuit Board Fabrication
Catalog
Microchip
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Mouser
Mouser
Mouser
Mouser
Mouser
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Total Price Total Price
Quantities
Price/Unit w/o Labor with Labor
Offered
Catalog Part # Required
$13.00
$13.00
13
2
1
PIC18F4455
$0.91
$0.91
0.91
100
1
ED3740-ND
$12.00
$12.00
$0.57
$0.57
0.57
100
1
CTX026-ND
$1.29
$1.29
0.65
100
338-1051-ND 2
$0.34
$0.34
0.11
100
399-2054-ND 3
$0.28
$0.28
0.28
100
399-2056-ND 1
$0.10
$0.10
0.01
1000
16
291-1k
Xicon
$0.01
$0.01
0.01
200
1
291-1.5k
Xicon
$0.18
$0.18
0.01
200
20
291-100
Xicon
$0.55
$0.55
0.55
100
154-7623PCB 1
$0.65
$0.65
0.65
100
154-7641PCB 1
$0.72
$0.72
0.72
100
787780-1-ND 1
$0.46
$0.46
0.23
100
2
WM4201-ND
22-23-2031
$1.02
$1.02
0.51
100
2
WM4207-ND
22-23-2091
$0.35
$0.35
0.35
100
1
WM4204-ND
22-23-2061
$156.00
$156.00
39
100
4
US Digital S1-512
$5.38
$5.38
5.38
100
DPR050030-P6P T309-P6P-ND 1
CUI Inc.
$0.26
$0.26
0.26
100
1
CP-002B-ND
PJ-002B
CUI Inc.
$100.00
$100.00
$294.07
$294.07
Subtotal
Table 11 - Final financial requirements
Manuf.
Manuf. Part #
40
Miscellaneous Resources
Poster
Project Plan Binding
Design Document Binding
Final Report Binding
Subtotal
Labor at $10.50/hour
Dahlke, Samuel
Fecteau, Peter
Pates, Daniel
Subido, Lorenzo
Subtotal
Total
Total Price w/o
Labor
$60.00
$12.00
$12.00
$12.00
$96.00
Total Price
with Labor
$60.00
$12.00
$12.00
$12.00
$96.00
$0.00
$0.00
$0.00
$0.00
$0.00
$390.07
$871.50
$1,092.00
$1,008.00
$997.50
$3,969.00
$4,359.07
Table 12 - Final financial requirements (continued)
4.2 Schedules
The following sub-section contains estimated schedules of work proposed by the team
and course advisors. Figure 18 displays the original estimated time planned for each of
the tasks outlined in the schedule of work in the Project Plan document and the revised
estimates. Figure 19 shows the set of deliverables expected from the team over the
course of the project.
41
ID
1
Task Name
Problem Definition
2
Problem Definition Completion
3
End-User Identification
4
5
Constraint Identification
Technology Consideration and Selection
6
Identification of Selection Criteria
7
Technology Research
8
9
Technology Selection
End-Product Design
10
Identification of Design Requirements
11
Design Process
12
Documentation of Design
13
End-Product Prototype Implementation
14
Identification of Prototype Limitations
and Substitutions
15
16
Implementation of Prototype
End-Product Testing
17
Test Planning
18
Test Development
19
Test Execution
20
Test Evaluation
21
Test Documentation
22
End-Product Documentation
23
End-Product Demonstration
24
Demonstration Planning
25
Faculty Advisor Demonstration
26
27
September
October
November
December
January
February
March
April
29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 6 13 20 27 3 10 17 24 1
i
Company Demonstration
Project Reporting
28
Project Plan Development
29
Project Poster Development
30
End-Product Design Report Development
31
Project Final Report Development
32
Weekly Email Reporting
Final - Task
Revised Estimate - Task
Original Estimate - Task
Final - SubTask
Revised Estimate - SubTask
Original Estimate - SubTask
Figure 18 – Gantt chart for project tasks
42
ID
1
2
3
4
5
6
7
8
9
10
Task Name
September
October
November
December
January
February
March
April
29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 6 13 20 27 3 10 17 24 1
Project Deliverables
Unbound Project Plan
Bound Project Plan
Project Poster
Unbound Design Report
Bound Design Report
Unbound Final Report
Demonstration
Bound Final Report
Weekly Email Reports
Task
Task Progress
SubTask
SubTask Progress
Figure 19 – Gantt chart for deliverables
43
5 Closing Material
Project team information is given in this section, followed by a brief summary of the
project.
5.1 Project Evaluation
This section describes the milestones for the project and the overall success of the
project and end-product.
Milestone
Score
Importance
Problem definition
100%
5%
Research
100%
10%
Technology selection
100%
6%
End-product design
100%
10%
Prototype implementation
100%
15%
End-product testing
60%
15%
End-product documentation
85%
7%
Project reviews
90%
7%
Project reporting
95%
15%
End-product demonstration
95%
10%
Total
91%
Table 13 - Project milestone evaluation
This project has been a success, as measured against the client’s specifications. The
client wanted a resolution of 1024 positions, and this group was able to double the
desired resolution to 2048 at no extra cost. The upgraded PCB was required to be of the
same dimensions as the original and it was designed as such. The new PCB has been
installed in the prototype and directly replaces the previous PCB with no modifications.
When the new circuit boards are manufactured in high volume they cost approximately
$14, which is about half of the client’s requested cost (not including the cost of the
optical encoders, as the client specified). The client also requested that the team
maintain the ability to have at least 16 pushbutton inputs. This group was able to
increase the number of pushbutton inputs to 23 by only adding some more resistors and
header pins to the circuit board. It was necessary to add an external power supply that
was not needed in the original design. The cost of the power supply is negligible
compared to the total cost of the controller and is not considered a negative aspect of
the design. In summary, this group far exceeded the client’s specifications at about half
the expected cost.
44
5.2 Commercialization
This product is an update of an existing commercial product, so commercialization is
definite result of this project. The four original potentiometers cost $12 each, and the
new optical encoders are $39 each, so the cost for the unit will be approximately $108
more. The client plans to offer these new components in new products that are sold, and
also offered as an upgrade that customers can send to product to have the new
components installed. It is not known how the client will price this upgrade.
5.3 Recommendations for Additional Work
The prototype meets all specifications from the client at this time. The coding is
independent of the type of encoder that is connected to the microcontroller, as long as it
has a two-channel quadrature output. The current microcontroller can handle 16 bits of
data, thus it could theoretically keep track of 216=65536 positions. Potentially, higher
resolution encoders could be added without making any other changes. There are also
many more pushbutton inputs possible than are currently being used. The team’s
design has already given much room for more resolution and added functionality should
the need arise.
A possibility for future work could be to add some more electronics to the steering wheel
housing. Possibilities include gauges to display RPM, fuel pressure, etc., or LEDs to
indicate the status of various features of the race car used in the game. Another
possibility would be to add forced feedback response to the steering wheel, but the client
has stated that they do not wish to add this feature.
5.4 Lessons Learned
The group was able to effectively split up the work on this project using the popular
divide-and-conquer approach. Tasks were split up based the expertise of the group
members. The group also took advantage of as much of the previous design work and
the pre-written code from Microchip as possible. This made the new design much easier
because there was a template from which to base the new design.
The new microcontroller was so new that it was initially hard to locate from a vendor. It
was also not supported on generic programmers. Although the new microcontroller was
pin-for-pin compatible, most of the inner workings were redesigned. For example, the
oscillator, USB, and memory were all redesigned. The initial datasheet was available,
but other resources and support were not in existence.
Interesting technical knowledge was gained during this project. The group learned about
the use of quadrature encoding and how this scheme increases the resolution of the
encoding. The group also received a refresher course in embedded programming by
learning the assembly language used in the Microchip microcontrollers. The use of
Eagle software, used to layout the circuit board was also learned. Some hands on skills
were also developed in soldering and installing the new components on the prototype
model.
A very important non-technical lesson learned was to make use of previous work as
much as possible. This of course does not mean plagiarizing or copying work that has
not been authorized to be used. Making use of a previous design and pre-written code
greatly simplifies design and saves enormous amounts of time. If following this approach
45
allows the client’s specifications to be met, exceeds expectations, is done on time, and
under budget, then it is a great approach to follow.
The most important thing to do, if the project could be done over, would be to start
implementation and testing earlier. This is a popular statement about what to do over in
senior design projects. Much of the first semester is focused on planning and reporting.
Implementation and testing tend to get pushed into the second semester. This approach
has a tendency for groups to end up with less than the ideal amount of time for
debugging, should it prove necessary.
5.5 Risk and Risk Management
This sub-section explains the forecasted risks, risks involved and how they were dealt
with.
5.5.1 Anticipated Potential Risks and Planned Management
Anticipated risks included the protection of all work, including hardware and software
used. It was forecasted that most of the work would have taken place in the senior
design lab, all PCB designs would have remained in the senior design lab, and any
programming would be done in the lab. Components and materials were to be stored in
the senior design lab in a secure storage locker.
In the event of a team member leaving, it would be in good faith that that team member
would not exploit any of the previous work. Though the team documented every team
member’s progress, there would have been a chance that some work would not be
recoverable. Having Mr. Bice as a resource (Mr. Bice is the original PCB designer),
successful project completion should remain feasible.
5.5.2 Anticipated Risks Encountered
Throughout the project, the team had not encountered any of the projected risks. The
majority of the work was performed outside of the senior design lab and all essential
material, both software and hardware, were kept in personal storage. The team
maintains the original members with no such loss in productivity.
Unanticipated Risks Encountered
The unanticipated risks involved in this project included the meeting of deadlines. In
particular, the part ordering was a complicated process that required paperwork to be
signed; however, it proved to be inefficient and delayed any progress on the project. To
keep on schedule, the team decided to have the faculty advisor purchase the necessary
parts.
Another unanticipated risk was the departure of Mr. Bice. Without his assistance, the
team did not have access to an IC programmer made specifically for the model of
microcontroller that was used. Since the microcontroller that was chosen was very new,
it was not well-supported by generic programmers. However, the team had gotten all
previous schematics and code from Mr. Bice before he left, so the team did not lose any
work.
It was not anticipated that the new microcontroller would not be well supported, because
it was so new on the market. The team expected to have full support for simulations and
also programming of the device. At the time of this draft of the report the group is still
trying to resolve problems with programming the microcontroller. It should be noted that
46
the benefits of using the selected microcontroller outweigh any risks, because it
simplified the design cycle so dramatically.
5.5.3 Resultant Changes in Risk Management
Because of the unforeseen risk of time management, the team was forced to expedite
the process for ordering parts. Additionally, the team increased the frequency of emails
or phone calls to advisors, customer service, and technical support personnel, in order to
meet deadlines.
The group has also reached out to a wide variety of sources to obtain support for
programming of the new microcontroller. These resources include Dataman Corporation,
ISU CIRAS, faculty advisors, and the EE/CprE department. Seeking out assistance from
these sources helped the group move forward when adequate support was not
immediately available from the products manufacturer.
5.6 Project Team Information
This sub-section includes client, faculty advisor, and team member contact information.
5.6.1 Client Information
Thomas Enterprises
David Thomas Sr., President
David Thomas Jr., Vice President
13859 Buffalo Road
Anamosa, IA 52205
319-462-3327
service@thomas-superwheel.com
5.6.2 Faculty Advisors Information
Dr. James Davis
2550 Beardshear
Ames, IA 50011
515-294-0323
davis@iastate.edu
Dr. Douglas Jacobson
2419 Coover
Ames, IA 50011-3060
515-294-8307
dougj@iastate.edu
47
5.6.3 May05-26 Team Members Information
Samuel Dahlke, CprE
7312 Frederiksen Court
Ames, IA 50010
515-572-7972
sdahlke@iastate.edu
Peter Fecteau,
CprE
6326 Frederiksen Court
Ames, IA 50010
515-572-7844
pfecteau@iastate.edu
Daniel Pates,
EE
205 South 5th Street, Apt. 907
Ames, IA 50010
515-450-4380
dpates@iastate.edu
Lorenzo Subido, EE
2355 Wallace
Ames, IA 50013
515-572-2090
lsubido@iastate.edu
5.7 Summary
Thomas Enterprises, a producer of top-of-the-line gaming and simulation steering wheel
controllers, needs to keep their product line competitive. To this end, they wish to use
optical encoders to increase the sensitivity in their controllers.
The team’s design provides the upgrade that Thomas Enterprises wishes to incorporate
into their product line. The end-product includes optical encoders that replace the old
potentiometers and a new microprocessor that interfaces properly with the current
hardware and software. The design is similar to the previous design and requires
minimal, if any, change in the manufacturing process by Thomas Enterprises, allowing
them to update the controller product line and existing controllers at low cost.
48