ECE 477
Digital Systems Senior Design Project
Spring 2006
Homework 4: Packaging Specifications and Design
Due: Friday, February 10, at NOON
Team Code Name: 2-Bit Robit
Group No. 2
Team Member Completing This Homework: Andy Brezinsky
NOTE: This is the first in a series of four “design component” homework assignments, each
of which is to be completed by one team member. The completed homework will count for
10% of the team member’s individual grade. It should be a minimum of five printed pages.
Evaluation:
Component/Criterion
Introduction
Commercial Product Packaging
Project Packaging Specifications
PCB Footprint Layout
List of References
Technical Writing Style
0 1 2
0 1 2
0 1 2
0 1 2
0 1 2
0 1 2
Score
3 4 5
9 10
3 4 5
9 10
3 4 5
9 10
3 4 5
9 10
3 4 5
9 10
3 4 5
9 10
Multiplier
6 7 8
6 7 8
6 7 8
6 7 8
6 7 8
6 7 8
Points
X1
X3
X2
X2
X1
X1
TOTAL
Comments:
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ECE 477
Digital Systems Senior Design Project
Spring 2006
1.0 __________________________________________________________________________
___Introduction
The 2-Bit Robit is a robotic dot matrix printing platform ideal for large scale outdoor
ground printing applications. The onboard computer is loaded with a design and once started,
transverses the print grid dropping small sprays of chalk or paint on the ground in predetermined
locations to generate an image. A positioning system ensures accuracy and precision in the
paint process.
2.0 Commercial Product Packaging
The uniqueness of the project is evident in the lack of prior commercial art found for the
design. The following review analysis will show a similar project for the spray subsystem as
well as a commercial robotic platform.
2.1 Product #1
The “Bikes against Bush” [1] project was designed as a protest tool for the 2004
Republican National Convention. Using a series of spray cans mounted on the back of bicycles,
protesters were able to quickly print large amounts of text banners on the ground with messages
provided via SMS messaging.
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ECE 477
Digital Systems Senior Design Project
Spring 2006
Illustration 1: "Bikes against Bush" ChalkWriter
Designed by Joshua Kinberg, the system features 5 spray cans side by side. A series of
solenoids placed along the bottom of the nozzles provide the necessary mechanical action to
trigger the spray. Metal U-hooks attach the cans to the Plexiglas box containing the electronics.
The transparency of the Plexiglas gives individuals an inside look into the inner workings
of the project. The ability to easily mold and shape Plexiglas to create a nice box is a plus.
However the project is mainly to be used outdoors and this is not a good choice for harsh
environments.
We plan on basing our can spray system off of this design as it's almost exactly what
we're attempting to do. The cans however will be mounted over a slot cut in the middle of the
robot instead of hung off the back like this design. We also plan on using Plexiglas for the
housing of the electronics and the battery cover. This is due to the ease of working with
plexiglass and the quality of the end result. This should give us a crisp cover for the battery and
solid and clean base for the electronic mount.
Since we are using a robotic platform as a driving mechanism compared to a bicycle we
have a few different requirements for mounting the spray cans. The solenoids will be mounted
in a vertical manner to minimize the width of the robot. If the cans were mounted on the robot
as shown in Illustration 1, the robot would need to be twice as wide as shown. Mounting them
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ECE 477
Digital Systems Senior Design Project
Spring 2006
vertically as opposed to horizontally also clears up room on the sides of the robot for the stepper
motor mountings.
2.2 Product #2
The Workman Robotic Platform by Kadtronix [2] is designed to be a platform to expand
upon. Constructed out of ABS plastic it provides a complete system of motors, controllers, and
a battery to decrease development time of projects.
Illustration 2: Kadtronix Workman Robotic Platform
The robot measures 15”L x 19”W and weighs in at 20 lbs. It is driven by 2 high torque
12v motors. The plastic casing allows for easy modification for mounting of sensors and
additional electronics. The design includes two front wheels and a rear floating castor.
The robot has an easy design because there are only two drive motors. This allows you
to spin the robot in place over an axis between the front wheels. The motors are simple wormgear driven devices that do not have any type of feedback as to position. This has a
disadvantage of not allowing you to know where you were without adding sensors. In addition
the ABS plastic and overall construction is not robust enough for outdoor use.
Our original design called for two powered wheels with a caster as this design uses,
however since our rotation axis needs to be around the center of the robot and not around the
center of the powered wheel axis, we need to drive both pairs of wheels directly. We plan on
expanding the use of ABS plastic for the shell in our design by using Plexiglas for its ability to
easily be modified and worked with.
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ECE 477
Digital Systems Senior Design Project
Spring 2006
The Robit will be powered by stepper motors instead of standard DC motors. This gives
us the necessary precision to detect our location using dead-reckoning and the ability to precisely
move our robot to the proper position to place the spray in the proper location.
3.0 Project Packaging Specifications
The Robit will be aluminum and Plexiglas [3] framed. Both of these materials are being
used to cut down on weight. Aluminum L channels will be used for primary structure while the
Plexiglas will be used for a mounting base and creating a shell to house the electronics and
battery. The robot will be powered off of a 12V Sealed Lead Acid battery of atleast 4 amp
hours. [4] The spray system will be built out of a vertical aluminum frame. The drive system
will be 2 stepper motors connected to both wheels via a sprocket and chain. [5]
Running in a perpendicular direction to the motion will be the 4 spray cans. Directly
behind them will be the motors and behind that will be the battery. Mounted on top of the
battery will be the circuit board and position system since the position sensor must be the tallest
item on the robot.
4.0 PCB Footprint Layout
Our primary chip, the MC9S12NE64 [6], comes in both 80 and 112 pin variants. We
have selected the 112 pin model for expandability. This requires us to use the LQFP package.
For our ATmega8 [7] chips used for distance and positioning, we have a choice of PDIP and
TQFP. We have selected the PDIP package currently because of unknowns in manufacturing
our boards. Should we be required to build our own boards for the beacons we will be taking
advantage of the ease of use of soldering PDIP. It also allows us to quickly test and experiment
in the circuits needed for positioning since they are dependent on a number of analog chips. For
the Cypress CY7C1366A [8] both TQFP and BGA packages are available. Since we do not
have the technology to handle BGA, the SRAM will be TQFP. With LQFP, PDIP, and TQFP
chips, assorted opamps, mosfets and optoisolators, we estimate our board size to be 6” square.
5.0 Summary
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ECE 477
Digital Systems Senior Design Project
Spring 2006
The 2-Bit Robit is a unique platform for producing large scale ground
drawings. We have identified a number of package requirements to complete
our design.List of References
[1] “Bikes Against Bush”
http://a.parsons.edu/~jk/thesis/vital_info.html
[2] Workman Mobile Robot by Kadtronix
http://www.kadtronix.com/workman.htm
[3] Plexiglas
http://www.professionalplastics.com/cgi-bin/pp.pl
[4] Powersports X5LB Battery
http://www.batterystuff.com/power-sports-battery/X5LB.html
[5] Linengineering High Torque Stepper Motor 5718 Framesize 23
http://www.linengineering.com//site/products/5718.html
[6] Freescale, MC9S12NE64 Microcontroller Datasheet
http://www.freescale.com/files/microcontrollers/doc/data_sheet/MC9S12NE64V1.pdf
[7] Atmel Atmega8 Summary
http://www.atmel.com/dyn/resources/prod_documents/2486S.pdf
Cypress CY7C1366A 9MB SRAM
http://rocky.digikey.com/WebLib/Cypress/Web%20Data/CY7C1366A,67A_
%20GVT71256C,512C.pdfAppendix A: Project Packaging Illustrations
The Robit will be 22” long by 15” wide and made out of a solid piece of 3/8” Plexiglas. The
sides will be reinforced with L channel aluminum. The battery case (represented in purple) will
be also made out of Plexiglas and will have the circuit board mounted onto. The robot will be
22”L x 15”W. Height will depend on the spray cans used.
Appendix B: Project Packaging Specifications
Tooling
Since we are building this robot from scratch, we will require a large number of tools. In addition
we're going to need raw aluminum L channel stock and sheets of 3/8” Plexiglas.

Drill

Dremel

Pop Rivet Gun
-69 Drawing 1: Initial Robit Design
ECE 477
Digital Systems Senior Design Project

Jigsaw

Plexiglas Weld-On
Spring 2006
Parts
Item
Weight
Cost
Battery (12V 5AH)
6 lbs
$36.00
Stepper Motors
2 lbs each
$45 each
Circuit Board & Chips
1 lbs
$50
Wheels
1 lbs
$25
Sprocket and chain set
0.5 lbs
$20
Aluminum
0.4 lbs
$20
Plexiglas
1 lbs
$50
Total
13.9 lbs
$291
Appendix C: PCB Footprint Layout
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ECE 477
Digital Systems Senior Design Project
Illustration 3- Board Layout for Robit
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Spring 2006