University of Portland
School of Engineering
5000 N. Willamette Blvd.
Portland, OR 97203-5798
Phone 503 943 7314
Fax 503 943 7316
Requirements and Functional
Specifications
Project RNG: A Radiation-Based
Random Number Generator
Team Members:
Ashley Donahoo (Fall Team Lead)
Colton Hamm (Spring Team Lead)
Alex Brotherston
Matt Johnson
Industry Representatives:
Mr. John Haner
Faculty Advisors:
Dr. Joseph Hoffbeck
Dr. Tammy VanDeGrift
Dr. Osterberg (secondary advisor)
Other Contributors:
Mr. Tony Chang
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Revision History
.
.
Rev.
Date.
0.10
9/10/2010 .
FUNCTIONAL SPECIFICATIONS
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REV. 1.0
Author
Colton Hamm
0.20
0.30
9/10/2010
9/17/2010
Ashley Donahoo
Alex Brotherston
0.40
0.50
9/19/2010
9/20/2010
Matt Johnson
Ashley Donahoo
0.51
9/20/2010
Matt Johnson
0.60
9/21/10
Alex Brotherston
0.61
9/18/2010
Colton Hamm
0.64
9/24/2010
Ashley Donahoo
0.65
9/24/2010
0.66
9/24/2010
Matt Johnson/Alex
Brotherston
Alex Brotherston
0.67
0.90
9/24/2010
9/24/2010
Colton Hamm
Alex Brotherston
0.91
10/3/2010
Team Chub
0.92
10/5/10
Team Chub
0.93
10/6/10
Team Chub
0.94
10/7/10
Team Chub
0.95
10/8/10
Team Chub
1.0
10/13/10
Team Chub
UNIVERSITY OF PORTLAND
PAGE II
Reason for Changes
Initial draft. Started Overview,
block diagram, and hardware specs
Started Ethical Considerations
Added risks and environmental
considerations.
Wrote Use Cases
Assumptions and High level
Diagram
MOSIS and Display components
draft, updated Use Cases
Added analog components and
general design overview
Added more hardware
specifications, facilities, equipment,
and physical specifications
Added in Conclusion and made
comments
Added Intro, comments, updated
Use Cases, added to digital logic
Added comments and analog parts
list
Basic revisions to overall document
Finished budget descriptions and
finalized document
Made changes and additions to
various sections of the document
according to advisor comments
Made more revisions to the sections
of the document according to
advisors comments.
Modified milestones and other
comments.
Fixed Table of Contents and Figure
2
Advisors, Dr. VanDeGrift and Dr.
Hoffbeck, approved document
John Haner approved document
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Table of Contents
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Introduction ...............................................................................................................................
9
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Requirements .........................................................................................................................
10
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Overview ......................................................................................................................... 10
Physical Specifications ................................................................................................... 11
Product Type ............................................................................................................. 12
Form Factor ............................................................................................................... 12
Enclosure ................................................................................................................... 12
Environmental Specifications ......................................................................................... 12
Temperature .............................................................................................................. 13
Relative Humidity..................................................................................................... 13
Shock and Vibration ................................................................................................. 13
Hardware Specifications ................................................................................................. 13
System Hardware...................................................................................................... 13
Board Hardware ........................................................................................................ 14
Radiation Sensor ....................................................................................................... 14
Voltage Amplifier ..................................................................................................... 14
Digital logic............................................................................................................... 14
Outputs ...................................................................................................................... 15
High Level Design ................................................................................................................. 15
Overview of System Architecture .................................................................................. 15
Component Details.......................................................................................................... 16
Standard Components............................................................................................... 16
Transformer............................................................................................................... 16
Geiger Tube .............................................................................................................. 17
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MOSIS Chip. ............................................................................................................. 17
. Display ........................................................................................... 17
Seven-Segment
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. Components ....................................................................................... 17
High Voltage
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Use Cases......................................................................................................................... 17
Use Case 1: User Presses the Power Button........................................................... 17
Use Case 2: User Flips the Hold Switch................................................................. 18
Use Case 3: User Presses the Reset Button ............................................................ 19
Use Case 4: User Turns Off Display ...................................................................... 19
Optional ........................................................................................................................... 20
Development Process ............................................................................................................ 20
General Approach ........................................................................................................... 20
Design........................................................................................................................ 21
Build .......................................................................................................................... 21
Implementation ......................................................................................................... 21
Assumptions .................................................................................................................... 21
Ethical Considerations ........................................................................................................... 22
Milestones .............................................................................................................................. 22
Customer Interview ......................................................................................................... 23
Functional Specification Draft .90.................................................................................. 24
MOSIS Chip: Timer built and tested in B^2logic ......................................................... 24
Functional Specification Draft .95.................................................................................. 24
Functional Specification Final ........................................................................................ 24
Simulate the Pulse Generator and Transformer in PSPICE: ......................................... 24
MOSIS Chip: Comparator built and tested in B^2logic................................................ 24
Simulate the voltage multiplier in PSPICE .................................................................... 24
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Deliver .edf file .to Dr. Osterberg .................................................................................... 24
. first draft Completed ........................................................................ 24
Design Document
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MOSIS Memory. tested and completed.......................................................................... 25
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Simulate the pulse generator, transformer, and voltage multiplier interfacing in
PSPICE ............................................................................................................................ 25
Design Document version .95 Completed ..................................................................... 25
.edf file testing completed ............................................................................................... 25
.edf file Completed and sent to Dr. Osterberg ............................................................... 25
Simulate the pulse generator, transformer, voltage multiplier, and load interfacing in
PSPICE ............................................................................................................................ 25
Design Document version 1.0 Completed ..................................................................... 25
All parts ordered .............................................................................................................. 25
Construct and test the pulse generator/transformer ....................................................... 25
Construct and test the prototype voltage multiplier ....................................................... 26
Construct and test the final voltage multiplier (w/ high voltage components)............. 26
Test the interface between the pulse generator, transformer, and voltage multiplier .. 26
Final Report First Draft Completed................................................................................ 26
Test the interface between the pulse generator, transformer, voltage multiplier and
load ................................................................................................................................... 26
Case built and the device completed .............................................................................. 26
Final Report version .95 Completed............................................................................... 26
Final Report 1.0 Approved ............................................................................................. 26
Founders Day Presentation Complete ............................................................................ 26
Risks ....................................................................................................................................... 27
Geiger tube is damaged ................................................................................................... 27
Geiger tube fails to generate desired output ................................................................... 27
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. radiation............................................................................................. 28
No useful level of
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MOSIS chip malfunctions
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Resources ...............................................................................................................................
28
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Personnel.......................................................................................................................... 28
Preliminary Budget ......................................................................................................... 28
1.1 Output ........................................................................................................................ 29
1.2 Serial Cable ............................................................................................................... 29
1.3 Oscillator ................................................................................................................... 29
1.4 Transformer ............................................................................................................... 29
1.5 Voltage Multiplier ..................................................................................................... 29
1.6 Sensing....................................................................................................................... 29
1.7 Power Source............................................................................................................. 30
Equipment........................................................................................................................ 30
Facilities ........................................................................................................................... 30
Conclusion ............................................................................................................................. 30
Glossary.................................................................................................................................. 31
References .............................................................................................................................. 31
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List of Figures.
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Figure 1. Block Diagram. of the Radiation-based Random Number Generator........................ 11
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Figure 2. System Architecture
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Figure 3. Overall Development Process...................................................................................... 21
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List of Tables .
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Table 1. Physical Specifications
for the Random Number Generator. ...................................... 12
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Table 2. Environmental .Specifications ....................................................................................... 12
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Table 3. System Hardware Specifications .................................................................................. 13
Table 4. Board Hardware Specifications .................................................................................... 14
Table 6. Project Milestones.......................................................................................................... 22
Table 7. Project risks and contingencies. .................................................................................... 27
Table 8. Preliminary Budget ........................................................................................................ 28
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Introduction .
.
. is defined as a computational or physical device designed to
A random number generator
generate a sequence of.numbers or symbols that lack any pattern. While pseudorandom
.
generators are fairly common,
it is very hard to generate truly random numbers using a
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deterministic algorithm. Typically, there are ways of predicting or finding patterns in most
“random” generators. For example, many computer programs generate numbers using
algorithms that appear random; however, if one knows the algorithm, that person can predict
the number.
Random numbers have many applications. Most can use pseudorandom numbers (random
enough for that application). However, there are times when truly random numbers are
needed. For instance, they are used in cryptography to create keys for ciphers. In this
application the number needs to be truly random or the coded information might be able to
be decoded by anyone who could predict the number. Other applications are: gambling,
statistical sampling and computer simulation.1
In researching sources of truly random numbers, Team Chub discovered that Geiger tubes
could be used to harness the natural entropy of radioactive decay. Further research showed
that an effective random number generator could be implemented simply using a Geiger tube
and a MOSIS chip, two technologies that Team Chub is extremely interested in learning
about.
The random number generator has three primary components: the Geiger tube, MOSIS chip,
and display. The Geiger tube, capable of detecting radioactive particles, is the key
technology for the device. If a large voltage is applied across the tube, ions created from
radioactive particles interacting with inert gas inside the tube will trigger a cascade effect,
producing a current spike at the output of the tube. This current spike will be shaped into a
pulse and sent to the MOSIS chip. The MOSIS chip compares the time between two sets of
pulses and produces a random bit based on the time difference. Once the MOSIS chip
collects 8 random bits, the random byte is sent to the display.
This document defines the scope of the project. The top level view of the project presents
the overall picture. Each of the detailed components is discussed. Finally the document
concludes with the development process, concerns in making the project, materials used and
much more pertinent project information.
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Requirements .
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Overview
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The basic requirements .for any random number generator are randomness and independence.
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Randomness means that there is no set pattern or algorithm for generating numbers. The
numbers are completely unpredictable, even to those that know how the generator works.
Independence means that if one state is known, the next state is still random. For instance, if
the first bit of a random number is known, the next bit should still have a 50% chance of being
a 0, and a 50% chance of being a 1.
Other requirements for a random number generator are speed and data output. Speed refers to
how quickly a random number can be generated. For most applications, the faster a generator
works the better. A random number generator must also have an output. Because many
applications for random numbers are computer-based, computer connectivity would be
desirable.
Because the random number uses radiation to produce random numbers, the speed at which
the device generates numbers is proportional to the number of radioactive particles passing
through the sensor. Because high levels of radiation are harmful to human beings, the random
number generator will use background radiation instead of its own radiation source. Because
of this, the device will generate random numbers relatively slowly. An 8-bit number is
expected to take on the order of one minute to generate. It can be said that the radiation-based
approach trades speed for true randomness.
The customer, Tony Chang, suggested the device connect to a Serial/USB/other port, allowing
the device to interface with a computer. It would make it easier for others to use and to test the
randomness of the numbers. Due to the scope of this project seven segment displays will be
used to present the random numbers. See the OPTIONAL section of this document for more
information about the possible use of a COM port for computer connectivity. For additional
functionality, the device will have a power switch, a switch to freeze the display, and a switch
to turn off the display. The freeze switch would prevent the display from changing, allowing
the user to see a certain random number for as long as necessary. There will also be a switch to
turn off the display. Users may wish to turn off the display when generating random numbers
for use with cryptology and security applications.
Finally, for safety reasons, the device will be battery powered. This will help prevent bodily
harm should the device malfunction or be used improperly. A battery powered device also has
the advantage of being more portable than a device requiring external power.
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. is composed of four main components: a high voltage supply, a
The random number generator
. to shape the output of the Geiger tube into pulses, a logic unit,
Geiger tube, analog circuitry
.
and a display. The main. components of the Random Number Generator can be seen in the
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block diagram in Figure 1.
The Geiger tube is a component whose functionality can be thought of as a radiation-activated
switch, which creates a momentary current spike when a radioactive event is detected. The
tube is powered by high-voltage, low-current electrical pulses, which will be created using a
battery, an oscillator, a transformer, and a voltage multiplier. When combined, these
components will provide the 500 volts necessary to drive the radiation sensor.
The hardware used to generate a random number is an application-specific integrated circuit,
also known as a MOSIS chip. The MOSIS chip will be connected to the radiation sensor and
produces random bits by comparing the time between radioactive events. By creating a series
of random bits, the chip is able to produce an 8-bit random number.
Once a random number is produced by the MOSIS chip, external circuitry is used to translate
the data into a form that can be displayed. The data is displayed using standard seven-segment
displays.
Figure 1. Block Diagram of the Radiation-based Random Number Generator
Figure 1 shows the block diagram of the Radiation-based Random Number Generator. The
high voltage pulse generator is seen powering a radiation sensor. The output of the sensor is
used to generate random numbers using a custom-made digital integrated circuit, known as a
MOSIS chip. A display, connected to the output of the MOSIS chip, displays the latest
random number.
Physical Specifications
Physical specifications include information about the physical properties of the
product; including product type, form factor, and enclosure specifications. The
physical specifications of the random number generator are described in Table 1.
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. Specifications for the Random Number Generator.
Table 1. Physical
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. Requirement
Value
.Product Type
Computer
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Peripheral1
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Form Factor
Enclosure
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Hand-held
Plastic
Computer connectivity may not be available in version 1.0 of the device.
Product Type
The device is classified as a Computer Peripheral because one of its primary purposes
is to interface with a computer to add functionality to the computer. However, the
device is capable of stand-alone functionality as well. For reasons enumerated in the
OPTIONAL section of this document, computer-interfacing may not be available in
version 1.0 of the device.
Form Factor
Because the device is battery powered and capable of standalone operation, it would
be desirable to make it a hand-held device. The device is expected to be roughly the
size of a hand-held Geiger counter, because it is based on the same technology.
Enclosure
Because the device creates random numbers based on radiation, the enclosure should
block as little radiation as possible. For this reason, the enclosure will be made out of
plastic, which offers less shielding against radiation than a metal enclosure. A plastic
enclosure is also safer than a metal one, should the high-voltage power supply
malfunction.
Environmental Specifications
Table 2 contains a list of the environmental specifications and their required values.
Table 2. Environmental Specifications
Requirement
Temperature
Relative Humidity
Shock and Vibration
Logic Unit
Geiger Tube
5 – 50 oC
Dry
Standard
-40 – 75 oC
Dry
Standard
Each of the sections below describes the individual specifications in more detail.
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Temperature
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All internal components
of the MOSIS chip logic unit are capable of operating within
. range.
the given temperature
The Geiger tube has an operating temperature range of .
40 to 75 degrees.Celsius.
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Relative Humidity
The device is not waterproof and should only be operated in dry environments.
Shock and Vibration
The device is handheld, and will be able to operate under typical vibration conditions
associated with this style. The device is not built or designed to withstand severe
shock or vibration, such as a drop or excessive shaking.
Hardware Specifications
System Hardware
Table 3 contains a list of the system hardware specifications and their required values.
Table 3. System Hardware Specifications
Requirement
Power Supply
Peripheral Devices
Radiation source
Value
9v battery
Computer
(optional)
Optional
Each of the sections below describes the individual specifications in more detail.
Power Supply
The random number generator uses a standard 9v battery as a supply, allowing for
portability and stand-alone functionality. Future versions of the device may be
powered by an external supply for the convenience of computer-based applications
where portability is not important.
Peripheral Devices
Future versions of the device will feature a COM port to allow for computer
interfacing. For more information, see the OPTIONAL section of the functional
specification.
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Board Hardware .
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Table 4 contains.a list of the board hardware specifications and their required values.
. Table 4. Board Hardware Specifications
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Requirement
Radiation sensor
Voltage Amp
Digital Logic
Outputs
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Value
Geiger Tube
9v->500v
MOSIS Chip
COM port, 7-segment
display
Each of the sections below describes the individual specifications in more detail.
Radiation Sensor
The radiation sensor used in the random number generator is a Geiger tube sensitive to
alpha, beta, and gamma radiation. A Geiger tube consists of a tube filled with inert gas
with an electrically isolated contact in the center. When ionizing radiation passes
through the tube, it reacts with the gas, creating ions. If a large voltage is applied
across the tube, these ions will trigger a cascade effect, producing a current spike at the
output of the tube. This current spike can shaped into a pulse suitable for triggering
digital circuits.
For safety reasons this device will use a Geiger tube that is sensitive to alpha radiation,
which is not harmful to humans under most conditions. An alpha-sensitive device will
also generate numbers more quickly, as it can detect more frequent radioactive events.
Voltage Amplifier
In order to create the 500 volts requited to drive the Geiger tube, a voltage amplifier is
needed. The voltage amplifier consists of three stages. The 9 DC volts provided by the
battery is turned into pulses using an oscillator. These pulses are then amplified from 9
volt pulses into 250 volt pulses using a step-up transformer. The 250 volt pulses are
then amplified into 500 volt pulses using a voltage doubler.
Digital logic
In order to create random numbers from radioactive events, digital logic must be used.
The radiation-based random number generator will use a custom-made, application
specific integrated circuit known as a MOSIS chip to create random numbers. The
MOSIS chip receives one bit from the radiation sensor, a 0 for no detection and a 1
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. is detected. Once the MOSIS chip receives three 1s it compares the
when radioactivity
. first and the second to the time between the second and the third. If
time between the
.
the second time. interval is longer than the first, a 1 will be stored in memory.
Otherwise a 0 will
. be stored. Once eight bits are stored in memory the random number
is output to the display.
.
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Outputs
To facilitate stand-alone capabilities, the random number generator has a built in
display. The display consists of three 7-segment displays, which will display the 8-bit
output in decimal format.
The device will also have a digital output, allowing for a COM port to be added to
future devices. The COM port will allow for computer connectivity. While a computer
is not necessary for device operation, many potential applications of the device are
computer-based.
High Level Design
The random number generator is predominately a system that depends on a Geiger tube and a
MOSIS chip to detect the radiation in the air and count the time between radiation events in
the air to produce a random number. To achieve this, it is necessary for a 9 volt battery to
produce 500V pulses to power the Geiger tube which senses the radiation, then sends a
voltage spike to the MOSIS chip. The chip starts counting and compares the times between
the detection of radiation particles. Once calculated, the MOSIS chip will drive the seven
segment display and the USB.
Overview of System Architecture
The system architecture is shown in Figure 2. The interface between each stage is
described below. Refer back to Figure 1 for the generalized block diagram.
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Figure 2. System Architecture
The power supply generates 500V pulses to the Geiger tube, which then detects radiation.
Once radiation has been detected, this enables the MOSIS chip to calculate the bit needed for
the random number. The device will be hand-held, about the size of Digital Multimeter. There
will be a hold and reset switch on the device. The hold switch allows for the user to freeze the
display for an extended period of time. The reset switch allows the user to reset the display
and start at 0.
Component Details
Standard Components
The radiation-based random number generator is made largely of standard, off-theshelf components, both active and passive.
Transformer
The transformer is the critical component in creating the high voltage necessary to run
the Geiger tube. The device requires a 30:1 step-up transformer, whose output is
passed through additional circuitry to yield the 500 volts necessary to detect
radioactive events.
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Geiger Tube
.
.
A Geiger tube is. a conducting tube with an electrically isolated electrode inside. The
tube is filled with
. inert gas. Radiation passes through the tube and interacts with the
gas, creating ions.
. If a large potential is placed across the tube, these ions will trigger a
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cascade effect, producing a current spike each time a radioactive particle passes
through the tube.
MOSIS Chip
The MOSIS chip has an input, from the radiation sensor, and an output, to the sevensegment display. There is also a clock signal and user switches (Hold and Reset)
going into the chip. It receives a one (high voltage) from the radiation sensor when it
senses radioactivity and a zero when nothing is sensed. The first one starts the first
timer. The second one stops the first timer and starts the second timer. The third one
received stops the second timer. At this point both timers are sent to a comparator
and a one is output if the first time is less than the second, otherwise a zero is output.
In case of a tie, the data will be thrown out and the timing process will start over when
the next particle is sensed. This creates the random bit which is stored in memory.
Once eight bits are stored in memory, they are sent to three seven-segment displays.
Seven-Segment Display
Displaying the random number generated by the MOSIS chip will be done using off
the shelf seven-segment displays. The chip will output 8-bits to circuitry which
converts the bits to a form that can be directly hooked up to the seven segment
displays, so that they will display 3 digits. For added functionality, a hold switch will
be added to freeze the display, should the user require such functionality.
High Voltage Components
On the high-voltage side of the device, capacitors, resistors, and diodes must be able to
handle the high voltage being supplied. We expect that we will have to order special
components to be able to handle the given power.
Use Cases
The following Use Cases outline the control the user has over the random number
generator and what the user needs to do to perform these operations.
Use Case 1: User Presses the Power Button
Primary Actor: User
Goal in context: Turn the random number generator on.
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. Battery must be installed. Ensure that all components are
Preconditions:
.
properly connected.
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Trigger: The
. user wishes to use the machine or turn off the machine.
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Scenario:
1. The user presses the Power button
2. The individual components receive power from the power supply. The
Geiger counter starts sensing.
3. The display will be blank until the MOSIS chip gets enough data, then
the random number will be displayed.
Exceptions:
1. The Geiger counter is unable to detect enough radiation to output a
random number.
Priority: Essential, must be implemented.
Frequency of use: Occasional.
Channel to primary actor: Direct physical manipulation of the device.
Use Case 2: User Flips the Hold Switch
Primary Actor: User
Goal in context: Freeze the display.
Preconditions: Battery must be installed. Ensure that all components are
properly connected.
Trigger: The user wishes to look at the current random number for an
extended period.
Scenario:
1. The user flips the Hold Switch.
2. The MOSIS continues generating the next random number, the output to
the seven-segment display freezes on the current random number.
3. When the Hold button is flipped again the MOSIS chip displays the
current random number.
Priority: Not essential, only implemented when desired.
Frequency of use: Occasional.
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Channel to.primary actor: Direct physical manipulation of the device.
Use Case 3: User Presses
the Reset Button
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. User
Primary Actor:
.
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Goal in context: Reset device to initial conditions.
Preconditions: Battery must be installed. Ensure that all components are
properly connected.
Trigger: The user wishes to clear the display and start over.
Scenario:
1. The user presses the Reset button.
2. The MOSIS chip clears output and resets timers.
3. The seven-segment display is shut off and displays the next random
number when it is generated.
4. The machine starts collecting data to generate a new random number.
Priority: Not essential, only implemented when desired.
Frequency of use: Rare.
Channel to primary actor: Direct physical manipulation of the device.
Use Case 4: User Turns Off Display
Primary Actor: User
Goal in context: Hide display.
Preconditions: Battery must be installed. Ensure that all components are
properly connected.
Trigger: The user wants to hide random numbers from view.
Scenario:
1. The user flips the Display power switch.
2. Power is cut to the display.
3. All else operates normally.
Exceptions: The user is unable to locate the Display switch.
Priority: Not essential, only implemented when desired.
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Frequency .of use: Occasional.
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Channel to.primary actor: Direct physical manipulation of the device.
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FUNCTIONAL SPECIFICATIONS
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Because many, if not most, applications of a random number generator are for
computer applications, it is desirable that the radiation-based random number
generator have the ability to communicate with a PC. However, time constraints and a
lack of knowledge of computer interfacing means that this feature may not be
implemented in version 1 of the device.
If implemented, communication with a computer will be done through the computer’s
COM port. Connection will require a COM cable. If the computer does not have a
COM port, COM-to-USB adapters are available.
As far as device hardware is concerned, a Parallel-to-serial shift register will be added
to the device to create the serial output necessary to communicate with serial ports.
Because the device does not require computer inputs, no hardware is necessary to
receive data from the computer.
In addition to additional hardware requirements, computer integration will require
custom software. While the requirements of this software are unknown at this time, it
is believed that it will work on all platforms.
Development Process
General Approach
The device will be taken from concept to reality in three main phases, as seen in the figure
below: design, build, and implementation. The bulk of the documentation requirements will be
divided evenly among the team members to ensure no one person becomes overwhelmed. In
general, the team of 4 will work on the design and implementation of the project in groups of
two, which will allow us to check each other’s work as we go, resulting in less editing and
corrections later in the process. The team will place priority on this project over other classes,
and set personal deadlines well before official deadlines to keep the project consistently ahead
of schedule.
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.
.
.
.
.
.
Design
.
.
•Documents
.
•Analog circuitry
FUNCTIONAL SPECIFICATIONS
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•MOSIS chip
REV. 1.0
Build
•Analog circuitry
•7-segment
display
•Device housing
PAGE 21
Implementation
•Integration of
analog and
MOSIS
•Final
documentation
Figure 3. Overall Development Process.
Design
The design phase is estimated to be August 30, 2010 to late September. This phase
will consist primarily of device design and documentation. The team will work
together on the two important documents due during this phase, the functional
specification and design document. Two members will focus on the design of the
analog circuitry, while the other two will be tasked with the complete MOSIS chip
design.
Build
The build phase is estimated to be late September, 2010 to mid-March, 2011. This
phase will consist primarily of physically constructing and testing the circuits not
dependent on the MOSIS chip. Two team members will build and test the analog
circuitry, while two members focus on the 7-segment display and device housing unit.
Implementation
The implementation phase is estimated to be mid-March, 2011 to April 12, 2011. This
phase will consist of final device construction documentation. The team will work
together to integrate the analog circuitry, MOSIS chip, and display to create the
finished product. We expect a lot of testing and debugging to occur during this phase.
The team will also work together to create the final report and presentation.
Assumptions
Given the scope of this project and the many parts, there are several things that need to be
taken into consideration. Here are some of the assumptions:

The MOSIS design software will work as expected, and a functional chip is
produced.

The 9V battery using a step-up transformer, an oscillator, and a voltage
multiplier will produce 500V pulse waves to power the Geiger tube.
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.
.
.
. available “off-the-shelf” and will work as stated by the product’s
Geiger tube
.
data sheet.
.
.
The time. between radiation events is random
.
Background radiation is on the order of 20 counts/minute (if an external
FUNCTIONAL SPECIFICATIONS
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

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source of radiation isn’t used). [1]
Ethical Considerations
This product allows everyday users to generate a random number by using the background
radiation around them. This product cannot be used to harm others or the property of others.
The misuse of this product could result in a pseudorandom number generator. This misuse
could happen if the user is not using the Geiger counter correctly. In order to generate a
number, the MOSIS chip compares the difference of times after three sequential hits of
radiation. If the radiation levels are compromised in some way such as creating a dependent
source of radiation then the randomness of the number is compromised. An application of a
random number generator is encryption. People working in the security industry find the
generation of random numbers useful in making a key. However, the product itself does not
have any security features to protect the display of random numbers. Thus anyone can steal
the numbers being produced.
The manufacturing and use of the product has minimal impact to the environment. All of the
materials used can be found in any electronic parts store. This product is not producing
radiation but rather detecting it, so the Geiger tube should not be a threat.
Milestones
Table 5. Project Milestones.
Number
Description
1
2
Customer Interview Completed
Functional Specification Draft .90 Completed
MOSIS Chip: Timer built and tested in
B^2logic
Functional Specification Draft .95 Approved
Functional Specification Final Approved
Simulate the pulse generator and transformer
interfacing in PSPICE
MOSIS Chip: Comparator built and tested in
3
4
5
6
7
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Completion
Date
9-16-10
9-24-10
10-3-10
10-8-10
10-15-10
10-15-10
10-17-10
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FUNCTIONAL SPECIFICATIONS
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8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
.
.
.
.
B^2logic
.
.
Simulate
the voltage multiplier in PSPICE
. Deliver .edf file to Dr. Osterberg
.Design Document first draft Completed
.
REV. 1.0
MOSIS Memory built and tested in
B^2logic.blt
Simulate the pulse generator, transformer, and
voltage multiplier interfacing in PSPICE
Design Document version .95 Completed
.edf file testing completed
.edf file completed and sent to Dr. Osterberg
Simulate the pulse generator, transformer,
voltage multiplier, and load interfacing in
PSPICE
Design Document version 1.0 Completed
All parts ordered
Construct and test the pulse
generator/transformer
Construct and test the prototype voltage
multiplier
Construct and test the final voltage multiplier
(w/ high voltage components)
Test the interface between the pulse generator,
transformer, and voltage multiplier
Final Report First Draft Completed
Test the interface between the pulse generator,
transformer, voltage multiplier and load
Case built and the device completed
Final Report version .95 Completed
Final Report 1.0 Approved
Founders Day Presentation Complete
PAGE 23
10-31-10
10-31-10
11-5-10
11-7-10
11-14-10
11-19-10
11-19-10
11-19-10
11-30-10
12-3-10
12-17-10
1-31-10
2-14-11
2-21-11
3-7-11
3-13-10
3-14-11
3-29-10
4-1-10
4-8-10
4-12-10
Customer Interview
As part of the Senior Design Project Requirements, a customer was found and interviewed.
Team Chub interviewed Tony Chang from Google. Tony works on Google Chrome, which
uses random number generation in a variety of ways. Tony shared ways that he receives
random numbers and how he uses them. It was very helpful in getting a customer’s
perspective for the project.
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.
.
.
. Draft .90
Functional Specification
.
. Chub to have the functional specification draft .90 be done by
It was critical for Team
.
September 24th in order. to give Dr. VanDeGrift and Dr. Hoffbeck enough time to make
comments on the document.
.
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MOSIS Chip: Timer built and tested in B^2logic
The timer part of the MOSIS chip design will be built in B^2Logic.blt. Also, once the timer is
constructed in B2logic.blt the .edf file will be sent to Dr. Osterberg in order to know the size
of the chip layout thus far. Testing is incorporated with the design.
Functional Specification Draft .95
The Industry Representative will review this draft. After draft .90 has been approved, it will
automatically become draft .95. It is critical to have this done on time in order to give the
Industry Representative plenty of time to review it.
Functional Specification Final
This is after the advisors, Dr. VanDeGrift and Dr. Hoffbeck, and the Industry Representative
have both approved version 0.95. Once approved this final specification is called version 1.0
Simulate the Pulse Generator and Transformer in PSPICE:
Simulate the circuit in PSPICE to provide help with the actual building and implementation of
the analog circuit.
MOSIS Chip: Comparator built and tested in B^2logic
This week the comparator part of the MOSIS chip design will be built in B^2logic.blt.
Simulate the voltage multiplier in PSPICE
Simulate a voltage multiplier in PSPICE to provide insight in how the circuit will work.
Deliver .edf file to Dr. Osterberg
Send initial .edf file to Dr. Osterberg. This is so he can keep track of how big the layout is
getting for the MOSIS chip.
Design Document first draft Completed
The required design document first draft will be completed by November 5th to allow time for
corrections and comments.
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.
.
. and completed
MOSIS Memory tested
.
.
This week the memory .needed in the MOSIS chip in order to store 8-bits will be constructed
in B^2logic.blt.
.
.
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Simulate the pulse generator, transformer, and voltage multiplier interfacing in
PSPICE
Simulating the pulse generator, transformer, and voltage multiplier in PSPICE to understand
how interfacing between each will work.
Design Document version .95 Completed
The Industry Representative will review this draft. After draft .90 has been approved, it will
automatically become draft .95. It is critical to have this done on time in order to give the
Industry Representative plenty of time to review it.
.edf file testing completed
Testing will be done on the .edf file constantly to ensure the correctness of the circuit. The
testing must be done by November 19th.
.edf file Completed and sent to Dr. Osterberg
The final edf file of the MOSIS chip will be sent to Dr. Osterberg.
Simulate the pulse generator, transformer, voltage multiplier, and load interfacing
in PSPICE
The pulse generator, transformer, voltage multiplier, and load interfacing will be done in
PSPICE to help with the understanding of how they will work in a real life scenario.
Design Document version 1.0 Completed
This is the final version of the design document. This document is approved after Dr.
VanDeGrift, Dr. Hoffbeck, and Mr. Haner have signed off on approval.
All parts ordered
All of the parts needed for the project will be ordered at this time.
Construct and test the pulse generator/transformer
The pulse generator and transformer will be constructed in Shiley 206.
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.
.
.
. prototype voltage multiplier
Construct and test the
.
. will be constructed and tested in Shiley 206.
A prototype voltage multiplier
.
.
Construct and test the
. final voltage multiplier (w/ high voltage components)
FUNCTIONAL SPECIFICATIONS
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The final voltage multiplier will be constructed with the high voltage components in Shiley
206.
Test the interface between the pulse generator, transformer, and voltage
multiplier
The pulse generator, transformer, and voltage multiplier will be interfaced at this time after
each component being tested several times.
Final Report First Draft Completed
The final report first draft will be completed at this date to ensure enough time to respond to
all comments given.
Test the interface between the pulse generator, transformer, voltage multiplier
and load
Connect the entire analog portion together. Doing this early allows for lots of time to debug
the circuit if needed.
Case built and the device completed
The case will be built for the device, and the device will be interfaced with all components.
This will leave two weeks of purely testing the device.
Final Report version .95 Completed
The Industry Representative will review this draft. After draft .90 has been approved, it will
automatically become draft .95. It is critical to have this done on time in order to give the
Industry Representative plenty of time to review it.
Final Report 1.0 Approved
This is the final version of the final report. This document is approved after Dr. VanDeGrift,
Dr. Hoffbeck, and Mr. Haner have signed off on approval.
Founders Day Presentation Complete
The Founders Day presentations are scheduled for April 12, 2011. Team Chub expects the
project to be entirely completed and presentation well rehearsed by this date.
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FUNCTIONAL SPECIFICATIONS
RNG
Risks
.
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REV. 1.0
PAGE 27
Table 6. Project risks and contingencies.
Risk
Severity Likelihood
Geiger tube is damaged
High
Low
Geiger tube fails to generate desired output
High
Low
No useful level of radiation
Low
Low
MOSIS chip malfunctions
High
Low
Geiger tube is damaged
The Geiger tube is the most expensive part of the device, accounting for about 45% of
the team's budget. As a result, no backup tube can be purchased if the current one
breaks. The tube is rated to operate under a maximum of 650 volts, and if this voltage is
exceeded, the tube could be damaged.
To prevent this risk, the circuit will be constructed and tested thoroughly before
inserting the Geiger tube, in order to ensure the operating voltage is well below the 650
volt mark.
In the event the tube does break, we will use a function generator to simulate the pulses
for input into the MOSIS chip that would otherwise be coming from the Geiger tube
output.
Geiger tube fails to generate desired output
There is a possibility that the Geiger tube will not output the expected current spike,
rendering its output incompatible with the input of the MOSIS chip. To prevent this, a
test circuit will be constructed and the tube's output verified.
If our circuit requires troubleshooting, we will detect this specific problem by
connecting the output of the Geiger tube to an oscilloscope and measuring the pulses,
which will help us identify a problem with the Geiger tube output.
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.
.
.
No useful level of radiation
.
.
There is a chance that.the amount of background radiation will be either too high or too
low for our device to operate
properly. In this event, we will use a function generator to
.
simulate the pulses for. input into the MOSIS chip that would otherwise be coming from
FUNCTIONAL SPECIFICATIONS
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the Geiger tube output.
MOSIS chip malfunctions
Though not likely, there is always a possibility that the MOSIS chip will return from
fabrication and not work properly. This could be due to an error in logic, or an error in
the fabrication process. To ensure no logic errors occur, the circuit will be designed and
simulated thoroughly in B2Logic before transforming it into a MOSIS chip design using
BLT. The entire process will be monitored by Dr. Osterberg for an additional layer of
error checking. To account for potential errors in the fabrication process, a packet of 5
MOSIS chips is delivered, increasing the probability that at least one will function
properly.
While the MOSIS is being manufactured, a CPLD will be created to be used for testing
purposes. In the event we receive no functioning MOSIS chips, we can use this CPLD
in our finished product to simulate the same logic as the MOSIS chip would provide.
Resources
Personnel
Identify who is working on the project and their general or specific role:

Ashley Donahoo. Fall Team Lead, MOSIS.

Colton Hamm. Spring team lead, Analog Circuit Design

Matt Johnson. MOSIS.

Alex Brotherston, Analog Circuit Design
Preliminary Budget
Table 7 contains the budget for Team Chub’s project:
Table 7. Preliminary Budget
Line Category
1
1.1
Description
Number
Seven Segment Display
# of parts
3
Materials
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Rate
Amount
Subtotal
$15
$45
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.
.
.
.
LED
. Cable
Serial
.
555
. Timer
Resistor
.
Capacitor
.
FUNCTIONAL SPECIFICATIONS
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1.2
1.3
1.4
1.5
1.6
1.7
REV. 1.0
20-1 Step-up Transformer
Diode, high voltage
Capacitor, high voltage
Geiger Tube
1Mohm Resistor
10Mohm Resistor
Filtering Capacitor, high
voltage
9V Battery
TOTAL
PAGE 29
1
1
1
2
2
1
3
3
1
1
1
.95
$8
.95
.25
.45
10.95
.15
.45
93.95
.25
.25
.95
$8
.95
.50
.90
10.95
.45
1.35
93.95
.25
.25
1
1
.45
4.00
.45
4.00
$167.95
1.1 Output
In order to show the 8- bit output of the MOSIS chip, 3 seven segment displays will be
required. An LED will be required to show when a particle is detected.
1.2 Serial Cable
A serial cable is required for the optional output expansion that allows the device to interface
with a computer.
1.3 Oscillator
A 555 timer, two standard resistors, and two standard capacitors are required for the oscillator.
1.4 Transformer
A 20-1 step-up transformer is required to achieve the voltage needed for the Geiger tube to
operate correctly.
1.5 Voltage Multiplier
Three diodes and three capacitors are required to further amplify the voltage for the Geiger
tube.
1.6 Sensing
The sensing unit requires a Geiger tube, 1 Mohm resistor, 1 10Mohm resistor, and a high
voltage filtering capacitor.
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.
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1.7 Power Source .
.
A 9-V battery is required. to power the device.
.
.
FUNCTIONAL SPECIFICATIONS
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Equipment
Basic lab equipment, such as DC power supplies, digital multimeters, oscilloscopes, LCR
meters, and soldering equipment will be necessary for the design and implementation of the
radiation-based random number generator.
Facilities
Designing and building the input and output parts of the device will require the space and
equipment in Shiley 306. Computers in the engineering building will also be used for design
and simulation of both the analog circuitry and the digital MOSIS chip
Conclusion
The design’s primary purpose is to provide a truly random number to the user. The RadiationBased Random Number Generator uses a 9-volt battery to power a Geiger tube which then
takes in radiation particles sending voltages to a MOSIS chip. The chip measures the time
between radiation events. Once three events have been detected, the MOSIS then compares
the two times between the three events. Once 8-bits have been assembled, the random
number is outputted to a seven segment display. The challenges and the successes depend on
the powering of the Geiger tube correctly to the MOSIS chip. These challenges will be the
most time consuming.
The main goal of this project is to design and implement a fully functional device that senses
radiation and then outputs a random number in a seven-segment display. An optional goal is
to interface the device with a computer, in order to give the customer a more viable way of
receiving the random numbers.
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.
.
.
.
Glossary
.
.
Passive Components: Electrical
components that do not require a power source, such as
.
resistors, inductors, and capacitors.
.
FUNCTIONAL SPECIFICATIONS
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Active Components: Electrical components that require a power source, such as amplifiers.
References
[1] http://en.wikipedia.org/wiki/Random_number_generation
[2] http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=132
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