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George Mason University Volgenau School of Engineering
Senior Design Project 2012
JACOB DILLES, PM!JASON HARTMAN!MARY HATFIELD!KEVIN NICOTERA!ELTON WILLIAMS!
DR. QILIANG LI, ECE SUPERVISOR!DR. MINGZHEN TIAN, PHYSICS SUPERVISOR!DR. PIOTR PACHOWICZ, COURSE COORDINATOR!DR. PELIN KURTAY, ASSOCIATE CHAIR!
Senior Design Project 2012
TEAM SPECTRUM!
In Progress Presentation
!" OSA = Optical Spectrum Analyzer !" We have spectrum analyzers to show:
!" Audio: up to !40kHz (10^4) !" RF: up to several GHz (10^9)
!" Optical frequencies: THz (10^15!) !" Can’t transduce these frequencies directly !" Need to shift optically
Can’t transduce these frequencies directly Need to shift optically
!" Scanning Fabry-Pérot Interferometer !" Two Mirrors = Optical Resonance !" Distance between sets 0
!" Piezoelectric motor (AKA PZT) “tuning”
!" ‘Q’ " ‘Finesse’ , Photo detector out
!" FSR mirror distance, c/2L !" Fixed mirror distance: peaks every FSR !" Moving mirrors (L): peaks every FSR
!" Fabry-Pérot OSA components: 1." SFPI: Maps I(!) " V(V) 2." Controller Ramps the SFPI 3." Measures and Display Output
The Digital OSA Controller (DSC) provides !" Numeric control over PZT voltage (DAC) !" Sampled photo detector signal (ADC)
Benefits include: !" No oscilloscope required, lower cost !" Computers are fast:
!" Real time DSP to clean up signal !" Convert units on the fly for display
!" Modernize the user experience.
1." Replicate existing functionality 2." Provide additional value !" Accuracy !" Data capture !" Usability
3." Reduce cost
Revision 5 2012 03 02 1647
Top Level Functions
• SFPI Control and Input Amplification• Signal Conditioning and Processing• Handle User Interaction:
- Select Displayed Data - Display Selected Data - Store Selected Data
• Automate: - Gain Control (AGC) - Window stabilization (anti-drift) - Unit conversion (FSR calculations)
SFPI Cavity
Piez
oele
ctric
Mot
or
Phot
odio
de
0-500V DC RampHV-BNC-F
BNC-FSmall Signal
OSA Controller - Level 0
Display PlotUser Input
Human
Persistant Storage
.CSV
!" USER INTERFACE MODULE (UIM) – USB to computer and hardware GUI
!" DATA CONTROL MODULE (DCM) – System controller; connects other modules, produces output, processes input.
!" INPUT PROCESSING MODULE (IPM) – Transimpedance amplifier for photodiode detector, 20 MHz ADC & filter.
!" SFPI OUTPUT MODULE (SOM) – Low noise, high accuracy DAC converter, HV (500V) supply & amplifier.
!" CHASSIS – Hardware and enclosure, mains power supply. Study, compact package suitable for daily use in a lab environment.
SOM(SFPI OUTPUT MODULE)
- Low noise DAC - HV (500V) amplifier - Safety Interlocks
IPM(INPUT PROCESSING MODULE)
- Detector amplification - High speed ADC - AGC hardware
UIM (USER INTERFACE MODULE)
- Handle user input - Plot selected data - Export CSV data - Unit conversion calculations - Window stabilization - Store configuration settings
AC Mains
Revision 3 2012 03 02 1648
CHASSIS
- Power supply - Enclosure Hardware - User Interface Mounting
Motor Position& Control
Detector Amplitude Processed Data
Power Supply
0-500V DC Ramp
HV-BNC-F
BNC-F
Small Signal
SFPI Motor
SFPI Detector
Status
Control
Control
DCM(DATA CONTROL MODULE)
- Function generation - Sample Aggregation - Real time preprocessing - Data buffering
Display PlotUser Input
Human
Persistant Storage
.CSV
OSA Controller - Level 1
Our project covers a wide range of technologies: HV DAC, RF Small Signal ADC, GTK/C Embedded DSP, USB, GUI and FS Storage
Human
0-500V DC Ramp
HV-BNC-F
BNC-F
Small Signal
OSA Controller - Level 2
PD Amp Analog to Digital (ADC)
HV Amp Digital to Analog (DAC)
Ramp & FunctionGenerator
Sample Processing
Unified ClockDivider
Sample Aggregation
Scan Buffer
Window Selection
DSP/ Render
AA LPF
LPFCrowbar andDisconnect
Gain Selection
GUI
Persistant Storage
CalibrationReference/Disconnect
ModeSelectionSFPI Motor
SFPI Detector
Revision 5 2012 03 02 1658
SOM
IPM
HV Monitoring
DCM UIM
Human
Window Selection
DSP/ Render
Gain Selection
GUI
Persistant Storage
ModeSelection
UIM
Kevin Nicotera, Module Manager
#"Embedded User Interface (UIM-E) #" LCD, LCDA #" Numerical Keypad, Five Buttons #" Two Rotary Encoders #" SD/MMC reader, and USB port #" Propeller Microcontroller, Raspberry Pi #" Sturdy, standard 19” rack mount enclosure #" Power: 12VDC @ 2A
!" 30-second hardware demo of what the UIM-E does
#"Software User Interface (UIM) #"1385 SLOC in C, gtk GUI interface #"Multithreaded GTK GUI #"USB communication w/UIM-E via libFTDI #"USB communication w/DCM via
libFPGAlinkData #"Real-time graph manipulation w/gtkDataBox #"Configuration and Settings windows #"Cross-platform code: tested x86 and ARM
architectures
Design
REV 0 - 2012.02.26
MODE AUTOOFF 312VEXP 63VCONF 94%FSR 1.5G
RUN - 5 Hz40 MHz / DIV
RUN/STOP
50µA / DIV
AUTO FSR
PEAK SNAP
CURSOR
AQUIRE
Implementation
!" UIM-E interface has been extensively tested !" All buttons are responsive and de-bounced !" Communication protocol is reliable over
extended durations !" Proof-of-concept test with FPGA
communication !" Need DCM implementation for actual testing
!" Development testing of software !" Timing simulations of graphing system
!" Interface Raspberry Pi with Hardware !" Used a Parallax Propeller Microcontroller to
handle low-level chores !" Communicate with Propeller via USB
!" Plot large amounts of data quickly !" Found GTKDatabox library, designed
specifically for this purpose !" Interfacing was a challenge, large effort
required
!" Scaled rotary encoder movement !" Fixed by each rotary encoder click equates
to one pixel on the graph (always constant movement no matter how many points of data)
!" CPU usage on Raspberry Pi !" Overclocking Raspberry Pi and
multithreading the user interface helped (still needs work)
!" Required: !" Save user defined settings and data !" Implement/test FPGA communication !" Improve real-time graphing algorithm !" Improve overall performance
!" Optional: !" Save user defined settings and data to USB/
SD card
Analog to Digital (ADC)
Digital to Analog (DAC)
Ramp & FunctionGenerator
Sample Processing
Unified ClockDivider
Sample Aggregation
Scan Buffer
Window Selection
DSP/ Render
ModeSelection
DCM UIM
IPM
SOM
Jason Hartman, Module Manager, DCM
#"Spartan 6 on Digilent Atyls board #"Integrated USB Connection to UIM #"16-bit Parallel connection to IPM on VHCDI
breakout board #"8-pin PMOD connection to SOM (blackbox) #"Power: 5VDC @ 4A
Hardware Breakdown
VHCDI Breakout
IPM ADC
Spartan 6 FPGA
#"Phase I/II Control Implementation #"2542 VHDL SLOC (including test benches) #"B-RAM based FIFO #"Register-based control #"FX2 USB interface to UIM
!" UIM and DCM connection has been tested with libFPGAlink sample code
!" Each component, including the top-level, was individually test benched in Xilinx ISE
!" Top-level component synthesized, and loaded
!" libFPGAlink poorly documented on the VHDL side !" Have not had successful communication with
“real” UIM !" Needs work
!" Memory Controller is Very complex !" Using B-RAM FIFO as a stop-gap until DDR2
FIFO is implemented
!" Memory Controller !" Requires interfacing Spartan 6 DDR2
memory with the current developed modules for the FPGA
!" Should take approximately 10 hours, very feasible
!" No alternatives exist due to the fact that the amount of data we will be dumping to the FPGA memory exceed the Spartan 6’s non memory resource allocation
Elton Williams, Module Manager, IPM
BNC-F
Small SignalPD Amp Analog to
Digital (ADC)AA LPFCalibrationReference/Disconnect
SFPI Detector
IPM
Sample Processing
!" LTC2203 (25 MSPS) Demo Board !" Came with DS919 USB test interface !" Works as specified
!" Photodiode (Transimpedance) Amplifier !" 4-bit 65-122dB Variable Gain !" End-to-end Original Design: !" Theory, Calculations, Simulation, PCB
!" All the stuff you teach us… actually works!?!
!" Original design from S12 (LT1226) did not function as expected !" Completely unstable under all conditions !" Back to the drawing board!
!" No good reference design exists for what we are trying to build !" Extensive research was required to
synthesize a solution from scratch
Three prototypes did not operate as predicted by SPICE Three prototypes did not operate as predicted by SPICE
!" Several issues were identified: !" Unexpected capacitive loading of the input:
RG-58 cable, BNC connectors, even the metal optics table. Order of magnitude off of initial estimate (600pF vs. 20pF)
!" PCB Parasitic are a HUGE concern for high-gain, high-bandwidth amplifiers
!" Required a more accurate SPICE model
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!" Arduino was used to set gain steps !" Diode laser and IR photodiode !" Test Results Indicate:
!" Predicted gain exceeded by 47%. Could be due to inaccurate current measurement
!" Very linear gain – R2 99.8%+ !" MSBit on V+ burned out !" Have extra PCB/Switches
y = 90048x + 18833 R" = 0.99887
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
900.00
1000.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Gai
n, k
V/A
Gain Step (4-bit)
kV/A+
kV/A-
kV/A(V#)
SPICE
Linear (kV/A(V#))
!" Mount in enclosure: !" Test RF shielding
!" Low Priority: !" Build second PCB for working V+ Bit 3
!" Integrate control with FPGA
Mary Hatfield, Module Manager, SOM
0-500V DC Ramp
HV-BNC-FHV Amp Digital to
Analog (DAC)LPFCrowbar andDisconnectSFPI Motor
SOM
HV Monitoring
Ramp & FunctionGenerator
!" LV circuit hardware completed !" PCB layout from last semester built !" On-board voltage supplies operational
!" HV unit 90% completed !" HV-HV section wired, HV-LV in progress
!" Several problems identified with PCB, after it arrived
!" Major issue was power supply trace in contact with ground plane !" Fix was to cut around the area with Dremel tool
and use a jumper wire to connect the trace !" Pad layout for DAC was too narrow
!" Fix was to fold leads under SOIC before soldering
!" Resistor numbering not consistent !" Fix: verify layout against schematic and note
errata to assist during soldering
!" Surface mount LED package polarization was different for each color. !" Each datasheet was printed and marked with
the corresponding color. !" Takeaways:
!" Triple check PCB before shipping it out! !" Triple check datasheet, assume nothing!
Implemented Safety Features: !" “Deadman” 5kV-rated vacuum relay physically
disconnects HV output from amplifier and shunts to ground
!" SCR Crowbar to discharge stray capacitance faster than relay (up to 50A/µS)
!" HV Best Practices used throughout construction – 1000% safety margin minimum
!" Low voltage fusing to protect 48V DC supply
!" Op amp section of LV circuit simulated in software
!" HV amplifier tested prior to constructing HV assembly
!" Need to develop software for microcontroller or develop alternative control solution before progress can continue !" Must implement I2C for programming DAC !" Must specify and implement protocol for
communication with DCM !" This is a challenging task
!" One transistor remains in the HV circuit !" Needs to be installed before HV testing
!" Testing SOM-LV
Jacob Dilles, Project Manger
#" Mount Points for Modules: #"UIM (&Screen/buttons) #"DCM (Demo board) #" IPM (custom PCB) #"SOM (custom PCB)
#" Provide DC power #"UIM – 12V 120W #"DCM – 5V 20W #" IPM – +5V 1.5A #"SOM - +12, +5, 48V
#" Fabricated Enclosure #"Rugged #"Bench Equipment “Feel”
#" COTS 48V 500W SMPS #" Linear regulators for
analog small signal #" COTS ATX Power for
all other needs
!" Total Labor: 400-420 Hours !" 5 Team Members !" 8 Team Meetings After & Including 31 August !" 5-8 Hours per meeting, plus individual time
!" Budget: !" $3,174.13 Spent !" $1,825.87 Remaining !" Under budget
Requirement Definition
P1
System Design/
Functional Partitioning
P2
Interface Deffinition/
Module Identitfication
P3
Research/Component Evaluation
P4
Module Design Documentaiton
P5
Design Review
P6
Project Proposal
P7
Initial Test Plan
T1
Test Design Docs
T2
Spring
Subo
ptim
al D
esig
n
Inte
r-mod
ule
issu
es
Technical Design
P8
Simulation/Verification
P9
PCB Layout/BOM
P10
Final Review
P11
Acquisition/Fabrication
P12
Test Tech Design
T3
Test Build
T4
Test Review
T5
Module Testing
I1
Integration
I2
System Testing
I3
Deliverable Prototype
I4
Fall
Epic
Failu
re
Fail
Layo
ut E
rror
Fab
Erro
r
Build
Erro
r
Integration
I2
System Testing
I3
!" Integration !" IPM to DCM !" SOM-HV to SOM-LV !" SOM-LV to DCM !" DCM to UIM
!" Testing !" DCM !" SOM-LV
!" Documentation
JACOB DILLES, PM!JASON HARTMAN!MARY HATFIELD!KEVIN NICOTERA!ELTON WILLIAMS!
DR. QILIANG LI, ECE SUPERVISOR!DR. MINGZHEN TIAN, PHYSICS SUPERVISOR!DR. PIOTR PACHOWICZ, COURSE COORDINATOR!DR. PELIN KURTAY, ASSOCIATE CHAIR!
TEAM SPECTRUM!
THANK YOU!!