Download - P14452: Detailed Design Review
P14452: Detailed Design
Review
Agenda
• Review (10 mins)• Updated Specifications
• Mechanical Design (30 minutes)• Temperature• Vibration• Solutions
• Analog Design (20 minutes)• Analog Signal Conditioning• Example Sensors• Power
• Digital Design (10 minutes)• Microprocessor Selection• Software Processes
• Moving Forward (10 minutes)
• Questions (10 minutes)
Review
Updated Specifications
Mechanical Design
Temperature
μC
Battery
Lid
Case
PCB
3D Model
Tamb = 55°C
ANSYS Results
Tamb = 95°C
ANSYS Results
ANSYS Results
Excel Model
Excel Formulas
Excel Results
Excel Results
Excel Results
Vibration
“Most component failures in a severe vibration environment will be due to cracked solder joints, cracked seals, or broken electrical lead wires.”
Vibration-related Failure
• Cause:• Due to stresses from relative
motion between component body, electrical lead wires, and the PCB
• Solutions:• Tying or cementing
component to PCB to eliminate resonance
• Proper component placement on rectangular PCB
• Attributes• Most severe during resonant
conditions• Can develop when component
body acts as mass and lead wires act as springs
• Most severe conditions at center of PCB
• On rectangular PCB, most severe conditions are when component part is parallel to short side of board
𝑓 𝑛=𝐶 √ 𝐸𝐼𝑔𝑤 𝐿4
Where C = Modal constant
E = 2.7e6b = 30mm =1.18 inchesh =1/8 inchI = bh3/12 = 0.000192g = 386 in./s2
p = 1850 kg/m³ = .0668 lb/in3
L = 35mm = 1.378 inchesW = pbhL = 0.0136 lbw = W/L = .00985 lb/in.
𝑓 𝑛=3.56√ (2.7∗106 )∗ .000192∗386.00985∗1.3784
𝑓 𝑛=8450Hz
Solutions
Aluminum Case• Aluminum Case for Harsh Environment• Watertight• Integrated Standoff
•No Integrated Flange Mount
Hammond Mfg.1590Z SeriesVarious Sizes Available
Plastic Case• Lightweight Plastic Case• Integrated Flange Mount• Integrated PCB Standoff• Black or Grey!!
Hammond Mfg.1551 FL SeriesVarious Sizes Available
Test Plan
Eng Spec Name Measure Method Instrument Passing
CriteriaES1 Easily Mountable Process -ES14 Mountable on Moving Part Possible -ES2 Small Size Volume Measure Volume Ruler Small (≈1in3)ES13 Harsh Environment Passing of Sub-
specifications
ES13.1 High Temperature Temp Raise ambient Temp
Test at CIMS Reaches 140F
ES13.2 High Pressure Pressure Raise ambient Pres Test at CIMS
Reaches 100psi
ES13.3 Oily Environment Possible Submerge in oil Oil tank Withstands oilES13.4 Withstand Vibration Acceleration Raise Vibration Vibe table Reaches 5G
ES3 Set Sampling Rate in Field Present -ES4 No External Wires Not Present -ES5 Universal Sensor Connector Present -ES7 Data Storage Capacity (Time) Store Data Computer Stores 60 min
ES7.1 Start Capture Present -ES7.2 Stop Capture Present -ES6 Types of Sensor # of Different Sensors -ES8 Power To Sensors Voltage ES9 Multiple Sampling
Frequencies Frequency ES10 Timestamps Accuracy ES11 High Sampling Frequency Max Sampling Frequency Measure Max Freq 20kHzES12 Digital Bit Width (Accuracy) Bits per Sample Max Accuracy 12bit
ES12.1 Voltage Accuracy ADC LSB ES15 Multiple Sensors Maximum Sensors -ES16 Sensor Voltage Range Voltage
Analog DesignSensing the World
Low-pass Filter
• Passes low frequency signals and attenuates signals with higher frequencies than the cutoff • Used for smoothing data • Reduces noise• Necessary for SAR style ADC
First order LPF
• Circuit above is a inverting op-amp with a RC 1st Order LPF
MAX7403 8th Order LPF• 8th order Low-pass
Elliptic Filter• 8 times faster cutoff
than 1st order LPF• Lower Band Reject
frequency• Lower ADC sampling
rate• Eliminates the need for
discrete resistors in the Analog Signal Path• Maxim EE-SIM
MAX7403 Interfacing
• I2C interfacing• Set the cutoff frequency
in software to accommodate other sampling rates• 8 pin package• About 1mV offset at 85C
Maxim DS4420• Programmable gain
amplifier• -35dB-40dB Range• -11 dB attenuation on 0-
10V range yields 0-2.818 signal• 2.88 mV accuracy with 12
bit ADC• Up to 8 devices on the
same I2C bus
Example Compatible Sensors
ADXL203• 2 –axis Accelerometer• +/- 1.7, 5 , 15 g range• 2.5 kHz bandwidth• 0 – 5V range
AC2626• 0.5 C Accurate Temperature
Sensor• -55 C – 150 C• 0 – Vs Voltage Range
LiPo Charging
• Spark Fun Power Cell – LiPo Charger/Booster• Micro USB charging• $19.99 breakout
board for testing• Eagle Files
Available for PCB layout
Schematic for LiPo Charging and Booster
https://www.sparkfun.com/products/11231
Components Required LiPo Charger and Booster
• MCP73831/2: LiPo Charging IC• Can get free samples
• TPS61200: 5 volt, 1.2A boost converter • Can get free samples • Used for powering sensors
and other components • JST connector $0.95• Micro USB SMD
Connector $1.95• Resistors and Capacitors
<$2.00
Li-Po Temperature Issues
• Prof. Landi, Chemical Engineering, said that he does not know of any technologies that can operate up to 200F
• Battery’s composition layers begin to breakdown at max temperature
• Risk explosion if operating over the indicated max operating temperature (60C)
Digital DesignAs easy as 0xABC123
Microcontroller Selection
Necessary Features
• ADC• 1-4 Channels• 12-bit Accuracy• 25 kHz Sampling Rate per
channel• Digital
• 1 SPI (SD)• 1 I2C (Attenuator Config)• 1 PWM (LPF Config)• 2 GPIO (Power Monitoring)
Freescale KL05
• 3 x 3 mm footprint• 48 MHz• ADC
• 12-bit• 12 Channels• ~800 kS/s Max
• SPI• I2C• PWM (6 Ch + 2 Ch)• ~$2 ea.• $13 FRDM-KL05Z Dev Board
Software Processes
Modes of Operation
• Charging• Not Sampling• Peripherals Disabled
• Delay• Not Sampling• Peripherals Initialized• Timer Running
• Normal• Sampling• Timer Running
Main Program Execution
Peripheral Initialization
Sampling Process (ADC Subroutine)
Write Process (SPI Subroutine)
Moving ForwardThe long road to graduation
BOM – Small Design
Component Price Quantity TotalPlastic Case $5 4 $20.00 MKL05Z32VFK4 (uC) $1.91 4 $7.64 DS4420N+ (Attenuator) $3.69 4 $14.76 MAX7403CSA+ (Low Pass Filter) $7.09 4 $28.36 MCP73831 (LiPo Charger) $0.64 4 $2.56 TPS61200DRCR (Boost Converter) $2.43 4 $9.72 LiPo 3.7 240 mAh $3.39 4 $13.56 CDRH2D18 (Inductor) $0.81 4 $3.24 DX4R005HJ5R2000 (Micro USB) $0.89 4 $3.56 SCHA5B0200 (microSD Socket) $1.48 4 $5.92 2 - layer PCB $83.70 1 $83.70 MISC $25.00
Total $218.02
BOM - Large DesignComponent Price Quantity TotalPlastic Case $5 4 $20.00 MKL05Z32VFK4 (uC) $1.91 4 $7.64 DS4420N+ (Attenuator) $3.69 16 $59.04 MAX7403CSA+ (Low Pass Filter) $7.09 16 $113.44 MCP73831 (LiPo Charger) $0.64 4 $2.56 TPS61200DRCR (Boost Converter) $2.43 4 $9.72 LiPo 3.7 450 mAh $4.00 4 $16.00 CDRH2D18 (Inductor) $0.81 4 $3.24 DX4R005HJ5R2000 (Micro USB) $0.89 4 $3.56 SCHA5B0200 (microSD Socket) $1.48 4 $5.92 2 - layer PCB $87.20 1 $87.20 MISC $50.00
Total $378.32
Budget Allocation
Component Cost
Small Design $218.02
Large Design $378.32
Programmer Cable $120
Dev Board $13
Total $729.34
Risk Assessment
ID Risk Effect CauseLikelihood
Severity
Priority Preventative Action
Person(s) Rsponsible
R1
Casing Rupture Total System Failure Material Failure 1 5 5
Prevent by selecting quality casing material and seals
Chris/Dennis
R2 Storage Full Data LossInadequate Storage 2 5 10 Capacity Theory and Testing Bryan
R3
Poor Timestamp Accuracy Unreliable Data
Poorly written code 2 4 8
Comparison of results with Lab DAQ Bryan
R4
PCB Manufacturing Latency
Delays in Implementation and Testing
Poor PCB Design or Assembly 2 5 10
Designs will be verified by third-party Matt
R5
Battery Overheats
Device Loses Power/Battery Explodes Temp too high 2 5 10 Reduce Operating Temp Dennis
R6
Electronics get too hot Innacurate Data Temp too high 2 4 8
Reduce Operating Temp, Temp Compensating Filters Dennis/Matt
R7
Internal Damage to PCB Vibration too high Poor dampening 1 4 4
Have proper vibration dampening for system Chris
Schedule (Break)
Week 1 2 3 4 5 6
Phase 0Matt PCB Design and OrderChris Determine Suitable Compressor Mounting LocationsDennis Research PCB Electrical Isolation and Heat Sinking TechniquesBryan Microcontroller Initialization
Schedule (MSD II)
Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Phase 1 2 3 4 5
Matt PCB Assembly PCB Functionality TestingPCB
PerformanceTesting
TechnicalPaper
Chris MountingSolutions
Design / Build VibrationTest Rig
PCB Vibration Testing
Dennis Case Modification and Preparation PCB Integration
Bryan Write Basic Firmware Test Firmware Additional Functionality
Questions?El fin.