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
3D Model
Lid
μC
PCB
Battery
Case
ANSYS Results
Tamb = 55°C
ANSYS Results
Tamb = 95°C
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
𝑓𝑛 = 𝐶
𝐸𝐼𝑔
𝑤𝐿4
Where C = Modal constant
E = 2.7e6
b = 30mm =1.18 inches
h =1/8 inch
I = bh3/12 = 0.000192
g = 386 in./s2
p = 1850 kg/m³ = .0668 lb/in3
L = 35mm = 1.378 inches
W = pbhL = 0.0136 lb
w = W/L = .00985 lb/in.
𝑓𝑛 = 3.56
2.7 ∗ 106 ∗ .000192 ∗ 386
.00985 ∗ 1.3784
𝑓𝑛 = 8450 Hz
Solutions
Aluminum Case
• Aluminum Case for Harsh Environment
• Watertight
• Integrated Standoff
•No Integrated Flange Mount
Hammond Mfg.
1590Z Series
Various Sizes Available
Plastic Case
• Lightweight Plastic Case
• Integrated Flange Mount
• Integrated PCB Standoff
• Black or Grey!!
Hammond Mfg.
1551 FL Series
Various Sizes Available
Test Plan
Eng Spec
Name
ES1 Easily Mountable
ES14 Mountable on Moving Part
ES2
ES13
ES13.1
ES13.2
ES13.3
ES13.4
ES3
ES4
ES5
ES7
ES7.1
ES7.2
ES6
ES8
ES9
ES10
ES11
ES12
ES12.1
ES15
ES16
Measure
Method
Process
Possible
Small Size
Volume
Harsh Environment
High Temperature
High Pressure
Oily Environment
Withstand Vibration
Set Sampling Rate in Field
No External Wires
Universal Sensor Connector
Data Storage
Start Capture
Stop Capture
Types of Sensor
Power To Sensors
Multiple Sampling Frequencies
Timestamps
High Sampling Frequency
Digital Bit Width (Accuracy)
Voltage Accuracy
Multiple Sensors
Sensor Voltage Range
Passing of Sub-specifications
Temp
Pressure
Possible
Acceleration
Present
Not Present
Present
Capacity (Time)
Present
Present
# of Different Sensors
Voltage
Frequency
Accuracy
Max Sampling Frequency
Bits per Sample
ADC LSB
Maximum Sensors
Voltage
Measure Volume
Instrument Passing Criteria
Ruler
Small (≈1in3)
Raise ambient Temp Test at CIMS Reaches 140F
Raise ambient Pres Test at CIMS Reaches 100psi
Submerge in oil
Oil tank
Withstands oil
Raise Vibration
Vibe table
Reaches 5G
Store Data
Computer Stores 60 min
-
Measure Max Freq
Max Accuracy
20kHz
12bit
-
Analog Design
Sensing 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
1
2π∗𝑅2 ∗𝐶
1
ω𝑐 =
𝑅2 ∗𝐶
• 𝑓𝑐 =
•
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
AC2626
•
0.5 C Accurate Temperature
Sensor
2.5 kHz bandwidth
•
-55 C – 150 C
0 – 5V range
•
0 – Vs Voltage Range
•
2 –axis Accelerometer
•
+/- 1.7, 5 , 15 g 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 Design
As 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 Forward
The long road to graduation
BOM – Small Design
Component
Plastic Case
MKL05Z32VFK4 (uC)
DS4420N+ (Attenuator)
MAX7403CSA+ (Low Pass Filter)
MCP73831 (LiPo Charger)
TPS61200DRCR (Boost Converter)
LiPo 3.7 240 mAh
CDRH2D18 (Inductor)
DX4R005HJ5R2000 (Micro USB)
SCHA5B0200 (microSD Socket)
2 - layer PCB
MISC
Price
Quantity
$5
$1.91
$3.69
$7.09
$0.64
$2.43
$3.39
$0.81
$0.89
$1.48
$83.70
Total
4
$20.00
4
$7.64
4
$14.76
4
$28.36
4
$2.56
4
4
4
4
4
1
Total
$9.72
$13.56
$3.24
$3.56
$5.92
$83.70
$25.00
$218.02
BOM - Large Design
Component
Plastic Case
MKL05Z32VFK4 (uC)
DS4420N+ (Attenuator)
MAX7403CSA+ (Low Pass Filter)
MCP73831 (LiPo Charger)
TPS61200DRCR (Boost Converter)
LiPo 3.7 450 mAh
CDRH2D18 (Inductor)
DX4R005HJ5R2000 (Micro USB)
SCHA5B0200 (microSD Socket)
2 - layer PCB
MISC
Price
Quantity Total
$5
4
$20.00
$1.91
4
$7.64
$3.69
16
$59.04
$7.09
16 $113.44
$0.64
4
$2.56
$2.43
$4.00
$0.81
$0.89
$1.48
$87.20
4
4
4
4
4
1
Total
$9.72
$16.00
$3.24
$3.56
$5.92
$87.20
$50.00
$378.32
Budget Allocation
Component
Cost
Small Design
$218.02
Large Design
$378.32
Programmer Cable
Dev Board
Total
$120
$13
$729.34
Risk Assessment
ID
R1
R2
R3
R4
R5
R6
R7
Risk
Effect
Casing Rupture Total System Failure
Storage Full
Data Loss
Poor Timestamp
Accuracy
Unreliable Data
PCB
Manufacturing
Latency
Battery
Overheats
Electronics get
too hot
Internal
Damage to PCB
Cause
Material Failure
Inadequate
Storage
Poorly written
code
Likelih Sever Prior
ood ity ity
Preventative Action
Prevent by selecting quality
5 casing material and seals
Person(s)
Rsponsible
1
5
2
5
2
4
10 Capacity Theory and Testing
Comparison of results with Lab
8 DAQ
Designs will be verified by third10 party
Matt
Delays in
Implementation and
Poor PCB Design
Testing
or Assembly
Device Loses
Power/Battery Explodes Temp too high
2
5
2
5
Innacurate Data
Temp too high
2
4
Vibration too high
Poor dampening
1
4
Chris/Dennis
Bryan
Bryan
10 Reduce Operating Temp
Dennis
Reduce Operating Temp, Temp
8 Compensating Filters
Dennis/Matt
Have proper vibration dampening
4 for system
Chris
Schedule (Break)
Week
1
2
3
4
5
Phase
0
Matt
PCB Design and Order
Chris
Determine Suitable Compressor Mounting Locations
Dennis
Research PCB Electrical Isolation and Heat Sinking Techniques
Bryan
Microcontroller Initialization
6
Schedule (MSD II)
Week
Phase
1
2
3
4
1
Matt
PCB Assembly
Chris
Mounting
Solutions
5
6
7
2
8
9
10
3
Dennis
Case Modification and Preparation
Bryan
Write Basic Firmware
Test Firmware
12
4
PCB Functionality Testing
Design / Build Vibration
Test Rig
11
13
14
5
PCB Performance
Testing
PCB Vibration Testing
PCB Integration
Additional Functionality
Technical
Paper
15
Questions?
El fin.