Final Presentation P14452
Overview ● MSDI Review ● MSDII ○ Customer Needs ○ Detailed Design Revisited ○ Requirements ○ Build ○ Functional ○ Test Decomposition ● Reflect ○ Concept Selection ○ Detailed Design ○ What Remains ○ Lessons Learned
MSDI Review
Customer Needs
Requirements
Functional Decomposition
Concept Selection
Benchmarking Device Our DAQ MSR145 MSR160 Slice Micro Total Cost ~$80 $1018 $1417 ~$7000 Number of 2 1 1 3 Sensors Max Sample 20,000 Hz 50 Hz 1,000 Hz 120,000 Hz Rate Capture 4M Samples 4M Samples 2M Samples 2M Samples Duration (8GB SD) (8GB SD) Input Voltage 0-2.5V 0-10V 0-10V 0.5-23.5V Bit Width 16 Bit 12 Bit 12 Bit 16 Bit
Detailed Design Overview ● Thermal Analysis ● Vibration Analysis ● Analog Signal Processing ● Digital Control
Thermal Analysis
Vibration Analysis ● Resonant frequency of compressor found to be 6 Hz in X and Z, and 12 Hz in Y ● Theoretical resonant frequency of PCB calculated to be 8450 Hz
Analog Signal Path ● 2.5mm Jack ● MAX7403 Filter ○ 8th order Low-pass filter ○ Adjustable cutoff frequency ● MAX9939 PGA Adjustable gain factor ○ 0.2 - 157 V/V ■
Digital Control ● Freescale KL25Z ○ 48 MHz ○ 32-bit ○ SAR ADC ■ 16-bits ■ 1 MSPS ○ SPI ○ USB
MSDII
Detailed Design Revisited ● Enclosure Selection ● Printed Circuit Board Design ● Microcontroller Roulette ● Bill of Materials
Enclosure Selection BEX Series 1 ● Aluminum ○ Gaskets and Endcaps ○ ○ Flange Mounts Perfect size for PCB ○ Needs Adapter Plate ●
PCB Design (Revision 1) ● Single Board Small Footprint ○ Low Profile ○ ● Freescale KL05Z ● Problems ○ Missing Protection Diodes USB Backwards ○ No Battery Connector ○ Signal Connector Pads ○ Incorrect Wrong SD Pads ○
PCB Design (Revision 2) ● Daughter Board Signal Conditioning ○ Power ○ ○ microSD ● Problems Battery Connector ○ ○ Diodes Backward Power Switch ○ Buck-Boost Enable ○ SD Pad inverted ○ ○ Header Spacing
Microcontroller Roulette ● STMicro STM32F373 ● Freescale KL05z 3 Sigma-delta ADC 48 MHz ○ ○ SD Interface 4 KB RAM ○ ○ $250 Dev Board No USB ○ ○ ● TI MSP430 ○ $13 Dev Board SAR ADC MBED ○ ○ <8 MHz Clock ● WINNER: Freescale KL25z ○ < $5 Dev Board 48 MHz ○ ○ ● Cypress PSOC ○ 16 KB RAM Analog Front-end USB ○ ○ Configurable Logic $13 Dev Board ○ ○ Small Input Range MBED ○ ○
Bill of Materials Item Quantity Cost FRDM-KL05Z 1 $12.95 BOX Exclosure 1 $10.93 PCB 1 $33 MAX7403 (LPF) 2 $3.76 ea. MAX9939 (PGA) 2 $1.68 ea. LiPo Battery 1 $1.20 Sensor Ports 2 $0.50 ea MISC ~$10 Total Cost: ~$80
Testing Overview ● Enclosure Vibration Testing ● PCB Testing ○ Power Conditioning ○ Analog Signal Path ● Software Testing ○ Microcontroller Firmware ○ DAQ Configurator
Enclosure Vibration Testing ● B & K shaker table ● SigLab software ● Accelerometer on shaker table and top of enclosure
Enclosure Vibration Testing Random - Chirp - w/o Rubber w/o Rubber Endcaps Endcaps Chirp - Random - w/ Rubber w/ Rubber Endcaps Endcaps
PCB Testing: Power ● The output of the boost converter is dependent on the resistors R1 and R2 ● The design had the resistors reversed but this was fixed
PCB Testing: Power ● The Li-po charging chip was working ● This is proved by the status pin being high when the battery is charging ● The status pin is connected to an input on the microcontroller
PCB Testing: Analog Path Output of Filter Output of PGA Sensor input from function Vout range 0.25V - VDD generator 0-2 Vpp input @ VCOM= VDD/2 VOUTA = VCC/2 - Gain * 1kHz VOUT = (VIN - VCOM) + VOS (VINA+ - VINA-) + Gain * VOS VOS-INHERENT = (VOUTA - VCC/2)/Gain
PCB Testing: Low-pass filter Fc= 1MHz, Fc= 1MHz, Fout= 10Hz Fout= 11kHz fC = fCLK / 100 Fc= 1MHz, Fc= 900kHz, Fout= 100Hz Fout= 10kHz
SW Testing: Firmware ● Completed: SD Card ○ Read ■ Write ■ ○ PWM (LPF) ADC ○ Internal Square ■ Wave ● In Progress: ADC External Signals ○ PGA ○ On-board 3-axis ○ Accelerometer
SW Testing: Configuration ● Completed: File Manipulation ○ New ■ Save ■ ■ Open Exit ○ Load / Store Settings ○ ● In Progress: ○ Generation of Standalone Executable
Reflect: What Remains? ● Mechanical ● Digital Seal Enclosure Complete Firmware Testing ○ ○ ○ Install Power Switch ○ USB Mass Storage ● Analog ● Documentation ○ Update PCB Design to ○ User Manual Fix Problems Found in Developer Manual ○ Testing Find replacement for ○ PGA (Wide Input)
Reflect: Lessons Learned ● Mechanical ● Electrical Existing enclosures are READ Datasheets ○ ○ abundant ○ Consult Experts Cross-Discipline Design Twice, Build Once ○ ○ knowledge is important Simulate Early, Simulate ○ Use intuition to validate Often ○ simulation results ○ Triple check designs before ordering
Reflect: Lessons Learned ● Computer ● Overall Best Processor != Best Communication with ○ ○ Solution Customer Dev Board vs. Full Frequency ■ ■ Custom Expectations ■ ADC Roulette Get it in Writing ■ ■ ■ PSOC Trap ○ Testing in MSDI SD Cards - Not That Easy Importance of a ○ ■ Prototype
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