Transcript Group 27-SenseWalk Project

Group 27SenseWalk
•
Mark Applegate
(EE)
•Sara
Belichki
(CpE)
•Matthew
Czarniak
(CpE)
•Nicholas
(EE)
Heintze
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
Improve the independence and quality of
life for the visually impaired.
Optimize a tool commonly used by the
visually impaired.

Sonar: detect upcoming obstacles and
vibrate a motor attached at the user’s
wrist.
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GPS: the SenseWalk will hold the user’s
saved routes to guide them when needed.
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Bluetooth: the user will be alerted of
upcoming instructions as they go about a
route.
MCU
Bluetooth
GPS
Digital
Compass
Power
Supply
SD
Card
Sonar
MCU
Bluetooth
GPS
Digital
Compass
Power
Supply
SD
Card
Sonar

The SenseWalk requires a microcontroller
that contains
 High flash memory-between 256 KB-512 KB
 High frequency
 ADC peripheral
 Supports UART connection
 Low power
MSP430F6659
ATmega2560
Voltage
Supply
1.8 V-3.6 V
Voltage Supply
5V
Frequency
20 MHz
Frequency
16 MHz
Flash
Memory
512 KB
Flash Memory
256 KB
ADC
16 channels
with 12-bit
resolution
ADC
16 channels
with 10-bit
resolution
Supports UART
Yes
IDE
Arduino IDE
Supports
UART
Yes
IDE
CCS/IAR
Price with
target board
$149.99
Price with target $58.95
board
MCU
Bluetooth
GPS
Digital
Compass
Power
Supply
SD
Card
Sonar
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Distance From 1 meter to 3 meters
Sonar operate at 40kHz
Not affected by noise
Microcontroller calculate distance
Vibrate a motor at different magnitudes
proportional to distance
Senscomp 600
Thickness
Diameter
Frequency
Voltage
Operating
Temperature
Beam Angle
Capacitance
Receiving
Sensitivity
Bandwidth Filter
0.46”
1.69”
50kHz
200V
-40 to +85o C
Air Ultrasonic
400ST/R
0.472”
0.63”
40kHz
20V
-40 to +80o C
15 o at -6dB
400-500pF
-42dB at 50kHz
55 o at -6dB
2400pF
-65dB at 40kHz
Unknown
-6dB per 2 kHz
555 Timer
 Square wave is highly distorted by load.
Phase shift Oscillator
 Square wave is distorted by load.
40kHz Crystal- CMOS Inverter Oscillator
 Minimum distortion
Hex Inverter
Quad Op Amp
MCU
Bluetooth
Digital
Compass
GPS
Power
Supply
SD
Card
Sonar
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Only needs to be able to cover a short
distance (Class 1 BT modules have a
range of ~100 m, Class 2 ~10 m).
Needs to have a good data rate to ensure
no delay.
Use UART to connected to embedded
system.
Low power consumption.
Must have appropriate Bluetooth protocol
to send out audio messages to headset.
PAN1315
RN-42
Data Rate
2.1 mbps
Data Rate
2.0 mbps
Distance
range
~ 10 m
Distance
Range
~10 m
UART
Yes
UART
Yes
Voltage
Supply
3.3 V
Voltage
Supply
3.3 V
Price
$13.71
Price
$15.95
RN-42
MCU
Bluetooth
GPS
Digital
Compass
Power
Supply
SD
Card
Sonar
ls20031
5 Hz update (10 Hz max)
Up to 66 channel input
Cold Start < 35 seconds
Accuracy to 3 meters
LSM303
I2C serial interface
Operating voltage: 2.5 to 5.5 V
Supply current: 10 mA
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San Disk 4 GB
Petite FatFS
SD Library
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Use route planner to create CSV / GPX
Upload CSV file with waypoints to SD
SenseWalk
SDCard
Compass
Bluetooth
Sonar
GPS
Init()
getDirection()
getCurrentCoordinates()
getCurrentWaypoint()
sendBluetooth()
calculateSonar()
determineRelativePos()
determineCorrection()
SDCard
OpenFile()
CloseFile()
ParseWaypoints()
CurrentWaypoint()
Compass
calibrateCompass()
currentDirection()
GPS
establishConnection()
currentCoordinates()
Bluetooth
ConnectHS()
Transmit()
Sonar
determineDistance()
sendMotorCommand()
MCU
Bluetooth
GPS
Digital
Compass
Power
Supply
SD
Card
Sonar

Energy Star Requirements have become industry standard
“AC-DC External Power Supply- An external AC-DC power supply is
an EPS designed to convert line voltage ac input into lower voltage dc
output.” [1]
Output Power:
14.4W
Minimum Efficiency Requirement: 73%
[1]
http://www.energystar.gov/ia/partners/prod_dev
elopment/revisions/downloads/FinalSpecV2.pdf
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High Efficiency 80+ % capable.
Least costly of all isolated switching power supplies.
Full isolation capable.
Ideal for 0-200Watts.
Limited to 200Watts due to high peak switch currents.
Magnetic & Capacitive
Component Issues
EMI design issues
Controller & FET
selection
CCM
DCM
CCM
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Lower ripple current
Lower transistor and diode peak
current requirements
Right Half Plane Zero requires
complicated control loop
Higher energy in transformer =
larger transformer
DCM
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Lower energy in transformer =
smaller transformer
Less windings = lower I2R Losses
Higher ripple current = output
capacitor ESR requirements
Higher transistor and diode peak
current requirements
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Primary Inductance: 1.078mH
Primary Peak Current: 0.75A
Max Input RMS Current: 0.32A
Max Output RMS Current: 2.08A
Turn Ratio: 8.94
Primary & Secondary Wire Size
Core Material Selection
Gap Length, Total Winding Area
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Power MOSFET required - 600V and >2 Amps.
Experiment with MOSFETs to find best fit for
efficiency.
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Switching losses - Low parasitic capacitances
and fast rise/fall times will combat switching
losses.
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Conduction losses - Low Rds(on) will combat
conduction losses.
MTP2N60E (ON Semi)
NDF03N60ZG (ON Semi) NDF06N62ZG (ON Semi)
VDSS
600V
600V
620V
ID
2A
3A
3.8A
Ciss
435pF
312pF
923pF
Coss
9.2pF
39pF
106pF
tr
21ns
8ns
19ns
tf
24ns
10ns
28ns
RDS(on)
3.3 Ohm
3.3 Ohm
0.98 Ohm
NCP1200
90
80
70
Efficiency %
60
50
40
NCP1200
30
20
10
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Load Current (Amps)
0.8
0.9
1
1.1
1.2
1.3
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Three states: Preconditioning, Constant Current, Constant Voltage
[2] Courtesy of Texas
Instruments
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Capacity: 2600 mAh
Working Voltage: 7.2V
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Peak Voltage: 8.4V
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Cut off voltage: 5.5 V
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Max Charging Current: 2 Amp
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Length: 2.8"
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Width: 1.45"
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Height: 0.8"
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Weight: 3.5 Oz
Linear
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Low Cost
Low Design Complexity
Low Noise
Small size
Poor Efficiency <40%
 High Heat Dissipation
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Switching
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High Efficiency 80+%
Extended Battery Life
Higher Cost
 Higher Design
Complexity

Progress Percentage
Research
Design
Part Selection
GPS
Bluetooth
Progress Percentage
Software
Sonar
Power Supply
PCB Design
0
20
40
60
80
100
Power Supply
Mark/Nick
Sonar
Mark/Nick
Navigation
Matt
Bluetooth
Sara
Microcontroller
Matt/Sara
Item
Price
Bluetooth Module
$37.97
Bluetooth headset
$14.99
Microcontroller + Target Board
$58.95
White Cane
$27.45
Electronic Components
$82.65
Lithium Ion battery
$44.90
Sonar transducers
$47.54
NCP1200 Demo board (AC-DC)
FREE
Vibration motors
$7.20
BQ24123 Battery charging demo board
FREE
Ls20031
$49.99
SD Card and Breakout Board
$19.99
LSM303
$19.99
Miscellanious
$129.98
Total
$541.60
Project Future Costs
$150
Max Budget
$1500