Group 27- SenseWalk Mark Applegate (EE) Sara Belichki (CpE) Matthew Czarniak (CpE) Nicholas Heintze (EE)

 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.  GPS: the SenseWalk will hold the user’s saved routes to guide them when needed.  Bluetooth: the user will be alerted of upcoming instructions as they go about a route.

MCU GPS Digital Compass SD Card Bluetooth Sonar Power Supply

MCU GPS Digital Compass SD Card Bluetooth Sonar Power Supply

 The SenseWalk requires a microcontroller that contains  High flash memory-between 256 KB-512 KB  High frequency  ADC peripheral  Supports UART connection  Low power

MSP430F6659ATmega2560 Voltage Supply 1.8 V-3.6 V Frequency20 MHz Flash Memory 512 KB ADC16 channels with 12-bit resolution Supports UART Yes IDECCS/IAR Price with target board $ Voltage Supply5 V Frequency16 MHz Flash Memory256 KB ADC16 channels with 10-bit resolution Supports UARTYes IDEArduino IDE Price with target board $58.95

MCU GPS Digital Compass SD Card Bluetooth Sonar Power Supply

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 600Air Ultrasonic 400ST/R Thickness0.46”0.472” Diameter1.69”0.63” Frequency50kHz40kHz Voltage200V20V Operating Temperature -40 to +85 o C-40 to +80 o C Beam Angle15 o at -6dB55 o at -6dB Capacitance pF2400pF Receiving Sensitivity -42dB at 50kHz-65dB at 40kHz Bandwidth FilterUnknown-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 GPS Digital Compass SD Card Bluetooth Sonar Power Supply

 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 Rate2.1 mbps Distance range ~ 10 m UARTYes Voltage Supply 3.3 V Price$13.71 Data Rate2.0 mbps Distance Range ~10 m UARTYes Voltage Supply 3.3 V Price$15.95

RN-42

MCU GPS Digital Compass SD Card Bluetooth Sonar Power Supply

ls 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

 San Disk 4 GB  Petite FatFS  SD Library

 Use route planner to create CSV / GPX  Upload CSV file with waypoints to SD

SenseWalk SDCard Compass GPS Bluetooth Sonar SDCard Compass Bluetooth Sonar GPS Init() getDirection() getCurrentCoordinates() getCurrentWaypoint() sendBluetooth() calculateSonar() determineRelativePos() determineCorrection() OpenFile() CloseFile() ParseWaypoints() CurrentWaypoint() calibrateCompass() currentDirection() establishConnection() currentCoordinates() ConnectHS() Transmit() determineDistance() sendMotorCommand()

MCU GPS Digital Compass SD Card Bluetooth Sonar Power Supply

 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] [1] elopment/revisions/downloads/FinalSpecV2.pdf elopment/revisions/downloads/FinalSpecV2.pdf Output Power: 14.4W Minimum Efficiency Requirement: 73%

Magnetic & Capacitive Component Issues EMI design issues Controller & FET selection 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.

CCM DCM CCM  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  Lower energy in transformer = smaller transformer  Less windings = lower I 2 R Losses  Higher ripple current = output capacitor ESR requirements  Higher transistor and diode peak current requirements

 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

 Power MOSFET required - 600V and >2 Amps.  Experiment with MOSFETs to find best fit for efficiency.  Switching losses - Low parasitic capacitances and fast rise/fall times will combat switching losses.  Conduction losses - Low Rds(on) will combat conduction losses.

MTP2N60E (ON Semi)NDF03N60ZG (ON Semi)NDF06N62ZG (ON Semi) V DSS 600V 620V IDID 2A3A3.8A C iss 435pF312pF923pF C oss 9.2pF39pF106pF trtr 21ns8ns19ns tftf 24ns10ns28ns R DS(on) 3.3 Ohm 0.98 Ohm

 Three states: Preconditioning, Constant Current, Constant Voltage [2] Courtesy of Texas Instruments

 Capacity: 2600 mAh  Working Voltage: 7.2V  Peak Voltage: 8.4V  Cut off voltage: 5.5 V  Max Charging Current: 2 Amp  Length: 2.8"  Width: 1.45"  Height: 0.8"  Weight: 3.5 Oz

Linear  Low Cost  Low Design Complexity  Low Noise  Small size  Poor Efficiency <40%  High Heat Dissipation Switching  High Efficiency 80+%  Extended Battery Life  Higher Cost  Higher Design Complexity

Power SupplyMark/Nick SonarMark/Nick NavigationMatt BluetoothSara MicrocontrollerMatt/Sara

ItemPrice 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 boardFREE Ls20031$49.99 SD Card and Breakout Board$19.99 LSM303$19.99 Miscellanious$ Total$ Project Future Costs$150 Max Budget$1500