1. BT-BOX
(BLUETOOTH)
Ben Valdovinos

2. Overview
• The BT-Box is a general purpose Bluetooth based data
acquisition system that connects computers or smart
phone to sensors
• BT-Box’s technology is general purpose and its
applications are very diverse
• Applications in the medical field
• Fall Detection
• Applications in the environmental field
• Temperature and humidity sensing

3. Requirements
• Small size: 3.5” x 2.5” x 0.75”
• Bluetooth communication between BT-Box and
computer/phone
• Data storage on micro SD card
• Accepts different sensors and is reprogrammable
• System runs on re-chargeable battery
• Implement Fall-Detection Algorithm
• Optional: Development of smart phone interface

4. BT-Box Small enough to be worn
at the waistline when used
All components inside small case for Fall Detecting

5. Fall Detection Application
• The costs of falls among elderly persons in the US have
Fall Detected!!
been calculated to be nearly 20 billion $ per year [1].

6. Existing Bluetooth Based Products
• EMANT380 Bluetooth Wireless 24 bit DAQ Module
• $159
• Wireless data acquisition (DAQ) module for learning purposes
• Used with a PC for data acquisition and control.
• Bluetooth connectivity to desktop PC, notebook, or mobile phone
• 25 pin D-Sub connects to the physical world
• Supports LabVIEW, C++, and Python
Great Product, but not geared towards fall detection
LabVIEW Display

7. Existing Fall Detection Products
• Tunstall’s fall detectors automatically senses if the user
has fallen and remains immobile
• Raises an alert via Lifeline Connect
• Summon help anywhere in the home
Great Product, but limited to in home
Base station placed
Worn on the waist inside home

8. System Level Block Diagram

9. Microcontroller
Operating Clock Flash IO
Brand RTCC Price
Voltage Speed Memory Pins
Microchip
50
PIC32MX250F 3.3 128 KB Yes 21 $3.18
MHz
128B
Flexis Coldfire 66
3.3 128 KB No 134 $3.21
MCF21X MHz
Atmel
66
AT32UC3A01 3.3 128 KB Yes 144 $4.40
MHz
28
Analog 10
3.3 32 KB No 14 $5.15
ADUC7060 MHz

10. Accelerometer
• ADXL345 from “Analog Devices”
• Really small: 3mm x 5mm x 1mm
• 23uA in measurement mode and 0.1uA in standby mode
at 2.5 V
• 3-axis measurement with 10-bit resolution
• Up to 16g (1° accuracy)
• Activity/inactivity monitoring
• Single and double-tap detection as well as free-fall
detection

11. microSD Card
Supply
Type Size (mm) Price Capacity
Voltage
SD 32 x 24 x 2.1 $4.95 2 GB 3.3
mini SD 21.5 x 1.4 $12.95 2 GB 3.3
micro SD 11 x 15 x 1 $5.95 2 GB 3.3

12. Rechargeable Batteries
Outp
Type Capacity Size (mm) Lifetime Price
ut
Lithium
3.7 V 1000 mAh 50.8 x 33.5 x 5.9 $11.00
Ion
Ni-Cd AA 1.2 V 1200 mAh 50 x 10.5 dia. $1.55
Ni-MH AA 1.2 V 2500 mAh 50 x 10.5 dia. $3.99

13. Bluetooth Module
• Connection to smart phones will be easier
with Bluetooth
• Adds usability, convenience, and ease-of-use
• Buying a module is faster than designing my
own PCB
• flash, crystal, filters, antenna, and amplifiers included
in RN-42
• UART communication with microcontroller

14. Bluetooth Modules
WT12 WT21 RN-41 RN-42
TX POWER 3 dBm 7 dBm 15 dBm 4 dBm
CLASS 2 1.5 1 2
RANGE 30m 100-200m 100m Max 20m
OP. VOLT 3.3 1.8-3.6 3.3 2.7-3.0
Sleep
Mode
1 mA 1.5 mA 2.5 mA 0.026 mA
Power 2 mW 5 mW 31.6 mW 2.5 mW
Cost $33.00 $20.00 $24.95 $17.42

15. Experimental Results
• Accelerometer interfacing with microcontroller
• Chipkit Uno32

16. Risks & Challenges
• Bluetooth implementation
• Familiar with UART
• Minimizing size and power consumption
• Last several hours ACTIVE mode, most the time in SLEEP
• Designing the Fall Detection Algorithm
• Designing the PCB with Eagle
• Working with a 32-bit MCU
• Familiar with PIC microcontrollers

17. EE Courses
• Microcontrollers – ES 310
• Electronics – ES 330/230
• Wireless Communications – ES 485-03
• Intro to Antenna Theory – ES 485-01
• Analog and Digital Communications – ES 442
• Electromagnetic Theory – ES 430

18. Bill of Materials
Item Cost Acquired
MCU $3.18 NO
ADXL345 Accelerometer $14.95 YES
RN-42 $17.42 NO
SanDisk micro SD $5.95 NO
micro SD Socket $3.95 NO
Lithium Ion Battery $11.95 NO
USB Connector $1.20 NO
USB LiPoly Charger $14.95 NO
PCB $169.00 NO
Wires, etc $16.00 NO
TOTAL $258.55 ($89.95)

19. Schedule
MCU Programming
Environment Ready
Fall Detection
Complete Bluetooth
Save Data on Works
1
SD Card
Assemble
PCB and Box

20. References
• [1] J. A. Stevens, P. S. Corso, E. A. Finkelstein, and T. R.
Miller, "The costs of fatal and non-fatal falls among older
adults," Inj Prev, vol. 12, pp. 290-5, 2006.
• [2] Microchip website: http://www.microchip.com
• [3] Dr. Farahmand’s website:
http://www.sonoma.edu/users/f/farahman/
• [4] SD Group Technical Committee, SD Card
Specifications: Physical Layer, Version 3.01

21. Advisors
• Project Advisor: Professor Jack Ou
• Industry Mentor: Ryan Press

22. Questions?
• www.benvaldo.com/senior-project-blog

23. Accelerometer

24. Accelerometer fall detection
• 8 interrupts
DATA_READY, SINGLE_TAP,
DOUBLE_TAP, ACTIVITY,
INACTIVITY, FREE_FALL,
WATERMARK, and OVERRUN
• Algorithm
• Determine the start of the fall
• Detect impact, which has
largest impact
• Aftermath: body doesn’t rise
immediately
• Comparing orientation
before and after.

25. Algorithm

26. SD card specifics
• Initial communication through synchronous one-bit
interface
• Host provides clock signal and can command card to
use different operating voltage
• Host prepares card for read/write of data block
• SDHC and SDXC cards can operate at 1.8-volt
• Formatting
• For SDSC cards: FAT16
• For SDHC cards: FAT32
• Power use 66-330mW (20-100mA) @ 3.3-V
• Max transfer of 50-Mbit/sec

27. Function boards
• Power, Ground, and various I/O ports
• Will be encased inside box
• Automatically identified by microcontroller

28. Basic Data Packet
Access Code Header Payload
Preamb Sync Trailer AM_ADDR TYPE FLOW ARQN SEQN HEC DATA
le Word
4 64 4 3 4 1 1 1 8 0-XXX
Accelerometer Data Payload
Header Board ID # Time Event
8 8 64 8