Department of Electrical and Computer Engineering Team BeepachU April 11, 2014 Final Project Review

Department of Electrical and Computer Engineering Team BeepachU Members Eric Wagner EE David Zeifman CSE Mark Wagner EE Quanquan Han EE

3 Department of Electrical and Computer Engineering This Presentation: Overview  Review: What is BeepachU?  Preview of Demonstration  Demonstration  Questions

4 Department of Electrical and Computer Engineering Review

5 Department of Electrical and Computer Engineering Review: What is BeepachU?  Problem: Lost items  Solution: Cheap tracking tag that makes sounds to lead you to your item  Key Fob transmits to tag  tag makes sound for user Where’s my Wallet?

6 Department of Electrical and Computer Engineering Block Diagram

7 Department of Electrical and Computer Engineering ANT SoC Block

8 Department of Electrical and Computer Engineering Block Diagram: ANT SoC  Contains the nRF51422 “ultra low power” ANT SoC  ANT, like bluetooth, is a network protocol  ANT is pre-implemented in software on the chip  Programmed in C

9 Department of Electrical and Computer Engineering Audio

10 Department of Electrical and Computer Engineering Block Diagram: Speaker System  LM 386 audio amplifier- $0.34  CU Ohm speaker- $1.01  NPN SOT-89, = 175  2.9mm height, 15mm diameter

11 Department of Electrical and Computer Engineering Packaging/UI

12 Department of Electrical and Computer Engineering Block Diagram: User Interface

13 Department of Electrical and Computer Engineering Power

14 Department of Electrical and Computer Engineering Block Diagram: Power Supply  3V CR-2032/VP Energizer coin cell battery  240mAh lifespan  0.79” diameter x 0.13” height  $0.20 per battery  One battery per keyfob, two per tag

15 Department of Electrical and Computer Engineering Antenna

16 Department of Electrical and Computer Engineering Block Diagram: Antenna + PCB  Planar Inverted F Antenna (PIFA) integrated onto PCB Isotropic, often used in cell phones Can be tuned manually by scraping copper off its end  Same PCB used for keyfob and tag  PCB = 1.2 x 1.5 inches

17 Department of Electrical and Computer Engineering Review: BeepachU Specifications  Range: 100m (outdoor line of sight)  Battery life: 6 months for both Keyfob and Tag  Weight: Keyfob <.5 lb, Tag <.5 Ib  Response time: under 2 seconds  Size: Keyfob < 4 square inches Tag < 3 square inches  Robust Tag will not be set off by interference signal  Cost: Each unit < $30 when mass produced

18 Department of Electrical and Computer Engineering BeepachU’s ACTUAL Specifications  Range: 101 m (outdoor line of sight) ………………  Battery life: Keyfob = 10 days, Tag = 43 days …………….  Weight: Keyfob = 0.055lb, Tag = 0.046lb ………….  Response time: Instant …………………………….  Size: Keyfob = 1.8 x 1.8 inches ………………………………… Tag = 1.7 x 1.7 inches……………………………………….  Robust Tag will not be set off by interference signal………………  Cost: Each unit = $27.50 ………………………….

19 Department of Electrical and Computer Engineering Power Specifications (with 3.3V source)  Keyfob (on) Sleep mode = 8.25uW (or 2.5uA) Transmitting as master device = 1.98mW (or.6mA) Transmitting + LED on = 3.47mW (or 1.054mA)  RX (always on) RX sleep/search mode (5% duty cycle) = 762.3uW (or 231uA) Paired as slave device = 8.58mW (or.231mA) Paired as slave + beep and blink = 1.815W (or 550mA)  How long will it last? 26 minutes of beeping = 9984 beeps 43 days of sleep/search for tag Keyfob can be on for 10 days (though typically off)

20 Department of Electrical and Computer Engineering Power Usage Blunder We failed to include a low frequency external clock (LFCLK) in our PCB We have a high frequency external clock (HFCLK) External clocks are used to wake the system from sleep mode. If we replaced the HFCLK with a LFCLK we would meet specs easily LFCLKHFCLK Power Usage7uA200uA Battery Life (days)142850

21 Department of Electrical and Computer Engineering Demonstration (Preview)

22 Department of Electrical and Computer Engineering What’s In Store  Presentation of fully packaged BeepachU pair  Demonstration of beep & hot/cold functionality  Demonstration of multiple tags per keyfob  System Specification Analysis Size measurement Range demonstration and data Battery life and response time System weight

23 Department of Electrical and Computer Engineering Demonstration Enjoy

24 Department of Electrical and Computer Engineering Range Data  Range Tested Empirically  Collected data shows non- zero probability of connection at 100m  Meets specs  Experience will vary in the presence of obstructions

Department of Electrical and Computer Engineering Questions? Thank You

26 Department of Electrical and Computer Engineering Antenna Efficiency Measurements  Band of Operation: GHz  S11 = measure of power not radiated by antenna  Max return loss within band = -15dB ≈ 3.1%

27 Department of Electrical and Computer Engineering Antenna Efficiency Measurements  Band of Operation: GHz  S11 = measure of power not radiated by antenna  Max return loss within band = -15dB ≈ 3.1%

28 Department of Electrical and Computer Engineering Cost Analysis  “Each unit < $30 when “mass produced”  Mass production = 5000 units or more made  NOTES: -Each BeepachU unit requires 2 PCB’s -only the Tag requires a speaker  Price Tag = $13.47 Fob = $14.01 Grand Total = $27.48

29 Department of Electrical and Computer Engineering Multiple Tags for a Single Keyfob?  ANT allows for “star networks” with one master (keyfob) and multiple slaves (tags)  Tags must be paired with masters during initial programming  multiple tags will have to be bought alongside the keyfob

30 Department of Electrical and Computer Engineering ANT Network Security  Can use Single Channel Encryption 128-bit AES-CTR (symmetric algorithm – single shared key) Supports multiple slaves per master on single channel, but only one channel per master

31 Department of Electrical and Computer Engineering

32 Department of Electrical and Computer Engineering Block Diagram: Network Diagram (using ANT protocol)  ANT Protocol uses time-division multiplexing to separate channels  Master and Slave devices are preset only to connect with eachother