Department of Electrical and Computer Engineering

Team BeepachUMarch 3, 2014

Comprehensive Design Review

Department of Electrical and Computer Engineering

Team 7 Members

Eric WagnerEE

David ZeifmanCSE

Mark WagnerEE

Quanquan HanEE

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This Presentation: Overview Review: What is BeepachU?

Preview of Demonstration

Demonstration

FPR Goals/Deliverables

Questions

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Review

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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?

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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

Cheap: Each unit < $30 when mass produced

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Block Diagram

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Block Diagram

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ANT SoC Block

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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

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Audio

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Block Diagram: Speaker System LM 386 audio amplifier- $0.34 CU-115 8 Ohm speaker- $1.01 2.9mm height, 15mm diameter

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Packaging/UI

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Block Diagram: User Interface

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Power

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Block Diagram: Power Supply 3V CR-2032/VP Energizer coin cell battery 225mAh lifespan 0.79” diameter x 0.13” height $0.20 per battery One battery per keyfob, two per tag

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Antenna

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Block Diagram: Antenna + PCB Planar Inverted F Antenna

(PIFA) integrated into PCB• Isotropic, often used in cell

phones• Can be tuned manually by

scraping copper off its end

Same PCB used for keyfob and tag (reduces cost)

PCB = 1.2 x 1.5 inches

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Demonstration (Preview)

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Review of Proposed CDR Deliverables Fully functional system

• Doesn’t necessarily meet specs, but works• Powered by battery• Implemented on custom PCB not development board• Hot cold feature implemented• Beep will work and will be audible

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Demonstration A tour of the BeepachU PCB Item location using “Beep” feature Item location using “Hot/Cold”

Enjoy

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FPR Deliverables, Team Responsibilities

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Proposed FPR Deliverables Fully functional system

• System works and meets specs• System fits into packaging and has professional-

looking UI

Multiple tags on a single fob• Because we know you want it

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Individual ResponsibilitiesDave ZeifmanPolish current “Beep” and “Hot/Cold” codeImplement power-efficiency into TX/RX functionsWrite code for multiple tags per keyfob

Quanquan HanProduce and integrate final BeepachU packaging

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Individual ResponsibilitiesMark WagnerConduct power-efficiency measurementsPolish audio driving code/speaker

Eric WagnerMeasure TX/RX rangeTune antenna if possible

Department of Electrical and Computer Engineering

Questions?

Thank You

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Power Specifications (with 3.3V source) Keyfob (on)

• Sleep mode = 8.25uW (or 2.5uA)• Transmitting as master device = 8.58mW (or 2.6mA)• Transmitting + LED on = 54.45mW (or 16.5mA)• Battery indication LED = 8.25mW (2.5mA)

RX (always on)• RX sleep/search mode (10% duty cycle) = 262.2mW (or

79.5uA)• Paired as slave device = 8.58mW (or 2.6mA)• Paired as slave + beep and blink= 640.2mW (or 194mA)

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Power Usage Estimations Keyfob (TX) is on for about 2 minutes per use

• Transmitting + LED on (for Hot/cold): 60s• Working mode (for Beep): 10ms• Battery indication LED: 120s• Total = 1290.02615mAs = 0.359 mAh

Tag (RX) is used for 2 minutes per use• Hot/Cold active : 60s• Beep & LEDs active: 5s• Sleep/search mode = 55s• Total = 1130.3725mAs = 0.314mAh

Tag (RX) is on sleep/search mode for the rest of the time

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Antenna Efficiency Measurements

Band of Operation: 2.4 - 2.5 GHz

S11 = measure of power not radiated by antenna

Max return loss within band = -15dB ≈ 3.1%

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Preliminary 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

Total PriceTag = $13.47Fob = $14.01Total = $27.48

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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

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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

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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