Department of Electrical and Computer Engineering

Team BeepachUApril 11, 2014

Final Project Review

Department of Electrical and Computer Engineering

Team BeepachU Members

Eric WagnerEE

David ZeifmanCSE

Mark WagnerEE

Quanquan HanEE

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This Presentation: Overview

Review: What is BeepachU?

Preview of Demonstration

Demonstration

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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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 NPN SOT-89, ᵦ = 175 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 240mAh 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 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

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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

Cost: Each unit < $30 when mass produced

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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 ………………………….

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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)

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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

LFCLK HFCLK

Power Usage 7uA 200uA

Battery Life (days) 1428 50

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Demonstration (Preview)

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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

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Demonstration

Enjoy

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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

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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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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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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

PriceTag = $13.47Fob = $14.01Grand Total = $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