Midway Design Review

Advisor: Professor Russell Tessier

Team:Michael Shusta

Lucas RootBrandon Thorpe

Gilbert T. Kim

Outline• MDR Deliverables and PDR Concerns

• Development Approach

• Design Decisions and Progress

• Current and Projected Costs

• Patenting and Competition

• Meeting MDR Goals

• CDR Goals

MDR Deliverables PDR ConcernsFor MDR:

– IDB finalized with preliminary implementation– Locking mechanism design and prototype– Simple routines on the AIRcable– BlackBerry “hello world”

PDR Concerns:– Current and power requirements– Power storage and delivery– Cost of device in pilot run– Competing technology

Development Approach

• Weekly PowerPoints to update progress– Discuss and plan design of hardware and

software components – Group insight into individual problems– Motivate progress

• Team email account

• Subversion for code and group documents, repository of resources

System Overview

Client

Server

Bluetag Database

Store Inventory

Locked Item

System Elements

Server:IDB

IDB• Can establish RSA secure XML based

channel with client software• Can connect to and query the Bluetag

database as well as a demo store database

• Currently handles client requests synchronously, multi-threading is incomplete

• MDR goals met

Lock• Mechanism View via Prototype Demo

– Linear, Pull-type, Spring-Loaded Solenoid– Rotating Latch Holds Clothing Pin– Coil Suppressor– Solid-State Relay Control– See MDR Design Report for in-depth

discussion of physics, parts selection, force diagrams, etc.

SolidWorks View

•3D printed using ABS plastic/photopolymer resin•Assemblies can be verified/animated before fabrication

AIRcable Update• Purchased chip and hand-soldered to DIP

connector

• Ran simple routines on the AIRcable, met MDR goal

• Unstable system

• Discontinued product

line

AIRcable Debugging• Ability to connect to and program AIRcable

sporadic• Troubleshooting steps:

– Installed and learned Linux Bluetooth support– Visual inspection, ohmmeter check– Pin voltage under different operating conditions– Continued dialog with development team

• What went wrong?– Damage while soldering– Faulty chip– Damaged during operation

Tag Bluetooth Redesign• Separate module and microcontroller with UART

communication

• Roving Networks RN-41:– Small, low power, configurable, DIP breakout, low

cost, UART, widely used

• PIC 16F688:– Small, low power, low cost, UART, DIP, advanced

development tools

TXRX

RXTX

RN-41 16F688

Powering Bluetag• Bluetooth Module and Microcontroller

– Rn-41: 30 mA connected, .25-2.5 mA deep sleep at 3.3 V

– 16F688: 640 uA normal operation, 11 uA deep sleep at 3.3V

• Solenoid– SS2EP: 7W at 100% duty cycle at ~3.3V

Important Specification: peak power delivery of battery system must be at least 7.101W (solenoid + transceiving)

Battery Life EstimateAssumption:•The idle mode dissipation (8.23mW) of the control circuitry dominates its power demands

Performance Metrics:•One: Assume an up-time and estimate the maximum number of purchases•Two: Assume a maximum number of purchases and estimate the up-time

Powering Bluetag

Battery Life Estimate

t7

u3600108.23- -3

β is the total energy capacity of the battery system in Joules∆t is the duration of time the solenoid is energizedu is the number of hours between rechargingτ is the number of purchases

Ex. Let u = 8 hours, ∆t = 5 seconds and a battery of 8 W-h is used: lock would last 816 cycles before fully exhausting its battery

Ex. Setting τ=5 for an 8 W-h battery with ∆t = 5 seconds gives an uptime of 966 hours, or about 40 days

31023.83600

t7-u

What do these metrics tell us?•Battery must deliver high transient power a few times per charge•Clothing pin should be spring-loaded to minimize power draw window•Lithium-ion battery is proper choice:

-highest energy density per unit weight of commercial chemistries-available rechargeable, cell voltage near 3.3V-see MDR Design Report for in-depth discussion

What don’t these metrics tells us?•Probabilistic model of battery life (purchasing is a Poisson process!)•Relationship between mass, volume and capacity of batteries•Battery terminal design techniques

Powering Bluetag

Programming the BlackBerry

• Decided on BlackBerry JDE Plug-in for Eclipse– Involved configuration but familiar

environment

• Use of Simulators

• Enabled real-time phone monitoring

Basic Flow of the Graphical UIWindow One:

Input username and password

Window Two:Item ID entry

Window Four:Continue Shopping

Yes

Window Three:Item info & confirm purchase

Yes No

No

The BlackBerry UI APIs• Screen components

- Standard screen layout - Default menu

• Field components- Standard UI element for options, check boxes, lists, text fields &

labels, and progress bar controls

• Layout managers- Horizontal- Vertical- Left-to-Right flow

User Interface Progress

• Simple UIs using BlackBerry simulators

• Formatted and installed UIs on BlackBerry

Progress Block Diagram

HelloWorldLabelFieldRichTextField

Sample GUIHorizontalFieldManagerVerticaltalFieldManagerBitmapFieldBitmapLabelFieldBasicEditFieldEditField

Accomplished

Processing

Current and Projected Costs• Prototype Cost: $193 - $243

– PIC 16F688: $2.31– Lithium Ion Battery: $10– Ledex 2EP Solenoid: $20– Crydom SRR: $1– 3D Printing: $75-$125– PCB Fabrication: $50– RN-41: $34.91

• Development Costs: $49.66– PIC Development Board: $15.95– PICKit 3: $33.71

Patenting and Competition

• Met with CVIP Director Nick DeCristofaro– Proceed after prototype– One year window after disclosure

• Potential Competition Includes:– Phone based barcode scanners– Resonant tags with data storage– DoCoMo cell phone purchasing

MDR and CDR Goals• All MDR goals met

– IDB– AIRcable– Lock Design– BlackBerry Programming

• CDR Goals– UI completed– Full SolidWorks– PCB– Embedded Programming