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Knowledge to Shape Your Future
Electric / Gas / WaterInformation collection, analysis and application
MekElekItroniks Design Review Battery Charger Project
November 19 2004
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Agenda
System Overview
Project Status
Mechanical Design
Electrical Design
Next Steps
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System Overview
Major Components–Plastic Injection Molded Charger Case
–Charger Labels
–Beryllium Copper Spring Electrical Contacts
–Battery Charger PCB
–Gang Connection PCB
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System Overview
Functional Requirements• User interface is the same as MC-06 with
similar front label and instructions • Same basic shape/color/material as MC-06• Vertical battery installation • Docks with MC-06, using same PCB gang
connection and wall power supply • Docks 2 Li-Ion battery packs• Flashing red LED for charge, solid green
charged• Cost similar to MC-06
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Project Status
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Battery Charger Development
Mechanical Design:– Rapid prototype generation, iteration, and
testing– SLA generated of Final Design Prototype– Spring contact design prototyped – Injection tooling formulation– Beginning Final Design Documentation
Electrical Design:– Schematic Design– EAGLE Layout– Voltage Regulation Prototype– MAX1737 Design, Prototype– Beginning Final Design Documentation
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Project Costing
Injection Molded Charger Case– Using cost estimate from MC-06– Top Plate - $2.97/unit– Bottom Plate - $1.77/unit
Electrical Spring Contacts– One time tool charge of $9,000 - $11,000– $.08 - $.12 per spring– 6 springs/unit yields a cost of about $2.92/unit
Charger PCB / Electrical Components– Cost of $26.86/unit for all electrical components
Total Cost– Materials - $35.66– Assembly - $3.83– Overhead and Profit - $17.73– Total Unit Price - $57.22
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Battery Charger Schedule11/0409/04 01/0512/0510/04 02/05 04/0503/05
Mech Design
Product Testing
PCB Layout
Elect Design
Inj. Tooling
Design Doc.
Design Doc.
Build Tooling
05/05
Manufacturing
20 Prototypes
Piece/Part Design
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MECHANICAL DESIGN REVIEW
Rory Olson
James Franklin
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Design Overview
Highlights–Updated Design
•Battery Alignment Slots
•Electrical Spring Contacts
–Accommodates Ergonomic Battery Pack
–Exterior similar to MC-06
Features–Curved Battery Pocket
–Drain / Mounting Boss
–Beryllium Copper Electrical Contacts
–Contact Alignment using PCB Design
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Design Overview
Battery Charger Top Plate–Curved Battery Pocket
•Designed around Battery Pack shape
–Three Contacts Slots
•Contact Alignment Fins
–Prevents Shorts
–Pass Core
•Contact Slots
•No need for Expensive Slide Mechanism
–Drain Boss
•Drain Foreign Materials
•Adds Surface Mounting Option
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Design Overview
Battery Charger Bottom Plate
–Similar to Previous Design
–Removed Interior Support Flanges
–Drain Boss Holes
•Moved small Label on Bottom
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Design Overview
Printed Circuit Board–Single Layer PCB
–Sandwiched between Top and Bottom Plates
–Beryllium Copper Spring Contacts
•Mounted underneath of PCB with PEM Nuts and Mounting Screws
–PCB Alignment Slots
•Spacing
•Prevents Shorts
–Battery Pocket Cut-outs
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Design Overview
Beryllium Copper Electrical Spring Contacts
–Beryllium Copper chosen for its formability, high electrical conductivity, high fatigue strength, and corrosion resistance
–Used deflection model to ensure 1/2 lb contact load per contact
–Optimized design using infinite fatigue life model
–Slope face to accommodate sharp battery edge
–Mounted directly to PCB with threaded PEM inserts
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Design Overview
Basic Assembly–Spring contacts mounted to PCB through PEM nuts using screws
–Board captured between case halves
–Two halves screwed together with six mounting screws
–Instruction label place on label surface
–Rubber feet attached to bottom plate using adhesive
–Units connected together using previous gang connection PCB
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Electrical Design Overview
Joe Cote
Lee Solum
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Design Overview
Highlights–Design new charging circuit
•Accommodate one cell Li+ battery pack
•Incorporate original gang connectors
•Maintain original display characteristics
–Meet FCC class A requirements
–Conform to PCB real-estate
Features–Safely and accurately charge battery
–Maintain interconnectivity with MC-06
–Maximize efficiency while minimizing cost
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Design Overview
Charging IC Selection–Logic vs. Microcontroller
•Pros and cons
–Designed for Li+ batteries
•Accurate charging capabilities
•Integrated safety features
–Incorporated Charge Status
•Voltage detection
•Current detection
–Maintain Charge
•Reverse leakage protection
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Design Overview
Voltage Regulation and Protection
–Input Voltage
•Maintain constant voltage
–Noise Prevention
•DC plug protection
•Emissions
–ESD
•Incorporated protection
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Design Overview
Alternate Design–MAX1737
•Incorporated Design
•Expandability
–Pros
•Size
•Component count
•Greater protection
–Cons
•Cost
•Cost
•Cost
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Design Overview
Layout–Software
•EAGLE
–Component Placement
–Routing
–Footprints
•OrCad
–Itron compatibility
–Conflicts
•Importing
•Cross Compatibility
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Next Steps
Mechanical Design:– Design Documentation / Fabrication Drawings– Formulate Plastic Injection Molding Tooling– Build Plastic Injection Tooling– Create Mechanical Prototypes– Assemble Prototypes– Product Testing
Electrical Design:– Design Documentation / Schematics– Create Electrical Prototypes– Product Testing