Portable Rechargeable Output Power Supply (PROPS) Mid-Semester Presentation February 28, 2008

Team Members Daniel Evans – Housing Charging Circuit Shane Morrison – PCB Fabrication PIC Interfacing Drew Mills – Testing Charging Circuit Josh Gentry – Output Circuit PIC Interfacing

Outline: Problem Statement SolutionConstraints Approach/Trade offs ReferencesQuestions

Problem Commercial Power Supplies: –Not Portable Bench top and Stationary Can only be used where AC is available Relatively large and heavy

Solution Portable Power Supply –Lightweight and Portable –Rechargeable –Variable outputs –Large display to show voltage and current output

Proposed Layout

Top Level Diagram

Technical Constraints Variable output from 1-12 volts ‒ 0.1 volt increments Tracking output from -10 to 10 volts Current up to 3.35 amps Output Ripple Voltage less than 5% Output error no greater than ± 50mV Runtime of 1 hour at full capacity

Power Supply Comparison TENMA [1] PS-1 [2] PROPS OutputVoltage 0 to 40 VDC 1.2 to 15 VDC 1 to 12 v -10 to 10 v tracking InputVoltage90~265VAC 24 VDC / 18 VDC Rechargeable Battery 120 VAC / 14.8 VDC Rechargeable Battery Price$200.00$180.00$250.00

Practical Design Constraints Economic –Manufactured for $ Built in Power Supply Rechargeable Battery Display Screen –Marketed for $250.00

Practical Design Constraints Manufacturability –Size 14” x 9” x 7” –Weight < 10 pounds < 10 pounds –Durability

Approach / Trade Off Trade-offs Researched –Rechargeable Battery –Voltage Regulation –Controlling Output Voltage

Approach / Batteries Rechargeable Battery –Lead Acid –Nickel metal hydride (Ni-MH) –Lithium-ion

Approach / Batteries Lead Acid (Ni-MH) Lithium ion PriceLeastExpensiveMore Expensive ExpensiveMost Memory Effect * YesNoNo WeightHeavyMediumLight *Memory effect, also known as lazy battery effect, is an effect observed in some rechargeable batteries that causes them to hold less charge.

Approach / Batteries Figure 2: 14.4V Ni-MH [4] 4.30" x 2.7" x 1.5“ 1.65 lbs Figure 3: 14.8V Li-ion. [5] 2.65“ x 1.5" x 3.0“ 0.8 lbs Figure 1: 12V Lead Acid [3] 5.3” x 2.6” x 2.4” 2.87lbs

Approach / Trade Off Charging Circuit –Microcontroller –MAX 745

Approach / Charging µC MAX 745 ProgrammingYesNo PriceLessExpensiveMoreExpensive PackagingDIPSSOP

Approach / Charging * Implementation of design has began results are pending.

Approach / Trade Off Input Voltage Supply –Linear Power Supply –Switching Power Supply

Approach / Power Supply LinearSupplySwitchingSupply EfficiencyLowHigh PriceLeastExpensiveMoreExpensive WeightHeavyLight

Approach / Trade Off Output Voltage Regulation –Linear Regulator –DC-DC Converters

Approach / Output Regulation LinearRegulator DC-DC Converter EfficiencyLowHigh PriceLeastExpensiveMoreExpensive SizeSmallLarge

Timeline JanuaryFebruaryMarchApril Research Prototyping Programming Testing

Reference [1] 7295/Switch%20Mode [2] s/ps1.html [3] tion=VIEWPROD&ProdID=2144 [4] tion=VIEWPROD&ProdID=2627 [5] tion=VIEWPROD&ProdID=3600

Questions