System Design Review

Power System for the Better Water MakerP14418

System Design Review

Agenda● Background

○ Problem Statement and Project Plan○ Customer Needs and Engineering Requirements○ Constraints and Design Drivers○ Project Risk Assessment

● System Analysis○ House of Quality Results○ Functional Decomposition○ Pugh Analysis

● Individual Concepts and Architectural Developments○ Concept and Schematic○ Risk Assessment○ Initial Cost Estimate○ Test Plan

● Feedback

Problem StatementThe Better Water Maker was developed to disinfect water in nations

with high mortality rates due to poor water and sanitation systems. The goal of our team is to provide a low cost, efficient power generation system for the Better Water Maker that does not tire the user, while it is fun and easy to use.

Project Plan

Customer Needs (Critical)

Primary needs● Generate adequate power● Is not tiring● Reduced cost● Maintain durability

Engineering Requirements

● Generate 25 Watts● Can be used for at least 5 minutes● Costs less than $150● Lasts for at least 180,000 gallons of water

Constraints & Design Drivers

Key Design Drivers• Functionality, Reliability, Cost, Usability,

Manufacturability• Durability, Efficiency

Constraints• Cost, Size, Weight, Strength of User

System Analysis: HOQ Results

Four highest weighted needs:

● Ease of Repair● Cost● Unit Life● Effort Required

Functional Decomposition

Timing Diagram

General Process Flow Chart

Pugh Analysis

Solar Concept: SchematicAcquire Water

Hook up

Battery

Communicates Readiness to User Plug

in BWM

Dispense Water

Engineering Analysis

Assumptions:● 30W Solar Panel● Surface Area: 0.262 m^2● Efficiency: 18%● 2-axis rotation● Clear-sky analysis● BWM requires 20.4-25.5W

Solar Insolation by Region

Port-au-Prince, Haiti Sun Chart: Hot Climate

Nepal Sun Chart: Cooler Climate

Calculations for 20° Latitude: Haiti

● 8AM to 4PM availability● Shade drastically reduces power

Solar Concept: Risk Assessment By Importance

● Reliability○ Weather○ Time○ Shading

● Theft● Battery

○ Shipping○ Cost○ Safety○ Life

● Additional Controls● Cost

○ Component

Solar Concept: Cost Analysis

● 30W Monocrystalline Solar Panel 18V- $71.06● 2-Axis Stand- $20-$30● AC Converter- $20● Wire extension- $10● 12V lead acid battery - $30

Total Cost: ~$150

● May end up outside budget, but the system will provide power for any device.

Solar Concept: Test Plan

● Use multimeter to verify the power.● Measure the power if a cell is shaded.● Collect data on battery charging capability.● Test ability of a child to use from start to finish.● Obtain a survey from users on its ease of use.

Leg-powered Concept

● Recumbent Bicycle● Direct- or Chain-Drive

Pros Cons

● More power in legs than arms● Less tiring than current design● Higher efficiency than current● Possibility to reduce amounts

of motors

● Might add cost● High forces on seating

structure● More complicated setup than

current design● Less portable than current

Pedals Mounted on Crankshaft

Pedals Mounted on Separate Sprockets

Seat

Seat

Backrest

Bucket

2x4

Current Generator

Current Generator

Leg-powered Concept: Schematic

Risk Assessment● Large forces in system● More complicated setup● Reduced component life● Complex seating requirements

Design Architecture

FeatureSeatCrank and MotorsLEDsWires, Chain, and Sprocket

Function AccomplishedPlace UserGenerate PowerCommunicate to UserTransfer Power

Leg-powered Concept: Cost Analysis

● Crankset - $10-20*● Pedals - $4*● Chain - $10● Keyed Shaft - $10 -17*● Sprocket - $5 - 10

Chain Drive - $39 - 61*Direct Drive - $24 - 41

Leg-powered Concept: Test Plan

● Have volunteers test for comfort● Measures forces on seat and pedals● Can run for 5 minutes or more● Run generator while attached to a voltmeter

○ Ensure voltage is limited correctly

Spring Concept: Schematic

SwingSingle Jump Platform

Double Jump Platform

Risk Assessment

●Solenoids create heato Proper heat sink

●Springs could breako Properly constrained

●Solenoid plunger must be correctly alignedo Prevent improper movement

●Oscillations may be erratico Use bridge rectifier

Spring Concept: Design Architecture

FeatureCasing/Spring EnclosureSolenoidSpringsRectifier

Function AccomplishedPlace UserGenerate PowerFacilitate Power GenerationRegulate Power

Spring Concept: Cost Analysis

● Springs - $3-10 each● Solenoid - $15-30 each● Rectifier - $0.50-3● Plywood casing - $5-10 per setup● Rope/chain - $0.70/ft

Swing - $30-68Single Jump Platform - $26-63Double Jump Platform - $52-123

Spring Concept: Test Plan

● Test the components for each output individuallyo Verify with expectations

● Test the ergonomics of the setup to determine whether it requires less effort than the original design

● Bring children in to set up and use the apparatus● Use DOE tools to validate the testing results

Recommendations:

●Solar Concept:o Has great potential, even beyond BWM, but has high risk

in reliability and cost.

●Leg-Powered Deviceo High reliability in combination with low cost and OTS

components make this a desirable concept.

●Spring Concepto Unknown reliability of power; this will need more anaysis

before moving forward, but it has great potential to be fun and easy to use, as well as low in cost.

Questions and Comments?

Springs (Century Spring Corp.)P/N: 7052 $3.84

OD: 1in

Length: 3in Max. displacement: 1.2in

k: 51lb/in Max. load: 60lb

P/N: 12556 $5.31

OD: 1in

Length: 4.45in

Max. displacement: 1.2in


P/N: 7056 $8.96

OD: 1.219in



P/N: 11860 $8.66

OD: 2.125in

Length: 5.38in

Max. displacement: 4in

k: 5.5lb/in Max. load: 22lb

P/N: S-3159

$13.20

OD: 2.875in



P/N: D-1306

$5.73

OD: .375in



Solenoids (ElectroMechanics Online)P/N: S-16-50 $27.73

Pull-type 18W

Long Pulse 25% Duty Cycle

Max. on-time: 50s

Actuation Length: <1.6in

P/N: S-10-50 $22.40

Pull-type 16W

Long Pulse 25% Duty Cycle

Max. on-time: 20s

Actuation Length: <1in

P/N: S-10-50 $22.40

Pull-type 8W

Intermittent 50% Duty Cycle

Max. on-time: 75s

Actuation Length: <1in

Rectifiers (Mouser Electronics)P/N: 625-2KBP02M-E4 $0.58

Current: 2A Max. current surge: 60A

Peak reverse voltage: 200V

Single Phase Bridge-style

P/N: 625-PB4006-E3 $3.02

Current: 4.4A Max. current surge: 400A



P/N: 512-GBPC3510 $3.05

Current: 35A Max. current surge: 400A



Gravity Feed (not power generation)

Pros Cons● Possible

elimination of pump (5+W)

● Less effort required

● Can be OTS

● Needs more structural support due to higher center of mass

● Need to use pump to regulate flow or use gate valve and throttle valve

● Users need to lift water into funnel

Solar Power Supplement to Current BWM Design

Pros:- Solar panel will

reduce load on user- Redesign of current

system may be minimal

- Reduced learning curve for current users

Solar Power Supplement to Current BWM Design

Cons:- Cloud cover and

night- time eliminate the improvement

- Solar panels are susceptible to theft

House of Quality

System Design Review

Documents

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