Bike Cellphone Charger

• Chris Battaglia (ME)• Ajeetesh Govrineni (EE)

• Kellen Warriner (IE)

Project Summary and Background

• Create a system that harvests human waste energy and converts it into electricity in order to charge a cell phone

• To be used in Haiti– Collect energy from riding a bicycle

• Previous team designed a system (upper right) but proved expensive, unappealing, difficult to manufacture, etc.

– Includes generator and cell phone holder• Current plan is to optimize old design and

achieve better results– Using MIT’s design (lower right) as the standard

to meet/exceed

Customer Needs

• Must be able to charge Nokia cell phones (250mA, 3.5V)– Ability to charge Blackberries (750mA, 5V) desirable but not strictly necessary

• Design should be adaptable and fit a variety of bicycle frames– Easy installation (little to no tool use)– User feedback is important, user wants to see the phone charging

• Total material costs should be <$15 with <1hr labor– MIT design is $11 but lacks phone housing– Willing to ship materials and more complicated components (breadboard,

generator, etc) but main assembly should be done on-sight with minimal supervision

– Should not use any machining equipment more complicated/expensive than hand tools

• Forgiving tolerances– Design should be simple enough to repair and/or cheap enough to replace if

broken

Customer SpecificationsCust.

NeedsSpec No Specification

Direction Units Marginal Ideal Notes

CN1 S1

Percent of tested phones that can be charged with the device max % 80%

90% + charges

Blackberry Nokia common in Haiti

CN1, CN2 S2 Output voltage target V 4.7-5.3 4.8-5.2

Standard cell phone requirements

CN1 S3

Current output at sustainable (specify) biking speed (15-17 mph?) or cadence (60-80 rpm) max mA >250 >750

need to research blackberry needs, seems like 750 mA needed, what is a sustainable biking speed?

CN1, CN5 S4 Maximum current output target mA 1500 1000

came from previous team, not sure why this is max.

CN1, CN2 S5 Uses standard connectors yes NA no yes i.e.. Usb

CN3 S6Range of bike tires accommodated max cm

40.6 - 71.1 (kids and adult

bikes)

60.6 -71.1 (adult bikes only)

CN9 S7People required to install the device min

# of people 2 1

CN9 S8Number of tools required to install the device min

# of tools 2 <=1

tools should be standard hand tools or supplied with device

CN9 S9 Time to install min min <10 <5

CN8, CN9 S10

Increased effort for bicyclist over biking with no device (heart rate or VO2) min % <10% <5%

CN12 S11Noise reduction over MIT device max % (db)

>10% (db) >20% (db)

CN4, CN13 S12

Cost (parts + machining & assembly labor + shipping estimate) min $ <25 <15

Assuming parts purchased and imported or made in Haiti at $2/hr, lots of 100

CN4 S13 Cost of installation min $ <3 0

Cust. Needs

Spec No Specification

Direction Units Marginal Ideal Notes

CN4 S14

Estimated maintenance/replacement part costs per year of life min <5 <1

CN4, CN7 S15

Manufacturing time reduction from previous device % >10% >25%

CN4, CN7 S16 Number of parts min #

same as current design

3 less than

current

CN4, CN6 S17

Number of expensive/specialized machine tools required for manufacturing min #

less than current 0

mill, lathe, drill press, specialized machines, etc.

CN5 S18Increased temperature to bike parts min oC 10 5

CN10 S19 Resists impacts/crashes max

IEC60529* Level

1-9 >5 >7

CN10 S20 Resists dust max

IEC60529* digit 1 Level

0-6 >4 6

CN10 S21 Resists water max

IEC60529* digit 2 Level

0-8 >4 >7

CN11 S22 Rough road test? not sure how to test…

CN13 S23 Weight min kg <current

CN14 S24

% of people rating it 4 or above on a scale of 1-5 for aesthetically pleasing max % >50 >70

CN14 S25

% of people rating the device as more aesthetically pleasing than the previous version max % >60 >75

CN15 S26

Reduced environmental impact (embodied energy) over previous device (estimated) max % >0% >10%

not sure what value to put on this as it is not a main requirement

CN15 S27

Reduced environmental impact (embodied energy) over MIT device (estimated) max % >0% >10%

not sure what value to put on this as it is not a main requirement

Test Plan

Project Risk Assessment

ID Risk Item Effect Cause

Likelihood

Severity

Importance Action to Minimize Risk Owner

Describe the risk briefly What is the effect on any or all of the project deliverables if the cause actually happens?

What are the possible cause(s) of this risk?

L*S What action(s) will you take (and by when) to prevent, reduce the impact of, or transfer the risk of this occurring?

Who is responsible for following through on mitigation?

1 Long lead time on parts Make the project late real world scenario9 9 81 Order long lead parts at end of

first quarter Kellen

2 Running out of budgetUnable to complete

projectmismanagement

of team funds3 9 27 Completion of budget to manage

costs Kellen

3 Design Malfunctions

Push project schedule potentially making

the project latePoor equipment or

design3 9 27 Accurate analysis of working

system AJ and Chris

4 Poor Team DynamicsUnable to Complete quality team work

Reduce quality of team project

1 9 9 Communication and even distribution of tasks team

5 Miss team deadlines

Unhappy client/Lower grade in

coursePoor management

of team time1 9 9 Complete team project timeline

team

6Team Scheduling

ConflictsUnable to complete

team work/discussionFlexibility of group

members3 3 9 Create fix schedules to meet

every week team

Technical Risk AssessmentID Risk Item Effect Cause

Likelihood

Severity

Importance

Action to Minimize Risk Owner

10Generator

Produces too much heat

Generator burns up

Generator spins too fast, Housing does

not dissipate heat, or phone requires too much electric load

for specified generator

1 9 9

End of generator shaft has

correct size wheel to run

at rated speed

Chris

11 Bike Charger damages phone

Burn the phone up or phone

won't charge

Circuit design does not protect phone 3 9 27

A voltage regulator is

used to prevent the phone from

receiving too much voltage

AJ

12

Bread Board produces to much heat

inside housing

Bread board

malfunctions

Enclosed Housing does not dissipate

heat9 9 81

Heat Transfer Analysis to determine heat sync required

Chris/AJ

Generator Housing Design• Same general design but with a

few modifications– Housing is made of cut stock PVC

pipe– End caps are glued along the

inner diameter of the PVC and are made of cut Plexiglas

• Opted for simplicity and low cost over complexity and utility (details in next slide)

• Not shown:– Weather stripping around

generator for cushioning– Small spring acting against

generator inside the housing• Shaft for generator rod has twice

the diameter in clearance• Will hopefully be enough to hold

generator shaft against any bike wheel. May need adjustments.

Generator Housing CAD Drawing

Generator Housing Concept Selection

• The need to machine metal (even just drilling) made choices undesirable

• Most of the options seemed too flimsy or expensive• Ultimately needed to “step back” and return to the

simplest solution for this project– Kept the “wiggle shaft” idea and made it internal

A B C D E

Cost 0 0 0 + -Durability 0 0 - - +Traction/Contact 0 + + - +Detachable 0 0 0 0 +Installation Tools 0 + + + +Components 0 + + + -Stability 0 0 - - +Manufacturability 0 + + + -Aesthetics 0 0 0 - +Sum (+) 0 4 4 4 5Sum (-) 0 0 2 3 3Sum (0) 8 4 2 1 0Net Score 0 4 2 1 2Rank 4 1 2 3 2

Zip Ties The Claw®Selection Criteria Current(Reference) Wiggle Shaft External

Spring

Frame Attachment• Needs to support 4+ times the housing’s weight under rough road conditions (-Prof. Lam)• Lack of machining equipment in Haiti prompts a purchased pre-manufactured component• Generator can be removed by hand later, but only with added cost (clamps, wing nuts, etc –

all more expensive)• No sure way to determine which options (See below) would be best. Luckily options are easily

interchangeable so we can experiment during testing• Will be used both on the frame and the generator housing

– No need to machine into the housing– Shouldn’t need an arm to bridge the two, but one can be made from plastic if necessary

$2.00 - $2.50 $2.50 - $2.75(Current Design)

$0.75 - $1.50$0.10 - $0.50

Circuit Board Housing Design• Decided to use a breadboard over

PCB– Cost

• Heat generation is the biggest concern mechanically– Analyzed under very

conservative conditions (no convection whatsoever)

– Nokia (3.75W) setup passes, Blackberry (10W) does not (see right)

• Current design is to place the breadboard in a separate housing– Made of same materials as

generator housing– Thermal testing may show that it

can be safely placed in the generator housing

• Generator shaft and any metal fasteners may dissipate enough heat

NokiaHeat Gen: 3.75 W

kbox: 0.19 W/m-K RHS: 14.00 K/WAbox: 0.023813 m^2 Rhsng: 0.70 K/Wdbox: 0.003175 m Rair,ext: 8.40 K/w

hamb: 5 W/m^2-KTamb: 30 °C

Tb1: 64.13 °CQmax: 3.90 W

BlackberryHeat Gen: 10 W

kbox: 0.19 W/m-K RHS: 14.00 K/WAbox: 0.023813 m^2 Rhsng: 0.70 K/Wdbox: 0.003175 m Rair,ext: 8.40 K/w

hamb: 5 W/m^2-KTamb: 30 °C

Tb1: 121.01 °CQmax: 0.26 W

Heat Transfer Calculations

Phone Housing Design• Alternative Design to the purchased

phone holder• More expensive• More labor intensive

• Not necessarily a bad thing• Can be manufactured in Haiti• Made out of cut sheet stock, glue,

and one metal dowel

Phone Holder CAD Drawing

Material Selection Material

Characteristics Metal Wood Rubber Aluminum Plastic

Durability 0 - 0 + 0

Stability 0 - - 0 0

Waterproofing 0 - + 0 +

Corrosion Resistances 0 0 + + +

Longevity 0 - 0 + +

Availability/Different Sizes 0 0 0 0 +

Cost 0 + + - +

Processing Tools 0 + + - +

Sum (+) 0 2 4 3 6

Sum (-) 0 4 1 2 0

Sum (0) 0 2 3 3 2

Sum Net Score 0 -2 3 1 6

Rank 3 5 2 4 1

Manufacturing

• Goal of project was to make device as cheap as possible

• Use of mass produced product– PVC pipe – Plexiglass– Steel rod and tubes

• Tools Used:– Handsaws, Cordless drill

Manufacturing

• User Assembled– Cheaper– Create jobs– Slow assembly time

• Learning curve• Incorrect assembly results

in device not working

• Preassembly– Costs more (labor in

U.S.)– Lower risk of assembly

mistakes

Circuit Selection

Circuit Simulation

Bill of Materials

Generator Housing

Part Part Supplier Price Price Each Leadtime Notes

2 in Stock PVC Lowes $6.67 $0.10 Purchase in 10 foot Sections

.25" Plexiglass Lowes $25/sheet $0.18 2'X4' Sections (sheets)

14 gauge wire Tractor Supply $19.95 $0.02 Spool

Rubber Connectors N/A $.10ea $0.20 Estimated, Unsure where to get

Loctite Rubber Cement Lowes $4.67 $0.25 10.2 oz tube for caulk gun

Generator Online $2.50 $2.50 1 week Shipping costs reduce for large quantities

Cost Per Unit: $3.25

Phone Housing

Part Part Supplier Price Price Each Leadtime Notes

.125" Plexiglass Lowes $25.50 $2.50 Purchase in 2'X4' Sections

Loctite Rubber Cement Lowes $4.67 $0.50 10.2 oz tube for caulk gun

.125"X8" metal dowel Lowes $6.08 $0.75 Rod is 6 feet long

Cost Per Unit: $3.75

Bill of Materials Part Manufacturer Distributer Serial Number Name Part name Level Revision

Make/Buy Name Part # Name Part # Unit Cost Quantity

Total Cost

1 5 V Voltage Regulator IC1 1 A BuyNational Semiconductor LM2940 Jameco 837505 1.39 1 1.39

2 USB A Connector SL3 and SL4 2 A Buy Adam Tech USB-A-S-RA Jameco 2096181 0.49 2 0.983 2 Pin Connector Male SL1 and SL2 2 A Buy TE Connectivity 440055-2 Digikey A100043-ND 0.16 2 0.324 10 µ F Capacitor C1 and C3 3 A Buy Jameco ValuePro R10/50 Jameco 29891 0.09 2 0.185 0.1 µ F Capacitor C2 3 A Buy Jameco ValuePro R0.1/51 Jameco 2151970 0.07 1 0.07

6 15 Ω Resistor R1 3 A Buy YagoFMP200JR-52-15R Digikey 15ZTR-ND 0.02 1 0.02

72 Pin Connector Female 2 A Buy TE Connectivity 440129-2 Digikey A100011-ND 0.1 2 0.2

8 Connector Pins 3 A Buy TE Connectivity 1735801-1 Digikey A103922CT-ND 0.1 4 0.4 Total 3.56

Part Manufacturer Distributer Serial Number Name Part name Level Revision

Make/Buy Name Part # Name Part # Unit Cost Quantity

Total Cost

1 Bread Board 1 A Buy Jameco ValuePro PCB-594 Jameco 206594 11.95 1 11.952 22 AWG red wire 2 A Buy Jameco ValuePro 820-2* Jameco 125795 10.95 1 10.953 23 AWG black wire 2 A Buy Jameco ValuePro 820-0* Jameco 125840 10.95 1 10.954 24 AWG white wire 2 A Buy Jameco ValuePro 820-9* Jameco 125831 10.95 1 10.95

Total 44.8

Moving Forward

• MSD II Project Plan• Address Issues in Detail Design Review• Purchase components with long lead times