a mechanism for ipad weight scale

A MECHANISM FOR IPAD WEIGHT SCALE

ME492 Engineering Project Presentation

DORUK ANGUNDept. Of Mechanical Engineering

Yeditepe University, ISTANBUL

Adviser: Asst. Prof. Namık Cıblak

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Outline

The Need and the Statement of the Problem

The Objective & The Scope Literature Survey Preliminary Design Alternatives Detailed Design Conclusion References

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The Need and the Statement of the Problem

People want IPAD to do multiple tasks.

Weighing an object is a common thing to do.

There is a demand for IPAD weight scale.

Weighing by using the position change of the slider.

Definition of the Need Statement of the Problem

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The Objectives & The Scopes

Low cost Accurate Precise Compact size Ease of

installation Esthetic look

Jewel bearing Registering a

touch Harmless to IPAD Using the screen

as much as possible.

Objectives Scopes

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Literature Survey

Parallelogram Linkage

Consists of two identical cranks fixed with a distance between.

Four straight sides. Opposing sides,

parallel and same length.

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Literature Survey

Slider-Crank Mechanism

Converts rotational motion in to translational motion.

Consists of a rotating driving beam, a connection rod and a sliding body.

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Literature Survey

Capacitive Touchscreen

IPAD 2 has a capacitive touchscreen.

In capacitive touchscreens, there is an insulator such as glass coated with indium tin oxide as conductor.

Touching, distortion in the electrostatic field, determining where the body is touching.

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Preliminary Design Alternatives

Involute MechanismSlider-crank mechanism

with guided stylus

Parallelogram with Slider-crank mechanism

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Mechanism Ideas

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Preliminary Design Alternatives

Battery-Powered Stylus Jointed Stylus Stylus with Wheel

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Stylus Ideas

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Preliminary Design Alternatives

Invo

lute

mec

hani

sm

Slid

er-c

rank

mec

hani

sm w

ith g

uide

d st

ylus

Para

llelo

gram

with

slid

er-c

rank

mec

hani

sm

0

10

20

30

40

50

60

Mechanism

Series1

%

Batte

ry p

ower

ed sty

lus

Join

ted

styl

us

Styl

us w

ith w

heel

0

10

20

30

40

50

60

Stylus (slider)

Series1

%

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Detailed Design

Parallelogram with Slider Crank Mechanism + Stylus With Wheel

+Weight Top part goes downExtension spring extends Slider goes forward

-Weight Extension spring relaxesTop part goes upSlider goes back

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Detailed Design

Analysis

FBD of Crank FBD of Slider FBD of Top

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Detailed Design

Numerical Implementation

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Detailed Design

MATLAB Calculations Inputs“1” represents the weight holder, “2” represents the crank and “3” represents the slider.  Masses (kg)

 m1=0.137, m2=0.172 , m3=0.086 Link Lengths (m)

r1=0.11, r2=0.15, r3=0.15 Connection points (m)

Length of the spring holder a=0.25*r2,

Distance between spring holder and the top of the link c=0.9*r2  Target mass range (kg)

W∈ [0; 0.427,5] Target θ range (degrees)

θ∈ [75; 15]

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Detailed Design

MATLAB Calculations Outputs

k = 664.2478 N/m L0 = 0.0752 m

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Detailed Design

Mass vs. Theta Slider Position vs. Mass

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Detailed Design

3D Modelling of the Design

7 parts Jewel (pivot hole) Pin Link Spring holders Base Top (weight holder)

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Detailed Design

3D Modelling of the Design

Jewel Bearing

Torus shape hole (bigger diameter)

+

Shaft(smaller diameter)

Minimum fricition, better than other bearings.

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Detailed Design

Manufacturing Process

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Detailed Design

Manufacturing Process

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Detailed Design

k=664.2478 N/m (MATLAB)

L0=0.0752 m (MATLAB) d= 1 mm (design criteria) D=5.85 mm ( ) C= 5.8499 ( )

NOT APPLICABLE (ADJUSTING IS DIFFICULT)

k=35.5 N/m (easy to adjust)

Adjustable hook (adjustable L0)

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Extension Spring Rubber Band

Spring Design

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Detailed Design

Final Design

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Detailed Design

Experimental Results

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Location Location Location Location Location Location Location Location77,5 g 127,5 g 177,5 g 227,5 g 277,5 g 327,5 g 377,5 g 427,5 g

6 43 52 101 125 182 247 3886 42 55 101 122 182 256 3916 42 55 101 125 182 259 3874 41 54 102 129 188 260 4114 41 57 104 125 183 265 4374 42 58 97 125 186 266 4174 42 57 96 125 193 276 4134 42 57 100 126 184 282 4134 40 57 103 129 191 267 4084 42 57 100 127 183 271 418

Mass(g) Location77,5 4,6

127,5 41,7177,5 55,9227,5 100,5277,5 125,8327,5 185,4377,5 264,9427,5 408,3

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Detailed Design

Experimental Results

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y = 3E-06x3 - 0.0044x2 + 2.1309x + 62.128R² = 0.99474

0 50 100 150 200 250 300 350 400 4500

50

100

150

200

250

300

350

400

450

Series1Polynomial (Series1)

Slider Position (pixels)

Mass (

g)

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Detailed Design

Experimental Results

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Position Weight (g) Average (g) Accuracy (%) Accuracy (AVG %) Precision (g)101 235,555403 234,868503 3,540836484 3,238902549 10,727584101 235,555403 234,868503 3,540836484101 235,555403 234,868503 3,540836484102 236,885824 234,868503 4,125636923104 239,525792 234,868503 5,28606241897 230,163719 234,868503 1,17086549596 228,798208 234,868503 0,570640879100 234,218 234,868503 2,952967033103 238,209281 234,868503 4,707376264100 234,218 234,868503 2,952967033

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Conclusion

In this project

A working mechanism for IPAD weight scale is created by Selecting its design among preliminary design ideas. Applying a load analysis by using MATLAB. 3D Modeling and assembling its parts on SOLIDWORKS. Manufacturing its parts. Calibrating it by conducting experiments.

Total Weight =823.71 grams

Dimensions=200mm*150mm*25mm

Capacity= 427,5 grams

Accuracy=+-3.25 grams

Precision= 10.73 grams

Total Cost= 450 TL

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References

[1] Tian, Y., Yao, Y.-A., Wei, X., Joneja, A. “Sliding-crawling parallelogram mechanism” (2014)

[2] H. Jiguang, Z. Chuanyan, Z. Weiyang, “Slider Crank Mechanism Design with Time Ratio and Minimum Transmission Angle” (2014)

[3] G. E. Burnett, D. R. Large, G. Lawson, S. De-Kremer, L. Skrypchuk “A comparison of resistive and capacitive touchscreens for use within vehicles” (2013)

[4] UBC. (n.d.). Stretching of Rubber Bands. Retrieved from http://c21.phas.ubc.ca/sites/default/files/rubber_band_write_up.pdf

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THANK YOU FOR LISTENING

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Appendix

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Appendix

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Appendix

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