Touch Screen Technology
`
`Topics covered:
`1) Resistance, Capacitance, Charge, Voltage, and Current
`2)
`Introduction to simple circuits
`
`
`
`Taking apart a tablet
`
`¢ For example, an iPad2
`
` Lots of
`
`
`
`Battery
`
`Inside!
`
`Display
`
`Motherboard
`
`CARDWAREEXHIBIT 2017, Page 1 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
`
`Topics covered:
`1) Resistance, Capacitance, Charge, Voltage, and Current
`2)
`Introduction to simple circuits
`
`
`
`Taking apart a tablet
`
`¢ For example, an iPad2
`
` Lots of
`
`
`
`Battery
`
`Inside!
`
`Display
`
`Motherboard
`
`CARDWAREEXHIBIT 2017, Page 1 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`
`
`Touch Screen Overview
`
`Finger touches the
`touch screen
`
`
`
`el
`
`An arrayed sensordetects
`someelectrical interaction
`
`Thefinger position is
`reported to the Ul
`
`Fitting algorithms are used
`to calculate finger position
`
`
`
`Sensed Touch as an image
`
`An “image” of the arrayed
`
`sensor response is created
`noise
`
`Apply filter to smooth
`
`Used “differential” masks to
`detect edges
`.
`cA
`weap
`Bs i iN te
`;
`ee
`Bestfit ellipses are defined
`
`for each touch andcentroids (1) Smooththe input image (f(x, ) = f(x,y)*G(x, y))
`are sentto the Ul
`(2) f, = S(x,y) * M, (x.y)
`-1 01
`‘
`‘
`M,=|-2 0
`2
`
`- 01|
`1
`1
`
`M.=|0
`
`0
`
`0
`
`(5) dir(x,y) = tan“(f,/f.) (6) If magn(x, v)
`
`(3)f,. =F(X.)*M(x,y)
`<a (4) magn(x,y) = f + f, |
`
`> T, then possible edge point
`CARDWAREEXHIBIT 2017, Page 2 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`What we’ll learn in this module
`
`• We’ll use the touch screen example to review fundamental electrical
`quantities (voltage, charge, current) and elements (resistors,
`capacitors, voltage)
`
`• We’ll analyze and design some resistor and capacitor-based circuits
`
`• We’ll get an early preview of sensing circuitry and introduce
`amplifiers
`
`• Useful videos for review and extra information:
`• http://www.ntspress.com/publications/circuits-second-
`edition/circuits-2e-faculty-resources/circuits-videos-from-berkeleys-
`ee-40/
`
`Main types of touch screens
`
`Resistive Touch Screens: Finger pressure
`makes an electrical contact in a circuit
`
`Optical touch screen: Finger contact
`blocks light traveling from edges of screen
`
`Acoustic touch screen: Finger alters sound
`waves traveling on screen surface
`
`Capacitive touch screen: Finger alters the
`capacitance of the touch position
`
`CARDWARE EXHIBIT 2017, Page 3 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`Resistive Touch Screen
`
`_ aes
`
`CONDUCTIVE.ELECTRODE
`
`x
`
`¢ Finger pressure “shorts” a specific location of a top layer to the
`bottom the bottom layer
`* The entire bottom layer then
`becomesbiasedat the top
`layer touch-point potential
`by modeling this as a voltage <
`« We can explain operation
`a
` PLASTIC FILM WITH TRANSPARENT,
`
`
`divider
`
`* To begin, we'll review voltage,
`current, and resistance
`
`LCD SCREEN
`
`RESISTIVE COATING ON TOP SIDE
`
`
`
`Reminder: Voltage
`
`* Voltage is analogousto pressure in a water delivery system
`
`High Voltage
`— currentflow
`
`Copper Wire
`
`Load (Fan)
`
`High Pressure
`
`Water Pipe
`
`Daeata.
`
`Battery
`
`current flow ——>
`
`Low Voltage
`
`(Water Wheel)
`
` +
`
` Load
`
`>
`
`Low Pressure
`
`Water Pump
`
`* Reminder: The changein voltage is defined as the work done per
`unit charge against the electric field.
`— Pushing a water droplet against the pump-induced flow is hard to do
`— If we pushthe droplet up, and thenletit go, it quickly goes back down,turning
`the water wheel
`
`— Similarly, an electron on the negative end of the battery flows through the wire to
`the positive end, spinning the fan
`
`CARDWAREEXHIBIT 2017, Page 4 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`Work
`
`Reminder: The changein voltage is defined as the work done per
`unit charge against the electric field.
`In other words, we are building up potential energy
`
`Gravitational
`
`potential energy
`
`
`Energy
`source
`
`Whencurrentflows, this is converted to kinetic energy
`What happensto the kinetic energy whenthe water “stops”asit hits
`the reservoir?
`
`
`
`Representing Circuit Components
`
`i
`
`--
`
`Resistor (more aboutthis in a minute)
`
`|
`
`Voltage reference (ground)
`CARDWAREEXHIBIT 2017, Page 5 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`Voltage, Current, and Resistance
`
`* Current is the “flow” of electrons
`
`¢ The driving force for the “flow” is the voltage
`¢ Resistance represents the “fight” the flow path imposes against the
`flow
`
`* Resistance is:
`— Denoted by: -/\/\/\/
`— Has units of ohms (Q)
`
`
`
`
`
`Resistance
`
`¢ The resistance of an objectis a function ofits:
`— Length: longeris moreresistive
`— Cross-sectional area: Wideris less resistive
`— Resistivity: A fundamental material-dependent parameter
`
`A = area
`
`
`L = length
`
`=
`ictivi
`p = resistivity
`
`:
`
`1.59 x 1078
`Silver
`1.7 x 10-8
`Copper
`2.44 x 1078
`Gold
`2.82 x 10-8
`Aluminum
`5.6 x 1078
`Tungsten
`10 x 10-8
`Iron
`Il x 1078
`Platinum
`a2 x 10-8
`Lead
`1.50 x 107%
`Nichrome?
`3.5 X 107-5
`Carbon
`0.46
`Germanium
`640
`Silicon
`i
`-
`i
`ictiva
`ae ee
`a
`* Question: whyis the resistivity of
`
`a material describedin units of Q:m?—Hardrubber es
`.
`Sulfur
`Quartz (fused)
`75 x 10!6
`
`L
`Hop =
`A
`
`Material
`
`Resistivity*
`(Q:m)
`
`i A\A
`R
`
`CARDWAREEXHIBIT 2017, Page 6 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`Conductance
`
`• Conductance is the reciprocal of resistance
`• Conductivity has a unit of Siemens (S)
`
`Useful Videos
`
`•
`
`Introduction: http://youtu.be/km2Ar7HWexQ
`
`• Charge and Current: http://youtu.be/4z5cYzacZk8
`
`• Charge, Current and Voltage: http://youtu.be/YqiW-c9vHl8
`
`CARDWARE EXHIBIT 2017, Page 7 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`Ohm’s Law
`
`• Ohm’s law describes the relationship between voltage,
`current, and resistance:
`V = IR
`
`Questions: Ohm’s Law
`
`• Why is the voltage at the top of the resistor ~12V?
`
`• Why is the voltage at the bottom of the resistor ~0V
`
`CARDWARE EXHIBIT 2017, Page 8 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
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`
`
`Detecting Touch: Simplest View
`
`No touch: No connection
`between plates – “Open”
`Circuit
`
`Touch: Highly conductive
`connection between plates –
`“Short” Circuit
`
`Open Circuits & Short Circuits
`Open circuit: no path for current flow
`R =
`Short circuit: no voltage drop
`R = 0
`
`CARDWARE EXHIBIT 2017, Page 9 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
`
`How can we modelthe resistor plates?
`
`“Z-
`
`Transparent Conductor
`(ITO)Top Side
`
`<j
`
`
`%
`
`
`Silver Ink
`Conductive Bar
`\ Transparent Conductor(ITO)
`WN’
`
`os<>
`
`
`
` gE
`
`
`A
`
`Bottom Side
`
`Silver Ink
`Conductive Bar
`
`Insulating Material (Glass)
`
`
`
`But it is a 2D sheet....
`
`CONDUCTIVE ELECTRODE
`ON BOTTOM SIDE
`
`PLASTIC FILM WITH TRANSPARENT,
`RESISTIVE COATING ON BOTTOM SIDE
`
`
`
`
`econ
`
`PLASTIC FILM WITH TRANSPARENT,
`RESISTIVE COATING ON TOP SIDE
`
`What about the conductive
`stripes?
`
`CARDWAREEXHIBIT 2017, Page 10 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
`
`Question: What about 2 resistors in series?
`
`Question: … and in parallel?
`
`CARDWARE EXHIBIT 2017, Page 11 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
`
`Exercise: Household Wiring & Safety
`
`• To begin: Here is a simplified model
`of the human body resistance
`• We need to add in the resistance of
`the skin contact:
`– Dry: ~100k
`– Wet: <1k
`• Q1: What is the resistance for a
`person touching a wire?
`• Q2: On average, men have lower
`resistance than women. Why?
`
`Exercise: Household Wiring & Safety
`
`• The internal resistance of a plug is <0.5. How should we model the
`circuit for a human touching an exposed wire at the plug by mistake?
`• What is the voltage the human sees?
`
`CARDWARE EXHIBIT 2017, Page 12 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
`
`Exercise: Household Wiring & Safety
`
`• Develop a model for a human
`touching an insulated wire.
`
`Useful Videos
`
`• Ohm’s Law: http://youtu.be/ZaBvpgw5pvg
`
`CARDWARE EXHIBIT 2017, Page 13 of 13
`SAMSUNG V. CARDWARE PGR2023-00013
`
`
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