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Capacitive Touch Sensors Sticking your finger into an electromagnetic field can be fun and useful! -By Jacob Hildebrandt.

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Presentation on theme: "Capacitive Touch Sensors Sticking your finger into an electromagnetic field can be fun and useful! -By Jacob Hildebrandt."— Presentation transcript:

1 Capacitive Touch Sensors Sticking your finger into an electromagnetic field can be fun and useful! -By Jacob Hildebrandt

2 Controller of an Icon The iPods click wheel is one of the most recognizable user interfaces in the world, but whats Capacitive touch sensors, of course! behind it?

3 How Capacitive Sensing Works Two electromagnetic fields are set up, by charging one plate, and grounding the other two. As finger moves…

4 How Capacitive Sensing Works Two electromagnetic fields are set up, by charging one plate, and grounding the other two. As finger moves… The EM fields change

5 Like an LVDT, the magnitude of these changes in EMFs are measured and compared to each other (as well as the previously measured values). From these values, direction and position can be easily computed. Unlike and LVDT, however, the fields can be manipulated by anything that can hold a chargelike human flesh.

6 iPod Click Wheel Chip provides 7-bit resolution128 different positions can be read. Alternating positive and negative electrodes eight of each Holes for traditional push- buttons

7 Signal Conditioning

8 Why Use Capacitive Sensing? Reliability – No moving parts – Virtually unaffected by changes in temperature, pressure, humidity, etc. – EMF can effect it, but is easily compensated for – Actual sensor array is virtually fail-proof User friendly – Intuitive, works as you would expect Relatively cheap and simple to implement

9 Why Use Capacitive Sensing? cont. A lack of physical buttons allows for: – Flat, sleek surfaces Easier manufacturing Weatherproof, easy to clean More freedom in design – Thin profile – Infinite resolution, number of buttons limited only by A-D hardware Can be defined by user though software No need for physical contact – Skins and faceplates, cases, etc. can be installed without effecting performance – Buttons can be placed behind LCD screens, embedded in plastic

10 Which iPods Use Cap. Sensing? Mini Video, Photo iPhone 3G Nano

11 Other Popular Devices that Use Cap. Touch Sensors UGOBE Pleo Microsoft Ultimate Keyboard Motorola KRZR Apple Mighty Mouse Laptop Touchpads


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