Presentation on theme: "Capacitive Touch Sensors"— Presentation transcript:
1Capacitive Touch Sensors Sticking your finger into an electromagnetic field can be fun and useful!-By Jacob Hildebrandt
2Controller of an IconThe iPod’s “click wheel” is one of the most recognizable user interfaces in the world, but what’sbehind it?Capacitive touch sensors, of course!
3How Capacitive Sensing Works Two electromagnetic fields are set up, by charging one “plate”, and grounding the other two.As finger moves…
4How 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
5Like 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 charge—like human flesh.
6iPod Click WheelAlternating positive and negative electrodes—eight of eachChip provides 7-bit resolution—128 different positions can be read.Holes for traditional push-buttons
8Why Use Capacitive Sensing? ReliabilityNo moving partsVirtually unaffected by changes in temperature, pressure, humidity, etc.EMF can effect it, but is easily compensated forActual sensor array is virtually fail-proofUser friendlyIntuitive, works as you would expectRelatively cheap and simple to implement
9Why Use Capacitive Sensing? cont. A lack of physical “buttons” allows for:Flat, sleek surfacesEasier manufacturingWeatherproof, easy to cleanMore freedom in designThin profileInfinite resolution, number of buttonslimited only by A-D hardwareCan be defined by user though softwareNo need for physical contact“Skins” and faceplates, cases, etc. can be installed without effecting performanceButtons can be placed behind LCD screens, embedded in plastic
10Which iPods Use Cap. Sensing? Video, Photo3GMiniNanoiPhone
11Other Popular Devices that Use Cap. Touch Sensors UGOBE PleoApple Mighty MouseMotorola KRZRMicrosoft Ultimate KeyboardLaptop Touchpads