Posts Tagged ‘motion sensors’

Tilt sensors and accelerometers

Wednesday 4 March 2009

ihandyOne of the cool features of the iPhone and iTouch is the tilt sensor. Turn the device and your screen turns from portrait into landscape mode. The motion sensor is capable of detecting very small movements. A simple free application iHandy can detect very small motions and also without motion the device can tell the angle at which you hold the device.

The technology making this possible is called Microelectromechanical systems or MEMS. A relatively new field of electronics combining electronic circuits with very small moving parts embedded into the circuitry. Accelerometers used in the iPhone is just one type, other include pressure sensors, temperature sensors and mirrors to redirect light. MEMS technology is used in a wide array of applications for domestic use such as motion stabalizers for camaras, inktjet printers, automotive airbag sensors, gaming controllers (Wii), step counters and indeed motion sensors for mobile phones and other personel electronics. 

The basic principle used in a MEMS motion sensor is a small section of silicon that can move relative to another section of silicon. By embedding conductor material on both parts and applying a voltage to them you get an electrical capacitor. The capacitors electrical property varies with the relative position of the two elements. And since one can move a variation can be detected and processed. A bit similar to the workings of the car detection loops in the road, although they use the capacitors electrical twin brother, the inductor.

If you are interested in the technology and more applications you can read the not so short introduction to MEMS.