Motion sensor

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X-rays of a motion sensor of a sleep phase alarm clock . Below zoom on one of the sensors with two metal balls.
Ankle cuff with data logger (MSR145), which contains an integrated motion sensor

A motion sensor is a component with which a change in position is converted into an electrical variable that can be evaluated with suitable wiring. In the simplest case, it is an electrical-mechanical component, e.g. B. a tilt switch . In general, however, movements are calculated as an integration over the measured values ​​of an acceleration sensor , since simple and inexpensive sensors are available for measuring accelerations and the results are often more precise.

Often motion detectors are also referred to as motion sensors.

mechanism

Most mechanisms detect the position of the sensor and deduce a movement from a change in position.

  • One or more movable, conductive bodies can, depending on the position with regard to the gravitational force, close a contact at the beginning or at the end of their range of motion or trigger an electrical impulse :
    • A ball can roll on one end of a tube.
    • A metal plate standing on the edge can tip to the left or right.
    • etc.
  • A perpendicular indicates the direction of the gravitational force, a spirit level indicates the horizon or a top indicates an original position in space; based on this, protractors can determine the current alignment.

Another method is the detection of an environmental change using (optical) sensors:

In some cases, a combination of movement sensors arranged at right angles is used, with which a position (change) in the 2- or 3-dimensional can be detected.

commitment

Motion sensors are used, among other things, to save energy if, for example, the function of an electronic device is only required during a movement process and the energy supply is limited by accumulators. One example are battery-operated bicycle taillights that only turn on when the bicycle is jolted. There are also battery-operated alarm devices (boxes or rope locks) that react acoustically to vibrations and with a radio signal after arming.

Sleep phase alarm clocks wake the user in a phase in which he is moving, which is why pure shock sensors are sufficient here.

Motion sensors are also used in computer games. See game controller # motion sensors

See also