Motoren mit Hall-Sensor

Hall effect 

If a current IS is applied to a semiconductor chip, the Hall voltage UH (the size of which is proportional to the magnetic induction B [vertical to IS] and the current IS is produced at right angles to the direction of the current. The Hall voltage UH is derived from:

RH     Hall constant

d       Thickness of semiconductor chip.

Circuit 

Since the Hall voltages are very small, they are amplified. If silicon Hall elements are used, the circuit for signal conditioning (e.g. a Schmitt trigger with subsequent driver) is integrated on the same chip. This component is then named Hall IC. The output is a transistor with open collector used to produce a switching function.

Characteristic curve 

A magnetic ring whose magnetic field permeates the Hall element is permanently attached to the armature shaft. When the armature shaft redates, the direction of the magnetomotive force in the Hall element changes. The output transistor is thus either switched through or open.

Applications for the Hall effect in DC motors 

If the produced output voltage pulses are counted, it is possible to determine the revolutions and thus the speed. If the rotational motion is converted into a linear motion, it is possible to determine the exact adjustment travel. If two Hall sensors are installed in a motor offset by a certain angle a, the direction of rotation can also be determined.

Schematic configuration in motor

Output signals