2.2.1.1 Sensor Control

Sensor control uses the Hall Effect arrangement at the back-end of the motor to detect the rotor position. Three Hall Effect sensors are placed 120 electrical degrees apart. These are digital Hall Effect sensors. The sensors detect the transition from the north pole to the south pole of the rotor. There are several disadvantages of Hall Effect sensors including:

• The sensors are very expensive.
• Sensing requires a magnetic disk.
• Additional mechanical parts and wiring issues cause reliability problems.
• Hall Effect sensors require an additional power supply.