
SENSORS, ADCS AND ACTUATORS 119
piece of iron (see Figure 3.35). e electromagnets are energized by an external control
circuit which sends pulses to the motor.
To turn the motor shaft, one of the electromagnets is given power fi rst, which makes
the gear’s teeth magnetically attracted to the electromagnet’s teeth. When one tooth of
the gear is thus aligned to the energized electromagnet (Electromagnet ‘B’ and tooth
‘6’ are aligned in Figure 3.35), others are slightly off set from the corresponding electro-
magnets. When the next electromagnet is turned on and the fi rst is turned off , the gear
rotates slightly to align with the next one, and f ...