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Conventional Motors

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Motor Properties

Motors convert electrical energy into rotational movement.

Conventional Motors - Two Connections

Normal motors run at a speed determined by the power supply voltage and the load on the motor. This is fine for devices like cooling fans or motors used to drive vehicles.

These spin in a fairly uncontrolled way.
They are useful for propelling vehicles, powering fans or spinning the washing.
It is possible to measure how fast the motor is spinning but the exact position of the motor is not generally known.
These motors can be any size including huge motors for driving ships or trains.
Difficult to control small movements
Easy to make a big powerful motor
Easy to make a motor that runs at high speeds
To control speed, a closed loop control system is needed with negative feedback of the speed measurement.
Simple switches or electronics used for power control
Efficient - most of the electrical energy is converted into mechanical form
QE2 Engine Room - Big Motors 9 metres across.

Motor Drivers

MOSFET switches are commonly used.
MOSFET source followers are used less often.
H-Bridge controllers containing four MOSFET switches are good for reversible motors.
Chips are available to control the motor power using pulse width modulation.
H-Bridge chips are available too. These prevent accidental misconfiguration of the H-Bridge circuit.