Post on 04-Jun-2018
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DC Motors
• The stator is the stationary outside part of a motor. Therotor is the inner part which rotates.
• Just as the rotor reaches alignment, the brushes move
across the commutator contacts and energize the nextwinding
• The brushes of a dc motor have several limitations; brushlife, brush residue, maximum speed, and electrical noise
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Brushless DC Motors
• A brushless dc motor has a rotor with permanentmagnets and a stator with windings. It is
essentially a dc motor turned inside out. Thecontrol electronics replace the function of thecommutator and energize the proper winding.
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Full Stepper Motor
• This animation demonstrates the principle for a stepper motor using full step
commutation. The rotor of a permanent magnet stepper motor consists of
permanent magnets and the stator has two pairs of windings. Just as the rotor
aligns with one of the stator poles, the second phase is energized. The two
phases alternate on and off and also reverse polarity. There are four steps. One
phase lags the other phase by one step. This is equivalent to one forth of an
electrical cycle or 90°.
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Half Stepper Motor
• This animation shows the stepping pattern for a half-step stepper motor. The
commutation sequence for a half-step stepper motor has eight steps instead of
four. The main difference is that the second phase is turned on before the first
phase is turned off. Thus, sometimes both phases are energized at the same time.
During the half-steps the rotor is held in between the two full-step positions. A
half-step motor has twice the resolution of a full step motor. It is very popular
for this reason.
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Stepper Motors
• Some stepper motor uses permanent magnets.Some stepper motors do not have magnetsand instead use the basic principles of aswitched reluctance motor. The stator is
similar but the rotor is composed of a ironlaminates.
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Half Stepping
• Note how the phases are driven so that the
rotor takes half steps
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Full Stepping
• Animation shows how coils are energizedfor full steps
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Stepping Sequence
• Full step sequence
showing how binarynumbers can controlthe motor
• Half step
sequence of
binary control
numbers
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H-Bridge:Enables you to control the motor in
both forward and reverse with a
microcontroller.
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• H-Bridge chips
NSC LMD18200
• H-Bridge driver chips
Intersil HIP4081A
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References
• http://mcu.st.com/motor.swf
• http://www.freescale.com/files/microcontrollers/doc/train_ref_material/M
OTORPRINTUT.html
• Practical electronics for inventors by Paul Sherz