DC Stepper Motor

1
DC Stepper Motor

• Typical Use Position Control
• Relative position (without feedback)
• Easy to control
• Steps moved number of pulses in
• Desired Velocity ? Step Rate
• Inexpensive
• Good holding torque
• No brushes
• Size Range
• 1.3L 10 oz-in 12.
• 9L 2000 oz-in 700.
• Can lose steps if load
• or pulse rate too high

2
Permanent Magnet DC Motor

• Typical Use Variable Speed Control
• Position control is possible but requires
  additional hardware
• Usually used with position or velocity feedback
  (optical encoder or tachometer)
• Control Speed ? Input voltage
• (DC or PWM)
• Reduction gear heads common
• Brushes wear out, spark, cause RFI
• Size Range
• Micro 0.5 L x 0.2D (pager vibrator) 5
• Big 13L x 4D 2 HP 1000

V2 gtV1
Torque
V1
RPM
3
Stepper Motor Speed vs Torque
fmax
Lost steps (stall)
Step Rate
Torque
time
TLOAD
No lost steps w/acceleration (slewing) control
No lost steps w/o acceleration control
Step Rate - Hz ( ? Desired RPM)
fmax
Ref. (Figure 2.75), T. Kenjo, Stepping motors
and their microprocessor controls, Oxford Press,
1984