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:
1.3”L 10 oz-in $12.
9”L 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 0.2”D (pager vibrator) $5
Big ”L x 4”D 2 HP $1000
V2 >V1
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