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 2000 oz-in $700. Can “lose” steps if load or pulse rate too high

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 13”L x 4”D 2 HP $1000 RPM Torque V1V1 V 2 >V 1

Torque Stepper Motor Speed vs Torque No lost steps w/acceleration (slewing) control No lost steps w/o acceleration control Lost steps (stall) Step Rate time f max T LOAD Step Rate - Hz (  Desired RPM) Ref. (Figure 2.75), T. Kenjo, Stepping motors and their microprocessor controls, Oxford Press, 1984