1. Electric Rotary Actuators (motors)
DC motors
AC motors
stepper (2-phase synchronous)
brushless (3-phase synchronous)
induction

2. Step Motors

3. Step Motors

4. Step Motor 12 step/rev, 1 phase on

5. Step Motor 12 step/rev, 2 phase on

6. Step Motor 12 step/rev, half-stepping

7. Step Motors

8. Selecting Step Motors
Torque
Speed
Current
Lead configuration

9. Torque/Speed

10. Series/Parallel Wiring

11. Step Motor Drives
Resolution (full, half, microstepping)
Current Limit (resistor or digital)
AC powered or DC powered
Pulse/Direction or Indexing

12. Resolution Full step/Half step Microstepping Max step frequency
x2,x4,x5,x8,x10,x16,x25,x32,x50,x64,x125,x128,x250,x256 common choices
Max step frequency
PLC: 7kHz pulse rate => 2100 RPM at x1, 8.2RPM at x256 (1.8deg motor)
Compumotor 6104: 2MHz pulse rate => 2300RPM at x256
Resonance problems

13. Incremental Encoders

14. Incremental Encoders
Encoders typically run on +5V, not +24V
Outputs are typ. not 24V compatible either

15. Absolute Encoders
doubling resolution requires adding another photodiode/LED pair
cost is much higher than incremental
does not require seeking to establish reference location

16. hybrid incr/absolute encoders
add more information to index channel to reduce amount of seeking required to find reference position.
interface requires lots of wires (parallel) or a special comm. protocol

17. Potentiometer
A potentiometer (or pot) is a variable resistor wired to obtain a variable DC voltage proportional to position

18. Magnetostrictive Pos. Sensor
Pulse sent down magnetostrictive material
Pulse reflects off position magnet’s field
Position is proportional to trcvd - tsent
Pulse propagates at ~2800 m/s
Resolution is ~.001” with tupdate ~1msec/in.

19. Magnetostrictive Sensor