Stepper Motors
Intro
Stepper motors are constant power motors. Unlike DC motors which rotate by create a reversing magnetic field stepper motors work by attracting a rotor core with magnetic coils aligned in a stator using discrete intervals called steps.
Steppers are usually run in open loop, meaning there is not secondary sensor monitoring the position. In some cases this makes it much easier to implement a digital controller for them. The errors associated with steppers are non cumulative so even running it in open loop will usually yield accurate positions.
Their flaws are usually in low torque, high virbation and limited speed. Also their resolution is limited to a multiple of it's step intervals.
Bipolar vs Unipolar
- Unipolar
- Bipolar (series)
- Bipolar (Parallel)
- Bipolar (series)
Drivers
- Constant Voltage (L/R)
- Constant Current (Chopper)
Stepping Schemes
- Wave Stepping - This is the most power efficient method for stepper but supplies the least torque.
| Phase | A | B | C | D |
|---|---|---|---|---|
| State1 | 1 | 0 | 0 | 0 |
| State2 | 0 | 1 | 0 | 0 |
| State3 | 0 | 0 | 1 | 0 |
| State4 | 0 | 0 | 0 | 1 |
- Full Stepping
| Phase | A | B | C | D |
|---|---|---|---|---|
| State1 | 1 | 1 | 0 | 0 |
| State2 | 0 | 1 | 1 | 0 |
| State3 | 0 | 0 | 1 | 1 |
| State4 | 1 | 0 | 0 | 1 |
- Half Stepping
- Micro Stepping
Wiring
- 4 wire - Bipolar
- 8 wire - Unipolar or Bipolar
Steps per revolution
Common Step angle 1.8 deg (200 steps per rev)
NEMA Sizes
NEMA 17
NEMA 23
NEMA 35
Vendor List
Japan Servo KH42HM2-951
References
Formulas
Step Angle = 360/S (S = steps)
