Stepper motor control usually uses bidirectional drive current, and motor stepping is achieved by switching the windings in sequence. Usually this stepper motor has three drive sequences:
1. Single-phase full step drive:
In this mode, the windings are energized in the following order, AB/CD/BA/DC (BA indicates that the winding AB is energized in the opposite direction). This sequence is called single-phase full-step mode, or wave-driven mode. At any one time, only one phase is powered.
2. Two-phase full step drive:
In this mode, the two phases are energized together, so the rotor is always between the two poles. This mode is called two-phase full stepping. This mode is the normal driving sequence of a two-pole motor and can output the maximum torque.
3 half step mode:
This mode combines single-phase and two-phase steps to power up: single-phase power-up, then two-phase power-up, then single-phase power-up..., so the motor runs in half-step increments. This mode is called the half-step mode, and the effective step angle of each excitation of the motor is reduced by half, and the output torque is also low.
The above three modes can be used to rotate in the opposite direction (counterclockwise), if the order is reversed, it will not work. Typically, stepper motors have multiple poles to reduce the step angle, but the number of windings and the drive sequence are constant.
Universal DC motor control algorithmSpeed ​​control of general-purpose motors, especially motors with two types of circuits:
Phase angle control
2.PWM chopping control
Phase angle control
Phase angle control is the easiest way to control the speed of a universal motor. The speed is controlled by the variation of the arc angle of the TRIAC. Phase angle control is a very economical solution, but it is not very efficient and is prone to electromagnetic interference (EMI).
The above diagram shows the mechanism of phase angle control and is a typical application of TRIAC speed control. The phase shift of the TRIAC gate pulse produces an efficient voltage that produces different motor speeds, and a zero-crossing cross-detection circuit is used to establish a timing reference to delay the gate pulse.
PWM chopping controlPWM control is a more advanced solution for general motor speed control. In this solution, the power MOFSET, or IGBT, turns on the high frequency rectified AC line voltage, which in turn produces a voltage that varies over time for the motor. Its switching frequency range is typically 10-20 KHz to eliminate noise. This universal motor control method results in better current control and better EMI performance, so it is more efficient.
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