Stepper motor control circuit

This machine uses the FD-CAS-923 1 stepper motor control experiment board and a 4-phase stepper motor. Its schematic diagram is shown in Figure 4-42a.
The JK1 head catcher is a 40-core flat cable plug. The signal arrangement is the same as EICE51 simulation. The interface is compatible and can be directly connected to the emulation port of EICEsl.
The +5v power supply is provided by EICE51, and the +12V power supply is externally connected through the rKl plug.
    1) According to the working principle of the stepper motor, use 8031 ​​Pl. 4-7 to drive and connect to the A, B, C, and D phases of the stepper motor respectively, and use software
to control the Pl port to output a pulse sequence to control the speed, direction, and step of the stepper motor. distance. At the same time, in order to observe the rotation status of the stepper motor,
status indicators are installed on the A, B, C, and D phase outputs.
    2) In the stepper motor drive circuit, Rs~R8 are current-limiting resistors, used to limit the current value in the coil. The diodes VD1~VD4 form a return loop of the coil current when
the transistor is turned off, also called a return diode. They should be selected when selecting Consider the supply voltage and coil current. VT1~VT4
are switching transistors.
  The control process principle is as follows.
  The operation of the stepper motor is controlled by pulse signals. The traditional method is to use a digital logic circuit - a ring pulse distributor to control
the stepping of the stepper motor. Figure 4-42b shows the control process waveform diagram.
    (1) Running direction control The stepper motor
works in a three-phase six-beat mode. If
the power is supplied in the order of A-- AB+ Ib-BC-, C+CA-.A, it will run forward.
If it is powered in the order of A- AC -C-CB- The sequence of B--BA--A
is reversed. (z) Control of operating speed It can be seen
    from Figure 4-42b that when the period of the CP pulse is changed , the width of the high and low levels of the ABC three-phase winding will change, which will lead to changes speeds. Changes cause the motor speed to change, so adjusting the period of the CP pulse can control the running speed of the stepper motor.     (3) Rotation angle control Because each input of a CP pulse causes the stepper motor's three-phase winding state to change once and rotate an angle accordingly , the rotation angle of the stepper motor is determined by the number of input CP pulses.     This machine uses an 8031 ​​microcontroller to control the operation of the stepper motor , and outputs a control code at the Pl port in a three-phase six-shot mode to make it rotate forward or reverse. Therefore , the change period of the Pl port output code controls the running speed of the motor: