This is the circuit for the driver to adjust the motor speed at STEPPER motor. This circuit can drive a motor 12v to 24V. This circuit is based on 74194. The test series are placed differently and show SN7474 in logic block form and LED lights are used to indicate the motor coil is removed. This is the figure of the circuit.
STEPPER motor circuit uses IC 555 astable oscillator produces a series of clock pulses fed to Pin 11 of integrated circuit SN74194. Every time the clock pulse goes HIGH (positive) in the country in the SN74194’s HIGH OUTPUT terminal (PIN’s 12, 13, 14, 15), transferred either UP or DOWN y one place. Referring to the “Stepper Motor Driver Waveforms” diagram. Shift direction is controlled by a switch S2.
When S2 is in the middle position OFF HIGH-state output will remain in last position and the motor will be stopped. When the base of Q6 is a shift to PIN LOWER 12-15 – 14 – 13-12. When the base Q7 is a shift to PIN LOW 12 – 13 – 14 – 15 – 12. Direction of the shift pulses determine the direction of motor rotation. The pulses from the OUTPUT’s of SN74194 four segments are fed Driver ULN2003. When the input of a segment is HIGH, it will activate the Darlington transistor and OUTPUT will conduct current through one of the motor coils. As the roll motor turned ON in order to follow the motor rotates these steps.
[Circuit source: home.cogeco.ca]
