Bipolar Stepper Motor Driver Circuit

Posted on Feb 5, 2014

Briefly, the circuit works as follows; the clock signal drives 4 D-flipflops in the control section which store the on/off state of each of the current directions for the two stepper motor coils. The flipflops comprise a FSM (finite state machine) which advances to the next step of a half-stepping sequence on each rising clock edge. The drive sect

Bipolar Stepper Motor Driver Circuit
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ion provides the current-driving capabilities to turn the control signals into coil-driving currents. The drive section also includes protection diodes to prevent back-EMF from the motor coils from destroying the NTE1749/L293 IC. This circuit is designed to power a 12V stepper motor, and use 5V for logic. If your stepper is not 12V capable the circuit will require modification. The circuit can be powered with a standard 12V lead-acid battery. Stepper motor speed is controled by how fast the current direction is switched through the coils (hmm, current direction switched, sound familiar like AC power ). The first step in controlling stepper speed is to generate a clock signal to run the d-flipflops in the control section. The frequency of this clock signal controls how fast the motor steps. The clock generation circuit shows one way of generating a square-wave signal (clock) at a specific freqeuncy. There are many good sites which describe the operation of the 555 timer IC used in this circuit, such as this one at the university of Guelph. The frequency of the square wave produced by the 555 is controled by the 0. 18uF capacitor and the 10k pot / 23k resistors. Timing is generated from the charging and discharging of the capacitor through the resistors. The switch between 2. 2k and 23k for R1 selects track (noraml) or slew (fast) modes. The 10k pot allows fine adjustment of the exact tracking speed. The 10nF capacitor...

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