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I'm trying to make a step counter using Hall effect sensor implanted near the rotor of a common hybrid-synchronous(1.8° in full step) stepper motor, and I'm confused as I'm not able to figure out when common stepper drivers executes a step, whether at the rising edge of pulse sent by controller or falling.

Edit: I'm referring to the output of the stepper controller to the stepper driver(Step Signal) not of stepper driver to stepper motor.

Help will be appreciated.

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  • \$\begingroup\$ What common stepper driver? \$\endgroup\$
    – Andy aka
    Feb 23, 2018 at 13:15
  • \$\begingroup\$ A4988 or DRV8825 \$\endgroup\$ Feb 23, 2018 at 13:23

2 Answers 2

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I'm confused as I'm not able to figure out when common stepper drivers executes a step, whether at the rising edge of pulse sent by controller or falling.

For the Allegro A4988 I would refer you to figure 3 in the data sheet: -

enter image description here

Following activation of a "step" command, it looks to me like the load current is changing on the leading edge i.e. pretty much instantly. There are other pictorial examples in that device's data sheet that confirm this.

For the DRV8825 it's a similar story: -

enter image description here

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A normal stepper motor uses two square waves which are offset in such a way that they produce a 'Gray code' pattern. Each change is one step:

enter image description here

Pure technically speaking the step is taken when the pattern changes. Thus if you take one step, the rotor moves when the pattern changes.

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