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DRV8835: DRV8835

Part Number: DRV8835
Other Parts Discussed in Thread: DRV8834, DRV8846, DRV8885

HI, 

We are using DRV8835 to drive a 0.9 degree/Step stepper Motor. We are able to make the Motor rotate 100 steps for 360 degree.

But how to we control the motor to rotate 400 steps for 360 Degree.

Do we have to control the timing of Enable and Phase Pins. Beacuse now we are giving the input in ms. If we further reduce the pulse width, we are not able to control the steps.

Any suggestion on the above problem.

  • Hi Hemanth,

    Can you provide the sequence used to make the motor rotate 100 steps for 360 degree?

    Can you provide the motor manufacturer recommended sequence?

  • HI Rick,

    Please find the attached waveform. Both Output and Input is captured.

    If we reduce the pulse width of Input we will not be able to turn the motor.

    Kindly let me know your suggestions.

    Regards

    Hemanth R

  • Hi Hemanth,

    How far did the motor move in the captured image?

    Please refer to Figures 14 and 15 of the DRV8834 datasheet. These figures are good examples of how to move a stepper with a device like the DRV8834 or DRV8835 using the PH/EN inputs.

  • Rick,

    The captured images is for 1 STEP, if we run the motor with the same timing for 100 steps, 360 degree will be completed.

    I will check the waveforms and come back.

    Regards

    Hemanth R

  • Rick,

    As suggested we are able to run the motor for 360 degrees, with lesser Ton time on Phase lines.

    Do you have any waveform data for microstepping. For our application we need to microstepping.

    Also, what is the maximum microstepping possible in DRV8835.

    Looking for your positive response.

    Regards

    Hemanth R

  • Hi Hemanth,

    For microstepping, you will need to control the current through the coils. The DRV8835 does not have this ability but you may be able approximate it by changing the PWM duty cycle.

    Please consider using the DRV8834 or DRV8846.

    Both devices have built in indexers to create up to 1/32 microstepping. External sense resistors allow for more precise current control.

     

  • Rick,

    Thank you for the suggestion. We have already desgigned the H/W with DRV8835. It will be very difficult to change the chip at this point of time.

    We will try changing the PWM pulses with DRV8835. Do you have any reference for the waveforms for microstepping with DRV8835.

    So that we can try to follow the same.

    Regards

    Hemanth R

  • Hi Hemanth,

    What level of microstepping is desired?

    There is one referred to as non-circular half step that is easy to implement. 3 steps of 100% and 1 step of 0% are used.

    Please refer to table 4 of the DRV8885 datasheet.

    If you are trying for more levels, it is more complicated. You can try PWM'ing at each desired step by using the formula:

    Duty cycle = (Desired current * Coil Resistance)/VM

    This will create an average voltage across the coils, but may not regulate the current as desired.