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Need DRV8811 Basic Help

Mike Tucker
Prodigy 90 points

Other Parts Discussed in Thread: DRV8811

I have been experimenting with the DRV8811 EVM board driving a Applied Motion HT17-275 Stepper Motor. I am looking for guidance on how to get the maximum torque out of the stepper motor. Right now, I have the motor connected to the evaluation board in a Bipolar Series configuration. My application is not complex--I need to run the stepper motor in both directions at a constant "slow" speed (I don't understand the acceleration/deceleration details).  The speed is not critical (now at approx 2 revolutions/sec)  I am using a step rate of 700 Hz.  I have found through experimentation that this works best.  Is there a phone number for TI tech support so I can brainstorm with someone about how to configure this chip?  I am using a motor voltage of 12 VDC and my power supply can deliver about 500mA before the voltage starts to drop below 12 VDC.  I would like to be able to get a bit more torque out of the motor without having to increase the size (VA rating) of the power supply (right now, I can stall the motor but if I use a supply rated at 12 VDC @ 1 amp, I get plenty of torque and the motor does not stall.  operation is not continuous--say 45 seconds of operation followed by several minutes of rest.

Can someone help?  What are best settings for DRV8811 parameters (e.g. Pulses Per Second, Current Control, Decay Control, Accel Rate, Time Base, etc.) to get max torque from a minimum 12 VDC supply?

Thanks!!

Mike

  • 0
    TI__Expert 8885 points

    Mike

    e2e fourm is best place to get answers to our technical questions. I don't think that we have any dedicated phone number to resolve techincal queries. The other way is to contact TI sales and field team in your local area to get support.

    motor torque is propotional to how much current is applied to it so to get the maximum torque, you should pump right amount of current to motor. In DRV8811 the current is control by VREF pin voltage and current sense resistor. Refer to eq1 in "current regulation" section of data-sheet. EVM gives the flexibility to change this value either through GUI or potentiometer. The other setting:

    1. PPS/Accel rate/ Time base: These are decide by application needs i.e. motor speed, ramp time to reach min/max speed. These are not specific to DRV8811.

    2. Decay mode: Mixed or fast decay mode is preffered for better current control.

    Please refer to  application reports "slyt482.pdf" and "sloa170.pdf" which will help you get better understading developing steppper applications.

    Best Regards

    Milan