• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 82 subscribers
  • Views 720 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28335: Servo Motor Doesn't Rotate with Low Duty Cycle PWM (below 30%)

Umer Daraz
Prodigy 200 points
Part Number: TMS320F28335

Hello,

I'm controlling a servo motor using a microcontroller (TMS320F28335) that creates a PWM signal that is fed to a MOSFET based H-bridge, the problem is that the motor only moves when I set the PWM with a duty cycle of 35% or higher, if it has a lower duty cycle it doesn't move and makes a noise. I've tried all PWM frequencies that the microcontroller can create and the higher the frequency the higher the duty cycle has to be to make the motor rotate. But if I use a power supply, directly connected to the motor, it works perfectly, for any voltage. All the test were made without any load.

The motor parameters are the following

R = 2.1 ohm

L = 277 uH

k = 0.0548

T = 30e-6

F = 25 khz

Kindly help and guide me

Thank You

Umer

  • 0
    TI__Mastermind 27240 points

    Hi Umer,

    You may need to add additional inductance in series to the motor to smoothen the current through the motor. I have a feeling that the current is discontinuous. You may have to monitor the current and voltage of the motor to make a determination.

    This being very generic, I recommend you to review the basic topology for debug information. It has nothing to do with the source of PWM. Hope you see the point.