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I have this motor, from datasheet it works on the 6-12V range and has a no load current of 0.52A, and a stall current of 20A. I want to test the motor before buying an expensive motor driver.

I have an L298N H bridge at home and a mbed microcontroller. I am using the mbed to generate the PWM control signal.

So far, I cannot get the motor to move. I have tried several PWM frequencies, from 50Hz to hundreds to 2kHz and higher.

With frequencies between 100-2kHz I get a buzz as I increase the PWM duty cycle but the motor doesn’t move.

The L298N has a max current of 2A per channel, so I was wondering that maybe it is not enough to start moving the motor. This motor is not high end quality but is very powerful.

My question is: Can I expect a better performance if I change the motor driver to one with more current output?

Edit 1

To clarify my problem I uploaded a video to YouTube https://youtu.be/7ZT4wXyWSXA.

I could not move the big motor so I moved to a smaller one. The yellow one in the video.

  1. As I increase the PWM duty cycle the buzz increases but the motor does not move.
  2. At some point the motor starts to move but at a very high speed to be taken as the initial speed.
  3. If I decrease the PWM duty cycle the motor keeps moving. I think is because is has some inertia, so now it’s easy to move even at low speeds.
  4. At some point the motor stops.

How can I make the motor move from beginning at low speeds?

Can a different motor driver improve the PWM performance?

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  • $\begingroup$ try using 100% duty cycle for 500ms and drop to 20% duty cycle after that ..... if that starts up the motor, then reduce the 500ms to 250ms .... keep trying different values to find out the shortest length of the initial "kick" to get the motor started ...... then try reducing the initial power 50% duty cycle .... anyway, i am sure that you get the idea $\endgroup$
    – jsotola
    Oct 31, 2018 at 19:48

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If you want to test the motor, just apply a DC source to it directly rather than using the l298.

A 12V car battery is a source you likely have access to that can supply enough current so you can test the torque and speed.

Regarding the pwm control, you need to have sensor feedback. Then you will be able to use a control algorithm to, in effect, sense when the voltage, as created by the pwm, has overcome motor inductance to generate enough current to create enough torque to break the static friction and then continuously adjust the pwm to accelerate and then maintain the velocity of the output to be what you want.

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  • $\begingroup$ Well, I also want to test how well the PWM is for the motor. But maybe I need more power for that. $\endgroup$
    – Luis
    Oct 31, 2018 at 13:13
  • $\begingroup$ I edited my question to clarify my problem. $\endgroup$
    – Luis
    Oct 31, 2018 at 14:47

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