PWM Divider advice

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PWM Divider advice

Post by yongkimleng » Thu Oct 01, 2009 12:18 pm


I found that the PWM divider affects the electrical stability of the openservo setup by a huge margin. My setup was very unstable when the divider was 0x10, somewhat stable at 0x40 and very stable at 0x60-0x80.

I have measured that my motor coil resistance is 25.6 ohms and it is rated for 6v operation but I'm using 9v while ensuring that the PWM value in the openservo code does not go above 170 (out of 255).

Does anyone have any advice why it behaves this way?

Thanks in advance

Best regards,

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Post by jharvey » Thu Oct 01, 2009 9:10 pm

About the voltage doubling idea, I think the problem there is space. It would be hard to fit on the PCB. I think you would be better off putting on a huge cap to help buffer instead.

About the PWM, I believe the PWM divider will allow the PWM duty to streach out. If you had a scope on it, I believe you would see a huge inrush. When the PWM is set high enough, that inrush is limited, such that you don't brown out.

So 9v/26ohms is .346 amps DC, while the impeadance is some other resistance, this will allow for a higher current draw when first turned on, which will eventually settle to .346 amps.

I'd bet a larger input buffer cap would allow for lower PWM dividers.

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Post by newyorkdd » Thu Jul 14, 2011 6:22 am


I am also looking answer for
I understand the pwm output on the arduinos is 0-5V. Is there a way i could make this voltage go from 0-10V?

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Joined: Thu Jan 30, 2014 6:28 am

Post by Janleex0 » Thu Jan 30, 2014 6:58 am

I am using a Futaba-Servo with PCB replaced to OpenServo V2, bought from watterott (sorry, but I can't type link on my first post).

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