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Author Topic: PWM freq  (Read 3944 times)

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Offline croy

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PWM freq
« on: June 28, 2011, 10:26:58 AM »
This may sound silly but i am at a loss and kneed to know what is the Frequency of the PWM

Offline Tweakie.CNC

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Re: PWM freq
« Reply #1 on: June 28, 2011, 11:26:43 AM »
The repetition rate (Frequency) for the PWM is programmable and is set here.

Tweakie.
KEEP SAFE !
Re: PWM freq
« Reply #2 on: June 28, 2011, 05:48:51 PM »
This may sound silly but i am at a loss and kneed to know what is the Frequency of the PWM

The PWM base frequency (repetiition rate) is programmable as Tweakie has stated. But keep in mind that as you set the base frequency of the PWM higher the resolution of the PWM decreases.

The PWM signal is created using the Mach3 kernel Interrupt.

If you are running the kernel at 25KHz and have a PWM base frequency of 50HZ then;

PWM resolution = Kernel Speed/PWM base Freq  = 25,000/50 = 500

This gives you 500 steps from 0 to 100% PWM signal.


If you are running the kernel at 25KHz and have now set a PWM base frequency of 200Hz then;

PWM resolution = Kernel Speed/PWM base Freq  = 25,000/200 = 125

This gives you 125 steps from 0 to 100% PWM signal. If you are using the PWM for speed control this will give 125 different speeds from 0rpm to max rpm.

You need to choose a base frequency that will provide speed control with sufficient resolution for your application.

Cheers,

Peter.
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Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com

Offline croy

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Re: PWM freq
« Reply #3 on: June 29, 2011, 01:38:07 AM »
Thanks you both, i an grateful for the answers.