Generate digital PWM (Duty Cycle control)

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janjoh
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Joined: 23 Oct 2016 16:57

Generate digital PWM (Duty Cycle control)

Post by janjoh » 20 May 2018 22:23

WHat is the best way to generate a digital PWM signal? Purpose is control of PWM controlled fan.

I understand that timers/servo library appears buggy right now?

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PoltoS
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Joined: 26 Jan 2011 19:36

Re: Generate digital PWM (Duty Cycle control)

Post by PoltoS » 23 May 2018 00:07

You can use GPT and Servo (they are no buggy), but much easier is to use analogWrite to drive one of the four PWM pins

janjoh
Posts: 35
Joined: 23 Oct 2016 16:57

Re: Generate digital PWM (Duty Cycle control)

Post by janjoh » 23 May 2018 08:34

PoltoS wrote:
23 May 2018 00:07
You can use GPT and Servo (they are no buggy), but much easier is to use analogWrite to drive one of the four PWM pins
Analogwrite does not work for me with these fans. They require a true "return to zero" signal and i have not been able to find a way to decrease the pwm frequency properly to acheive this. AnalogWrite for all intents and purposes generates an analog level, not a discernable duty cycle. IN most applications this is a plus. But in this case, it is a minus :)

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PoltoS
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Re: Generate digital PWM (Duty Cycle control)

Post by PoltoS » 23 May 2018 20:34

analogWrite generates real return to zero, but at 488 Hz. If the input capacity is to big, your signal will become smoother like real analog.

For your case use FastPins and delays

janjoh
Posts: 35
Joined: 23 Oct 2016 16:57

Re: Generate digital PWM (Duty Cycle control)

Post by janjoh » 26 May 2018 13:37

Hm, i wonder what would happen with an external pulldown resistor...

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