DC12V fan controlled by PWM => Noise

Projects Programming
8

@TomGeorge , thanks a lot! So the problem is the fan technology, I didn´t know about these "inteligent" low consumption fans.

Please, anyone can explain me what means:

TCCR0A = _BV(COM0A1) | _BV(COM0B1) | _BV(WGM01) | _BV(WGM00); // Used to reduce motor harmonics
TCCR0B = _BV(CS01); // Used to reduce motor harmonics from PWM
OCR0A = 180;        // Used to reduce motor harmonics from PWM
OCR0B = 180;        // Used to reduce motor harmonics from PWM

As I read from @Ballscrewbob #4 2nd link:

imagen
imagen985×352 58.2 KB

but I can´t see a clear relation between code and the link information, I don´t understand the low programing code

Here is how I am doing to set PWM frecuency for timer0 (I can´t use other pins because I am using other libraries like IRremote and AltSoftwareSerial), I also don´t understand very well how this works, it´s very low programming for me:

  TCCR0B = TCCR0B & 0b11111000 | 0b101; //Timer 0 (pin 5&6) with 1024 prescaler at 8MHz = 30,5Hz 
                                        // 31KHz   =>  0b001; (preescaler = 1)
                                        // 3,9KHz  =>  0b010; (preescaler = 8)
                                        // 488Hz   =>  0b011; (preescaler = 64)
                                        // 122Hz   =>  0b100; (preescaler = 256)
                                        // 30,5Hz  =>  0b101; (preescaler = 1024)

Then I set the dutty cycle, with analogwrite (pin,dutty-cycle) command.

analogwrite (5,190);

Can I configure more frecuency values that the commented for the different prescaler values? How?

Or this is the most that can be done for controlling PWM frecuency vs PWM noise for motor/fan speed control aplications?

Thanks again!