10HZ PWM Automotive Fan

Other Hardware Product Design
6

You're in luck my friend. Another user found this to work (albeit with a different requirement). I made the changes to match your requirement. Give it a shot.

int analogPin = A0;
int val = 0;
uint16_t duty = 0;

void setup() {
  // put your setup code here, to run once:
  PWM_init();
}

void loop() {
  // put your main code here, to run repeatedly:
  val = analogRead(analogPin);
  duty = map(val, 0, 1023, 0, 22500);
  OCR1B = duty;
  delay(50);
}

void PWM_init(void)
{
  /***************************
  Initialize the PWM hardware
  ***************************/

  // set OC1B output pin
  DDRB |= 1<<PORTB2;

  // set TIMER1 for Fast PWM mode, non-inverted output on OC1B pin
  TCCR1A = 1<<WGM11 | 1<<WGM10 | 1<<COM1B1 | 0<<COM1B0;
  TCCR1B = 1<<WGM13 | 1<<WGM12;

  // disable interrupts
  TIMSK1 = 0<<OCIE1B | 0<<OCIE1A | 0<<TOIE1;

  // set TOP value to generate initial 10 Hz [250 KHz / 25000]
  OCR1A = (25000 - 1);

  // set initial duty cycles at 10%
  OCR1B = 2500;

  // start TIMER1 at 250 KHz [DIV64]
  TCCR1B = 1<<WGM13 | 1<<WGM12 | 0<<CS12 | 1<<CS11 | 1<<CS10;

  return;
}

Potentiometer input on A0 and PWM signal out on D10