Arduino PWM to PC fan Problem :S

Using Arduino Motors, Mechanics, Power and CNC
1

So I have my arduino hooked up to the PC fan PWM input, although it is a 12v fan to play it safe i wanted to get it working with the arduino with a 9V battery before I hook it up to the mains. It is a 4 wire fan and I'm connecting the Arduino PWM pin directly to the pwm wire on the fan as you can see below:

the problem I'm having is that the analogWrite() code I'm using doesn't seem to work, there is no difference in fan speed when I set it to 255 or even when I set it to 0. To make your lives easier I've included the code below:

int pcFan = 3; // PC fan is connected to the Digital pin 3
int led = 13; // I'm using the built-in LED on pin 13 to tell me when the fan should be moving at full speed or not.

void setup()
{
  pinMode (pcFan, OUTPUT);
  pinMode (led, OUTPUT);
}

void loop()
{
  analogWrite(pcFan, 0); // Turn Fan and LED off for 5 seconds
  digitalWrite(led, LOW);
  delay(5000);

  analogWrite(pcFan, 255); // Spin Fan at full speed and turn on LED on for 5 seconds
  digitalWrite(led, HIGH);
  delay(5000);
}

any help would be most appreciated,
thanks in advance.

2

Hi bro........ Is there any library for controlling bldc motors with esc using arduino>>>> i cant understand the way to control it ...will this work:(

#include <Servo.h>
Servo.motor;
void trottle() {
speed(0);
delay(1000);
}
void speed(int rpm) {
int angle = map(rpm, 0, 100, 0, 180);
 motor.write(angle);
}
void setup() {
motor.attach(9);
trottle();
}
void loop() {
speed(40);
delay(1000);
}
3

@missisipihipi

Hi
so the cabel to control your motor is connected to a digital pin on your Arduino. Why do you use an analog command then?

analogWrite(pcFan, 0);

You have to use an digital command ( sorry if that is called different ).

digitalWrite(pcFan, 0);

So try it with this code :

int pcFan = 3; // PC fan is connected to the Digital pin 3
int led = 13; // I'm using the built-in LED on pin 13 to tell me when the fan should be moving at full speed or not.

void setup()
{
  pinMode (pcFan, OUTPUT);
  pinMode (led, OUTPUT);
}

void loop()
{
  digitalWrite(pcFan, 0); // Turn Fan and LED off for 5 seconds
  digitalWrite(led, LOW);
  delay(5000);

  digitalWrite(pcFan, 255); // Spin Fan at full speed and turn on LED on for 5 seconds
  digitalWrite(led, HIGH);
  delay(5000);
}
4

I use the "analogWrite()" command because that is the only way to PWM a pin, "digitalWrite()" (if i'm not mistaken) can not do PWM signals, it can only do "HIGH" or "LOW"

5

Did you tried it? It won´t damage your Arduino?

6

i have tried it and i get exactly the same result as before, fan spins at same speed regardless of weather i put a "255" or a "0"

7

Ok I dont know what is wrong then but i found a similar Tutorial in a book called 30 projects fo the evil Genius. Here is the Website: www.arduinoevilgenius.com

But anyway here is the code:

int motorPin = 11;

void setup()
{
  
  pinmode(motorPin, OUTPUT);
  analogWrite(motorPin, 0);
  Serial.begin(9600);
}


void loop()
{
  if (Serial.available())
  {
    char ch = Serial.read();
    if (ch>= '0' && ch<= '9')
    { 
      
        int speed = ch - '0';
        analogWrite(motorPin, speed*28);
     }
   }
}

I quickly copied it from the book so if there are any mistakes in the code you can download it from the link at the top. When you send values from 0 to 9 to your Arduino you can control the speed of the motor.

BEFORE UPLOADING:
This project requieres additionaly to th arduino and the fan an BD139 power transistor and a 270Ohm 0.5W resistor.

Connecting it: (sorry I didn´t find a circuit diagramm :()

Arduino:
Digital Pin 11 to 270 Ohm resistor

Transistor:
B:270 Ohm Resistor
C:Motor
E:GND

Motor:
12V
Collector of Transistor

With this tutorial you also don´t have to worry about the 2 other cables on the Motor you just need the positive an negative cabel. But remember THIS IS NOT MY TUTORIAL.

Hope I could help you.

8

thank you for your reply and i am aware that it is possible to achieve a similar result with the use of an NPN transistor, but i specifically bought the fan because of its PWM capabilities and would really rather be able to do it directly (but thanks anyway)

9

Seriously does noone have any idea why this isn't working? i'm at my wits end! :~ :blush: =(

10

From this document - http://formfactors.org/developer/specs/4_Wire_PWM_Spec.pdf ?

2.1.4 PWM Control Input Signal
The following requirements are measured at the PWM (control) pin of the fan cable connector see
Figure 7 and Table 1:
PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz
Maximum voltage for logic low: VIL = 0.8 V
Absolute maximum current sourced: Imax = 5 mA (short circuit current)
Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)
This signal must be pulled up to a maximum of 5.25V within the fan.

The default Arduino PWM frequency is 488Hz.