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Topic: Fan control help needed (Read 1 time) previous topic - next topic

Tisa

Hi guys, I'm posting for the first time but I have been reading the forums alot and have learned alot aswell. But now I've come to an impass and I need some help.

My problem is that I'm trying to control a computer fan(Arctic Cooling F8 PWM) with the PWM pin from an Arduino Due but nothing happens. I'm sure I've gotten the connections and the code right since it works on a different fan.

The fan itself turns on when connected to a 12V battery, but analogWrite() does nothing. Now I've done some research but I'm not really sure what I'm looking at. There's alot of mention of PWM frequency which I don't fully understand. I read that most of the CPU fans work on a 25kHz frequency but I'm not sure what this has to do with my Due.

Basicly what I need is that I need to understand how all this works, any explanations and documentation are greatly appreciated.

bullroarer

What code are you trying to run on the Due?

Tisa

Code: [Select]
int LDR = A0;                 
int LDRValue = 0;                   
int light_sensitivity = 750; 

void setup()
  {
    Serial.begin(9600);           
    pinMode(13, OUTPUT);   
  }

void loop()
  {
    LDRValue = analogRead(LDR);       
    Serial.println(LDRValue);                 
    delay(50);                                             

    if (LDRValue < light_sensitivity)
      {
         analogWrite(13, 100);
        }
        else
        {
          analogWrite(13, 200);
          }
          }



This is the code I got running. Basicly it's hooked up to a lightresistor so when the lights dim, the fan turns on. Like I mentioned earlier it works on another CPU fan I got, the problem might be the PWM frequency.

alnath

how is all this wired ?
could you post a schematic ?


monkeyhacker

IIRC 3 pin fans cannot be controlled with PWM through the fan itself.

If it's a four pin fan then you need a common ground between the Arduino and the fan.

If it's a 3 pin fan you can still control it via PWM, but you will need to add a transistor to switch it via PWM.

Tisa

#6
Apr 24, 2014, 09:14 am Last Edit: Apr 24, 2014, 08:50 pm by Tisa Reason: 1
Sorry, I forgot to add the common ground. It is a 4 pin fan. I'll try the transistor and see if it helps.

Tisa


IIRC 3 pin fans cannot be controlled with PWM through the fan itself.

If it's a four pin fan then you need a common ground between the Arduino and the fan.

If it's a 3 pin fan you can still control it via PWM, but you will need to add a transistor to switch it via PWM.


Sorry for the late reply, I added a TIP120 transistor and some diodes and got it to work. Thank you very much for the tip!

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