Fan speed don't go to 100%

Projects Programming
1

Hi,

I'm a newby with programming and now am fiddling for days with the following.
I want a fancontroller pwm that goes faster when it's closer to the maximum temperature.
Buy in my sketch the fan speed don't go past 50%.
Hopefully somebody can help me.
My code is:

    /**
     * ReadSHT1xValues
     *
     * Read temperature and humidity values from an SHT1x-series (SHT10,
     * SHT11, SHT15) sensor.
     *
     * Copyright 2009 Jonathan Oxer <jon@oxer.com.au>
     * www.practicalarduino.com
     */

    #include <SHT1x.h>

    // Specify data and clock connections and instantiate SHT1x object
    #define dataPin  10
    #define clockPin 11
    SHT1x sht1x(dataPin, clockPin);
    int tempMin = 22;
    int tempMax = 24;
    int alertLed = 8;
    int fanSpeed;
    int fanLCD;
    int fan = 9;
    
    void setup()
    {
       Serial.begin(9600); // Open serial connection to report values to host
       Serial.println("Starting up");
    }

    void loop()
    {
      float temp_c;
      float temp_f;
      float humidity;
      pinMode(alertLed, OUTPUT);
      pinMode (fan, OUTPUT);
      

      // Read values from the sensor
      temp_c = sht1x.readTemperatureC();
      if (temp_c < tempMin) {
          fanSpeed = 0;
          digitalWrite(fan, 0); 
                            } 
          if((temp_c >= tempMin) && (temp_c <= tempMax)) 
               { 
                fanSpeed = map(temp_c, tempMin, tempMax, 32, 255); // the actual speed of fan
                fanLCD = map(temp_c, tempMin, tempMax, 0, 100); // speed of fan to display on LCD
                analogWrite(fan, fanSpeed); // spin the fan at the fanSpeed speed
               }
      if(temp_c > tempMax) 
               {
               digitalWrite(alertLed, HIGH);
               }   
      else {
          digitalWrite(alertLed, LOW); 
      }
        Serial.print("TEMP: ");
        Serial.print(temp_c); // display the temperature
        Serial.print("C ");
        Serial.print("FANS: ");
        Serial.print(fanLCD); // display the fan speed
        Serial.println("%");
        Serial.print(fanSpeed);
        delay(200);



      delay(2000);
    }

If this is working i will try so start fan at 30% even when it's lower than the minimum temperature.

2 
      pinMode(alertLed, OUTPUT);
      pinMode (fan, OUTPUT);

Why are these in loop()? They belong in setup().

Have you written a sketch that simply varies the speed of the fan? Maybe the problem isn't with the code.

3

i moved pinmode to setup, still no lucht though. I will let you know soon, if I can alter the speed. Tnx

4

the map function is integer math which truncates values. MIght be the cause?

5

this one... map 22..24 to 32..255
I'd check this again..
Try as simple as IF...

6

as said map is truncating,

float t = getTemperature();
float fanspeed = 0;

if (t =< 22) fanspeed = 32;
else if (t >= 24) fanspeed = 255
else fanspeed = 32 + (t - 22) * 111.5;  // 111.5 = (255-32)/(max-min) in float math
7

It now works thx.

I just started over again, and now it goes perfect.

Tomorrow i can try to add a minimum start speed of 20%, so it will never drops below that.

@robtillaart
Tomorrow i will try your code also, I now still have the "map" code , but i noticed the speed goes up only if the temp is up a full degree, and with your setup i think it the fan speed will also increase if temp goes up only a few decimals.

Bedankt :wink:

8

let us hear if it works (or not)

9

@Rob.

Everything works, many tnx for it.

I think my code is a bit messy, don't know how to make it better but it works.

This is my code so far.

  #include <SHT1x.h>
    #define dataPin  10
    #define clockPin 11
  
    int fan = 9; // pwm lan
    int led = 8; // Allert led 
    SHT1x sht1x(dataPin, clockPin);
    
    int tempMin = 23; // Temp to accelerate more dan minimun Fan Speed
    int tempMax = 30; // the maximum temperature when fan is at 100%
    int fanSpeed;
    int fanLCD;
    int minFanSpeed = 30; // minimal speed fan in % 
     
    void setup() {
    Serial.begin(9600); // Open serial connection to report values to host
    pinMode(fan, OUTPUT);
    pinMode(led, OUTPUT);
  
    }
     
    void loop() {
        
     float temp = sht1x.readTemperatureC();
     float humidity = sht1x.readHumidity();
     
     if (temp < tempMin) 
         {
         fanSpeed = minFanSpeed * 2.55;   
         }
       else if (temp >= tempMax)
         {
       fanSpeed = 255; 
       digitalWrite (led, HIGH);
         } 
     else 
         {
     fanSpeed = (minFanSpeed * 2.55)  + (temp - tempMin) * ((minFanSpeed * 2.55)/(tempMax-tempMin));  // 2.55 is to make from procent to a 255 value  
     digitalWrite (led, LOW);
   delay (1000);
         }
     
 

   analogWrite(fan,fanSpeed);  
   Serial.println (temp); 
   Serial.println (fanSpeed);
   Serial.println (fanSpeed/2.55,0); //For LCD display in the future with no decimals
   delay(2000);  

    }

Tnx

10

lxx_28:
I think my code is a bit messy, don't know how to make it better but it works.

Press CTRL-T in the IDE for one.