Very much a beginer with Arduino stuff I am fighting with something that was working fine the first time I tried. I must have messed something but after multiple checks I still can't find where.
I am trying to control a 4 pin fan using pwm on an Arduino Uno and a lm135 sensor. I got the variables right but the fan is jumping from its minimum rmp to the maximum as soon as the "actual Fan speed" is above zero but far from the maximum. I got this on the console
Actual Fan speed: 0
Temp: 29ßC
FANS: 0%
Actual Fan speed: 0 //Fan at minimum speed
Temp: 29ßC
FANS: 0%
Actual Fan speed: 32 //Fan at 100%
Temp: 30ßC
FANS: 0%
Actual Fan speed: 32
Temp: 30ßC
FANS: 0%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
Actual Fan speed: 32
Temp: 30ßC
FANS: 0%
Actual Fan speed: 32
Temp: 30ßC
FANS: 0%
Actual Fan speed: 37
Temp: 31ßC
FANS: 2%
I use this code:
#include <SoftwareSerial.h>
#include <LiquidCrystal.h>
//source: http://www.electroschematics.com/9540/arduino-fan-speed-controlled-temperature/
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
int tempPin = A1; // the output pin of LM35
int fan = 11; // the pin where fan is
int led = 8; // led pin
int temp;
int tempMin = 30; // the temperature to start the fan
int tempMax = 70; // the maximum temperature when fan is at 100%
int fanSpeed;
int fanLCD;
//source: bens at http://forum.arduino.cc/index.php/topic,10697.0.html#6
void setup() {
// configure hardware timer2 to generate a fast PWM on OC1B (Pin 10)
// set pin high on overflow, clear on compare match with OCR1B
TCCR2A = 0x23;
TCCR2B = 0x0C; // select timer2 clock as 16 MHz I/O clock / 64 = 250 kHz
OCR2A = 249; // top/overflow value is 249 => produces a 1000 Hz PWM
OCR1B = 125; // set the PWM to 50% duty cycle
// open the serial port at 9600 bps for debuging
Serial.begin(9600);
pinMode(fan, OUTPUT);
pinMode(led, OUTPUT);
pinMode(tempPin, INPUT);
lcd.begin(16, 2);
}
void loop() {
temp = readTemp(); // get the temperature
if (temp < tempMin) { // if temp is lower than minimum temp
fanSpeed = 0; // fan is not spinning
digitalWrite(fan, LOW);
}
if ((temp >= tempMin) && (temp <= tempMax)) { // if temperature is higher than minimum temp
fanSpeed = map(temp, tempMin, tempMax, 32, 255); // the actual speed of fan
fanLCD = map(temp, tempMin, tempMax, 0, 100); // speed of fan to display on LCD
analogWrite(fan, fanSpeed); // spin the fan at the fanSpeed speed
}
if (temp > tempMax) { // if temp is higher than tempMax
digitalWrite(led, HIGH); // turn on led
} else { // else turn of led
digitalWrite(led, LOW);
}
Serial.print("Actual Fan speed: ");
Serial.println(fanSpeed);
Serial.print("Temp: ");
Serial.print(temp);
Serial.print((char)223);
Serial.println("C ");
Serial.print("FANS: ");
Serial.print(fanLCD);
Serial.println("% ");
lcd.print("TEMP: ");
lcd.print(temp); // display the temperature
lcd.print((char)223);
lcd.print("C ");
lcd.setCursor(0, 1); // move cursor to next line
lcd.print("FANS: ");
lcd.print(fanLCD); // display the fan speed
lcd.print("% ");
delay(500);
lcd.clear();
}
int readTemp() { // get the temperature and convert it to celsius
temp = analogRead(tempPin);
return temp * 0.48828125;
}
The fan is always sniping even at zero %, normal as far I understand, 20% is the very minium speed for this kind of fan
Schematic looks like attached (without the Fan sens wiring)
Any help welcome
Thanks
