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Help: Temperature controller with ATTINY85 and LM35

Discussion in 'AVR' started by ozgur84, Feb 9, 2014.

  1. ozgur84

    ozgur84 Member

    Feb 8, 2013
    Hello everybody,

    I designed a circuit which reads a LM35 temperature sensor, blinks 2 LED and turns on and off a Fan over a MOSFET. However, it does not function as I want it to do. Here is the schematic and the code (LED colors are different in the original circuit but it does not matter)


    #define analogPin 3 // Data cable connected to the analog pin
    #define YelPin 1 // yellow LED pin for Temp>35
    #define RedPin 0 //red LED pin for Temp>39
    #define FanPin 2 //Fan connected to the MOSFET will be high Temp>35
    int val=0; // variable to store the value of temperature reading

    void setup(){
    pinMode(YelPin, OUTPUT);
    pinMode(RedPin, OUTPUT);
    pinMode(FanPin, OUTPUT);
    function0(); // for the temperatures out of the interested range
    function1(); //for the temperatures lower than 39 and higher than 36
    function2(); //for the temperatures higher than 39


    void loop(){
    val = analogRead(analogPin)*0.48828125; //conversation of the analog reading to the centigrade
    if(val<35 && val>60){
    if(val>=35 && val<39){
    if(val>39 && val<60){

    void function0(){ //function which should work only when the temperature is out of interested range
    digitalWrite(YelPin, LOW);
    digitalWrite(RedPin, LOW);
    delay (2000);

    void function1(){ //function which should work only in 35-39 degrees
    digitalWrite(YelPin, HIGH);
    delay (2000);

    void function2(){ //funtion which should work only after 39 degrees
    digitalWrite(YelPin, LOW);

    The circuit was programmed with an Arduino Uno as ISP and the clock frequency is 8MHz
    When I power up the circuit, It waits for a while, then turns the Yellow LED on as well as the fan for half a second and turns off. If I heat the sensor further, it turns the red LED on as well as the fan and stays on half a second as the previous case and waits and does the same....

    What I want to have
    Read the temperature,
    if temperature <36 and > 60 do nothing
    if temperature >36 and < 39 turn the yellow LED as well as the fan on
    if temperature > 39 and <60 turn the red LED as well as the fan on

    What am I doing wrong here?

    Last edited: Feb 9, 2014

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