Need help.

//this is the code that I wrote

//include the LCD library and initialize

#include <LiquidCrystal.h>

LiquidCrystal lcd(2, 3, 4, 5, 6, 7);

//pin connections

const int redLed = 13;

const int yellowLed= 12;

const int greenLed = 11;

const int speaker = 10;

const int fan = 9;

const int tempraturePin = A1;

    int freq = 440;

    int duration = 1000;

  //  tone(pinOut, freq, duration);

//tempratures 

int temprature=0;

const int minTemprature = 30;

const int midTemprature = 35;

const int maxTemprature = 40;

void setup() {

  pinMode(fan, OUTPUT);

  pinMode(speaker, OUTPUT);

  pinMode(redLed, OUTPUT);

  pinMode(yellowLed, OUTPUT);

  pinMode(greenLed, OUTPUT);

  pinMode(tempraturePin, INPUT);

  lcd.begin(16, 2);                  //the size of the LCD

}

void loop() {

  temprature = readTemprature();

  if(temprature > minTemprature){

    digitalWrite(greenLed, HIGH);

    digitalWrite(redLed, LOW);

    digitalWrite(yellowLed, LOW);

    lcd.setCursor(12,1);         

    lcd.print("ON");

  }

else if(temprature > midTemprature){

    digitalWrite(yellowLed, HIGH);

    digitalWrite(greenLed, LOW);

    digitalWrite(redLed, LOW);

    lcd.setCursor(12,1);         

    lcd.print("ON");

  }

  else if (temprature > maxTemprature){

    digitalWrite(redLed, HIGH);

    digitalWrite(yellowLed, LOW);

    digitalWrite(greenLed, LOW);

    digitalWrite(fan, HIGH);

    tone(speaker, freq, duration);

    lcd.setCursor(12,1);         

    lcd.print("ON");

  }

  else{

    lcd.setCursor(12,1);         

    lcd.print("OFF");

  }

   //print a static message to the LCD

   lcd.setCursor(0,0);         //move the cursor to the beginning of the LCD

   lcd.print("Temprature:");   //prints the word Temprature:

   lcd.setCursor(12,0);        //move cursor to 12

   lcd.print(temprature);      //display the temperature

   lcd.setCursor(14,0);        //move cursor to 15

   lcd.print((char)223);       //prints the degree character

   lcd.print("C");             //prints the word C

   lcd.setCursor(0,1);         //move cursor to second line

   lcd.print("Fan is:");       //prints the words Fan is:

   delay(1000);

   lcd.clear();  

}

// get the temperature and convert it to celsius

   int readTemprature() { 

     temprature = analogRead(tempraturePin);

     return temprature * 0.48828125;

}

you need resistors in series with the LEDs and should invert the drive by having the Arduino sink the low side of the LED to ground, use a 220+ ohm resistor.

the LM35 circuit leave a bit to be desired, look to page 11 in the TI data sheet http://www.ti.com/lit/gpn/lm35. at room temperature your only getting maybe 200-250mV out of the device, this is very low relative to the capability of the ADC in the Arduino and the default ADC range is 0 - 5000mV (5V) so only 5mV per step equating to 1/2deg C. If you change the reference voltage of the ADC to use the 1.1V band gap internal reference you will improve the measurement capability considerably (1mV per step). An alternate approach would be to use a digital temp sensor or put an OP Amp between the sensor and the Arduino.

if your speaker and motor (Not shown in the schematic) are also being connected to the Arduino and being driven directly you will at a minimum have noise on the supply and it will also drop the supply value by some amount and this will affect the ADC measurement as it is also used as the reference for the ADC the affect being that the temp will rise significantly as your basing your reading on the 5V as a reference.

mathematically

5V\1024 = 4.88mV per step

20degC @ 10mV per deg = 200mV

reading would be 200\4.88mV = 40 - 41 on the ADC

* .48828125 = 20.00 deg... works great

now assume the volts dropped to 4.5V instead

4.5\1024 = 4.39mV per step

reading 200mV/4.39mV = 45.55

*4.8828125 = 22.24 so an increase of 10%, this would be 25deg (+20%) if the volts went down to 4v, noise on the supply from motot and speaker could make this even worse.

to fix this and improve the stability set the ADC to use the band gap or use a separate PSU for all the loads (And decouple the output of the LM35 as shown on page 11 of data sheet)

either way you should not drive the speaker and motor/Fan directly from the Arduino, it will cause you problems.

One last thing, breadboards are notorious for creating noise if your not careful (All those connections), a 10uF +.1uF cap or something on the supply close to the LM35 will help eliminate noise but wont prevent the supply drop effect.

I hope I have provided a little insight into accurate measurements and highlighted a few pitfalls to watch out for.

Peter

if i'm right, please click correct answer

you need resistors in series with the LEDs and should invert the drive by having the Arduino sink the low side of the LED to ground, use a 220+ ohm resistor.

the LM35 circuit leave a bit to be desired, look to page 11 in the TI data sheet http://www.ti.com/lit/gpn/lm35. at room temperature your only getting maybe 200-250mV out of the device, this is very low relative to the capability of the ADC in the Arduino and the default ADC range is 0 - 5000mV (5V) so only 5mV per step equating to 1/2deg C. If you change the reference voltage of the ADC to use the 1.1V band gap internal reference you will improve the measurement capability considerably (1mV per step). An alternate approach would be to use a digital temp sensor or put an OP Amp between the sensor and the Arduino.

if your speaker and motor (Not shown in the schematic) are also being connected to the Arduino and being driven directly you will at a minimum have noise on the supply and it will also drop the supply value by some amount and this will affect the ADC measurement as it is also used as the reference for the ADC the affect being that the temp will rise significantly as your basing your reading on the 5V as a reference.

mathematically

5V\1024 = 4.88mV per step

20degC @ 10mV per deg = 200mV

reading would be 200\4.88mV = 40 - 41 on the ADC

* .48828125 = 20.00 deg... works great

now assume the volts dropped to 4.5V instead

4.5\1024 = 4.39mV per step

reading 200mV/4.39mV = 45.55

*4.8828125 = 22.24 so an increase of 10%, this would be 25deg (+20%) if the volts went down to 4v, noise on the supply from motot and speaker could make this even worse.

to fix this and improve the stability set the ADC to use the band gap or use a separate PSU for all the loads (And decouple the output of the LM35 as shown on page 11 of data sheet)

either way you should not drive the speaker and motor/Fan directly from the Arduino, it will cause you problems.

One last thing, breadboards are notorious for creating noise if your not careful (All those connections), a 10uF +.1uF cap or something on the supply close to the LM35 will help eliminate noise but wont prevent the supply drop effect.

I hope I have provided a little insight into accurate measurements and highlighted a few pitfalls to watch out for.

Peter

if i'm right, please click correct answer