Temperature Sensor.

Reauben Samson has made an incubator and we need to check if it is working. We used a digital thermometer,
it gives us different readings after every 15 minutes and we concluded it does not work so now we are
building a temperature sensor using the Arduino Uno board and LM35 temperature sensor. The main aim is to keep
a constant temperature using a light bulb as our heat source. We will be using a CPU fan to cool down the light bulb
and to keep the incubator at a certain threshold temperature.

Parts list: CPU fan LED Light bulb (230 VOLT, 75 WATTS)
LM 35 (temperature sensor)
Diode (2N3904 - E25)
Relay (JQC-3F 6 VOLT)
Wire
Arduino Uno


Arduino Code LM 35 Temperature Sensor


float tempC; // create variable to store the temperature in.
int tempPin = 0; // Attach vout to analog pin 0.
int led = 13; // attach led to pin 13.
int fan1 = 3; // attach base of transistor to digital pin 3.
int pos = 0; // create variable to store the position of the servo motor.
void setup() // Will execute once at the start of the code.
{
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
pinMode (led, OUTPUT); // sets the led pin 13 up as an output.
pinMode (fan1, OUTPUT); // sets the fan1 pin 3 up as an output.

}
void loop() // code here will continue to replay nutil powered off.
{
tempC = analogRead(tempPin); // read the analog value from the lm35 sensor.
tempC = (5.0 * tempC * 100.0)/1024.0; // convert the analog input to temperature in centigrade.
Serial.print((byte)tempC); // send the data to the computer.

if (tempC > 38) // creates bool expression for analyzation. if it evaluates to true,
{ // the body of the if statement will execute.

digitalWrite (led, HIGH); // turns on led.
digitalWrite (fan1, HIGH); // turns on fan1.

}
else // if the if equation evaluates to false the else statement will execute.
{
digitalWrite (led, LOW); // turns off led.
digitalWrite (fan1, LOW); // turns off fan1.

}
delay(3000); // wait 3 seconds before redoing the loop.
}