## Introduction:

Temperature is a significant part of our daily life. Too high Temperature and too Low temperature are not comfortable for human as well as electronics around us.

This can be controlled by having an airflow around our system. Airflow can cool down our system and also stable our temperature.

For temperature sensing, we use LM35 which is a low-cost and precise sensor with easy operations.

Detailed Temperature sensing can be found here

For proper operation, we have to average some samples of temperature so in this tutorial we are using 100 samples.

Connection:

Note: Here DC source is required as Motor is DC and it should not exceed 9V

## Procedure:

• Place LM35 on evive’s mini breadboard
• Join Vcc and ground.
• Attach Out with A0
• Connect Relay with Motor, Battery and evive.
• Start coding.

## Coding Algorithm:

• Set pin as Input and output
• initialize sampling array and threshold
• Threshold is temperature in Degree Celcius
• Start averaging function as at 0
• Averaging loop add samples at very fast rate
• After adding divide it to the total number of samples.
• The total temperature will be 0.48* temp ( HOW? )
• CheckThreshold and turn ON of OFF fan

## CODE:

```/*temperature dependent fan
* made for evive IoT tutorials
*
* On 20 December 2017
*/
#define lm35 A0 //ldr input pin
#define fan_relay 2 //fan_relay shown in pin
#define threshold 30 // thershold to turn on or off output
#define samples 100
int state[samples] = {0};
int temp = 0;
void setup() {
// put your setup code here, to run once:
pinMode(lm35, INPUT);
pinMode(fan_relay, OUTPUT);
}

void loop() {
int avg = 0; // this is used to start average function
for (int i = 0 ; i < samples ; i++) // adding readings
{
avg += state[i];
}
avg = avg / samples; // averaging readings
temp = 0.48 * avg; // to get temperature in celcius at +5v multiply with 0.48
Serial.println(temp); // serial print data
temp = 0.48 * avg;
if (temp > threshold)
{
digitalWrite(fan_relay, HIGH);
}
else
{
digitalWrite(fan_relay, LOW);
}
}```

## Why 0.48 only?

As total Resolution of 0 – 5V is from 0 to 1023 we can have 4.88 mV ( 5/1023 V)

Now LM35 shows 10mV increase per degree Celsius so one reading of value ( 0 – 1023) shows 0.488 degree Celsius ( 4.88 / 10 degree Celsius)

Therefore total Temperature is 0.48 * Value.

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