Question

this is for those who did Arduino projects

this code is supposed to work this way, there is a temperature sensor in the Arduino Uno along with a motor. the motor should turn on only when the temperature in the sensor exceeds 23 degrees Celcius. Here is the code

float AnalogToVolts(int reading);

void setup()
{
Serial.begin(9600);
pinMode(13, OUTPUT);

}

void loop()
{
int reading;
float volts;
float temperature_in_celsius;
reading = analogRead(A1);

volts = AnalogToVolts(reading); //Function call

if ( temperature_in_celsius > 23)
{
digitalWrite(13, HIGH);
}
else
{
digitalWrite(13, LOW);
}
  

Serial.println(temperature_in_celsius);
Serial.println(volts);
}

// Function Definition
float AnalogToVolts(int reading)
{
float temperature_in_celsius;
float volts;
volts = reading/1023.0 * 5.0; //Perform conversion

temperature_in_celsius = volts * 100 - 50;

  

return temperature_in_celsius;
return volts; //Return result
}

but it does not work. it properly shows the temperature and all, but the motor do not respond correctly with the temperature. Please fix this. Thank you

Answer 1

Hey below are some errors that I noticed:

1. A function in a C program cannot have more than one return statement.
2. The variables float volts; float temperature_in_celsius; inside the void loop( ) are the local variables to this method only.

No other function has access to them unless you pass them those variables.

1. The variables float temperature_in_celsius; float volts; declared inside function AnalogToVolts( int reading ) are local to this function.

It is not like , if we update temperature_in_celsius inside function AnalogToVolts , it doesn't mean that the temperature_in_celsius inside void loop( ) gets updated.

______________________________________________________________________________________________________________________________________________________________________________

float AnalogToVolts(int reading);

void setup()
{
Serial.begin(9600);

// setting A1 analog pin to read input from the sensor.

pinMode(A1, INPUT);
pinMode(13, OUTPUT);
}

void loop()
{
int reading;
float volts;
float temperature_in_celsius;
reading = analogRead(A1);

volts = AnalogToVolts(reading); //Function call

// updating temperature_in_celsius
temperature_in_celsius = volts*100 ;

if ( temperature_in_celsius > 23)
{
    digitalWrite(13, HIGH);
}
else
{
    digitalWrite(13, LOW);
}

Serial.println(temperature_in_celsius);
Serial.println(volts);
}

// Function Definition
float AnalogToVolts(int reading)
{
// the temperature_in_celsius variable , we don't need to declare one here

// float temperature_in_celsius;

float volts;

// MODIFICATION 1
// I also found that the conversion has some small error,
// Most of the standards say that.

// volts = 5*reading/1023
// multiplying the above with 100 gives the temperature in celsius

// volts = reading/1023.0 * 5.0; //Perform conversion

// temperature_in_celsius = volts * 100 - 50;

volts = 5.0*reading/1023.0;

// No need to update this local variable here
// return temperature_in_celsius;

// only returning volts
// there in the loop() we update temperature_in_celsius value
return volts; //Return result
}

____________________________________________________________________________________________________

THANK YOU!!