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Author Topic: Binary Thermostat - First Project  (Read 983 times)
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This is my first arduino project.  I am not much of a programmer or an electronics guy so I am looking for some feedback.  Be as kind or cruel as you like.

FYI, I combined CIRC-02 and CIRC-10 from ladyada's experimentation kit.

Code:
int ledPins[] = {2,3,4,5,6,7,8,9,10}; // Initialize array of led pins
int temperaturePin = 0;  //Initialize temperature pin

void setup()
{
  for(int i = 0; i < 9; i++){  //set led pins as outputs
  pinMode(ledPins[i],OUTPUT);
  }
}
void loop()
{
  float tempC = getVoltage(temperaturePin);  //getting the voltage reading from the temperature sensor
  tempC = (tempC - .5) * 100;          //converting from 10 mv per degree wit 500 mV offset
  float tempF = tempC*1.8+32;         //convert C to F
  int abstempF = fabs(tempF);         // take abs value of temp in F
  if(tempF <0)                        //light red pin if temp in F is negative
    digitalWrite(ledPins[8],HIGH);
  else
    digitalWrite(ledPins[8],LOW);    //do not light red pin if temp in F is positive
  for(int i = 7; i >= 0; i--){      
  if (pow(2,i) <= abstempF) {        //converts decimal to binary one digit at a time (assumes temp in F cannot be above 127)
    digitalWrite(ledPins[i], HIGH);
    abstempF=abstempF-pow(2,i);
  }
  else
    digitalWrite(ledPins[i], LOW);
  }
  delay(1000);
}
float getVoltage(int pin){
 return (analogRead(pin) * .004882814); //converting from a 0 to 1024 digital range
                                        // to 0 to 5 volts (each 1 reading equals ~ 5 millivolts
}


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Looks pretty good.  I have a few suggestions:
Code:
//// Since these values don't change I'd recommend using the 'const' storage type.  This will allow
//// the compiler to warn you if you accidentally try to change them at run time.  It also allows for
//// better optimization because the compiler knows the values won't change.

const int ledPins[] = {2,3,4,5,6,7,8,9,10}; // Initialize array of led pins
const int temperaturePin = 0;  //Initialize temperature pin

//// Since you treat the red LED (#8) separately it might be clearer to have it in a separate declaration:
const int redLED = 10;
const int ledPins[] = {2,3,4,5,6,7,8,9}; // Initialize array of led pins


void setup()
{
//// Rather than use a magic constant here you can use a formula that will always match the size of the
//// array of pins:
  for(int i = 0; i < (sizeof ledPins/sizeof ledPins[0]); i++)
////  Note that the 'sizeof' operator gives an answer in bytes. 
//// We have to divide by the size of a single element to get the array size in elements
    {  //set led pins as outputs
  pinMode(ledPins[i],OUTPUT);
  }
////  And if we treat the red LED as separate:
    pinMode(redLED, OUTPUT);
}
void loop()
{
  float tempC = getVoltage(temperaturePin);  //getting the voltage reading from the temperature sensor
  tempC = (tempC - .5) * 100;          //converting from 10 mv per degree wit 500 mV offset
  float tempF = tempC*1.8+32;         //convert C to F
  int abstempF = fabs(tempF);         // take abs value of temp in F


  if(tempF <0)                        //light red pin if temp in F is negative
    digitalWrite(redLED,HIGH);
  else
    digitalWrite(redLED,LOW);    //do not light red pin if temp in F is positive

////  Since HIGH and LOW are synonyms for 'true' and 'false' this can simplify to:
    digitalWrite(redLED, tempF < 0);  // Light the red LED if the temperature is below 0


  for(int i = 7; i >= 0; i--){      
////
//// WARNING: the pow() function works on float values and the conversions can cause round-off errors
//// For integer powers of 2 it is best to use the left shift operator <<
////
  if ((1<<i) <= abstempF) {        //converts decimal to binary one digit at a time (assumes temp in F cannot be above 127)
    digitalWrite(ledPins[i], HIGH);

////  When you have something that looks like "variable = variable op value" you can use the C shorthand assignment operators;
////
////   X = X + Y;  can be written X += Y;
////   X = X - Y;  can be written X -= Y;
////   X = X * Y;  can be written X *= Y;
////
    abstempF -= (i<<i);
  }
  else
    digitalWrite(ledPins[i], LOW);
  }
  delay(1000);
}
float getVoltage(int pin){
 return (analogRead(pin) * .004882814); //converting from a 0 to 1024 digital range
                                        // to 0 to 5 volts (each 1 reading equals ~ 5 millivolts
}

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John,

Thanks!

-Dan
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Hi Dan looks good,

I was just passing by and noticed your post. If you want to have some fun with this, I have an open source project going where you could add a few lines of code to this and post your values onto the nimbits data logger system (www.nimbits.com) and your temps can be relayed onto twitter, facebook, email alerts etc.

Anyway I just noticed that your arduino code is similar enough to what I posted under the arduino example on nimbits.com and since it's connected to an ethernet shield it should be pretty easy. Just thought i'd mention it.

- Ben
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