Silly IF question..negative integer

Using Arduino Programming Questions
#1

Hi!

Ok, so this is my first Arduino Project and im trying to make a thermometer.

It works as intended except for one thing…i can get the else if for negative values to execute…

else if (tempC < 0)

any ideas?

Here is the rest…

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
#define TEMPERATURE_PRECISION 9


#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
 #include <avr/power.h>
#endif

#define PIN 6

// Parameter 1 = number of pixels in strip
// Parameter 2 = Arduino pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(16, PIN, NEO_GRB + NEO_KHZ800);

// IMPORTANT: To reduce NeoPixel burnout risk, add 1000 uF capacitor across
// pixel power leads, add 300 - 500 Ohm resistor on first pixel's data input
// and minimize distance between Arduino and first pixel.  Avoid connecting
// on a live circuit...if you must, connect GND first.

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);

int numberOfDevices; // Number of temperature devices found

DeviceAddress tempDeviceAddress; // We'll use this variable to store a found device address

void setup(void)
{
 // start serial port
 Serial.begin(9600);
 Serial.println("Dallas Temperature IC Control Library Demo");

 // Start up the library
 sensors.begin();

 strip.begin();
 strip.show(); // Initialize all pixels to 'off'


 
 // Grab a count of devices on the wire
 numberOfDevices = sensors.getDeviceCount();
 
 // locate devices on the bus
 Serial.print("Locating devices...");
 
 Serial.print("Found ");
 Serial.print(numberOfDevices, DEC);
 Serial.println(" devices.");

 // report parasite power requirements
 Serial.print("Parasite power is: "); 
 if (sensors.isParasitePowerMode()) Serial.println("ON");
 else Serial.println("OFF");
 
 // Loop through each device, print out address
 for(int i=0;i<numberOfDevices; i++)
 {
   // Search the wire for address
   if(sensors.getAddress(tempDeviceAddress, i))
{
Serial.print("Found device ");
Serial.print(i, DEC);
Serial.print(" with address: ");
printAddress(tempDeviceAddress);
Serial.println();

Serial.print("Setting resolution to ");
Serial.println(TEMPERATURE_PRECISION, DEC);

// set the resolution to TEMPERATURE_PRECISION bit (Each Dallas/Maxim device is capable of several different resolutions)
sensors.setResolution(tempDeviceAddress, TEMPERATURE_PRECISION);

Serial.print("Resolution actually set to: ");
Serial.print(sensors.getResolution(tempDeviceAddress), DEC); 
Serial.println();
}else{
Serial.print("Found ghost device at ");
Serial.print(i, DEC);
Serial.print(" but could not detect address. Check power and cabling");
}
 }

}

// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
{
 // method 1 - slower
 //Serial.print("Temp C: ");
 //Serial.print(sensors.getTempC(deviceAddress));
 //Serial.print(" Temp F: ");
 //Serial.print(sensors.getTempF(deviceAddress)); // Makes a second call to getTempC and then converts to Fahrenheit

 // method 2 - faster
 float tempC = sensors.getTempC(deviceAddress);
//  Serial.print("Temp C: ");
//  Serial.print(tempC);
 // Serial.print(" Temp F: ");
 // Serial.println(DallasTemperature::toFahrenheit(tempC)); // Converts tempC to Fahrenheit


}

void loop(void)
{ 


int numberOfLeds = 16;
int tempC=-10;
int PixelIndex;
int wheelIndex;
int MappedTempC;

 if (tempC > 0)
 {
   MappedTempC = map(tempC,0,30,8,16);
   for (PixelIndex = numberOfLeds/2; PixelIndex < MappedTempC;)
   {
   // Light up warm side     
   wheelIndex = map(PixelIndex, 8, 16, 127, 0);  // map pixel position to a wheel position
   strip.setPixelColor(PixelIndex, Wheel(wheelIndex ));
   PixelIndex++;
   Serial.print("Its hot, ");
   }  
 } 


 else if (tempC < 0)
  {
   // Light up cold side
   MappedTempC = map(tempC,0,-20,7,0);
   for (PixelIndex = numberOfLeds/2; PixelIndex < MappedTempC;)
   {     
   wheelIndex = map(PixelIndex, 8, numberOfLeds, 128, 255);  // map pixel position to a wheel position
   strip.setPixelColor(PixelIndex, Wheel(wheelIndex ));
   PixelIndex++;
   Serial.print("Its cold");
   }  
  
  }

 else

 {
   // Light up 1 and -1 LED, these two indicate zero degrees
   wheelIndex = map(7, 7, numberOfLeds, 255, 0);  // map pixel position to a wheel position
   strip.setPixelColor(7, Wheel(wheelIndex ));
   wheelIndex = map(8, 8, numberOfLeds, 255, 0);  // map pixel position to a wheel position
   strip.setPixelColor(8, Wheel(wheelIndex ));
   Serial.print("Its Zero");
 }



 strip.show();

 
 // call sensors.requestTemperatures() to issue a global temperature 
 // request to all devices on the bus
 Serial.print("Requesting temperatures...");
 sensors.requestTemperatures(); // Send the command to get temperatures
  Serial.println("DONE");
 
 
 // Loop through each device, print out temperature data
 for(int i=0;i<numberOfDevices; i++)
 {
   // Search the wire for address
   if(sensors.getAddress(tempDeviceAddress, i))
{
// Output the device ID
Serial.print("Temperature for device: ");
Serial.println(i,DEC);

// It responds almost immediately. Let's print out the data
printTemperature(tempDeviceAddress); // Use a simple function to print out the data


} 
//else ghost device! Check your power requirements and cabling

 }

 

}

// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
 for (uint8_t i = 0; i < 8; i++)
 {
   if (deviceAddress[i] < 16) Serial.print("0");
   Serial.print(deviceAddress[i], HEX);
 }
}



// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
 WheelPos = 255 - WheelPos;
 if(WheelPos < 85) {
   return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
 }
 if(WheelPos < 170) {
   WheelPos -= 85;
   return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
 }
 WheelPos -= 170;
 return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}



void TempToLEDs(void)
{
int numberOfLeds = 16;
// for (int i = 0; i < abs(tempC);)
// {
Serial.print("aaaa");
int tempC=20;
 if (tempC > 0)
 {
   for (int l = numberOfLeds/2; l < abs(tempC);)
   {
   // Light up warm side
  
   int PixelIndex = map(tempC,0,30,8,16);
    Serial.print(l);
    
   int wheelIndex = map(l, 0, numberOfLeds, 255, 0);  // map pixel position to a wheel position
   strip.setPixelColor(l, Wheel(wheelIndex ));
   l++;
   }  
 } 


 else if (tempC < 0)

 {
 // Light up cold side
 }

 else

 {
 // Light up 1 and -1 LED
 }

 

// }



 strip.show();
Serial.print("Slut");
}

Yea, im a noob LOL!

/Ma3a

#2

Please read Nick Gammon’s two posts at the top of this Forum for the proper way to post code using code tags. You’ll get a better response if you follow those guidelines.

#3

It works as intended except for one thing…i can get the else if for negative values to execute…
else if (tempC < 0)

Cover the sensor with ice…

or

put the treshold on another level

and read a real temperature instead of assigning it with a hard value.

int tempC=20;

#4

Assigning with hard value is just for testing...

#5

It works as intended except for one thing…i can get the else if for negative values to execute…
else if (tempC < 0)

What does this mean? Was there a “not” omitted from that sentence? How do you KNOW the else if block is not being executed? Or that it should be?

#6

I had to clean up the code a bit…

The blocks in IF and ELSE executes but not in the ELSE IF, changing tempC to a negative value
doesnt run it…i must be overlooking something really trvivial here…
There is no message to the serial monitor, thats how i know its not run.

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
#define TEMPERATURE_PRECISION 9


#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
  #include <avr/power.h>
#endif

#define PIN 6

// Parameter 1 = number of pixels in strip
// Parameter 2 = Arduino pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(16, PIN, NEO_GRB + NEO_KHZ800);

// IMPORTANT: To reduce NeoPixel burnout risk, add 1000 uF capacitor across
// pixel power leads, add 300 - 500 Ohm resistor on first pixel's data input
// and minimize distance between Arduino and first pixel.  Avoid connecting
// on a live circuit...if you must, connect GND first.






// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);

int numberOfDevices; // Number of temperature devices found

DeviceAddress tempDeviceAddress; // We'll use this variable to store a found device address

void setup(void)
{
  // start serial port
  Serial.begin(9600);
  Serial.println("Dallas Temperature IC Control Library Demo");

  // Start up the library
  sensors.begin();

  strip.begin();
  strip.show(); // Initialize all pixels to 'off'


  
  // Grab a count of devices on the wire
  numberOfDevices = sensors.getDeviceCount();
  
  // locate devices on the bus
  Serial.print("Locating devices...");
  
  Serial.print("Found ");
  Serial.print(numberOfDevices, DEC);
  Serial.println(" devices.");

  // report parasite power requirements
  Serial.print("Parasite power is: "); 
  if (sensors.isParasitePowerMode()) Serial.println("ON");
  else Serial.println("OFF");
  
  // Loop through each device, print out address
  for(int i=0;i<numberOfDevices; i++)
  {
    // Search the wire for address
    if(sensors.getAddress(tempDeviceAddress, i))
 {
 Serial.print("Found device ");
 Serial.print(i, DEC);
 Serial.print(" with address: ");
 printAddress(tempDeviceAddress);
 Serial.println();
 
 Serial.print("Setting resolution to ");
 Serial.println(TEMPERATURE_PRECISION, DEC);
 
 // set the resolution to TEMPERATURE_PRECISION bit (Each Dallas/Maxim device is capable of several different resolutions)
 sensors.setResolution(tempDeviceAddress, TEMPERATURE_PRECISION);
 
 Serial.print("Resolution actually set to: ");
 Serial.print(sensors.getResolution(tempDeviceAddress), DEC); 
 Serial.println();
 }else{
 Serial.print("Found ghost device at ");
 Serial.print(i, DEC);
 Serial.print(" but could not detect address. Check power and cabling");
 }
  }


}

// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
{
  // method 1 - slower
  //Serial.print("Temp C: ");
  //Serial.print(sensors.getTempC(deviceAddress));
  //Serial.print(" Temp F: ");
  //Serial.print(sensors.getTempF(deviceAddress)); // Makes a second call to getTempC and then converts to Fahrenheit

  // method 2 - faster
  float tempC = sensors.getTempC(deviceAddress);
//  Serial.print("Temp C: ");
//  Serial.print(tempC);
  // Serial.print(" Temp F: ");
  // Serial.println(DallasTemperature::toFahrenheit(tempC)); // Converts tempC to Fahrenheit


}

void loop(void)
{ 
int numberOfLeds = 16;
int tempC=10;
int PixelIndex;
int wheelIndex;
int MappedTempC;

  if (tempC > 0)
  {
    MappedTempC = map(tempC,0,30,8,16);
    for (PixelIndex = numberOfLeds/2; PixelIndex < MappedTempC;)
    
    {
    // Light up warm side     
    wheelIndex = map(PixelIndex, 8, 16, 127, 0);  // map pixel position to a wheel position
    strip.setPixelColor(PixelIndex, Wheel(wheelIndex ));
    PixelIndex++;
    Serial.print("Its hot, ");
    }  
  } 


  else if (tempC < 0)
    {
    // Light up cold side
    MappedTempC = map(tempC,0,-20,7,0);
    for (PixelIndex = numberOfLeds/2; PixelIndex < MappedTempC;)

    {     
    wheelIndex = map(PixelIndex, 8, numberOfLeds, 128, 255);  // map pixel position to a wheel position
    strip.setPixelColor(PixelIndex, Wheel(wheelIndex ));

    PixelIndex++;
    Serial.print("Its cold");
    }  
   
  }

  else

  {
    // Light up 1 and -1 LED, these two indicate zero degrees
    wheelIndex = map(7, 0, numberOfLeds, 255, 0);  // map pixel position to a wheel position
    strip.setPixelColor(7, Wheel(wheelIndex ));
    wheelIndex = map(8, 0, numberOfLeds, 255, 0);  // map pixel position to a wheel position
    strip.setPixelColor(8, Wheel(wheelIndex ));
    Serial.print("Its Zero");
  }

   strip.show();

  
  // call sensors.requestTemperatures() to issue a global temperature 
  // request to all devices on the bus
  Serial.print("Requesting temperatures...");
  sensors.requestTemperatures(); // Send the command to get temperatures
   Serial.println("DONE");
  
  
  // Loop through each device, print out temperature data
  for(int i=0;i<numberOfDevices; i++)
  {
    // Search the wire for address
    if(sensors.getAddress(tempDeviceAddress, i))
 {
 // Output the device ID
 Serial.print("Temperature for device: ");
 Serial.println(i,DEC);
 
 // It responds almost immediately. Let's print out the data
 printTemperature(tempDeviceAddress); // Use a simple function to print out the data


 } 
 //else ghost device! Check your power requirements and cabling
 
  }

  
 
}

// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
  for (uint8_t i = 0; i < 8; i++)
  {
    if (deviceAddress[i] < 16) Serial.print("0");
    Serial.print(deviceAddress[i], HEX);
  }
}



// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if(WheelPos < 85) {
    return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  }
  if(WheelPos < 170) {
    WheelPos -= 85;
    return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
  WheelPos -= 170;
  return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}
#7

Isn't it

really
hard
to. read
stuff when
it wanders all over the page?

Please use the auto format tool before posting your code again.

#8

Yea, well, im still learning.

#9

The if is working. Your problem is here:

    MappedTempC = map(tempC,0,-20,7,0);
    for (PixelIndex = numberOfLeds/2; PixelIndex < MappedTempC;)

When tempC is -10, what is MappedTempC? With PixelIndex = 8, how many iterations of the for loop will be executed?

Regards,
Ray L.

#10

Aha, i see the error of my ways! Thanks man!

#11

Why are you reading the temperature once in setup() and using it over and over in loop()?

#12