Code Help for an Arduino Temperature Controller

[clownfish chris]

I have built a few things now with Arduino. A dosing pump, and a light timer were the two major projects that were met with success. I have also built a digital thermometer that works very well. Now I am wanting to add a pair of solid state relays (shield) to turn on and off a heater and DIY chiller.

I added this code to my thermometer:

 if ((float)raw / 16.0 <= 26.5)
  {
    digitalWrite(Heat, HIGH);
    digitalWrite(Chill, LOW);
  }
if ((float)raw / 16.0 >= 27)
  {
    digitalWrite(Heat, LOW);
    digitalWrite(Chill, HIGH);
  }
  else
  {
    digitalWrite(Heat, LOW);
    digitalWrite(Chill, LOW);
  }

After adding if and else statements, every thing works just as it did before except that the relays do not trigger. I have tested them using "Blink" and they work fine. I believe the problem is in the if and else statements.

Take it easy in your explanations as I have a very crude understanding of C++ which is most likely my over all problem.

Complete Code:

#include <OneWire.h>
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3f, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
int Heat = 3;
int Chill = 5;

OneWire  ds(2);  // USE 4.7K PULL DOWN RESISTOR!!!

void setup() {
lcd.begin(16, 2);
lcd.backlight();
lcd.clear();
lcd.print("Hi Chris,");
delay(3000);
lcd.clear();
lcd.print("How are you? ");
delay(3000);
}

void loop() {
byte i;
byte present = 0;
byte type_s;
byte data[12];
byte addr[8];
float celsius, fahrenheit;

if ( !ds.search(addr)) {
ds.reset_search();
delay(250);
return;
}
for ( i = 0; i < 8; i++) {
}
if (OneWire::crc8(addr, 7) != addr[7]) {
return;
}
// the first ROM byte indicates which chip
switch (addr[0]) {
case 0x10:
type_s = 1;
break;
case 0x28:
type_s = 0;
break;
case 0x22:
type_s = 0;
break;
default:
return;
}
ds.reset();
ds.select(addr);
ds.write(0x44, 1);        // start conversion, with parasite power on at the end
delay(1000);     // maybe 750ms is enough, maybe not
// we might do a ds.depower() here, but the reset will take care of it.
present = ds.reset();
ds.select(addr);
ds.write(0xBE);         // Read Scratchpad
for ( i = 0; i < 9; i++) {           // we need 9 bytes
data[i] = ds.read();
}
int16_t raw = (data[1] << 8) | data[0];
if (type_s) {
raw = raw << 3; // 9 bit resolution default
if (data[7] == 0x10) {
// "count remain" gives full 12 bit resolution
raw = (raw & 0xFFF0) + 12 - data[6];
}
} else {
byte cfg = (data[4] & 0x60);
// at lower res, the low bits are undefined, so let's zero them
if (cfg == 0x00) raw = raw & ~7;  // 9 bit resolution, 93.75 ms
else if (cfg == 0x20) raw = raw & ~3; // 10 bit res, 187.5 ms
else if (cfg == 0x40) raw = raw & ~1; // 11 bit res, 375 ms
//// default is 12 bit resolution, 750 ms conversion time
}
if ((float)raw / 16.0 <= 26.5)
  {
    digitalWrite(Heat, HIGH);
    digitalWrite(Chill, LOW);
  }
if ((float)raw / 16.0 >= 27)
  {
    digitalWrite(Heat, LOW);
    digitalWrite(Chill, HIGH);
  }
  else
  {
    digitalWrite(Heat, LOW);
    digitalWrite(Chill, LOW);
  }
celsius = (float)raw / 16.0;
fahrenheit = celsius * 1.8 + 32.0;
lcd.clear();
delay(500);
lcd.setCursor(0, 0);
lcd.print("Your Aquarium Is");
lcd.setCursor(0, 1);
lcd.print(celsius);
lcd.print(" C");
lcd.setCursor(9, 1);
lcd.print(fahrenheit);
lcd.print(" F");
delay(1000);
}

Thanks in advance!

 

[Psiber_Syn]

Have you tried else if?

 

[clownfish chris]

No. What is the difference? All I do is switch the two?

 

[Psiber_Syn]

It looks as though your if statement should look like

If (this true)
This happens
Else if (this true)
This happens
Else (neither true)
This happens

 

[ReeferMadness0347]

I’ve written quite a bit of code. Not a lot for arduino specifically but generally it’s the same with the 8 languages I’ve learned, when writing a new piece or part like this, I’d start with a fresh script. If needed load some demo data into a variable you can use for testing. It makes debugging much easier.

 

[DarkSky]

if ((float)raw / 16.0 <= 26.5) { digitalWrite(Heat, HIGH); digitalWrite(Chill, LOW); } if ((float)raw / 16.0 >= 27) { digitalWrite(Heat, LOW); digitalWrite(Chill, HIGH); } else { digitalWrite(Heat, LOW); digitalWrite(Chill, LOW); }

With this code block your heater will always be set to LOW. This is why:

//if raw / 16 is less than or equal to 26.5, set heater to high
if ((float)raw / 16.0 <= 26.5)
{
   digitalWrite(Heat, HIGH);
   digitalWrite(Chill, LOW);
}
//if raw / 16 is greater or equal to 27, set heater to low
if ((float)raw / 16.0 >= 27)
{
   digitalWrite(Heat, LOW);
   digitalWrite(Chill, HIGH);
}
else // set heater to low if condition above isn't true
{
   digitalWrite(Heat, LOW);
   digitalWrite(Chill, LOW);
}

Because your two statements are not joined in an "else if" block, it will evaluate and run both.

To make this section a bit more readable, you can do this:

temp = (float)raw/16;
if (temp <= 26.5)
{
     digitalWrite(Chill, LOW);
     digitalWrite(Heat, HIGH);
}
else if (temp >= 27.0)
{
     digitalWrite(Heat, LOW);
     digitalWrite(Chill, HIGH);
}
else {
     digitalWrite(Heat, LOW);
     digitalWrite(Chill, LOW);
}