Nuts and Volts - September 2013

 case -1: Serial.println("Sensor 0 Checksum
  error"); break;
  case -2: Serial.println("Sensor 0 Time out
  error"); break;
  default: Serial.println("Sensor 0 Unknown
  error"); break;
}
 
 
Serial.print("Sensor 0 Humidity (%): ");
Serial.println((float)DHT220.humidity, DEC);
 
 
Serial.print("Sensor 0 Temperature (°C): ");
Serial.println((float)DHT220.temperature, DEC);
 
 
Serial.print("Sensor 0 Temperature (°F): ");
Serial.println(DHT220.fahrenheit(), DEC);
 
 
Serial.print("Sensor 0 Temperature (°K): ");
Serial.println(DHT220.kelvin(), DEC);
 
 
Serial.print("Sensor 0 Dew Point (°C): ");
Serial.println(DHT220.dewPoint(), DEC);
 
 
Serial.print("Sensor 0 Dew PointFast (°C): ");
Serial.println(DHT220.dewPointFast(), DEC);
Serial.print("Read sensor 0: ");
 
 
int chk1 = DHT221.read();
 
 
switch (chk1)
{
  case 0: Serial.println("Sensor 1 OK"); break;
  case -1: Serial.println("Sensor 1 Checksum
  error"); break;
  case -2: Serial.println("Sensor 1 Time out
  error"); break;
  default: Serial.println("Sensor 1 Unknown
  error"); break;
}
 
 
Serial.print("Sensor 1 Humidity (%): ");
Serial.println((float)DHT221.humidity, DEC);
 
 
Serial.print("Sensor 1 Temperature (°C): ");
Serial.println((float)DHT221.temperature, DEC);
 
 
Serial.print("Sensor 1 Temperature (°F): ");
Serial.println(DHT221.fahrenheit(), DEC);
 
Serial.print("Sensor 0 Temperature (°K): ");
Serial.println(DHT221.kelvin(), DEC);

■ FIGURE 15: Two DHT22s on handheld prototyper.

 Serial.print("Sensor 1 Dew Point (°C): ");
  Serial.println(DHT221.dewPoint(), DEC);
 
 
  Serial.print("Sensor 1 Dew PointFast (°C): ");
  Serial.println(DHT221.dewPointFast(), DEC);
 
  delay(2000);

temperature and humidity both inside and outside of the castle. We will look at an algorithm in a moment that lets us set trip points so our attic fan (Figure 14) will come on and draw fresh air through the vent box (refer back to This provides the data to the serial monitor shown in Figure 13.

Figures 1 and 2) to provide us with inexpensive cooling or heating as needed.

Fresh Air Controller Design

We hook up the I2C mini terminal part of the handheld prototyper as shown in Figures 15 and 16. This combines the Arduino proto shield and the I2C mini terminal into the handheld prototyper used in this system.