Project Eight - Thermostat


The final project in our series may seem complex, but is quite simple. We use the potentiometer to allow user input of a temperature value, and using the temperature sensor – if the ambient temperature rises above the value set via the potentiometer the relay is activated.

  1. Connect the Temperature Sensor to the Analog A0/A1 input jack, like it was in Project 7.
  2. The Grove produces an analog voltage on its D1 output, which is connected to Arduino A0 analog input on the A0/A1 input jack.

  3. Connect the Potentiometer to the Analog A4/A5 input jack.

  4. The Potentiometer produces an analog voltage on its D1 output, which is connected to Arduino A4 analog input on the A4/A5 input jack. Connect the Relay to the D2/D3 input jack.

  5. The Arduino’s D2 pin sends a signal to the Relay on the D1 connector. The Relay’s red light indicates whether the relay is on or off, and the relay makes a clicking sound when it switches.

Now upload the following Arduino sketch:

// Project Eight - Thermostat

int a,c,d;
int z=3975;
int relaypin=2;
float b, q, resistance, temperature;

void setup()
  pinMode(relaypin, OUTPUT);

void loop()
  if (d>=c)
    digitalWrite(relaypin, HIGH);
  if (d<c)
    digitalWrite(relaypin, LOW);

Try turning the potentiometer to the right and left and see if the relay turns on or off.

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