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# 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:

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 // 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() { a=analogRead(4); b=0.0488*a; c=int(b); q=analogRead(0); resistance=(float)(1023-q)*10000/q; temperature=1/(log(resistance/10000)/z+1/298.15)-273.15; d=int(temperature); if (d>=c) { digitalWrite(relaypin, HIGH); delay(500); } if (d<c) { digitalWrite(relaypin, LOW); delay(500); } } 
Try turning the potentiometer to the right and left and see if the relay turns on or off.

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