Basic Circuit

For the temperature probe, I used the MAX6675, Type K thermocouple module. The wiring was not straightforward. The literature that I could find on the web was meant for the Arduino controller. Either way, I had to determine how the serial input was read. If you follow the diagram below and adhere to the Python Program, you will have the temperature input working just fine.

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The linear actuator that I used has a simple 12V direct current motor. The arrangement shown below illustrates the wiring with 2 relays. To drive the motor in one direction, you simply activate either Relay 1 or Relay 2. If you use the linear actuator from Progressive Automations, it has built in limit switches (not shown in the diagram), so once the stroke has reached it's limit it will open the circuit. For the power supply, I cannibalized an old charger that was used for a kids toy.

Here you see a more graphical representation of one relay.

For the pin connectivity to the Pi, I just jumpered Pin 34 and Pin 17 from relay to relay. The input pin for activating the relay will be shown in the Python Program. I used Pin 32 (GPIO 12) for damper open, Pin 36 (GPIO 16) for damper close.

You will need a 3rd relay if you wish to control the fan (recommended). I took one leg of an extension cord and spliced it into the NO and COM. Then I used Pin 16 (GPIO 23) to activate the relay once temperature is achieved. Again, I jumpered GND and VCC from the previous relays/Pi GPIO.