The group goal was to implement a drying grain system. The process of drying should start with the press of a button, after that, a fan speed is controlled based on a “dry curve” and the reading of a luminosity and temperature sensor. With 3 minutes the routine is finished, and the machine should wait for another button press to start the system again.
The hardware of the control system consists of:
- An ATmega2560 Microcontroller
- An LDR to sense the luminosity
- An NTC sensor for the temperature
- A Push-Button to start the system
- LEDs for behavior visualization
- A “4N25” Photocoupler to protect the Microcontroller from the load
- An NPN transistor with a diode for circuit protection
- Power supply to the Fan
- Some resistors
The last picture represents the components, an Arduino Mega board is used to facilitate communication with the microprocessor, the DC motor illustrates the fan. Since the LDR and NTC sensors are a variable resistance for the desired domain, a voltage divider is applied to convert the input voltage to a measured voltage. An operational range should be specified in this type of configuration, in the example of the NTC temperature sensor, the fixed resistor was chosen based on its measured resistance at the ambient temperature which, for 25 °C is approximately 50Ω.