Smartening the air conditioner

We have developed an intelligent air conditioner using the STM32F103C8T6 microcontroller. The objective of this project was to automate the control of the air conditioner based on the indoor temperature and the selected working mode (winter or summer). By integrating a microcontroller and a temperature sensor, we were able to achieve this goal. The manual control of the air conditioner was replaced with an automated system that utilizes an optocoupler connected to the on/off button.

To power the circuit, we employed the WX-DC24025 module, along with a 7805 regulator to convert the module’s 12V output voltage to the 5V required by the microcontroller. Additionally, essential information is displayed on a character LCD, providing a user-friendly interface.

In order to set the desired temperature, we incorporated a potentiometer connected to the microcontroller’s ADC. However, we encountered significant noise in the resistance readings from the potentiometer. To address this issue, we implemented a filter that effectively reduces the impact of noise on the ADC readings. The filter applies a weighted average, combining the previous ADC value with 0.1 times the new ADC value, and then dividing the result by 1.1. This approach ensures that any noise present in the new ADC reading does not significantly affect the accuracy of the target temperature.

The PCB design for this circuit was created using Altium Designer software. Below, you can find images showcasing the PCB layout. The design incorporates all the necessary components and connections to ensure the smooth operation of the intelligent air conditioner.

Overall, our project successfully transformed a manually controlled air conditioner into an intelligent system capable of automatically adjusting its operation based on the indoor temperature and selected working mode. The integration of the microcontroller, temperature sensor, and various modules enables efficient and convenient control while providing accurate temperature readings for optimal comfort.

Here you can see a video of the circuit’s initial test.

As seen, when the mode button was pressed and the mode changed from summer to winter, the word “ON” changed to “OFF” and the air conditioner turned off.