Smart Home Thermostat-University

What?

Designing and building a smart home thermostat using an ESP32 microcontroller, capable of controlling a fan and heater based on thermistor sensor readings, with the ability to override settings via voice commands or wireless control through a web interface

How?

Hardware

The system was built around an ESP32 microcontroller, which interfaced with all peripheral components.
Power Management:
- A 12V external power supply was connected via a barrel jack.
- Voltage regulators stepped down voltage for 5V components.
- A buck converter was used to supply higher current to power-demanding components such as the heater.
Relay Control:
- A 2-channel relay module was used to switch the fan and heater ON/OFF based on user-defined temperature limits.
Communication Protocols:
- I2C: Used for interfacing with the temperature sensor.
- I2S: Used for driving the speaker amplifier.
- SPI: Connected to the microSD card reader.
- Serial: Used to control relays.
- PWM: Implemented for controlling fan speed (RPM).

All components were soldered onto a prototyping board using 22-gauge wires.
Male and female headers were used to ensure components were modular and easily replaceable.

Software

The ESP32 was programmed using Arduino IDE and C++, with custom firmware handling sensor input, relay control, and communication protocols.
Temperature control logic included hysteresis to avoid rapid toggling of the fan and heater around threshold values, improving system stability and extending component lifespan.
A responsive HTML web interface was hosted on the ESP32, allowing users to wirelessly monitor temperature and switch between manual and automatic control modes for both the fan and heater.

Mistakes?

A key oversight was the omission of a protection diode between the linear voltage regulator and the ESP32. As a result, when the ESP32 was powered via USB from a laptop while the external 12V power supply was disconnected, reverse current flowed from the microcontroller back into the regulator. This led to damage and eventual failure of the ESP32. Adding a diode would have blocked reverse current and protected the microcontroller in this scenario.

Results?

Key lessons included integrating hardware components and effectively managing power. implemented wireless overrides through a web interface and writing code for different communication protocols.

Power Management: Using linear regulators and buck convertors to manipulate voltages.
Wireless Communication: Built an HTML web interface to wirelessly control the Smart Home settings.
Code for Communication Protocols: writing code for hardware components with different communication protocols.