Temperature Based Fan Speed Controller using ESP8266 and Arduino IDE

This advanced climate control system operates by combining environmental sensing, dual-microcontroller processing, and AC phase-angle power regulation. At the heart of the sensing network is the DHT11 sensor, which continuously monitors ambient temperature and humidity. The ESP8266-01 Wi-Fi module processes these readings and connects to a web interface for remote monitoring and IoT capabilities, while a PIC12F675 microcontroller manages low-level timing and control tasks. When the ambient temperature changes, the system alters its output to regulate an AC load. To achieve noise-free fan speed control without generating high electromagnetic interference, the circuit employs an isolated switching architecture. The control signal from the logic side triggers an MMBT2222A transistor, which drives the MOC3021 optocoupler (featuring a triac driver). This optical isolation safely separates the low-voltage DC control circuitry from the high-voltage AC mains. The MOC3021 then fires the BT136 Triac, which acts as an electronic switch to control the alternating current delivered to the fan motor. Power conversion from high-voltage AC mains to a stable low-voltage DC rail is handled safely by an HLK-PM03 Hi-Link 3.3V power supply module alongside an MB10S bridge rectifier, smoothing capacitors, and protective resistors. Additionally, a 12mm buzzer provides audible feedback for system events or alerts, while custom PCB layout ensures reliable routing for both high-voltage and low-voltage sections.