Designed and built a full IoT pipeline to control an air conditioner remotely over the internet. The system captures original AC remote signals, decodes them, and re-transmits them on command via MQTT, eliminating the need for proprietary apps. It is built around an ESP32 with a custom IR transceiver circuit, covering the whole path from circuit design in KiCad to firmware and remote control. As a result, the AC can be operated from anywhere with an internet connection.

• IR receiver circuit captures & decodes existing AC remote codes (power, mode, temperature, swing)
• IR transmitter circuit (IR LED + 2N2222 transistor + 220 Ω resistor) replicates decoded signals
• MQTT protocol enables real-time control from any internet-connected device
• ESP32 DevModule handles Wi-Fi connectivity, MQTT client, and signal processing
• Full hardware assembled on breadboard with custom circuit design

Built a compact GPS tracker that acquires live coordinates and pushes them to an MQTT broker over a cellular network, without using any high-level MQTT library. All MQTT packets are constructed manually via raw AT commands sent to the SIM900 GSM module. The system reads location data from a NEO-6M GPS module, parses the NMEA sentences, and sends the result over GSM, so it can track position without depending on WiFi. The hardware was designed with a custom PCB layout in KiCad.

• NEO-6M GPS module for coordinate acquisition with NMEA sentence parsing
• SIM900 GSM module for cellular data connectivity using raw AT Commands
• Manual MQTT packet construction over AT Command (no library abstraction)
• Full hardware development cycle: schematic design and PCB layout in KiCad
• Live location data transmitted to MQTT broker in real time

Designed and implemented a WiFi-connected smart lock that controls a solenoid mechanism via digital input or MQTT commands. The hardware includes a full protection and driver circuit that lets the ESP8266 safely switch the solenoid through a relay. The schematic and PCB layout were created in KiCad and the firmware was written in Arduino IDE. The result is a lock that can be operated locally or remotely over the network.

• Solenoid relay controlled by BC547BG transistor as current driver
• 1N4007 diode for back-EMF protection; L7805CV voltage regulator for stable 5 V supply
• MQTT protocol for remote WiFi open/close commands
• KiCad schematic and PCB layout — full hardware design cycle
• Arduino IDE firmware with dual control: physical digital input + remote MQTT