HEAT
HEAT is a DIY smart hot plate designed for precise thermal control, primarily for SMD soldering, thermal experiments, and controlled heating tasks. The system combines a microcontroller, solid-state relay, thermistor feedback, and software algorithms to deliver stable and repeatable temperature profiles on a small, fast-heating plate.
- ROLE
- PCB, firmware, enclosure
- CONTROL
- Smart Pulse & Coast STM32F103 · zero-cross SSR
- STACK
- KiCad · Fusion360 · C
A DIY hot reflow plate with precise temperature control for SMD soldering.
Small, low-mass heater plates heat extremely quickly, making standard PID control unreliable - overshoot, thermal inertia, and measurement delay caused unpredictable temperature swings. This project solves the challenge of achieving precise, repeatable heating while maintaining safety and user control, without relying on classical PID techniques.
- 01
HEAT uses an STM32F103C8T6 microcontroller as the central control unit, providing fast ADC sampling and internal flash storage.
- 02
The heater is driven through a zero-cross AC SSR for safe, low-EMI mains switching, while a 100 kΩ NTC thermistor provides accurate temperature feedback filtered and converted via the Beta equation.
- 03
Temperature control is handled by a Smart Pulse & Coast algorithm, which applies observation-based heating to account for thermal inertia and prevent overshoot.
- 04
The system includes an SSD1306 OLED display (128×64, I²C) with three buttons, allowing users to monitor temperature, setpoints, and heater power.
- 05
A 2-wire DC fan is software-controlled using PWM for active cooling, and all user settings such as setpoints and hold times are saved in internal flash.
- 06
Safety is enforced through fuses, MOVs, over-temperature detection, and immediate shutdown on errors.
- 07
The firmware is modular, with separate modules for control, heater, fan, UI, thermistor, and storage to ensure clarity and maintainability.