Pressure Sensor
- Analog transducer with 0.5–4.5 V output
- Read via ADC with averaging filter
- Converted to MPa/psi for control & display
Display
We use a 128×64 OLED (SSD1306) connected via I²C to present real-time temperature and pressure, along with the on-device menu controlled by a rotary encoder.
Sensors
MAX6675 Thermocouple (K-Type)
- Replaces the original bimetallic strip control
- Accurate boiler temperature sensing
- With PID, we target ≈ ±2 °C around setpoint
Control Electronics
PID Controller
Computes control output in 0–100 % based on error to setpoint.
MCPWM (PWM Generator)
Maps PID output to a duty cycle (0–100 %) to regulate the heater.
SSR-40DA Solid-State Relay
Switches the heater according to PWM, providing isolated on/off control for AC load.
Dimmer / PSM for Pump
Phase-Skip Modulation with zero-cross detection adjusts effective AC power to the pump, enabling indirect pressure control.
Microcontroller
ESP32 runs the dual-loop control, sensor sampling/filtering, OLED UI, rotary encoder input, PWM generation (MCPWM), and the PSM dimmer interface.
Mechanical / 3D-Printed Enclosure
Two-box design: Interface box (OLED + rotary encoder) and Components box (ESP32, SSR/triac, sensors). Inspired by Gaggiuino; printed in PETG with M3 heat-set inserts.
Print & Assembly Notes
- Printing Parameters: PETG (warm the filament before printing) · 0.4mm nossle
- Printer Settings: 0.4mm layer · 20-30% infill · Print Speed < 300 mm/s · Outer Brim: 5mm
- Supports: They are optional for printing
- Componets Enclosure: Use 2.9mm x 13mm self-tapping screws to secure the lid in place
- Knob and Screen Interface: Use M2.5 screws to secure the enclousure
- Magnets are used to hold the interface on the machine, use an epoxy adhesive to attach magnets on the petg interface