Control Logic and Functional Details

This page summarizes control flow, state machines, and key parameters based on firmware logic to help you understand why the system behaves the way it does.

Runtime State Machine (PIR Driven)

The system uses the PIR sensor to control three states:

1. Idle: no activity detected, system is in standby.
2. Detecting: continuous motion detected; after the trigger delay it enters working state.
3. Working: temperature control and fan logic run. If the off delay is exceeded, it exits.

Default parameters (modifiable in settings):

• PIR trigger delay: 25 seconds
• PIR off delay: 50 seconds

When work ends, the system enters the “print complete exhaust” flow if enabled in the material profile.

Exhaust Fan Control Logic

The exhaust fan supports two drive modes: 2-wire DC and 4-wire PWM. Key logic:

• Below allowed temperature: keep minimum speed
• Over +5°C: increase to medium speed
• Over +10°C: increase to maximum speed
• After printing, strong exhaust may run for a duration defined by the material profile

Heating and Temperature Control

The system uses a “dual PID + safety first” strategy:

1. Chamber temperature PID: targets the minimum chamber temperature for the selected material
2. Heater plate PID: limits heater plate temperature below the protection value
3. Final output takes the smaller PID value to prioritize safety

Additional protection:

• Hard over-temperature: if heater plate temperature ≥ protection threshold, heating stops immediately
• Over-current soft reduction: if current exceeds the set value, PWM output is reduced
• PWM slope limiting: prevents sudden power changes and temperature oscillation

Heater Fan Strategy

When the heater plate temperature is significantly higher than chamber temperature, the heater fan is enabled to transfer heat into the air.

Main Control Board Fan Strategy

The main control board fan is enabled based on combined load conditions:

• Forced on when MCU temperature exceeds 60°C
• Or based on current, fan status, and LED status

Default Material Parameters (Excerpt)

The following are firmware defaults and can be modified and saved on the screen.

• PLA: chamber 0–40°C, exhaust fan 30–100%
• PETG: chamber 25–50°C, exhaust fan 30–80%
• TPU: chamber 0–40°C, exhaust fan 0–30%
• ABS/ASA: chamber 40–70°C, exhaust fan 10–30%
• PC/PPA: chamber 50–90°C, exhaust fan 10–30%
• CUSTOM: chamber 0–40°C, exhaust fan 0–100%

Sensors and Error Handling

When heating is enabled, the system checks sensor errors:

• NTC error: ADC value out of range or invalid
• AHT error: I2C no response or error result
• INA226 error: I2C address error or invalid readings

If an error occurs, the system enters an error page and stops heating.

Notes

• For first-time use, reduce heater current and temperature protection values and observe stability.
• 4-wire PWM exhaust fans are more stable; 2-wire fans may fail to start at low speed.