Introduction

The ALPS pressure module is a pressure sensing solution based on the ADS131M02 design, specifically developed for automatic Z-axis homing and mesh bed leveling of 3D printers. Through high-sensitivity pressure detection and real-time signal processing, the module can accurately perceive the contact status between the print head and the mesh bed, achieving millimeter-level leveling accuracy, eliminating errors caused by traditional mechanical limit calibration, and significantly improving the first-layer printing success rate.

Parameter Comparison

Usage of the APLS Pressure Module

Recommended to Use with Wiping Functionality

When using the APLS pressure module, it is recommended to use it with the wiping function to ensure the cleanliness of the nozzle, thereby improving the precision and stability of leveling.

XH2.54 4Pin Wiring Diagram

The module can be directly inserted into the mainboard's UART interface or connected to the UART interface of the expansion board. If there is no UART interface, two pins can be found on the mainboard, paying attention to the positive and negative poles of the power line.

Installation Precautions

1. Ensure that the module is installed securely to avoid poor contact due to vibration during printing.
2. Check whether the wiring is correct to avoid the module failing to work due to incorrect wiring.
3. Before first use, it is recommended to perform multiple leveling tests to ensure that the sensitivity and accuracy of the module meet expectations.

Status Light Display

• Power-on State: The green light frame status light stays on continuously, indicating that the module is working normally.
• Trigger State: The red light frame status light flashes, indicating that the module is in the trigger state.

Status Light Fault Diagnosis

• If the status light does not light up, please check whether the power connection is correct.
• If the status light keeps flashing, it may indicate that the module detects an abnormal signal; please check whether the probe is stuck by foreign objects or damaged.

Configuration Guide

Replace the probe and homing parts in the original configuration file with the following configuration:

Example Configuration File

The following is the recommended content of the configuration file; please adjust according to actual needs:

[homing_override]
axes: xyz
set_position_z:10
gcode:
       G91
       G1 Z10 F3000
       G90
        SET_PIN PIN=_probe_ready VALUE=0
        ## _LIFT_Z
       {% set home_all = 'X' not in params and 'Y' not in params and 'Z' not in params %}

       {% if home_all or 'X' in params %}
            G28 X
       {% endif %}

       {% if home_all or 'Y' in params %}
            G28 Y
            G0 X{printer.toolhead.axis_maximum.x / 2} Y{printer.toolhead.axis_maximum.y / 2} F6000
       {% endif %}

       {% if home_all or 'Z' in params %}
       # If eddy plus pressure sensor is used simultaneously, uncomment the following line
            #SET_PIN PIN=_probe_ready VALUE=1 
            G28 Z 
            #SET_PIN PIN=_probe_ready VALUE=0
            G1 Z10 F3000           
        {% endif %}

[output_pin _probe_ready]
pin: PA9 #En #Enable pin
shutdown_value: 0
value:0

[probe]
pin: ^PA10 #out #Probe pin
x_offset: 0                  # X-axis - sensor offset relative to nozzle
y_offset: 0               # Y-axis - sensor offset relative to nozzle
z_offset:0                # Z-axis - sensor offset relative to nozzle
speed: 8                 # Leveling speed
samples: 3                   # Number of samples
samples_result: median       # Value selection method (default median - median value)
sample_retract_dist: 2     # Retract distance during leveling
samples_tolerance: 0.05      # Sampling tolerance (note that too small a value may increase the number of samples)
samples_tolerance_retries: 3 # Retry count when exceeding tolerance
activate_gcode:
           G4 P500
           SET_PIN PIN=_probe_ready VALUE=1
deactivate_gcode:
           SET_PIN PIN=_probe_ready VALUE=0  

Reference for Adjusting Z Offset Value

Use this command to adjust z-offset:

PROBE_CALIBRATE

• Before adjusting the z-offset value, refer to the Klipper documentation tutorial: Paper Test

Note

• If you want to use the pressure module as a Z-axis limit switch, replace the original endstop_pin configuration with: endstop_pin: probe:z_virtual_endstop