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Introduction

The ALPS pressure module is a pressure sensing solution based on the ADS131M02 design, specifically developed for automatic Z-axis homing (Home) 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 success rate of the first-layer printing.

Parameter Comparison

Using the APLS Pressure Module​

When using the APLS pressure module, it is recommended to pair it with a 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 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 polarity of the power lines.

Installation Precautions​

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

Status Light Display​

  • Power-On State: The green and red frame status light remains on, indicating that the module is working normally.
  • Trigger State: The red frame status light blinks, indicating that the module is in the trigger state.

Status Light Troubleshooting​

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

Configuration Guide​

Replace the existing configuration file's probe and homing sections 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 using eddy and pressure sensor together, uncomment below
            #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

[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 endstop, override the original endstop_pin configuration to: endstop_pin: probe:z_virtual_endstop