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# Hall filament width sensor

This document describes Filament Width Sensor host module. Hardware used for developing this host module is based on two Hall linear sensors (ss49e for example). Sensors in the body are located on opposite sides. Principle of operation: two hall sensors work in differential mode, temperature drift same for sensor. Special temperature compensation not needed.

You can find designs at Thingiverse, an assembly video is also available on Youtube

To use Hall filament width sensor, read Config Reference and G-Code documentation.

## How does it work?

Sensor generates two analog output based on calculated filament width. Sum of output voltage always equals to detected filament width. Host module monitors voltage changes and adjusts extrusion multiplier. I use the aux2 connector on a ramps-like board with the analog11 and analog12 pins. You can use different pins and different boards.

## Template for menu variables

    [menu __main __filament __width_current]
    type: command
    enable: {'hall_filament_width_sensor' in printer}
    name: Dia: {'%.2F' % printer.hall_filament_width_sensor.Diameter}
    index: 0

    [menu __main __filament __raw_width_current]
    type: command
    enable: {'hall_filament_width_sensor' in printer}
    name: Raw: {'%4.0F' % printer.hall_filament_width_sensor.Raw}
    index: 1

## Calibration procedure

To get raw sensor value you can use menu item or QUERY_RAW_FILAMENT_WIDTH command in terminal.

1. Insert first calibration rod (1.5 mm size) get first raw sensor value

2. Insert second calibration rod (2.0 mm size) get second raw sensor value

3. Save raw sensor values in config parameter `Raw_dia1` and `Raw_dia2`

## How to enable sensor

By default, the sensor is disabled at power-on.

To enable the sensor, issue ENABLE_FILAMENT_WIDTH_SENSOR command or set the `enable` parameter to `true`.

## Logging

By default, diameter logging is disabled at power-on.

Issue ENABLE_FILAMENT_WIDTH_LOG command to start logging and issue DISABLE_FILAMENT_WIDTH_LOG command to stop logging. To enable logging at power-on, set the `logging` parameter to `true`.

Filament diameter is logged on every measurement interval (10 mm by default).

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