Filament Width Sensor Prototype Version 3

This is a prototype for an optical sensor that measures the width of plastic filament in real time as it goes into a 3D printer or a filament extruder. It is prototype #3 (other 2 are on Thingiverse as well ).
The idea is that with a real-time width measurement the 3D printer could compensate the extruded flow for changes in filament width. Also if there is variation between spools of filament, there is no need to calibrate for that when slicing. The g-code is independent of the filament diameter. For filament extruders, the measured width can be used as feedback in the extrusion process.This version includes a custom designed pc board as well as a housing. A version of Marlin is modified to use the sensor data.
The sensor outputs a voltage in milimeters (3v=3mm) that is shown on the voltmeter.
I made some changes to Marlin to read the filament diameter real-time and compensate the extrusion rate. Code uses a buffer to manage the transit delay between the sensor measureme