Filament Runout or Jam Sensor

23-10-2019 NEWS FLASH!!!! ..... I have uploaded a microprocessor based design that is programmed using an Arduino Uno. I think it has more functionality and is easier to use. See www.thingiverse.com/thing:3926841 .......NEWS FLASH!!!!

(UPDATED 21-7-19.... The circuit will need to be modified for 3D printers that use 256x microstepping. I have uploaded updated instructions that include the resistor value change that is needed for this. ....UPDATED)

(UPDATED 21-7-19.... I have improved the box design to allow the idler arm to move back from the filament further to allow a larger rubber o-ring to be used if desired. I have also removed a section of the right axle support to allow more adjustment of the location of the photodiode and phototransistor board, as I found that sometimes the disc would touch the photodiode causing the disc to stop turning resulting in a false jam detection. I have also adjusted the dimensions of the filament inlet to the device so a