Throughout our research for methods to detect filament errors, we came across a few concepts worth considering.
For our design, we decided to use RGB color sensors to detect color changes on a marked wheel. The wheel will be rotated by the filament being fed into the nozzle. Explained in previous posts, we were also considering a rotational sensor. Rotational sensors had more complexity than was necessary. To use rotational sensors, they would have to be fixed to the feeder motor, filament itself, or an extra wheel component attached to the filament. This is because the rotational sensor detects movement physically, not optically. The extra friction on the filament or print head could end up causing more problems in printing. The rotational sensors require more space than RGB sensors and this project must be designed for a very small area in the print head. Simple RGB sensors proved more useful especially if to be used by inexperienced DIYers looking to fix their desktop 3D printer.
The LEGO Mindstorm NXT Intelligent Brick was another device, utilizing RGB sensors, considered for this project.
LEGO products are known for their great user experience and would be great once again for desktop 3D printer users looking for simplicity in detecting filament errors. However, this specific device is priced at $170, not even including the actual color sensor, which is another $40 . Compared to the Arduino sensor setup, valued around $35 for the RGB color sensor AND the UNO Rev3 microcontroller board, LEGO just was not worth it.