Contained within the Da Vinci 1.0 extuder is a small PCB.

It serves a few functions:

1. Header connection for the extruder fan
2. Header connection for the extruder thermistor
3. Counting of idler wheel revolutions using a photo-transistor and LED pair
4. Detection of filament using a photo-transistor and LED pair
5. Collate all the signals into a single header that interfaces to the main controller

Each of the functions above are labelled below for reference.

I thought it would be worthwhile to trace out the PCB whilst I had the extruder removed. All component values were determined except for 3 capacitors which were found to be in parallel (I don’t see the value of knowing their value when they are serving a filtering role). Click here for a copy of the schematic.

The positions of the headers on the schematic match that of the physical PCB just to remind you.

On the back of the idler wheel are white and black segments. These segments are measured by the photo-transistor LED pair labelled “Idler” on the schematic.

An educated guess suggests that the printer is using the Idler photo-transistor and LED pair to measure how quickly the idler wheel is rotating and the direction it is rotating.

To determine the presence of filament in the extruder is another photo-transistor LED pair that I labelled “4” in the photo of the PCB closeup. Some testing revealed that the filament photo-transistor signal outputs 0V when there is filament present. When there is no filament present, the signal increases to 2.5V.

For more ways to improve your Da Vinci prints, check out the Tips and Tricks page.