Low Friction Filament Sensor

This is my idea for a filament run out sensor. I wasn't happy with the Chinese filament sensors. They are difficult to guide filament through and add a decent amount of friction. This sensor uses a 10mm ball bearing and a switch with a wheel to reduce friction. It also has a better designed filament guide allowing filament to be loaded and unloaded with ease. You can print it without the hex shaft and use it directly on top of the extruder or with the hex shaft for use with the swivel mounts. If a mount for your model printer is not available you can send me some measurements for me to design one for you. I have designed a print in place pivoting mount for the sv06 and sv06+. It mounts under the stock spool holder using the original screws. I have also created an Ender 5 mount for my friends printer but have not tested it yet. All pieces are press fit. No screws necessary. Some soldering is required. I will be selling these complete for people that are not interested in building it.

Required materials;
-roller micro limit switch kw12-3

-10mm od, 5mm id, 4mm bore ball bearing mr105-2rs

-Mini Micro JST 2mm 3-Pin Female Connectors Plugs with wires and the male plug to match for the sensor

-2.54mm JST Connector 3p female with wires to plug into the motherboard

-(Optional) 1.25mm micro jst connector 3p female if you prefer to plug into the hot end.

Start by bending the outer wire tabs on the limit switch to the inside. You can cut off the middle normally open(no) pin as it is not used(note: you can opt to use this in favor of the normally closed(nc) pin if your firmware requires.) 

Solder the normally closed(nc) pin and common(c) pin of the limit switch to the two pins on the male 2mm micro jst connector that align with the red and black wires. Solder the male 2mm jst connector directly to the normally closed(nc) pin to hold it in place and use a wire to jump the other 2mm connector pin to the limit switches common(c) pin. 

Solder the black and red wires from your female 2mm micro jst plug to the black and red wires of your female 2.54mm jst plug(or optional 1.25mm jst plug if plugging into the hotend). The YELLOW WIRE IS NOT USED. DO NOT CONNECT YELLOW WIRES.

Now finish installing the switch and plug that are soldered together into the housing. 

You can slide a piece of filament through to hold the switch while you install the bearing(filament guide hole may need cleaned if filament does not pass through smoothly). 

Now run the filament in and out and listen for the switch to make a click. If the switch is not clicking bend the tab on the switch until it clicks while adding and removing filament. 

Use a multi-meter to test for resistance between the red and black wire. With filament in the sensor and the switch closed there should be an open load between the red and black wire. With no filament in the sensor and the switch open there should be a low resistance load between the red and black wire.

Once you have confirmed your sensor is working as it should, install the face by lining up the pegs and firmly pressing it in place(glue is optional). 

If you are using it without the mount it is now ready to install. (Contact me if you need a mount for your specific printer)

For use of the mount partially insert the sensors hex shaft into the receiving end of the mount(note: a firm twist to break free the print in place bushing may be necessary depending on your printers calibration). Lubricate the bushing and rotate it. 

Install the sensors hex shaft into the mount by pressing firmly. It is best not to press it all the way in leaving a small gap to allow more free movement. 

Mount the sensor under the spool holder of the sv06 using the existing screws. Plug the sensor into the motherboard and update firmware if necessary.

Enjoy, and please post your makes!

UPDATE 11/30/24

I added 3 models starting with mr115 for use with a mr115 bearing. I have not printed this version…