Hybrid Filament Runout Sensor

thingiverse

**2020-01-19** One user suggested that I make the lever a little thinner, about 0.6mm thinner. So it won't stick against the casing. I uploaded an updated version for that. **2019-08-20** I found that if the lever wasn't printed well enough (I'm currently testing 3 of them, 1 has an issue with only a spool of PLA), the sensor will generate false run-out signals. I modified the shape to make it more reliable. # Introduction This is a filament sensor inspired by Prusa MK3S. It could be used with 1.75 filaments only. It combines the strength of mechanical and optical sensors. The goal is to provide a reliable and durable filament runout sensor that uses magnetics to reset the lever position. (it should handle wearing well enough.) I was using a microswitch-based solution before. The downside of switch-based solutions is that when reversing the filament, it could jam and break the switch. The IR only filament sensor couldn't handle transparent filaments well. This design theoretically allows the filament to go from both directions. And tested with transparent filament without any issues. The casing could be printed with PLA, I printed with 0.2 layer height. The hard part might be getting the PCB and soldering the components. Unfortunately, there is no stock part of this. You have to make your own. The PCB part features an active low signal. And two LEDs to indicate states. Green LED lights up when the filament is detected, and red if not. # Parts You will need the following extra hardware parts: | Amount | Model | | ------ | ---------------------- | | 2 | M3*10 flat head screws | | 1 | M3*8 round head screw | | 1 | M3*6 round head screw | | 2 | 8mm x 4 mm magnet | | 1 | 7mm ball | And the electronic design is also included, BOM as below: | Part | Value | Device | | ---- | ----- | ---------- | | C1 | 100nF | 0603 | | D1 | RED | 0603 | | D2 | GREEN | 0603 | | JP1 | | XH2.54-3TH | | R1 | 680 | 0603 | | R2 | 330 | 0603 | | R3 | 10K | 0603 | | R4 | 10K | 0603 | | R5 | 10K | 0603 | | R6 | 330 | 0603 | | U1 | | ITR20403 | | U2 | | LM393 | # Assembly Instructions 1. Insert the magnets into the slots in both lever and bottom casing. Notice that the polarity should be positioned so that the lever pushes away (towards the filament) 2. Use the M3*8 screw to fix the lever, don't tighten it too much, you need to leave space for the lever to turn. 3. Mount the PCB with M3*6 screw. 4. Install the top cover and fix it with 2 M3*10 flat head screws.