Compact Filament Runout Sensor for Ender 3 V3 SE

I built a compact and affordable filament sensor for the Ender 3 V3 SE, aiming to use spare parts and keep costs low. This sensor can handle filaments with loose tolerances, like rPET, which often jams standard filament sensors.

Parts List:

• Micro Switch: MS-1A-14.5-P (Ali) or SHOU HAN JL010-125 (LCSC), 1pc
• JST XH Connector:
  • 3-pin JST XH connector (LCSC) - 1x3P, 2.5mm pitch, original, 1pc
  • JST Housing Contact (LCSC) - 22~28 AWG, original, 6pcs
  • 3-pin Housing for JST Connector (LCSC) - XH, 3-pin, original, 1pc
  • 4-pin Housing for JST Connector (LCSC) - XH, 4-pin, original, 1pc
  • Alternatively, you can get a JST XH connector kit with clone-compatible connectors like this one from Ali.
• AWG24 stranded wire - 3 wires, each approximately 1.2m long, required for the wiring, which can be taken from an old Ethernet patch cord.
• Solder, hot glue, PETG plastic
• 4mm paracord, approximately 1.2m long and 5mm OD heat shrink tubing (optional, for added wire protection)

Assembly Instructions:

Print and Fit:

• Print the sensor parts and test the cover fit over the main part. If it doesn’t fit, use the version with wider holes or widen the holes manually.

Prepare the Micro Switch and JST Connector:

• Bend the switch leads with needle-nose pliers as shown in the 3rd image. Dry-fit the switch and JST connector to ensure alignment.

Glue and Solder:

• Apply hot glue beneath the switch, avoiding the moving parts. If you accidentally get glue in the way, remove it with isopropyl alcohol and reposition the connector. Then, reapply a suitable amount of glue.
• Glue in the XH connector the same way, then solder the 3 leads.

Cover Assembly:

• Fit the cover and ensure a snug fit. Apply glue between the switch and connector, quickly close the cover, and hold until the glue sets.

Wiring to the Ender 3 V3 SE:

Locate the Filament Runout Sensor Connector:

• The Ender 3 V3 SE motherboard has a 4-pin JST XH connector located to the right of the high current terminals. For guidance on positioning the sensor and routing the wire, refer to the sensor installation guide below and the images included here.

Cable Preparation:

• Cut three 120cm pieces of AWG24 stranded wire. Crimp both ends using a 4-pin and a 3-pin JST XH connector, making sure the wires are placed in the same order from pin 1 onward. Pin 1 is on the left, usually marked by an arrow at the bottom.
• Optionally, thread wires through paracord for protection and secure with heat shrink tubing.

Install the Sensor:

• Route the wire through the left aluminum extrusion and connect it to both the motherboard and the sensor. Secure the sensor near the filament spool with hot glue or a mounting bracket.

For newcomers to crimping, I highly recommend Teaching Tech’s crimping tutorial below and the IWISS 3220M crimping tool. Check the images in this guide for additional details on setup and wire routing.