Creality Filament Runout Sensor - custom firmware?


I’m trying to get an official creality filament runout sensor working on my Ender 3 Pro (MB 4.2.2) and am having trouble. I had no trouble installing it but the printer seems to be interpreting the sensor opposite to what it should be. If I run the filament through the sensor and then to the extruder, the printer starts the “change filament” process when I start a print. If I bypass the sensor but leave it connected to the printer, it prints fine. It seems as if the printer thinks there is filament present when there isn’t and vice-versa.

I’m using firmware that I downloaded from the Creality website that supports my BL-Touch and seems to support the filament runout sensor.

I think that I need to build my own firmware to get it working correctly. Is this correct? Am I missing something?

Thanks for your help

I’m not sure what you mean by “bypass the sensor”. The sensor is most likely just a switch. Do you mean you are putting a jumper across the switch?

Like most switches, the switch will likely have a common (C) connection and a Normally Open (NO) and Normally Closed (NC) connection.

I don’t have a runout sensor at all, much less the Creality one to look at as a reference, but looking at the photos on 3DPCs web site, I see it has a 3-wire connector. Use an ohmmeter to see which pair of wires are connected when no filament is present and which pair are connected when a filament is there. Whichever wire they have in common is (C). You can now swap the other two wires to reverse the functionality of the filament detector.

Having said all that, when I see a 3 wire system, I’m also mindful that it could be a powered sensor with a data line. Black would be ground, Red would be 5V and Yellow would be the data output. If that’s the case, then the ohmmeter test won’t be conclusive. If that’s the case, then you’ll have to change the behaviour in firmware.

The only reason I try to avoid changing settings in firmware is that if you update the firmware at any point, you’ll have to remember to re-implement all your manual changes, whereas a hardware fix is permanent.

let me chime in on this one as well, the creality sensors are not digital which means they do have an NC/NO circuit system. This being said the easiest way by far to reverse the functionality of the sensor is to repin the wire.

Sorry - by “bypass the sensor”, I meant that I didn’t route the filament through the sensor.

And yes, the sensor is just a switch, with an LED to show the status of the switch.

Here is a wiring diagram - xxxxxxxxxxxxxxxxxxx (link removed because of possible damage to MB if used)

I will test out the sensor with my ohm meter to verify how it operates.

Thanks for your response.

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Actually, in the photo you linked to, it expressly states:
“These switches can vary.
GND (ground, common) will be the center pin (black wire).
–>> Swap the outer two if the signal is incorrect <<–”

I saw that note, but wasn’t confident that it was reliable info. I will give it a try after a bit more fiddling around with my multimeter.

Thanks for your help.

Nope - that didn’t work. Swapping the yellow and red wires caused my printer to reboot everytime the filament sensor transitioned from having filament to not having filament.

I’m going to open up the printer to check that the motherboard matches the diagram I included above.

I had a whole write-up in progress that I was fact-checking as I went along and I’ve just deleted it all because I discovered this: (It’s not the firmware discussion that’s interesting - it’s the board photo toward the bottom of the page)

Note the diagram on this page from Creality showing the wiring of the runout sensor. Note that the wiring is exactly backward from what is shown in the diagram you posted earlier. If THIS diagram is correct, it would mean your sensor is shorting V+ to Ground when it’s being triggered - which would reset the board.

Wow. So not only is the first diagram wrong re: wiring (red and yellow wires swapped), it is also wrong in suggesting that a swap of the red and yellow wires might “fix” the problem if the signal is wrong.

I’m glad that I didn’t fry my board when I swapped the 2 wires!

I guess my options are:

  1. update firmware for inverse switch behaviour (i.e., low <-> high)
  2. (somehow) hack the sensor so that its behaviour is reversed
  3. build a new filament sensor using a different switch (one that I can easily get access to the correct pins for the desired NO/NC behaviour)
  4. buy a smart filament sensor like the BigTreeTech one.

So I know this is an old thread but I just found it. I installed the official Creality runoff sensor on my Ender 3 v2 and used the Jyers custom firmware. Never had an issue with it, so maybe try loading that instead of the Creality firmware?

Hi @leafsfanatic Welcome to the forum, thanks for your post. I have never used the creality sensor with Jyers but good to know it also works.