Duet3D Roto Filament Monitor FFC Cable Length?

[bug2k22]

I have a revo roto extruder with a roto toolboard but mounted slightly differently to how the documentation shows. I see that it says the maximum length of FFC cable from the duet3d roto filament monitor to the toolboard should be no longer than the supplied 30mm length. Is this a hard limit? I'm probably going to need something like 40-50mm or so, is this likely to be an issue?

Thanks.

[dc42]

@bug2k22 a 50mm FFC should work. However, the capacitance between the FFC and nearby metal parts changes the frequency, so it is very important to ensure that capacitance is stable. Don't let the FFC flop around, and don't secure it directly to any metal parts. You can secure it to plastic parts to prevent it moving.

Be sure to get the right sort of FFC. Some have the connections on opposite sides at the two ends, some have the connections on the same side.

[bug2k22]

@dc42 Thanks. I think I may just use the existing duet rotating magnet filament monitor that I used with the previous extruder. This is located off the print head before the ptfe tube that feeds the extruder, it's simple to run the wire along with the power/can cable to the roto toolboard and I wouldn't have to worry about routing/securing the ffc cable near the filament feed. I don't think the integrated duet roto filament monitor offers any advantage over the original rotating magnet filament monitor, I don't have a use for the feature button.

[dc42]

@bug2k22 I didn't read your post carefully enough and I thought you meant the FFC for the inductive sensor. The FFC for the filament monitor is less critical. You can route it close to metal if necessary, preferably metal that is connected to Duet ground.