At current count, I have 15 separate conductors running through my cable chain to the toolhead:

2 for the extruder fan (+12V, ground)
2 for the part cooling fan (+12V PCM, ground)
2 for the heater cartridge (+12V PCM, ground)
2 for the hot end thermistor (?)
4 for the extruder motor (?)
3 for the inductive sensor (+5V, ground, signal)

I was thinking that there are 4 separate ground wires, as well as two constant voltage wires (+12V for the extruder fan and +5V for the inductive sensor). Any reason I couldn't use a single ground wire for everything, and maybe replace the 5V inductive sensor with a 6-26V sensor and use the same +12V line for the extruder fan and the sensor? I'd probably leave the heater cartridge with its own ground since it goes to a separate tap on the power supply, but I could end up with:

1 Common ground
1 +12V for extruder fan and sensor
1 for the part cooling fan (+12V PCM)
2 for the heater cartridge
2 for the hot end thermistor
4 for the extruder motor
1 for the inductive sensor (only signal)

for a reduction of 3 conductors.

Does this make any sense? Any pitfalls to watch out for?

You can use the same +12V wire for the hot end heater, both fans, and the 6-26V sensor. Saves 3 wires. The other wires should be kept separate.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
You can use the same +12V wire for the hot end heater, both fans, and the 6-26V sensor. Saves 3 wires. The other wires should be kept separate.

Good point - I was thinking high-side switching where a common ground would work, but obviously if they're low-side switched the +12V would be the common wire. I'll have to take a look at the RAMPS 1.4 schematics and my external MOSFETs and see what's what. Thanks!