Combine Tool Wiring



  • Hello,

    New Duet Wifi user here trying to figure out how to combine the wiring going to the toolhead, or in other words what are the minimum number of wires I need to "send" to the toolhead.

    These are the things that need connecting:

    • Heater.
    • Thermistor.
    • Hotend Fan.
    • Part Fan.
    • Limit Switch (NC).
    • dc42's IR Sensor.

    I understand that Heater and the two Fans, need 4 wires (1 positive and 3 negative) considering I do understand correctly that switching is happening on the negative side (?), but I am not sure about the rest.

    Any help is appreciated.

    Thanks!



  • Instead of x/y limit switches you can use motor stall detection. You can find schematic here https://github.com/T3P3/Duet/blob/master/Duet2/Duet2v1.04/DuetWifi_Schematic_v1.04.pdf , e.g. to confirm low side switching.

    BTW, Duet 3 will use serial communication to the head with a secondary board that will distribute the signals/power to the fans, heater, sensors, etc.



  • Thank you for the link.
    So from the looks of it, I need 10 wires, or 9 if I do use stall detection instead of switch, but I am not sure yet. I feel safer with limit switches.
    A simple distribution board is exactly what I am trying to make BTW. Using serial on the head sounds very nice for v3 (but I have v2), so I will have to roll some sort of custom, yet simpler solution.

    Thanks!



  • Hi,

    I've used igus chainflex CF884.006 which packs the following cores into one cable of about 9 mm diameter:
    3 pairs of 0,14 mm^2 twisted pair sensor wires (shielded)
    4 wires of 0,14 mm^2 (for fans, LEDs)
    4 wires of 0,22 mm^2 (for 1 stepper)
    2 wires of 0,5 mm^2 (for 1 heater element)

    there is another shield around the whole package. It's made for energy chains, so it allows for quite tight radii and is flexible enough so it won't break. I fit a print head with direct drive, heater, sensor, 2 fans and a bltouch (and even an optical endstop) with this cable, I can see if I can still find the according diagram later at home.

    Best regards, Niklas



  • @sonderzug

    Hey, thanks. That looks like a good wire indeed, but unfortunately the problem for me, is not actually the number of wires per-se, but rather the number of connectors entirely for spacing reasons. Right now I use these NPP wire-to-wire connectors (https://grobotronics.com/wire-connector-npp-4-pin-female-2.5mm.html?sl=en), and each one is taking up quite some space (for no good reason). Of course I could always not use wire connectors but I want to 100%.

    Thus I thought of creating a small distrubution board on a prefboard with all wires from board directly soldered in and leading to JST XH connectors for heater, fans etc. The whole assembly seems to take much less space than all the NPP connectors I am using now. I also thought of using JST XH wire-to-wire, but it's not really good idea I think.
    Maybe there are some type of very small wire-to-wire connectors I do not know.


  • administrators

    @nuverian said in Combine Tool Wiring:

    Hello,

    New Duet Wifi user here trying to figure out how to combine the wiring going to the toolhead, or in other words what are the minimum number of wires I need to "send" to the toolhead.

    These are the things that need connecting:

    • Heater.
    • Thermistor.
    • Hotend Fan.
    • Part Fan.
    • Limit Switch (NC).
    • dc42's IR Sensor.

    I understand that Heater and the two Fans, need 4 wires (1 positive and 3 negative) considering I do understand correctly that switching is happening on the negative side (?), but I am not sure about the rest.

    Any help is appreciated.

    Thanks!

    That setup needs 10 conductors. 4 for the heater and fans as you suggest, 2 for the thermistor, 3 for the IR sensor, and 1 for the endstop switch. The ground wire for the endstop switch can share the ground with the IR sensor.



  • @nuverian I have used perf board quite successfully, as you have been thinking. You're right: it does allow a very compact, bespoke, solution without having to search for hours to find the right plug! Even then, I never came across that lovely cable @sonderzug suggests.
    I used common header pins and dupont connectors both sides of the board so that I could plug in the whole cable one side and have separate connectors to the individual head components on the other allowing them to be changed easily. It should also work nicely with soldered wiring to your board. The perf board/header is shrouded by a small print.The blue plug in the photo is a female header in hot glue/heat shrink. A bit fiddly to make. For the heater connection I used 2 pairs of pins to carry the current. I found it best to use through hole plated proto board which gives the pins a better mechanical fixing.
    4_1558964042055_DSCN0981.JPG 3_1558964042055_DSCN0980.JPG 2_1558964042055_DSCN0979.JPG 1_1558964042055_DSCN0978.JPG 0_1558964042054_DSCN0977.JPG


  • administrators

    I advise using separate connectors for the "high voltage" wires (fans, heaters) and the "low voltage" wires (thermistor, sensor, endstop - assuming the sensor amd endstop need no more than 5V). Otherwise it is far too easy to mis-wire the pins, or get a short between them. Feeding 12V or 24V into the +3.3V or +5V rail will destroy the Duet.



  • @pawprinter This is lovely. Super compact (even more than I'd imagine using JST XH). The double sided idea is a very good one. I might just steal it with your permision 🙂

    @dc42 Yep, that is understandable, hence the reason why I was thinking JSTs (separate and with correct orientation), but then again, this is uber compact if that is the uter goal, along with it's potential shortcomings that is.

    Thanks for your replies everyone!



  • @nuverian Thanks, no prob, steal away 🙂 I can see that it is very error prone when wiring it up, so do take care. You may also notice that my plug can be put in the wrong way around. However, more by luck than judgement, my pin arrangement is tolerant of that error, other than the fact it won't work. I marked my plug so that I never put it in the wrong way - ha ha yeah right that didn't work! You probably should contrive a way to ensure that it cannot be wrong.


 

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