Fan connection documentation.



  • Hello,
    I was looking for documentation for the fan connectors and voltage selection jumpers but having some trouble finding it.
    Maybe because it is quite self explanatory. Anyway my extruders always on fans are 24V Vin. But my parts blowers are 5V. Is there a way to set the jumpers to split the always on and PWMs voltage. If not I guess I coud always set all the connectors to 5v and connect the 24v fans to Vin directly. Or is there a better way? I even see a PWM V_IN in the key but not in the wiring diagram itself.


  • administrators

    You are right, I forgot to write a page about fan connection. I suggest you set the jumper to 5V and then connect the positive ends of your 24V fans to either +Vin or the 3rd pin on the jumper block. Always on fans can be connected directly to Vin as you say.

    PWM fan output 1 is typically used to control a hot end fan thermostatically. That's why it defaults to on at power up.



  • Thank you for your answer as always.

    I finally decided to make myself a small "fan" extension board for the 24V always on fans since I'll have more than 1.
    The thing is I couldn't find the small blowers I needed in 24V, although I would have prefered to have all fans with a single voltage.

    Also reading this bit "by default the board runs off USB power, but moving the jumper from "5V internal" to "5V external" allows you to power the board from the 5V in pin." from the power connection page,
    Looking at my board I see both jumpers are in place… Is that intended or should I remove one?
    Alternatively can I pipe my 24V Vin to the 5V in connector? or is there some circuitry in between, a small schematic would be great 😉
    Also it would have been nice to have 1 or 2 connector just to extract gnd and Vin, actually (one more wish for next gen).



  • You can find some info about fans (all Duets) here : http://otocoup.com/aql/#hlp:allb/fans



  • thank you! but should i remove one of the 2 jumpers?


  • administrators

    You should have the 5V_EN jumper installed if you want to use the on board switching regulator to provide the 5V supply, or the 5V_ATX_EN jumper installed if you want to provide 5V from and external supply via the 3 pin connector.



  • Thank you. All clear.



  • Sorry, that text on the wiki was kind of ambiguous. I've clarified it a bit, though it's still not clear to me what happens if both the 5V internal and 5V external jumpers are set. Presumably if neither is set you have to use USB.

    I'd add a fan connections page to the wiki, but only administrators can edit the overview page. Worth noting: some of your always-on fans may not need to always be on. The Duet WiFi can set one or more of the PWM fans to be on any time a particular thermistor reads above a particular temperature, so you could have a heatsink fan that was on whenever that hot end was above, say, 70 C.

    I'm still not clear about whether RepRapFirmware can turn the stepper motors off when they've been idle for long enough; in fact I'd prefer the firmware to automatically turn the ATX supply off and on when needed, but I realize that "when needed" is a little complicated given that steppers lose microsteps when powered down and hotends can jam if the heatsink is not cooled when it needs it. So for the moment I have G-code to cool the hot end and then shut down ATX power at the end of a successful print; cancelled prints require the user to shut down by hand.



  • If there is nothing connected on the 5V input, the fact the the external jumper is set will not do anything. This may be bad if there is another supply.

    About the USB connection, when starting the Fisher I asked confirmation (to RRP) that it was ok to have simultaneous 5V supply from USB and internal source, and they confirmed it (prior this answer, I was removing all 5V jumpers when using USB).
    I also commented to T3P3 that this shall be in documentation when buying the Duet 0.8.5 (in dec 2015).

    About the steppers, you can turn them on and off by G-code anytime without need to set them idling first.
    You can create a cancel.g macro which will be executed when you cancel a print instead of resuming it, see useful macros: http://otocoup.com/aql/#hlp:allb/macros


  • administrators

    @peridot:

    I'm still not clear about whether RepRapFirmware can turn the stepper motors off when they've been idle for long enough; in fact I'd prefer the firmware to automatically turn the ATX supply off and on when needed, but I realize that "when needed" is a little complicated given that steppers lose microsteps when powered down and hotends can jam if the heatsink is not cooled when it needs it. So for the moment I have G-code to cool the hot end and then shut down ATX power at the end of a successful print; cancelled prints require the user to shut down by hand.

    By default, RRF reduces motor current to 30% of normal when all motors have been idle for 30 seconds. The percentage and the timeout can be adjusted using the M906 command.

    You can write a macro file to cool the hot end down and then turn the ATX PSU off.

    In a future version of RRF, I intend to add the facility to move all motors slightly to a position that corresponds to how they will power up again. That should reduce the risk of the motors jumping steps when you power off and on.


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