24V Thermostatic Fan and 5V Print Cooling Fan Connections

  • I am currently using a Duet 2 Wifi with all 24v fans, and I am trying to upgrade to a new design with 24v hotend fan and two 5v print cooling fans.

    Other posts in the forum seem to be about one of them as always on but that's not what I am looking for so I hope I can get a confirmation on how I should connect them.

    So I will probably have the heat sink thermostatic fan on Fan1 as standard, and I believe a way to connect the 5v fans is with one leg on the 5v pin and the other leg on the fan1/3 -ve connector, is that correct? Do I need any diode or resistor?

    My 5v fans are rated at 0.15A, can I have them connect in parallel and use a single fan port?

  • I did read the page before and the closest thing seems to be this (for 12V fan in 24Vin)

    Put a jumper on V_FAN at the VIN end. Wire the buck regulator input to an always-on fan output. Wire the positive wires of 12V fans directly to the buck regulator output, and the negative wires to the FAN- pins of the controlled fan outputs as usual

    So instead of a buck convertor, can I use the on board 5v and can I connect them in parallel.

    edit: wiki seems to be referring to always-on instead of thermostatic, still not sure if it can be applied to my case.

    edit 2: Got another paragraph regarding this but I still want confirmation just to be safe

    Mixed-voltage setups are not directly supported on the Duet 2 WiFi/Ethernet, but the Duet switches the fans' connections to ground, so you may be able to connect each fan's positive side to the appropriate voltage and its negative side to the appropriate pin on the Duet. Each controlled fan can be configured in firmware as a gcode controlled fan or as a thermostatically-controlled fan.

  • Second paragraph that you found is accurate.

    Duty cycle switching is all done at the ground side, so you can connect multiple positive voltages to different fans, and the Duet will switch the ground side for control. I am running both 12V and 24V fans, with plans to run all fans at 12V once I get around to switching out the remaining 24V units.

  • Thanks for the confirmation

  • @jackal Always on fans are, as the name implies, always on. You can't control them (because they are always on). So everything else apart from supply voltage in the wiki applies to fans that are not "always on".

  • Just to report that I have connected my two 5v fans in parallel and +ve to on board 5v and -ve to Fan2-
    Everything seems to working fine, tested with M106 P2 S255.

    So worried that I was gonna fried the board, I killed the thermistor fuse not long after the board arrive so please bare with my paranoia.

  • @jackal It's better to be overly cautious IMO. ☺

  • administrators

    If you have fans of different voltages on your system, then V_FAN must be the highest fan voltage. In your case that's 24V, so put the VFAN jumper in the VIN position. Connect your 24V fan as normal.

    To connect the 5V fans, connect the red wire to +5V (which you can get for the spare pin of the VFAN jumper block) and the black wire to the FAN- pin of the chosen 2-pin fan connector.

  • Thanks for the VFAN jumper 5v suggestion, that makes the wiring a bit cleaner

  • administrators

    @jackal, be very careful not to short +5V to +24V !

  • I am very careful with the more obvious stuff, just not sure when it involves adding resistors/dioides or splitting the +ve -ve connections.

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