Duet 3 fan wiring question. 5v and 24v

  • I have both 24V and 5V fans that I need to connect to a Duet 3. On other duet boards, this was accomplished just by adjusting a jumper that either set voltage to V_IN or 5V. On the Duet 3, I am confused what the jumpers on the diagram are telling me. It seems like it can take voltage from either a 12V-36V power source, or 12V, but it doesn't seem able to drive 5V fans from what I can tell on the diagram. Currently, I am only powering the board with a single 24V power supply.

    Can someone help explain how this works and correct my understanding? I would like to avoid frying anything through trial and error 😛

  • correct, you'd need to add a jumper wire from a 5v source to the V_OUTLCn pin in question, or wire the positive lead of the fan directly to a 5v source.

    hopefully we'll see a 3-way jumper adding 5v as an option in a future revision, this was my suggestion:

     V_FUSED o
    V_OUTLCn o o  5V_EXT
     12V_EXT o

  • Moderator

    The 12v regulator is nice, but I still kinda miss the V_fan pin.

  • @Phaedrux said in Duet 3 fan wiring question. 5v and 24v:

    but I still kinda miss the V_fan pin.

    instructions unclear.. the V_OUTLCn pin is the equivalent of the V_fan pin is it not? Or do you mean the whole old Vin/V_fan/5V jumper. I think the rationale was more and more people will go for voltages above 12v and there is a limited selection of fans in 24v or more (12v fans are usually cheaper as well); but still we could have had it both ways.

  • Yeah, my main thing is I still use small 5V blowers for some cases, so its sad to see the 5V option gone... guess I will just need to use a buck reg. Thanks for the help.

  • @bass4aj said in Duet 3 fan wiring question. 5v and 24v:

    guess I will just need to use a buck reg.

    if you stay under 3A total for 5v and 3.3v you can just run a female-female jumper wire from a 5v pin over to V_OUTLCn, skipping the buck converter.

  • administrators

    On Duet 3 we removed the built-in support for 5V fans, because we now provide a built-in regulator for 12V fans, and because a number of users have wrecked their Duets because of shorts between VIN and +5V in the fan wiring. I'm not aware of any good reason to use 5V fans rather than 12V fans, other than that you might have some already.

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