12V 2A fans on 24V Duet Wifi 1.04



  • Hi,

    I got fed up with trying to find good quality 24V turbine fans and decided to try a good quality 12V turbine.

    Looking at history here and the documentation, I still find myself unclear on a number of things (not being an electrical engineer doesn't make this any easier 🙂 ).

    1. If I read docs right, I can use a buck converter connected to an always on fan output to drop from 24V (everything else I have with the duet is 24v) to 12V and connect only the + wire into V_FAN - which in turn will feed the 12V achieved this way to the three fan connectors on the board. Is this correct? Since it'd be a common ground buck converter, I don't have to worry about the negative wire.
    2. Do I understand correctly fan outputs (FAN0, 1, 2) can each supply a 2A fan and not all of them combined? The one thing I missed when buying my turbine fans is that they are 2A and not something lower.
    3. If not and I don't have ready access to a bigger mini blade fuse - would using a mosfet (like the one used for a hotbed) make sense to protect the board? I have a spare mosfet that I could use if this idea makes sense.

    The other fans I would like to power through the Duet are Noctua 12V fans - one would be for hotend, one to provide extra cooling to the board. Those would both take no more than 0.2A.



  • @pkos As far as I remember each fan port can provide 1.5A. Though I am not 100% sure about this right now.

    Also I think the always on fan connectors also provide what V_FAN is seeing. So you might need to take your 24V directly from the PSU.

    But if it is only this one fan that takes that much current and you do have one of the heater connectors unused you can also use these to provide power to the fan and remap it accordingly. This was a new feature introduced in RRF 2.01 or 2.02. The heater connectors are good up to 6-10A (don't remember any better, sorry).



  • @wilriker Huh... the heater idea sounds great too 😮 I would need some guidance though as to how to get everything connected. Can the buck converters handle the PWM signals sent through the heater connector? I could then just use two buck converters - one for fan connectors, another for the heater connector that would feed this single part cooling fan - if that makes sense 🙂



  • @pkos Even when connected to the heater connector the scheme on switching PWM on GND is globally used on the Duet. You would still provide 12V constant via a buck down converter that is fed 24V from PSU/VIN and then connect the V+ of the buck to one the positive of your powerful fan and V- of the fan would go to the negative screw terminal of the heater. It is more or less the same as with V_FAN just that there is a specific pin on the board for fans and when using the heater connector you have to do this yourself.

    But yes, you would probably use two buck converters in this case.

    If you did now buy the Noctua fans already you can get 5V versions of many of their fans as well and the Duet can provide 5V to the fans natively.



  • Yeah, no 🙂 I already have all of the fans and I can't return the Noctua's anymore. The blowers I could try, but I like the idea with the heater and two buck converters. Saves a lot of hassle and risk.


  • administrators

    @pkos said in 12V 2A fans on 24V Duet Wifi 1.04:

    Hi,

    I got fed up with trying to find good quality 24V turbine fans and decided to try a good quality 12V turbine.

    Looking at history here and the documentation, I still find myself unclear on a number of things (not being an electrical engineer doesn't make this any easier 🙂 ).

    1. If I read docs right, I can use a buck converter connected to an always on fan output to drop from 24V (everything else I have with the duet is 24v) to 12V and connect only the + wire into V_FAN - which in turn will feed the 12V achieved this way to the three fan connectors on the board. Is this correct? Since it'd be a common ground buck converter, I don't have to worry about the negative wire.

    Correct.

    1. Do I understand correctly fan outputs (FAN0, 1, 2) can each supply a 2A fan and not all of them combined? The one thing I missed when buying my turbine fans is that they are 2A and not something lower.

    The recommended max continuous current is 1.5A per fan output, with 2A allowed for a few seconds during fan start. If you run them above 1.5A continuous, check the temperatures of the fan mosfets.

    1. If not and I don't have ready access to a bigger mini blade fuse - would using a mosfet (like the one used for a hotbed) make sense to protect the board? I have a spare mosfet that I could use if this idea makes sense.

    The other fans I would like to power through the Duet are Noctua 12V fans - one would be for hotend, one to provide extra cooling to the board. Those would both take no more than 0.2A.



  • @dc42 Great. Thanks for confirming the data.
    I'll give @wilriker 's idea a try. Seems like a very good solution to my problem. And if it turns out that the fans are too powerful, I'll try to find some weaker ones, although I'm somewhat in love with those maglev turbines 🙂



  • When I first put my Duet system together, I did not have the 12V buck-boost, but a large number of 12V fans, and a decided lack of 24V fans.

    My interim solution while I waited on delivery of the buck boost was to run 2 fans in series at 24V, which works fine. Total current draw is the same as a single fan at 12V, but my fans are all low current, so maybe a slightly different solution. I also have 12V LED strips for lighting at the top, where I run 2 of them in series on 24V. I saw no need to change that, since I didn't want to get rid of the second LED strip. For the fans, I ended up with a couple of different sized fans running underneath the printer where they weren't needed, and just increased potential points of failure.

    If you are running 2 of the same size/type, it's an option.



  • @supraguy Thanks for the hint, but not an option for me.

    I only have a single fan that's this powerful - and as luck would have it - it's the part cooling fan, which absolutely needs to be fully controlled. 🙂

    I'm down to trying the heater idea, the mosfet to protect the board, or I just found that the fans I want to use have a weaker version at 1.4A. Now I just need to find if I can buy them somewhere it doesn't take two months to arrive.



  • 2x 12V 2A ?! Are you using them to pull a vacuum to hold prints down?



  • @dc42 said in 12V 2A fans on 24V Duet Wifi 1.04:

    @pkos said in 12V 2A fans on 24V Duet Wifi 1.04:

    1. If I read docs right, I can use a buck converter connected to an always on fan output to drop from 24V (everything else I have with the duet is 24v) to 12V and connect only the + wire into V_FAN - which in turn will feed the 12V achieved this way to the three fan connectors on the board. Is this correct? Since it'd be a common ground buck converter, I don't have to worry about the negative wire.

    Correct.

    Are you sure that it will work to take the 24V for the buck converter from an always on fan connector and then feed the resulting 12V to V_FAN? According to this diagram the always on connectors also provide whatever is fed into V_FAN.



  • @mrehorstdmd said in 12V 2A fans on 24V Duet Wifi 1.04:

    2x 12V 2A ?! Are you using them to pull a vacuum to hold prints down?

    That would be a bold move. 😂


  • administrators

    @wilriker said in 12V 2A fans on 24V Duet Wifi 1.04:

    Are you sure that it will work to take the 24V for the buck converter from an always on fan connector and then feed the resulting 12V to V_FAN? According to

    You are absolutely right. Here are some ways of wiring it that will work:

    1. Wire the buck regulator input directly to the VIN terminals, and the output to the centre pin of V_FAN.

    2. Wire the buck regulator positive input to the VIN end of VFAN, the output to the centre pin of V_FAN, and ground to any power ground connection (possibly the ground side of an always-on fan output).

    3. 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.

    With #1, all the fans must be 12V and there is no fuse protection.

    With #2, all the fans must be 12V and the input of the buck regulator is protected by the 1A fuse.

    With #3, the connection of a 12V fan is more complicated, but you can use 24V fans as well. The buck regulator input is fuse protected.



  • @dc42 I really like #2. I will do that in my upcoming conversion to 24V. 👍



  • @mrehorstdmd Heh, no. I bought two of them to have one spare.
    I bought a 2A one because the vendor didn't have anything weaker, and I loved the idea of a maglev fan from a brand I know and like. I doubt I will ever run them at full speed, but I don't like leaving things to chance. If there is something I can do to prevent a failure of the device - especially if it's a small effort - I'll do it. Granted, I'll do a lot of research first, ask a lot of dumb questions - but that's also the way I learn what I don't know 🙂

    So here, this me me just making sure I won't damage the fans, the board and risk anything worse. I like the Duet too much to mishandle it like that 🙂



  • @pkos Can you post a link to these beasts? You made me curious to see what kind of turbine you purchased. Something like this comes to my mind immediately 😂
    alt text



  • @dc42 OK. I really dig option 2 and/or 3. One question though - and please be patient with me here. I'm not 100% clear on how a 1A fuse can allow us to use a 1.5A load on each of the fan connectors.

    To be even more transparent, I have three fans (all 12V).
    1x 2A Sunon MagLev 5015 blower for part cooling,
    1x 0.2A Noctua A6x25 fan for the board,
    1x 0.05A Noctua A4x10 fan for the hotend.

    Will that 1A fuse be OK with those, or should I replace it to something closer to 2A?



  • @wilriker Naah, I use that one to cool the bedroom on hot summer nights 🙂 You feel almost as if you were floating 😛

    Here's a link to the blower I have:
    https://www.tme.eu/pl/details/mf50151vx-a99/wentylatory-dc-12v/sunon/mf50151vx-b00u-a99/

    And here's a link to the weaker 1.2A one that I just ordered two of (1 extra just to have a spare).
    https://www.tme.eu/pl/details/mf50151v1-a99/wentylatory-dc-12v/sunon/mf50151v1-b00u-a99/

    As for the other question (although @dc42 already answered that) I was paraphrasing the Duet docs right here:
    https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans#Section_Using_12V_fans_when_VIN_is_24V



  • @pkos I think you might have gotten something wrong here. These blower fans have 2 Watts not 2 Ampere (or 1.2W instead of 1.2A respectively). The bigger one only uses 0.17A. So no need to go down the heater connector route in the first place. Everything well within limits. 😂

    EDIT: that part of the documentation is obviously wrong. I will fix that. FIXED.



  • Now this is embarassing...

    You are right. I got so hooked up on Amps and limits of current the board can handle it totally clouded my vision.

    Thank you for helping me realising this mistake.


 

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