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Connecting x4 12v fans to 24v (umo+)

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I'm thinking of using x4 25x25x10 fans for my mod setup for A different multi-extrusion approach - UM tool / printhead changer


The think it's that, because I already burned some transistors in the past I think it's better to ask around before burning something again :D (sorry I'm hyper noob on the electronics/voltage area).


I want to plug x4 fans of 12v to my UMO+ 24v connection. To do this do I need to connect 2 pairs in serial in parallel? I mean x2 fans in serial and both pairs connected in parallel.


Something like Daid said on this post to connect 12vs to 24v



I mean this:



It's that correct?


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I would be careful putting 2 12V fans in series on a 24V source. If one fan is spinning up later the other gets the full 24V. Or for example a finger is in the way the other fan might dye and if your transistor on the board survives the event.....

You will be running those fans also at low rpm where you can easily get into unbalances. You could add zeners in parallel on the fans but you don't have much headroom to play with.

I would personally not do that get 24V fans or modify your design so they can run on 12V. Putting 12V fans in parallel on a 12V source is fine.

If you can repair your ultimaker pcb easily then feel free to experiment but if not then don't take the risk. I didn't want to risk my ultimaker board so I added additional transistors to run all my fans at 12V on a 12V source. And I made a 12V out of my 24V power supply.


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Hmm the default UM2 fan setup has 2x 12 Volt fans in series on 24V power if I'm correct .... you say this is an issue ?

PrintheadCable Ultimaker2

Our do you mean it's only an issue to do this 2x ? (doubling the power use)



I'm also planning on adding a extra 5V hot-end-isolator fan in parallel to the existing 5v fan, doubling the power use .. would like some confirmation this is ok ....


Alternative is to power the side fans and hot end isolator fans of the 2th head separately, but this would be a lot less practical....


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The 5V I don't think it's a problem since that will go in parallel to the 5V exit of the board and that area don't have transistors etc. The fan/led exit has that power control (to control speed/etc) so that it's more sensitive.

I don't think that (for what I have been reading) that it should be much a problem to do what I think. At worst the fan might die if one of them it's off. Since all the amps it's way far from the transistor limit. But for stability the zeners might be a must.

I think that to go on the 'safe' I'll just go with x4 24v fan in parallel. I was thinking about 12v fans because I wanted to use 25x25x10 fans, and that ones are very hard to find in 24v. I'll just jump to 30x30x10 on 24v. 0,5cm should not be a big issue.


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Your suggested setup may work fine but there is no guarantee as there are many things that can go wrong like zoev89 says. His best example is if a finger stops one fan it might get all or most of that 24V!


I'll just go with x4 24v fan in parallel


That is best idea.


Since all the amps it's way far from the transistor limit.


I'm glad you checked.


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Just one question. Since the 'serial' setup isn't the best way to go, why Ultimaker does it on the UM2? What can happen if one of the fans die while printing over night and the other gets 24v? Does that mean that UM2 should have 24v bolt parallel fans or zeners like Zoev89 suggested?


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