12V 2A fans on 24V Duet Wifi 1.04

dc42

@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:

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

wilriker

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

pkos

@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

wilriker

@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
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pkos

@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?

pkos

@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

wilriker

@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.

pkos

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.

wilriker

@pkos No worries. I was running blindly through the night more than once and this forum usually is very good at helping to open the eyes again. So: you're welcome!

dc42

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

@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?

Now that we know that your 2A fan is really a 0.17A fan, 1A will be plenty. Also, the buck regulator should be around 90% efficient at high loads, so you will be able to draw something like 1.8A from its output before you exceed 1A in the fuse.

The page on spare part numbers says that you can replace the 1A fuse by a 2A or 3A one if you are using higher current fans than usual.

SupraGuy

Something else just occurred to me. Sorry that it's not directly on-topic, though it seems at least partially relevant.

In another thread, I remember that the v1.04 board's 1A fuse handles current from Vin to where the jumper for V_Fan is. The fuse connector can also take a couple of spade terminals. On the feed side, it will get VIN, and the other side is connected to where the V_Fan jumper is, where you can select VIN or 5V for the fans. If I were going to run 12V for V_Fan, that fuse is no longer necessary, or even in circuit. Could the +12V feed from a voltage converter be fed in via the fuse terminal?

Currently, I use a 3 pin duPont connector with 12V to the center pin, and the other 2 unpopulated, because I really don't want that 12V to touch the 5V pin, since shorting 12V to the 5V bus seems like a really bad idea. A spade terminal into the fuse connector seems more secure, and less likely to be installed one pin off with the disastrous results that could cause. I'm pretty sure that shorting 12V to the 24V rail wouldn't be a great idea either, though it's the converter that will take the damage there, which is at least a lot cheaper than replacing the Duet.

I was giving thought to clipping the lug from the Duet for the 5V at the fan voltage selector, but I have always had an aversion to doing things that are basically irreversible, so I haven't yet. Who knows, one day I may want to convert to 5V fans...

In any event, I like fuse protection on things, and even if I bypass the on-board fuse, there will be a fuse on the fan power.

dc42

@supraguy, yes you could insert the buck regulator in place of the 1A fuse, with an additional wire for the buck regulator ground terminal.

pkos

Right, so fans replaced - everything works and hasn't exploded yet
The only thing that bugs me a tiny bit (I expected it, but want to be sure).

I have an E3D V6 hotend - regular kit - without the titanium heatbreak (for now, I'll probably order it soon). The radiator is much warmer now with the Noctua. I see a lot of people are using the Noctua and even Prusa use it for their cooling of the V6, so I guess this warmth won't cause issues with heat creeping too high up and clogging the heatbreak with PLA and such... right?

Thanks for all the help.

Now I just need to do a PID tune and start printing!

Phaedrux

@pkos If it's the 10mm Noctua it has a lower static pressure rating, meaning that in a constricted flow situation it will perform worse. The 20mm Noctua has a higher static pressure and works better in such situations as blowing into a heatsink fins.

One way to improve the performance of the 10mm fan in this situation would be to flip it around so that it's sucking air out of the heat sink fin area rather than trying to blow in. By creating suction it will bring in fresh air from anywhere it can in the heat sink which can really help in such a tightly packed area.

Regardless, even if the performance of the heat sink cooling is worse, it may not be enough to actually have an impact. If you notice increased stringing after long prints then you may have an issue. If you're printing in an enclosed or semi enclosed build volume you may want to consider a different fan. But otherwise, I think it will be fine.