Use the WRONG parts on any 3D Printer!
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- เผยแพร่เมื่อ 23 พ.ค. 2019
- Want to use 12V parts in a 24V printer? Fancy giving your stepper motors a boost by running their drivers at a higher voltage? In this video I'll show you how!
Fuses go.toms3d.org/fuze/
Full power supplies go.toms3d.org/powah/
Cheap 3A Buck converters (for fans etc) go.toms3d.org/cheapDCDC/
Boost converters go.toms3d.org/booooost/
Cloned Pinda Probe go.toms3d.org/pinda/
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Watch it with those buck convertors. The downside of those thing is, if they break, they can forward the full voltage. So if you use a 5v buck convertor to run a raspberry pi of of a 24 PSU, and the buck convertor dies (as you said; they are VERY cheap), it will kill your pi as well. For relatively low loads (
@@soundspark Same here, but it toasted a noctua fan
this is the type of video I subscribed to this channel for
Finally a very good explanation on how to use buck/boost converters with PWM control!
Great video. This has made me think again about converting my UMO to full 24v in order to drive an upgraded E3D hotend, when I could be a bit more sensible about the power application.
For fans I typically use a single buck converter to get a 12V power source (from the 24V from the PSU, which directly runs the steppers and heaters). I then use a single (free and pwm capable) arduino pin as the "fan" pin and drive a trivial/standard transistor as the 'switch'. It literally takes 3 components: transistor, resistor for the gate and possible a diode if it's a inductive load like a motor/fan to protect the transistor.
In most cases I need additional outputs anyway, since a RAMPS for example only has 1 fan connector and I need at least 4 loads (part cooling, hotend, stepper/board cooling, printing lights on hotend and/or for the whole print area), so I need something like the transistor/mosfet anyway (or use any expansion board that basically has exactly that in a ready-to-use package).
This also allows you to just run 24v to your hotend (for example), which you already have there anyway since the heater is using the mentioned low-side-switching, add 12V step down converter and run just one (signal) wire up there per fan you want to control (hotend fan and potentially multiple part cooling fans). All this even weighs next to nothing, too. So you reduce needed wires.
Thank you. It's always a problem for me to describe how to connect the 12V fan on 24V electronic for lots of people, but you made a fantastic video.
Hey, I remember that printer. Great to see you still getting some use out of it.
Nice wrap up of information that took me several hours to get myself for my build. I used a DC-DC fixed module for driving my 24V PSU to 12V for the fans as i bought the wrong ones. Those modules cost a bit more but you do not need to calibrate them and they come in an isolated plastic case which you can just bolt onto your printer. Because i installed them near the mains voltage cabling i feel much safer about it.
This is yet another reason why the Duet 2 is awesome. Converted my CR-10s to a Duet 2 Maestro on 24v, I managed to keep 12V fans and bed probe by running a buck converter off one of the few board locations that gives you VIN for a positive and then relying on the negative side regulation. Works perfectly.
It's not using the wrong parts, it's simply understanding the voltage (and current) requirements. Thanks for an excellent video! Lots of lots of useful tidbits to get everything connected up properly.
Nice!
I like the idea of a test rig for 3d printer parts!
...and indeed - 3d printing really made me appreciate the humble buck-converter even more :)
Invaluable info Tom. Thank you
Thank you, this has been quite enlightening in terms of how to correctly wire the buck converter on my Creality 4.2.2 board!
Great video (as usualy). In my case I use 24v, from a boost converter, just for the motors, turning the pins VMot of the drivers TMC2208 upside down. My heated bed works at 240v controled by a solid state relay and the extruder direct from the Ramps 1.4.
Best regards and,... keep the nice work you are doing
Excellent video... got 95% in the first pass and just had to rewind 2 bits to understand the rest. Packed a lot of useful information in a such a short video Very well done.
Great timing! I was just thinking about doing something similar to this. Good info. Thanks
Tom, I salute your bravery in producing this video. Your faith in humanity’s ability to avoid bright flashes, loud bangs, and copious magic blue smoke is impressive.
Greatest problem of a maker/youtuber ---- Must resist the temptations to mod the review samples......
Lovely video. Now a question.
Can I use one converter 24v->12v to power both part cooler and hotend fan. They are both switching on the low side.
I did this and the hotend fan on idle got -5v and on idle for partfan, -10v.
But when they are both on at full, they are both getting 12v.
1. Use a fuse no matter what. It's not only cheaper than a new mainboard, it's also cheaper than rebuilding parts of your house due to fire damage.
2. If you use a 12-24V converter, check if the ground is actually connected internally. This is NOT necessarily the case.
3. If you use 12V components on a 24V mobo, you might destroy the mobo nonetheless, as the same power on half the voltage meands twice the current, which your mobo _might_ not be able to handle. Will work fine most likely though.
I might add... do those motor drivers work on TTL signals or what? What about cable length, cable ratings, ground loops.... The FET voltage capability advice at the end of the video is on point but it's difficult for anyone to check if they couldn't figure out the whole thing by themselves. I have mixed feelings about this video: on one hand I'm glad it's encouraging creativity, tinkering and hacking, but there are so many things that can go wrong here.... it worries me.
I would like to use the IGUS Chainflex for my own 3D printer build and I was wondering which one you used for this build? Thanks
Amazing video, I am planning to run my heated bed on 20V while the rest of my system is a 12V RAMPS. Your last statement about the board being able to block the 24V left me wandering ...
I have a question I did the switch off with a ramps 1.4 with a dc boost converter 150 watts
the source is 650 watts atx 12 v pc power supply
the thing is it works it heats up the hot bed and hot end but it heats up the negative leads from the source and the mosfets boil like hell is it possible to fix this? Thanks for the excellent information everything is runing on 12 v and dc convert 24 v to the hot end and hot bed
That machine is a total Frankenstein monster. I love it!
Did the same with my Prusa MK2.8. Einsy Board with 24V but the heatbed from the upgrade kit with 12V. Works without issue as the Einsy has separate power rails for system / motors and heatbed.
Thanks for this video! I too always assumed the mainboards were high side switching (because I'm a mechanical engineer, and because that's how you have to do it for Mains wiring to be safe) the diagrams were very helpful and I found myself regularly saying "wow, that's pretty clever". Also, I like your test bed, I think it'll suit your needs nicely, though that has to be the worst machine volume to build volume ratio I've ever seen ;)
Awesome Bro !
Good input.
When wiring it also maybe an idea to follow the standard of cable colours for an atx power supply or at least use different for 24/12/5v just helps to identify at a glance
hello Thomas Question for you I gotten one of those silent fans that is 12v and my 3d printer (Cr10s Pro v2) that is 24v so is that means I have too get buck converters and turn the voltage up too 24v for the fan but wont that burn the fan and short circuit the fan ? I hope someone would answer my question thanks
LOVE that contraption :)
So on a 12v printer if I use a 24v hotend that draws 3A and wire in a 12v to 24v step-up converter as you have shown, how much will the converter be drawing on the 12v side?
@Thomas Sanladerer - Could you do a video comparing 1/4, 1/8 and 1/16 stepping on TMCs? I have an Ender 3 with MKS board and TMC2208s. Is it worth the hassle to go through Marlin? Please and Thank You. I appreciate all the content and testing.
Can't find anything else to this topic. I hope u still read the comments here.
I installed a phaetus rapido 24V hotend on my 12V mega x and a new beefy heated bed with 12V 250W.
Heated bed 12V wiring stayed the same, just swapped out the cables but for the hotend I got a 24V psu.
The hotend works but as soon as I want to heat the bed klipper shuts down the printer.
But if I disconnect the negative connection from the 2 psus hotend and bed work but hotend ist very slow.
Maybe u know what I am doing wrong. I'm literally clueless. Checked wiring a couple of times now, can't find any flaws.
I love this in depth stuff, man. Thanks for the great info.
Wtf just happened
Very interesting! I've been waiting for this video!
Would you recommend to to directly change the supply voltage of the stepper drivers? And could you possibly use 36 V for example with the TMC 2208? Would this be even more effective?
Just make sure the capacitors are rated for that voltage. I could see some people in asia trying to squeeze for the last cent by using 25V (or 35V) rated capacitors, instead of at least 50V rated ones. Actually, with DC bias voltage derating you should probably go for 63V or even 100V rated capacitors in a 36V system, but i guess most "3D printer hackers" don't even know or care about stuff like derating capacitors anyway...
What do you think about using an mosfet to do the switch?
is that a complete new printer from scratch or a your old mendle90 workhorse
By the way, care to share the STL for your x carriage? I'd love to use diverging modular like that!
How would one use 24v for stepper motor (drivers) when the drivers are soldered directly to the board? Especially on that of the Duet 3. I would prefer to run the stepper motors at 24v rather than the supplied 12 from the board, is there something else I can use to do this?
Very useful and well explained 👍😊
Nice simpel solution, thanks!
What was the reflection in the power supply that was scrolling? Do you write a script and use a teleprompter?
Great video so here is my question. I want to run a 24v hotend on my 12v Prusa MK2 that uses the mini-rambo 1.3a board which I believe is rated to atleast 24v. Would I use a 12-24v stepup converter and tie its input ground to the board/PS gound then use the + output from the converter straight to the hotends + side and leave the hotends neg side still to the board? Hope this makes sense!
Did you get any solutions?
I want to run 12v e3d V6 on a 24v ender 3, how can it be done?
Hey first of all thank you for all the videos and informatio you give us for free. I was wondering why you use these powersupply's while you could use a Computer ATX Power supply, Why im asking about this, ATX Computer supply's have build in efficienty to convert AC into DC, so my thoughts are you are consuming less power from the wall outlet for your printer with an ATX Computer power supply, why is nobody doing this ??
i have a MW SE 350 48 that was used for led's, i want to drop to 24v to power a mpcnc or hypercube
Hello, I'm using a step down (LM2596 3A) after 24V PSU to obtain 12V to running 2 case's fan. I use both positive and negative wires directly from the PSU but I forgot a fuse on the positive wire. How much big must be this fuse, knowning the 3A max load from step LM2596, please?
I Love to See you getting more technical again. Liebe Grüße aus der Pfalz.
I just eliminated the 12V psu as it drew only 500mA or less as all components are 24v except the cool break and led light. I use a buck converter for that. Now that the heated bed is mains powered I can swap out the 24v 15A with fan with a 24v laptop psu which is fanless. I measured less than 2A load on 24V so a 150W psu should be more than sufficient.
Incredibly useful. Thanks!
Spooky I just got an ender 3 pro yesterday and the main 24V cooling fan makes an horrible vibration that resonates through the printer and into the cupboard the printer sits on, I have a Noctua 12V fan to try so I put 2 330R resistors in parallel then in series with another pair (to spread the ~.5W across the 1/4 resistors,) this gives me 12V for the fan and the resistors get to about 38 degrees. This will do to test out the theory and until I can get a voltage converter to make it permanent, my only worry is that the airflow from the Noctua is enough.
Thank you so much for this video, in wanted to switch my TMC 2130 Drivers to 24v but i thought i have to replace EVERYTHING -.- now i know better :)
Hi. I can hardly get normal (not silence) 40 x 40 24 volts fans but I can find 25 x 25 24 volts fans easily. Is this 25 x 25 enough to keep cool the extruder?
Would I be able to use a boost converter on an 24v direct drive extruder.
yeeeeesss you have finish as you said the other day, going back to test things YAAAAAYYYYY i miss that videos :D
My buck converter blew up the other day.. What do I do to prevent this from happening again? I was using it to drop it from 24 to 12 for my LED lights
what wire are you using in the drag chain
I heard that you can easly fry stepper motor drivers (like tmc2208) using 12V for electronics and 24V for steppers when 24 volts shows first on the board, before 12v. That is why in this particular case is advised to use some additional delayed relay (like 1-2 seconds), to make sure that board is powered from 12v before 24v for stepper drivers show. Is it true?
Yes, but only if you get the black PCB version. The blue version has a voltage regulator on board and doesn't care about power up / down sequence. It's is explained on Winnicott's Github.
Does anyone know of boards that have a separate stepper motor power input? I found the big tree tech pro. Any others around?
I've got 12 and 24V PSU before it was cool! :D
The Duet has a separate circuit for the fans and you can just remove a jumper and attatch the positive lead from your buck converter.
Some time back I released a video or two explaining how to upgrade a RAMPS1.4 to run 24V to the bed but 12V to everything else.
It’s pretty easy and means you can have a bigger bed or heat it faster. Feel free to check it out if you’re considering a larger build.
Careful throwing a higher voltage supply on those switching components, yes low side switching won't care about the voltage, however the increased voltage will almost certain increase the current, which at least on the printers I've used seems to be pushing the capabilities of their mosfets at standard voltage. I'd recommend using breakouts with higher power rated mosfets honestly
Hi THomas, You did a glidecam build way back in 2014, is there an update? its been 5 years. There has to be a more better way to do it now...
Custom dual extrusion video please.
If you are going to power more than a couple steppers off a different voltage (or especially heaters) I'd just get a second mains supply. They around $20 and will give you all the power you could need. Sure a boost converter may be an option but it just won't have the same load/line regulation ability of a supply for such a demanding load. This is in part due to the size of the magnetics (inductors) but also larger output capacitors and a full supply is far more likely to use a multi-phase output stage for better regulation than common little boost circuit boards. Additionally the capacitors on the buck/boost converter will need to be able to take the ripple current of the application, while they can often supply the rated current most of these little converters dont have the caps spect to stand up to a switching output load (such as pwming a heater). The effect of ripple current on the cap is heating, so if your caps dont get hot to the touch under use your fine. If they burn you (and they could get hot enough to boil water) they will have a very shortened life.
In general, what you say about getting a second PSU is correct, but it might be worth considering spending more money to get a single, higher-quality PSU (probably in whatever voltage you want for your heated bed, as that's almost certainly the highest load by a wide margin), and use DC-DC converters to get whatever voltage you need for everything else. (Assuming that buying TWO higher-quality PSUs is out of your budget, of course!)
Yes, you can get no-name PSUs for not much money, but the reliability will be questionable, the output filtering will likely be poor (thus giving you a lot of voltage ripple on the output), the input filtering will probably also be poor (feeding high-frequency noise back into the mains wiring of your house, which then acts like antennae and broadcasts that noise throughout the house - which might even technically be illegal), they probably won't be able to deliver their advertised output current at all or for long periods, and they may even have safety issues (fire or electric shock, mostly). The higher-quality ones are also likely to be more efficient, which will both save you money on your electricity bill, AND cause it to run cooler, allowing it to use a quieter fan, or, if it has a temperature-controlled fan, will allow it to run the fan slower (it'll also be more likely to have a temperature-controlled fan!)
You don't necessarily need to spring for a PSU from Meanwell, Delta, or Lambda - though by all means please do so if you can afford it - but at least look for something a step up from the absolute cheapest you find on Amazon/eBay/AliExpress, or preferably buy one from a reputable 3D printing retailer in your country/region (e.g. E3D), or from a reputable electronics supplier. In the UK that would be somewhere like Rapid, CPC/Farnell, RS. Elsewhere, Digi-Key, Arrow, and Mouser all ship pretty much worldwide. Arrow is currently/indefinitely offering free international shipping *with no minimum order value*, and they tend to be cheaper than Digi-Key and Mouser as well - although they also have a somewhat more limited range of products and a more-frustrating website! Or you can go to their equivalents in your country.
Great video, I'm trying to use a DC DC step down right now LM2596, I think it doesn't have the strength for the peak amperage of the process. The voltage drop is severe under load from 7.2v to 0.6v under load. Might be something to think about when ordering (he mentions this briefly) make sure to order a much higher rating than listed because they seem to exaggerate a bit on the ratings.
you might be able to get away with using a zener to cut the peak voltage, and set the output higher so it doesn't fall as much under load, but you'd probably be better off paying 10 bucks for a 300-600W converter which will handle anything if you don't mind the slight inefficiency.
@@satibel good call, that's what I ended up trying (should arrive today). I thought I could sneak by with the 2-3 amp but the motor is pulling more I think. So the larger converter should clear it up (fingers crossed). The only problem I can really tell is inefficiency as you mentioned, then size and finally cooling. But I figure it's easier to add a cooling fan as opposed to redesigning a whole project. Especially when you're stuck with a specific power source to save money or convience.
@@RevampedOutdoors 2-3 amps is good for 2 steppers, but not much more.
I completed building a corexy modular testing platform last week. but it's nothing like this beast! Look at that *THICC* cables and drag chains!
So much for reducing weight of moving parts :-)
@@FlorianHofmann yeah that's right
I'm using 12/24 in my Mendel90 as well. I just have one 24v power supply though and a DC-DC step down. But I'm doing the opposite of you. I'm using 12v into RAMPS for all the motors, and using external MOSFETs (with heatsinks) to switch the full 24v for the hot bits.
I always wanted my duet to run at 24 while my high power/ expensive to replace heaters ran on a 12 volt separate supply, might need to look into his
I may still separate how ground comes back with a mosfet tho
If you change supply voltage to your stepper drivers, would you then need to change the output power to keep from overloading the steppers? I'm not actually sure if the tuning pots on the stepper drivers adjust current, voltage, max or standard duty cycle or something else.
The pot adjusts the current. Not need to be changed if you increase the voltage.
@@moczikgabor but if you double the voltage, you're doubling the power (wattage) through the motor. Power is usually what translates to strength, but also what contributes to over heating etc.
youtube brought this up 2 years later !, but that's a monster of a perfect 3d printer, you could make gigantic bed that way ;)
Could you use 24v on a main board and a external mofset at 12v for my existing hotend ?
The PWM from the hotend output would go to the modest , but the input power for the modest would be 12v
I’m not 100% how that would work?
A heater cartridge for 24v is cheaper than an external mosfet. Why would you do this?
@@GvanderWindtMusic because I already have the parts. A mosfet was like 12$ a 12v E3D hotend I would be re-purposing was like 60-70$. I guess I can spend the 9$ and go all 24v
yes, new video! cool
I'm not that sure low side switching is the best idea, I think it isn't allowed anymore, even in PELV circuits. I mean yea, it's the most convenient solution for 2 PSUs in parallel, but are the boards made for doing this? At least, I dont know how to connect the wires to get it switching that way. It's easier to use Zener diodes to cut the voltage for lower driven parts I guess. Using external mosfets or SSR (no high frq switching) for the 2nd PSU controlled by the board might be a solution, too.
I gonna try some zener for fans and LEDs on my ender3. A combination of a PC psu and a 24v one might be interesting, too. U get secured 12v 5v and 3.3v out of the ATX connector without any major changes.
Many ways lead to Rome...
Where should be the problem with low-side switching? Most FETs are rated for way more than 24V Vds(max)... Also "not even allowed"? Who imposes that?
If u r using another power supply better to add external mosfet and take input signal from the mobo and add 24/12v to the heatbed and hotend as u like rest will run on 12/24
I learned nothing new but i love you regardless. Will save me a bunch of work when people ask questions of the kind.
What I meant to say part 2 : Coming from an auto electrical side,and just learning this type of 'electronics', My mind is saying Current returns along the + so joining up the 2 PSU on the black line would be putting 36v into the system. Which I know isn't right as you didn't loose any magic smoke, So therefore I must learn to switch it around in my mind when playing with these ? Another thing I thought was, why mess with a 12v supply to the hot end, a heater cart is pennies to buy why not just put a 24v one in ? Wouldn't just a resistor in the fan wire be enough to drop it from 24v to 12v ? Thanks
Electrons do, yes, but most of the time people are referring to conventional current flow. Don't be a smart-arse ;)
@@AndrewGillard LOL Well I wasn't being a smart arse, it seems most of what I types went AWOl. I'll re type the whole thing out again, hang on
I'm using a Boost-Converter to up the 24V to 32V. The Steppers love higher voltages and the TMC-drivers are capable of pushing this voltage. No need for another PSU...
Whats the point to raise voltage up tp 24 or 32v with tmc drivers? Are they ever quieter?
@@1111111115297 faster and more powerful motors.
Do you then just connect the boosted positive output to the Vm input on the driver? I've got TMC2130 drivers on my printer and want to try and run them at a higher voltage than the current 12V I have
@@adamplastow509 yup. Exactly.
And what about those capacitors mentioned by Tom? On my board (MKS Gen L 1.0) under each drivers have a 100uF/35V.
I checked the trace on the PCB, actually looks I see an option to cut the trace and that could separate the "VMot" traces and still keep connected the capacitors, but cutting the trace and soldering a wire on to the PCB is not the most decorative solution.. Do you fitted any or not neccessary?
Or another option powering the whole board 24V and using the trick to feeding the hotbed/hotend and fan from the 12V line?
Bad setup on the psus because the already too small fan on the back one is half blocked.
What's up with the huge cables? What r they for?
They are multi-conductor wires that seems to have a bunch of twisted pairs (you can see a quick shot of a few at 1:21). It just cleans thing up for multiple wires like stepper motors.
But there are 4 of them going into the hot end part.. Which seems unusual
@@phenix_labs He said that this machine is for testing lots of future hardware - so it's just lots and lots of future-proofing. Most of those wires probably aren't being used *YET*, but it's way easier to run a load of extra cables while building it, even if you don't end up needing them all, than to find in a year's time that you need more cables!
Before I fry something let me check - I want to move my machine toward 24v. Everything is ready for that except the bed which I don't want to replace yet. Using this technique I could run everything on 24v except the bed on a separate 12v power supply? No mosfet needed?
If the heated bed is working fine with 12V now, it will still work fine after converting everything else to 24V. But you might want to upgrade that as well since the 24V beds often heat up much faster.
I suggest with every change to the platform, you increment the number by one. I want to get it over 9000 ASAP.
you could take 2 atx power supply float the minus on one of them and have crazy stable 3.3v, 5v, 12v, and 24v, with overkill on the amps side (any ATX has Way more safety build in than any of chines PSU)
Also note using two supplies to power different things is different. You can use two of the same, or a 12 volt and 24 volt supply, as long as they're powering different items and controlled through mosfets etc correctly. It's the simple bridging the outputs together on switching supplies that is problematic.
How will you call that baby? The Sanladerer 1.0 ? Can't wait to see it in action
dc - dc buck converter is fine for higher current needs but is overkill; in most cases, a simple 3 leg regulator like LM340T-12 can provide a steady 12 volts from the 24 volt supply at 2amps.
And convert 12V x 2A = 24W to heat...
5:48 Not all DC-DC converters have common ground terminals, I've encountered some that use low-side switching as well and therefore have a common high side!
Those are called "inverting" DC-DC converters, which are increasingly rare and used for specialty applications around audio and signal transmission.
that cable chain is nuts
Well since it's not no-nut november, go right ahead, we don't mind.
Nice, exploiting the ground switching is cunning indeed!
Another way that seems to work great when you want to use eg. 12V blower on 24V system is put a resistor (with high enough power rating) in series. For a blower that has nominal current of 100mA, so 1.2W, 120Ohm resistor does the trick. Yes, you dump another 1.2W of power into heat (preferably placing a 10W+ resistor in the electronics box), but it's a very simple solution.
Question of Buck/ boost or 2 power sources is almost pointless. Each power source used with a 3d printer is technically a buck converter and does almost the same as its small brother. (Generate high frequency pulses and then smoothing them out). Newest Buck / boost converters are excellent and does the job very well if they are made for the required power. So I suggest to have one higher voltage 24 or 48 V with enough power reserve. I suggest at least 30% - 50%. Togehther with quality buck converters with high speed switch "transistor" and high quality condensers. It works very well.
As a Veritasium fan, thank you for mentioning him. Nice video by the way, I'll probably never be able to test out components but love you doing it.
Awesome work Tom. I was thinking about going exactly same route - mixing voltages for motors and board. BTW : your Mendel 9000 looks awesome.
Thanks
Ok I'll bite- whose signature is that @1:04
Using two power supplies, are you using a 12v and a 24v supply? Or are you doubling up two 12v supplies to achieve 24v? What would the difference be in the wiring?
You can run many/all 12V components on a 24V supply by limiting the power (wattage). See Marlin's PID_MAX + MAX_BED_POWER + FAN_MAX_PWM + CONTROLLERFAN_SPEED.
My buck converters only can go up, i tried to get it to 12v from 24v and doesnt work, any one knows why ?
buck converters are to step down not up
You should use some Wago terminals on that printer.
Those would definitely come in handy on that printer!
i felt the explanation of how the motors can work harder is a little off, i am sorry to be so picky. the motors are not able to work harder, just faster. the static torque should not be changed by the driver, just more control over current from inductance can improve motor speeds because the higher voltage allows current to flow as the resistance increase from the speed of the motor movements increasing changing frequency and inductance. the current of the motor ideally would be constant, the voltage goes up and down to keep current under control.. this may not be a perfect explanation, and it is possible to set a higher working current than spec because of higher voltage, but if the parts work in spec, then the motor will work the same other than better performance from the speed. thanks. and i do see from your perspective that torque drops of the faster a motor turns, and the torque drops off less as the voltage increases.
Server PSU, ie. HP 750W: 15$
Breakout board: 10-15$
DC-DC Buck converter(s): 0.5-15$ a pop depending on the type, quality and size.
Get the exact voltage and power you need where you need at quite high efficiency. Server PSUs go upto around 98%, same with buck converters.
The typical PSU with 3d printer is not even 80+ certified and comes with no guarantees of efficiency, i would expect the typical china cheapo to be just around 60-70% efficient as that would be about cheapest to produce.
Don't even need the breakout board if you know how to solder.
I run most of the things at 24V and I use 12V fans... but never have I even thought about using 2 psus... what a waste. Seems you don't know how to properly use dc/dc... you can't use a pwm to power it up (you power buck converter with a steady 24v)... you do switch the output of it with a 12v pvw via FET.