12V vs. 24V Powersupply for SKR Pro 1.2?


Are there any downsides to powering the SKR Pro 1.2 with 24V?

The documentation seems to recommend a 12V power supply, but I have a 24V one lying around from a previous project that I could recycle?

I understand that the SKR Pro can be powered by both voltages, but are there other downsides, besides incompatibilities with 12V accessories? I’m not going to use the MPCNC with an extruder.

Do I need to adapt some firmware settings and recompile it do make this work or is the dual end stops firmware ready to go as is?

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It should work as it is.

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I upgraded my skr to a 24 volt power supply and it will work without changing the firmware.
However there is a setting for the stepper drivers in config.advanced to change the input voltage from 12 to 24 this will change the chopping profiles to work better with the higher voltage after I changed mine I was able to increase my fast travel speed without skipping steps.


Do you remember what the setting is called and what value you have set it to?

I will check later today when I get home from work.

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Thank you.

I’m always amazed about what I pickup when I keep up with this forum, so thank you. A quick look at configuration_adv.h yields this define:


And here are the other possible values for CHOPPER_TIMING from tmc_util.h:

#define CHOPPER_DEFAULT_12V  { 3, -1, 1 }
#define CHOPPER_DEFAULT_19V  { 4,  1, 1 }
#define CHOPPER_DEFAULT_24V  { 4,  2, 1 }
#define CHOPPER_DEFAULT_36V  { 5,  2, 4 }
#define CHOPPER_PRUSAMK3_24V { 3, -2, 6 }
#define CHOPPER_MARLIN_119   { 5,  2, 3 }
#define CHOPPER_09STEP_24V   { 3, -1, 5 }

Yeah, me too! No, wonder I didn’t find anything while searching for “voltage” or “21V”. :wink:

You beat me to it :slight_smile:
It is located at line 2477 in configuration_adv.h
Just change the 12 to 24 and recompile, on a side note it could just be me but I believe the steppers are quieter using 24 volts.


Interesting. I learn something new all the time on this forum. Not hard being that I’m still an MPCNC novice. :grin:

@diff-arch I’ve been using 24V since I built my Primo and haven’t had any issues with missed steps.

I didn’t realize there was a configuration change so I’ll need to try that when we get back from vacation to see if I notice any difference. It’ll also be my first attempt at recompiling so we’ll see how smoothly that goes. :crossed_fingers:t3:

@conrad404 are you using the latest firmware version? I’m on 509D and haven’t had any issues so I don’t really want to upgrade unless there are some good bug fixes/features with the new version.

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The version I downloaded from V1 is, Marlin_V1CNC_SkrPro_Dual_2209_2.0.7.2_510-src,
The change to 24 volts should be the same on the version you have. With the exception that the line number in the configuration_adv.h may be slightly up or down a couple lines. Following the V1 engineering help guide, PlatformIO - V1 Engineering Documentation, compiling will be a breeze. The best part was flashing the SKR Pro which was easier than flashing my 3d printers duet 2 WIFI.
If you run into any trouble there will be plenty of help for you on this forum.


FWIW, I would feel pretty confident running 24V with the 12V chopper limit. We aren’t breaking any speed barriers with the cnc compared to corexy or delta printers. But YMMV. If it is a pain, or worrying to recompile, I wouldn’t bother. If it is something you’re interested in, then it is probably worth it.


Thanks for the info guys! I’ve been wanting to dip my toes in firmware changes and this looks pretty simple so I’ll give it a go.


FW change and recompile was a piece of cake! VS & PIO software install took the longest, like the instructions said, but it was actually pretty quick on my system. I need to try some TFT FW customization next. :grin:

Can you share where you changed the speed limits when you get a chance?

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OK, beer with me its late on a saturday :). This change will be a little more trial and error than the power supply voltage change was This started on.

What I started with was going into the configuration.h file around line 755 you should see the following;
752.* Override with M203
753.* X, Y, Z, E0 [, E1[, E2…]]
755. #define DEFAULT_MAX_FEEDRATE { 50, 50, 15, 25 }
I changed, but don’t recommend, the X&Y from 50 to 300, I knew 300 was too fast but my delta printer is set for that so I said go big or change it and try again :).
Again I do not recommend 300 the weight of the router was to much. But I did have a good laugh watching it jockey left and right as it traveled down the rail. Luckily nothing broke like a grub screw loosening up, that reminds me make sure your grub screws are tight before trying breaking the warp barrier.

After this first failed experiment I left the FW alone and adjusted the federate VIA the EEPROM setting.
programmers note;
I installed the optional eeprom chip on the skr pro v1.2 and added code to the firmware to support using the chip. The Stock SKR Pro v1.2 uses EEPROM emulation writing it to the sd card by default.
from BTT website;
If using an SD card for EEPROM emulation, then making sure the card stays with printer is vital;
In short without the i2c eeprom chip the sd card is your eeprom. I had issues were my eeprom settings would be erased after power shutdowns so I chose to install the i2c chip.
This is a completely different topic but if you are interested BigTreeTech SKR Pro V1.1 or V1.2; Adding a EEPROM : 5 Steps - Instructables
Using the the touch screen I went to the gcode console and entered slower speeds until I got to my target accuracy [M203 X100 Y100]. Utilizing my spring loaded micrometer to test the repeatability of each speed in each direction. It is worth saying at this time my target accuracy is 1/16 of an inch (1.5mm) the picture below was staged tonight not actual file footage of the test!

I had ok results around 120mms but my result was 5/64 (1.98mm) which was greater than my target.
100 mms was twice as fast as the stock FW and very consistent for me within .03 inches (.7mm) traveling the full length of my bed 910mm.
I wrote my own gcode to run the test which is mandatory! Pressing the X +100 button on the touch screen 9 times would drive me insane never mind the 100 full cycles I put the cnc through.

G0 X910
G0 X0

copy and paste 100 times

After I found my target accuracy at a repeatable speed I went back to my computer and changed the FW
755. #define DEFAULT_MAX_FEEDRATE { 100, 100, 15, 25 }

My next mission will be the Z axis speed. I have veered off of the stock setup and change the stock T8 4 start 2mm pitch to a T8 2 start 1mm pitch.
Initial tests are looking good less backlash but at a slower speed, time to engage warp 9.


I just feel like pointing out that in vi (my preferred text editor) that command would be:


I’ll see myself out…


I am still Learning, I have only edited Gcode using notepad++ now you have me downloading a new program to learn. I want to understand yj100P. I hate typing and this could be a shortcut! I hand wrote the file to plane my spoil board because I did not like the tool path estlcam output.

Best Forum Ever, Give advice get advice!

Oh man, I am sorry. Vim is very hard to learn. It is awesome, but if you are not frequently editing text, it is not worth it. If you’re interested, I am sure there are 10k videos about it, and why it is awesome or hard.

To break that command down:

y: start a “yank” command (copy)
j: A movement, just like pushing the down arrow, but it tells the yank to grab the line you were on, and the next one
100: Do the next thing 100 times
P: paste (above the current line)

To exit would then be :wq for write and quit.

It is really an excellent editor, but it makes no sense in text. It only makes sense when you get the muscle memory and it comes naturally. At that point, you can’t be trusted to recommend it, because you’ve invested so much :slight_smile:

Thanks for the heads up. I only have to edit my gcode a handful of times per year. The spoil board file and my optimization tests are one offs. It may not be worth my time to learn but since it’s installing I’m at least going to look at it. If I could only say that it’s not worth my time to the professor that forced the class to learn ruby. Haven’t used it since…

Long time Unix guy here, so very accustomed to vi.

vi is a very powerful text editor, but not until you’ve used it for many hundreds of hours. It’s difficult to get used to, easy to really screw things up, and about as friendly as a junkyard dog. “Are you sure?” isn’t even close to anything in its vocabulary. For that matter, neither is “undo” It’ll do what you tell it, using cryptic mnemonic commands with no online help, even if what you said wasn’t what you meant.

Not recommended.

Newer Unix or Linux installations have much friendlier editors, just as powerful (so they tell me, I’m a creature of habit) and easier to use. Notepad++ is good for me on Windows machines.