12vdc or 24vdc for lowrider

Newbie question.
So just finished my lowrider 3 with skr pro 1.2
My question is , if I change my power supply from 12v to 24vdc. Do I need to change anything in firmware. Or will stock firmware still be fine and just a matter of changing power supply.
Also I would need to convert 24vdc to 12vdc for my 12v fans unless I change the 12v fans to 24v ones.

So it’s more a question of would changing the psu need any other firmware/software changes?


Do you have an skr pro? If the board can support it, then out doesn’t require firmware changes. The fans need to be rated for 24V, or you need to power them from the old power supply.

The 24V doesn’t get used almost all of the time. Only when moving very fast.

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Yeah I have a skr pro :slight_smile:

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Or wire 2 12V fans in series?

Edit: The internet, especially the funny opinionated folks on reddit, recommended using buck converter and wiring 12V fans in parallel, rather than 2 12V fans in series. Curious what folks here think?

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Of course, why didn’t I think of that… derrrrrrr.
Series! Great thinking. Thanks Aaron

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Presumably because if the characteristics of the two series wired fans is not identical then one of then will be running overpowered and one under. I would however doubt it makes enough of a difference to worry about it ( especially as the fan windings are being actively cooled :slight_smile: )but, yes, the correct way would be to use a down converter and wire your fans in parallel.
That’s what I think.


Yeah. They have to be very well matched for that to work. If one is double the resistance of the other, then it will end up with 16V and the smaller one 8V. I am not even thinking about the effects of the inductive load.

It isn’t like LEDs, where they have a fixed voltage drop.

I think you would only be risking your fans though.


Yeah… in theory, series sounds great, but reality has a way of telling theory to “hold my beer”.


The effective resistance of a fan might be intermittent as the fan rotates. It will do at least some switching and it’s possible that it could be choppy with short intervals of very high resistance.

It’s also possible that it’s fine, if the fans act like simple resistive loads.

It’s probably worth trying.


I used an old laptop power supply that was 19 volts, so ended up with a buck converter for the 12v fans from my parts box. They were inexpensive enough I got a box of 5, and so far have only found a use for one more.


How’s it going? About to try this too.

Don’t need to change firmware. However, there’s an optional code tweak that seems to have a small benefit, did you already see…

Did 24V work as-is? How are your fans?

I haven’t done it yet, just awaiting delivery for my power supply.
I believe accessing the configuration_adv.h involves recompiling firmware which I have no idea how to do or where to start.
If it doesn’t then that’s a bonus.

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There are instructions here: platformio

You should start by building the firmware without changing anything. Then make small changes and build often. If the build fails, then you have fewer things to look at.

For this small change, you should be able to do that without any trouble. If it doesn’t work, oh well. But it will probably work and you will have a new skill.

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Also, if I’m wiring 24v to the skr pro v1.2,
Will this mean that everywhere on the board labled as 12v will now be 24v or does the the skr pro have a built in step down to make all onboard 12v pins.

Also the 3x fans (fan0,fan1,fan2), will they be 24v now on a 24v system or will the remain 12v even on a 24v system?

It will all be 24V. The fans too.

From the SKR v1.2 schematic -The way I see it is…

It is possible to power your stepper drivers with 24v and keep 12v for the input to everything else on the board. POWER is supplied to the board, which goes through F1 fuse and then D3, a SS34 schottky diode for reverse connection protection, it then becomes 12v/24v which is fed into U2, a 5v 3a regulator where it becomes DC_5v and from there into U4 where it is regulated down to 3v3. 12v/24v is also fed into U5 where it becomes VCC_12v.
It is perfectly feasible (indeed easy on this board because it actually has a separate Vmot input power connection) to use 24v for the steppers and 12v for everything else so you can keep your 12v fans while enjoying 24v to the steppers. If you do this, everywhere you see 12v/24v on the board will be 12v and everywhere you see Vmot will be 24v. Of course this will require two power supplies, one 12v and one 24v.



Ok so, I’ve made a custom relay/power supply box.

240v (10A fused) supply.

The wiring has been tidied up since this pic, and I’ve added inline fuses to protect the 24v (3A fused) and 12v (1A fuse) supply.
24V main power supply, with step down transformer to get 12V supply.

Relays are controlled via db9 port which will then connect to another db9 port on skr enclosure which gets the fan outputs from skr board.
3 relays to control 3x 240v devices (vacuum, router, spare)
The green leds on top show that 12v and 24v supply is currently active, and the 3x red leds show which relay is on/off.
24v dc output via dc port to power on stepper motors, and 12v dc output to power on skr board.



The 240v supply has 2 forms of protection, fused 10a and 10a circuit breaker

I can see you have a fan with the enclosure but keep an eye on the temperature inside, especially your 24 to 12 down converter. Also those solid state relays are 3v to 32v and your controller outputs 3.3v through some pretty thin wiring and a parallel LED. If you get switching problems you might need to fit a level changer to give a bit more overhead. Maybe a blob of silicone on the ends of those self tappers!