Okay, this one’s a guide to modifying or building your own printer.
Because I’ve just modified and built my own printer, and it uses both a 12 and 24V
components in the same system, using two power supplies.
Let me tell you why that makes sense and how to do it on your own machine.
So this is my Mendel9000.
This thing has been many printers before and I’ve had it kind of queued up for a long
time, but essentially, this is going to be my modular testing platform.
Yeah, it looks kind of rough, but that’s not the point.
I’ve grown tired of tearing apart perfectly good printers to just test a single components
like a new hotend or a different mainboard, the problem isn’t that the conversion to
that new part would be hard, it’s that the conversion back to stock is usually, well,
impossible.
So now I’ve got a bunch of machines that are permanently mutilated and, frankly, at
this point, I’m running out of good, stock printers that I can just use without them
having some weirdness to them.
So this one’s built to be easily modifiable, it’s got all standard connectors, it’s
got plenty of wiring, the entire X-carriage is just a grid of threaded holes where I can
attach anything I want anywhere with a simple adapter, the Y-carriage is this flat sheet
where I can just tap holes where I need them, even the linear axes are built to be super
simple and modular.
And the other thing that this printer has is two power supplies.
Because I have plenty of 12V components, but also want to run for example the motor drivers
at 24V and be able to test 24V parts in the future.
And you can actually do the same for your printer, in both ways.
If you have a 12V system you can run the motor drivers at 24V because they’ll perform better
if they have more voltage to work with, so they can push the motors harder, especially
at higher speeds, but you can also just as easily use a secondary 12V supply in a 24V
printer if you’re having trouble finding for example 24V fans and want to use cheaper
12V ones instead.
Or even 5V parts, totally works as well.
And you can also add a second power supply of the same voltage if, for example your mainboard
has the capacity to run a new heated bed, but your old power supply isn’t up for it.
But you don’t even have to use a full separate power supply if all you need is running parts
of the “wrong” voltage and you’re not trying to run, say a heated bed from that
secondary supply, which I am, but if you’re not, than you can use one of these buck or
step-down converters to go from 24V to 12 or 5, these are literally like 30ct, it’s
incredible, link in the description below, or use a boost or step-up converter to go
from 12 to 24V, for example to drive your motors.
So, with a separate DCDC module you may be tempted to just strap that into the output
of the mainboard and then run your components from that, and that can work, but as soon
as the board tries to regulate the output power, say, to a hotend, you’re rapidly
turning the entire converter on and off, several hundred times a second and every time all
the capacitors and components get hammered with fully discharging and then getting that
rush-in current again when it starts back up, it’s just not particularly elegant.
But what we can do instead is to directly supply our load with that secondary voltage.
For that we need to look at what the mainboard is actually doing.
Now, you might think that when the board is turning on or off a component it’s actually
applying and removing the supply voltage.
That would be called “high-side switching”, but that’s not what’s being done here.
It’s actually cheaper and simpler to switch the ground of the output than it is to switch
the supply voltage, but the effect on the load is the same.
You’re cutting that circuit and it means no current will be able to flow through through
the output.
This is called “low-side switching” and what this means in practice is that the output
has its positive terminal basically connected straight to the power input of the mainboard,
and it’s the negative terminal that’s doing the switching.
So knowing that, we can just disconnect the positive side of the load and reconnect it
to a different supply.
So, keeping the negative side of your load connected to the board, we can use a separate
power supply or a DCDC converter to supply voltage to the load instead.
So let’s go through how to wire these up.
First, the separate power supply.
Connect both supplies to the mains, as usual, be careful here, mains voltage is dangerous,
get a friend to help you out if you’re not totally competent or comfortable doing this,
then connect the ground or negative output from both supplies together and run a separate
wire for the positive output to your load.
The negative side of your load is still going to the mainboard’s negative output and from
there the current will travel back to the new power supply through the wiring you already
have.
Circuit complete!
You can also add a fuse if you want to protect your mainboard, totally makes sense and fuses
are way cheaper than buying a new board or spending the time to fix a blown one, links
to the fuses I like below.
Now, if you want to use a DCDC buck or boost converter, the wiring looks much the same.
A DCDC converter will have its input and output negative side tied together internally anyways,
so you only need to connect one of the two to ground, either anywhere on the mainboard
if its just a fan or directly to the power supply, just not to the negative output on
the board.
Then, the positive input of the DCDC converter goes to supply voltage, here you can use the
output on the mainbard and that’s probably a good idea if there are fuses built into
the board, or you can also directly go to the input or power supply output and add a
fuse there if you feel like it.
Then the output of the DCDC goes to your load and the load’s negative terminal goes to
the negative terminal of the mainboard’s output.
And this goes for both Buck or step-down converters that output a lower voltage and for boost
or step-up converters.
The only difference is that while buck converters specify output current, boost converters are
usually rated for input current, so if you want to run a 2A, 24V load in a 12V system,
you actually need at the very least a 4A boost converter since on the input, it will be drawing
4A to get the same power.
Or in reality, closer to 5A, since the converters aren’t perfectly efficient.
So if you want to run motor drivers at 24V in a 12V system, it’s the same idea.
You tie together ground and then supply the output voltage of the Boost converter either
to the motor driver input on the board if you have a separate input for just the drivers,
or if you have socketed drivers, you can also solder in the pin for the V_MOT supply upside
down and jumper the supply voltage directly into the driver.
Though this should be a backup-only solution since the mainboard usually has a bunch of
capacitors that buffer the supply voltage for the drivers and you’re completely skipping
those if you wire in the supply directly.
Before you connect any load, though, you should adjust the output voltage of that DCDC module,
use a multimeter to check or grab a converter with a display.
There’s one more thing you should check for if you’re wanting to run a 24V load
in a 12V system, and that is that your board is actually rated for 24V, because the Mosfet
on the board is having to block that full 24V when it’s switching the load off.
So, yeah, that’s how to use components that need different voltages in the same system.
Again, if it’s just fans, it probably makes more sense to just use a simple, cheap converter
than scavenging around for 24V fans, but of course you can also mix and match parts however
you like now.
All the stuff is linked below, like, share, subscribe, hit that notification bell, that’s
actually really important as Veritasium recently explained, and yeah, thanks for watching,
see you in the next one!