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!
