Power Supply Calculations made easy

JoshMcCullan

So I was calculating the power to source a power supply suitable for it. (via the wiki https://duet3d.dozuki.com/Wiki/Choosing_the_power_supply )

Its is just that I found some difficulty since some measurements are in Watts and others in Amps yet its not specified if it is 12v or 24v, that is talked about.

For my calculations I'll give a small listing, I want to use 24v on a Duet2 + Duex5 + PanelDue5i (hand me downs)

Bed AC -> zero on psu
Hotend-Heater: 24v at 40 to 80 watts depending what tool I use. -> 1.7-3.5A if conservative.
Stepper motors
z -> 1x Nema23 23HS5628 rated at 2.8A but will run lower current. ( I think)
e0-> Nema17 rated at 1.33A
x + y -> 2x Nema17 17HS4401 rated at 1.7A each. (or another pair i got laying around 2 at 2.2A)
(So do i still need to multiply these by 50% that would mean 11A!!? )
Fan 2x 12v0.7A fans running from the Duet 2 board
Part cooling fan (assembly) 24v1.5A
Duet itself 2W (I don't know what this value is, it will be influenced by 'always on fans' and part cooling fans mentioned above)
DueX5 ???
PanelDue5i (Less than 3.5W) ???
Various small servos and sensors and switches (nonexistent power)

Has somebody else found complete numbers for an example so it would be easier to calculate them?
I don't think from past experiences that 15A if i overestimate be 10% as i currently calculated it is correct, but I could be wrong.

(if model numbers are considered adds feel free to remove them, it's just what i got laying around)

Thank you well in advance
Josh

mrehorstdmd

@joshmccullan The motor calculation is for power, not current. If your stepper is rated for 2.8A at 3V, it will require 8.4W.

Size the power supply based on total Watts plus a healthy margin (30-50%). A 200W power supply costs about $5 more than a 150W power supply and is only slightly larger. Don't be penny wise and pound foolish.

JoshMcCullan

@mrehorstdmd

So taking what you said and to recap on it. I found the following

Bed AC -> zero on psu
Hotend-Heater: 24v at 40 to 80W depending what tool I use. -> 80W
Stepper motors
z -> 1x Nema23 23HS5628 rated at 2.8A (&( 2.5v) but will run lower current. -> 7W
e0-> Nema17 rated at 1.33A ->3W
x + y -> 2x Nema17 17HS4401 rated at 1.7A each. 1.7^2 / 2.8 = 1W, 2 motors 2W + power-loss -> 3W (or another pair i got laying around 2 at 2.2A) -> 9W
Fan 2x 12v0.7A fans running from the Duet 2 board (17W) -> Accounting for 12v conversion -> 20W
Part cooling fan (assembly) 24v1.5A -> 40W
Duet itself -> 2W
DueX5 -> 3W
PanelDue5i -> 3.5W
Various small servos and sensors and switches (nonexistent power)

So counting for max allowance, for that it would be with 20% power to spare it would be just 201W
Was thinking if get away with 240W, so I think that would be a good option.

I do agree on your comment about not needing to go cheap on it.
That wasn't why I asked.
I could just use a 24V16A power supply but then I would just waste electricity in the long run trough losses in conversion.

Thank you for your time.

mrehorstdmd

@joshmccullan 40W for a print cooling fan seems beyond excessive. You're liable to blow the print right off the bed! It's going to sound like a vacuum cleaner, and you'll have a hard time keeping the nozzle up to print temperature. The same goes for the other two fans, whatever they'll be doing. You don't need much air movement to keep the duet board or the hot-end cool.

I run a 5", 220V fan at 117VAC to slowly and silently blow air through the electronics enclosure. It switches on with the main power switch and keeps the Duet board cool as a cucumber. I use a similar arrangement to blow air over the 500W chamber heater- the fan is wired parallel to the heater so it kicks on any time the heater has power. It moves just enough air to keep the heater at a safe temperature but not so much that it cools the print (and causes warping or layer separation).

I use a bunch of 5 position Wago lever nuts to set up power busses for 24VDC , 117VAC, and the DC and AC grounds. It makes it quick and easy to do the wiring, and very easy to make changes later. You can hot-melt glue them wherever you need them or print brackets that can be screwed down.

dc42

@joshmccullan, as @mrehorstdmd it's most unlikely that you have a 40W part cooling fan. It's also unlikely that your 12V fans draw 0.7A each, unless they are large fans. The DueX5 draws only a tiny amount of power, much less than 1W.

JoshMcCullan

@dc42 said in Power Supply Calculations made easy:

The DueX5 draws only a tiny amount of power, much less than 1W.

Thanks I think that is missing in the documentation, or I was just unable to find it.

@mrehorstdmd
@dc42
On the Part cooling, whilst I agree that is seems much. It's an allocation for a combination of multiple fans and cooling options I was tinkering with.
I wanted to try out a 'HevACS' part cooling combined with some axial fans.

Thanks you on both being helpful!

The main thing why this post was made is that the power that can be allocated to the printer limited is due to the place the printer will be set in.