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Stealing addtional power from PSU  

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SpecialT
(@specialt)
Eminent Member
Stealing addtional power from PSU

Hello.

i try to set up my rasp 3 B+ with cam etc.
As i want no additional power suplly, i want to steal some power directly from the PSU which goes to the the other side
where the einsy sit and there i go through a step down converter(24v--->5v/max 10A) to my rasp with GPIO header.

is the PSU suitable for this?  becouse i have the black psu which only has 4 connector on the PSU where i would put my connection over the existing ones?
or should i buy as people mentioned, the Mean Well RSP-320-24 becouse the original is lacking some power out of the stock.

Posted : 25/04/2019 8:43 pm
Nikolai
(@nikolai)
Noble Member
RE: Stealing addtional power from PSU

To avoid any issue, I recommend to use separate power supply for Raspi. The last thing you want is unstable working Raspi only because of some weird noise/issues on the PSU line.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 25/04/2019 9:50 pm
Olef
 Olef
(@olef)
Honorable Member
RE: Stealing addtional power from PSU

Use separate power for the Raspi. Then each device gets it own clean power without impact from the other.

Posted : 26/04/2019 6:03 am
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU

I know is netter if i Use a separate Supply. But i want  a clean system  wich only one  Supply.

Today i finshed  building all together and mit runs  smooth  rasp get stable 5,10v. I only print Pla and abs so i think the supply doesnt Run in some power problems. Bevor i try to print petg or anything  similiar  i change the Supply becouse  as All know  There would a giant bottleneck from the original one.

Posted : 26/04/2019 3:40 pm
Nikolai
(@nikolai)
Noble Member
RE: Stealing addtional power from PSU

If you made your decision already, then there is no need to ask :).

"Clean" is always a matter of definition. For me it's much cleaner to have a separate PSU. In order to see what's really happening during print, you would need to hook up an oscilloscope and check various situations.

In regards to enough power, just make sure it's not overheating. PLA/PETG is not a big difference.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 26/04/2019 4:06 pm
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU

Yes the decision was made. My question was if it is a good idead to steal some power from the stock PSU or change the complete PSU
Yeah i know what you mean with 2 seperate PSU, i think myself why not use the given PSU if it is cabable. So i have one think less that botheres me if something failed.

As you say for PETG most people warned me to use the stock PSU becouse they only deliver 240W and with PETG it wants 260W+ so there
is a potential Part that could fail and set my printer on fire^^.

Posted : 26/04/2019 4:41 pm
vintagepc
(@vintagepc)
RE: Stealing addtional power from PSU
Posted by: SpecialT

Yes the decision was made. My question was if it is a good idead to steal some power from the stock PSU or change the complete PSU
Yeah i know what you mean with 2 seperate PSU, i think myself why not use the given PSU if it is cabable. So i have one think less that botheres me if something failed.

As you say for PETG most people warned me to use the stock PSU becouse they only deliver 240W and with PETG it wants 260W+ so there
is a potential Part that could fail and set my printer on fire^^.

I've done a fair amount of PETG on the stock PSU without issue... Have to wonder if those with issues got marginal supplies. There has to be a reason PR switch to the new Delta black supplies...

 

 

Posted : 26/04/2019 4:54 pm
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU

Yeah does print but it use more power that the PSU can give and that is always bad becouse the best is tu use 30% better 50% more A to eliminate these Spikes which can happen.
But the i cant tell it by myself i bevore i wanted to connect rasp direct to the PSU read al little bit about it and some people mention the PSU ist not cabable for PETG in some circumstances.

as i know the max 240W that it can deliver. i warmup the printer today an messure the consumption and post my results to determine if the people that mention that its not cabable correct or not.

Posted : 26/04/2019 5:12 pm
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU

i testet it know at 20c° envoirment. 13W consume in normal/standby and 268W warmup for ABS .

Posted : 26/04/2019 5:19 pm
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU
Posted by: SpecialT

i testet it know at 20c° envoirment. 13W consume in normal/standby and 268W warmup for ABS .

but please beware these are messured on the input so you must calculate with the Efficiency rate of the PSU.
And if someone know the Efficiency rate please let us know it ^^

Posted : 26/04/2019 5:58 pm
Nikolai
(@nikolai)
Noble Member
RE: Stealing addtional power from PSU
Posted by: SpecialT

As you say for PETG most people warned me to use the stock PSU becouse they only deliver 240W and with PETG it wants 260W+ so there
is a potential Part that could fail and set my printer on fire^^.

All the PSU failures which were mentioned in this forum happened absolutely random. Original PSU can handle max load without any issues. And the max load is being pulled if you move x/y/z/extruder and at the same time heating up bed + extruder. It doesn't matter if it's for PLA/PETG/ABS/Nylon .... or any other material. 

It's good to be cautious about fire risk. But then you should be cautious for any power supplies in your house. In general you shouldn't keep or store something which is highly inflammable near the printer. Any sparks coming from the PSU can't put the plastic parts on fire.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 26/04/2019 8:58 pm
Vojtěch
(@vojtech-3)
Honorable Member
RE: Stealing addtional power from PSU

The silver Mk3 Prusa PSU is a rebranded T-Led TLPZ-24-240 v2 PSU with quality Chemicon capacitors:

http://tled-web.mywac.cz/download.asp?appid=1&oid=A2000000015A

And as such it should have around 83% efficiency at optimal load (typically 70% load). The efficiency will be much worse at small loads.

The new black Mk3/Mk3s Prusa PSU is supposed to be a custom PSU manufactured by Delta, so no datasheet is available. Hopefully the efficiency is better.

Regarding stealing power for RPi from the PSU using a DC-DC step-down, I think it's possible. The RPi isn't all that power hungry. Just add your wires to the clamps on the Einsy. It doesn't matter whether you choose the Bed clamps or the Motor clamps, they're all connected together anyway. The power budget is tight on the Mk3, if all would be running at full power at the same time, the CPU will go into overload, but it is designed to withstand a 20% overload for short amounts of time.

So you'll most likely be fine, and if not, the PSU should simply shutdown.

Posted : 26/04/2019 9:43 pm
SpecialT
(@specialt)
Eminent Member
Topic starter answered:
RE: Stealing addtional power from PSU

Okey  than i will stay on my way  to steal a little  bit juice from the psu.

Thanks for all your advice and help.

Posted : 26/04/2019 9:58 pm
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