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Will this be alright?

Posted by rich1051414 
Will this be alright?
March 19, 2017 01:27PM
So today my hictop prusia i3's power supply died, no violence or anything to make it interesting. First I checked the fuse, and it did not pop. Saddened, I tossed the power supply.

I have no other power supplies in that style, but I have a ton of other power supplies. First I tried rewiring an ATX power supply, but the bed wouldn't heat fast enough. I realized the problem was the 12v output. My printer wanted 24v.

So I had a brilliant idea. I have 2 identical long pack style 12v 15a power supplies, so I decided to throw caution at the wind and try to hook up their output in series. These were in my recycled parts bin, so I didn't care if they went pop. Wired the hot of one output to the negative of the other, and the left over negative from one supply and positive from the other is the actual 24v output. Worked perfectly, it now functions as a 24v power supply.

My question is, should the power supply's be fine since they are matched, or should I expect magic smoke to come out at any time?
Re: Will this be alright?
March 29, 2017 04:13PM
Should be ok but you need to ensure that the two power supply cases do NOT touch each other in case the cases are tied to ground (the two grounds are not at the same potential)
Re: Will this be alright?
April 09, 2017 10:16AM
You can put the power supplies in series, no problem. You may even put them in series if they're not the same. You may f.ex. have a 12V 15A PS and another 12V 40A PS, and you still cann connect one ground line to the other +12V line and have a fully working 24V PS, but you may only get 15A out of it. The weaker one limits the current.
And as dart16 wrote, be careful if the metal cover is wired to GND, they MUST NOT touch. The metal covers should be connected to PE (protective earth, this is the big free contact at the power plug) - you should check if the GND output is connected to PE, and if it is, you need to disconnect. Some HP server's PS need this mod, just google for it.

What you usually can't do, at least without some more electronic & magic stuff around, is to wire two PS in parallel to make a 12V 30A PS out of your two 12V 15A PS.
Re: Will this be alright?
April 10, 2017 06:48AM
These are plastic shelled PSU's, so it isn't a concern. These are long pack PSU's, like you would see for laptops. They were intended to power long strings of LED's, btw. Thanks for confirming that it should be ok. I am a programmer, so my electronics knowledge is strictly theoretical smiling smiley

I have connected a hall effect ohmmeter to each power supply, and the load seems to be balancing nicely, that was my major concern. Pretty confident it will be fine at this point. Even tryed to stress the psu by simultaniously heating the bed and hot end at the same time from cold, which the firmware doesn't even attempt, to try to coax out issues, but no, handled it just fine.

Edited 4 time(s). Last edit at 04/10/2017 06:57AM by rich1051414.
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