Power Supply Troubles

I have been running my printer for a while now and a recurring problem I am facing is my power supply dying mid print. I am using a converted ATX power supply that is well over-spec I believe (http://www.newegg.com/Product/Product.aspx?Item=N82E16817170010). I soldered all the 12v lines into two main lines that attach to my RAMPS 1.4. I did the same with my ground lines. I soldered the 3.3v sense to the 3.3v line and I also have a 10ohm resistor attached to the 12v line to supply stability under low load. I know there are hundreds of possibilities but I was wondering if anyone had any experience with the problem. Worse comes to worse, I spend $40 on a new one from lulzbot.

Thanks,
Tom

Never heard of that brand before and that could spell trouble. 550 is the bare minimum I would use but being a really off brand how much of that 550w quote is true? One thing I know about is computers and I know in the computer world an off brand PSU is just asking for trouble.

edit: Ahem 19 dollars for a 550w PSU? Junk I say (probably made by the One Hung Low company) as a quality 550w that can be trusted is a good 60 to 100 dollars. My 650 cost me 100 dollars a few years back made by Corsair and the 550w I had was made by Antec.

Edited 1 time(s). Last edit at 09/16/2012 09:52PM by Dark Alchemist.

It's got 25 Amps on the 12 V line, so even if it is over-rated it should be just fine. Try putting the load resistor on the 5 V line rather than the 12 V. For our application we don't need a high-end supply, as long as it outputs close to 12 V and doesn't spike or drop too much from there it is probably good enough. We aren't running computers that require an accurate voltage supply.

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NewPerfection Wrote:
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> It's got 25 Amps on the 12 V line, so even if it
> is over-rated it should be just fine. Try putting
> the load resistor on the 5 V line rather than the
> 12 V. For our application we don't need a
> high-end supply, as long as it outputs close to 12
> V and doesn't spike or drop too much from there it
> is probably good enough. We aren't running
> computers that require an accurate voltage supply.

That was my point as many of the One Hung Lo pieces of crap has burnt out many a computer because it says it does X amount but in reality does crap. Might not be his problem but there is a problem in buying a no name PSU for 20 dollars that says it does 25amps on the 12v line. Not for 20 dollars or at least not for too long and I lay odds it is probably a real 200w PSU or, at most, 250-300w but continuous duty probably 200w. Seen it too many times as a PC tech to even begin to count.

Now doesn't the PSU power the ramps, motors, heating elements and fans if any? That should be a good bit of amps for all of that together.

Edited 1 time(s). Last edit at 09/17/2012 12:03AM by Dark Alchemist.

Dark Alchemist Wrote:
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> Now doesn't the PSU power the ramps, motors,
> heating elements and fans if any? That should be
> a good bit of amps for all of that together.

Including a standard Prusa heated bed, total current draw should be about 16 amps. I use 200 W XBox 360 power supplies on some of my printers, which is about 16.5 amps at 12 V, which works quite well. These are power supplies that can actually supply the rated current continuously, however.

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NewPerfection Wrote:
-------------------------------------------------------
> Dark Alchemist Wrote:
> --------------------------------------------------
> -----
> > Now doesn't the PSU power the ramps, motors,
> > heating elements and fans if any? That should
> be
> > a good bit of amps for all of that together.
>
> Including a standard Prusa heated bed, total
> current draw should be about 16 amps. I use 200 W
> XBox 360 power supplies on some of my printers,
> which is about 16.5 amps at 12 V, which works
> quite well. These are power supplies that can
> actually supply the rated current continuously,
> however.
Alright that is a little less than what I was thinking of 20amps.

Not trying to sound mean or anything I was just stating a fact that these el cheapo power supplies really has caused so many woes for consumers in the PC market that it is possible it could be doing the same here. From extremely unclean power (bad for the ramps regardless how much current the PSU can supply) to being as much as 1/3 of the rated power.

Dark Alchemist Wrote:
-------------------------------------------------------
> Not trying to sound mean or anything I was just
> stating a fact that these el cheapo power supplies
> really has caused so many woes for consumers in
> the PC market that it is possible it could be
> doing the same here. From extremely unclean power
> (bad for the ramps regardless how much current the
> PSU can supply) to being as much as 1/3 of the
> rated power.

I totally understand, and would never use a power supply like that for a computer. For the most part it will work just fine with a RepRap though, since the linear regulator does a pretty good job of giving a clean 5 V to the Arduino (if you are printing stand-alone) and the stepper drivers are pretty tolerant seeing as they can go up to 36 V. If you are getting 5 V off of your computer's USB port, then it is probably even less of a worry.

I would still, of course, recommend a better power supply if budget allows.

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Even standard stand alone switching power supplies can be not so good for Reprap machines. I purchased some S-240-12 power supplies brand new from ebay. They should have been 12 VDC 240 watt power supplies good for 20 amps at 12 VDC. Even with the adjustment pot, they only got to a maximum of 12 VDC under no load. When under a 15 amp load, the 12 volt line dropped to only 9.6 VDC. Supprisingly, the printer still kept working, but the heated bed would only heat to a maximum of 100° C - not good.

I think it's a bit of a crap-shoot with the cheap Chinese supplies. I have a 30 A 12 V supply that I got for $35. I have successfully run it at the full 30 A and it maintained 12 V pretty well. I did have to remove the underrated thermal fuse, replace the regular fuse with a higher rated one, and modify the fan so it would run continuously to keep it cool enough. After that it works very well.

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I used to use (12 years ago) those el cheapo all in silver power supplies until one blew and it took everything with it in my computer. It was always so hot compared to the better versions too.

Now the one thing that has changed over the past 6 to 8 years is that more power is on the 12v rail (used to be rail then went rails and finally sense came back and it became a single rail again but oddly enough the One Hung Lo models would say multi rail but internal was only one rail) and less on the 5v since 5v is hardly used in PCs these days and what is needed is taken from the 12v and stepped down. I always wondered why that changed until I was watching a computer show and it made sense.