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Author Topic: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers  (Read 2577 times)

Offline Gingerbread Man

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Well, I found out where they were stashing the magic smoke that was making my latest 3d printer work...

I picked up an Prusa i3 parts kit from Alunar a few weeks back and considering its cost and design, it has quickly become my 'experimentation' printer.'

Over all, I would say that I cannot, in good conscience, recommend this printer/kit.

The design, as a Prusa i3 clone is good, excellent even, however, this Chinese knock-off of a knock-off (they are 'biting' the Anet a8, which in turn is a rip off of the Hesine M505) is not the best interpretation of that design.

But, that is another post entirely ;)

So while this printer has some VERY questionable design choices, and some pretty amateur engineering oversights, once it is up and running, it is a hell of a printer at this price point. Accurate as all get-out and simple where it can get away with it, this is a great design for someones 'first printer'. Prusa is a pimp.

Well, I decided one day that I needed to run Octoprint on this puppy so that I could do networked printing like all the Dutch boys in the YouTube videos, and a Raspberry Pi seemed like the best fit.

So rather than take up an extra outlet, I decided I would just put a 5v USB port on the power supply. Then I could have a more modular design should I need to service anything, but I could still just use the on-board power supply.

Well F#@K!! This think does not have a 5v rail...Just 12v...hmmm.

So I figured I would just remove the guts from a wall-wart charger, wire that into the mains BEFORE it was stepped down by the power supply, and just stick the guts inside of the power supply enclosure.

Easy enough eh?

So I epoxy in the USB port, solder in the leads from the wall wart PCB, and I just use the same screw terminals that the mains uses to interact with the power supply.

Plug it in...power...but no 5v...no Raspberry Pi....:(

So I figured I must have gotten mixed up with this crazy Chinese wiring...and I reverse the negative and the ground...

A quiet 'pop'...and the machine goes dead...F#@K!!!

Totally dead. Nothing. So I remove the wiring for the 5v transformer...Still nothing.

Damn it! I must have fired the power supply! I just hope my controller board did not fry...or my steppers for that matter.

Fucking Schematic Kiddie Strikes Again!!!

So I call around for a new power supply...my local shop only has 100w on the shelf...so thats not going to work...

And that lead me to the 'upgrade' that most folks with a home-brew 3d printer make eventually...Wiring an ATX PSU to supply your power.

We ALL have piles of them laying around...Once your relative hear that you are the guy who WANTS their old computer gear...the pile can accumulate pretty quickly...

So I went out to 'the graveyard' and rummaged around for something that would work. And I settle on this puppy...250w...2003s finest...A power supply so confident in its abilities it does not need a brand name, or even any English on the case ;)



Now I forgot to take a 'before' pic...so this one is AFTER I epoxied a SPST switch into the case...more on that later...



Oh, and start warming up the old 937...and yes...it is a knock-off :P



So when you open this baby, and even before that, you are greeted with the usual rats nest of wires. For the purposes of this project trim off all connectors and wire management ties. We don't need 'em.



Now you should ALWAYS already know what you are doing if you are going to use one of my 'tutorials' (more like cautionary tales eh?)...but just in case you do not...

BE CAREFUL HERE!

The obvious "don't open electronics while they are plugged in' applies...but also, be aware that this unit, like many modern electronics, can carry a serious electrocution risk even after it is disconnected from the mains power supply.

See those HUGE capacitors in there? Those are the BOOM STICKS. Tap one of those with a screwdriver and you are going to feel it :P. These things can stay charged for a surprising amount of time after they have been disconnected from a power source.



If your power supply has been energized AT ALL in the last 24 hours, use caution. The hardcore folks will say that a wait of 10 minutes should be enough to dissipate the charge...but I have PERSONALLY pulled a spark from a cap that was sitting on my bench for almost a week...who is to say what the charge was...but it was more than I would willfully dump into my nervous system...

Play safe. If you do not know how to discharge a capacitor to avoid electrocution risk LMGTFU!!

So look at all these freakin' wires!!! What do they all do??



Well lucky for us, they are all color coded...And while there may be some variation, the primary colors are always the same.



So for this project we can pretty much just write off the 3.3v...and I do not intend to incorporate a standby or wake function...so purple is out...

So that leaves us with the usual suspects:

Black -- Ground
Yellow -- +12v
Red -- +5v
Blue -- -12v
White -- (if you have it) -5v

But also:

Green -- ?
Pink -- ?
Brown -- ?
Grey -- ?

So...what do you suppose all these extra single wires could be?

Well since this is an ATX power supply, the green wire is the 'on' wire. This wire allows the PSU to determine if it is indeed connected to a motherboard or if it is just sitting on a bench. When the green wire is connected to ground, the power supply knows everything is hooked up just right and it turns itself on. Some folks will just hard wire the green to a ground, but I prefer to use this as an opportunity to put in a power switch (as the Alunar kit did not include one for some reason). When the switch is open, the power supply is still energized, but it will not provide power to the rest of the system.

It is a little hard to see here, but I wired the green wire and one of the grounds into the SPST switch I mounted in the case earlier. Shrink tubing for safety ;)



OK...green is off the list...but what about the rest?

Well, lets go back to that connector we removed right when we started:



Do you see how some of the ports in the connector have more than one wire mounted inside of them? Well those are 'sensor' wires. They are another check to ensure that the power supply is both connected and functioning properly. Some PSU do not have them, but this one did...one for 5v and one for 3.3v.

Just make a note of the doubled-up sockets in the connector and recreate those 'shorts' to convince your PSU that everything is A-OK and that it should go ahead and fire up now. Of course, trim them to a reasonable size first :P



Now for this project I am only going to need one line of 12v and one of 5v...the rest can be trimmed back and soldered together. You are going to want to cap the loose ends with shrink tubing or hot-melt glue or silicone or something similar to ensure that there is no electrical hanky-panky going on where it should not be.

DON'T USE TAPE. The constant hot-cold cycling and the vibration sometimes present in these units will play hell with pretty much ANY adhesive, and loose wire ends are known for doing their damnedist to make sure you release that magic blue smoke at just the *most* inopportune times.

You can also use flush cutting snips to take the wires all the way down to the PCB...but even then I would put a big blob of silicone or epoxy on top just to make double sure.

In the interest of future hacks, I generally leave a few extra leads full length and just cap them off with some heat shrink tube and coil them up inside. It is much better to have a few extra leads inside of the case then to have to try and solder to some nub of a cable, .1mm from a sensitive component, buried in a nest of wires. A little foresight goes a long way, as you will see.

So once you have the unused wires trimmed back and capped off...Once you have the 'control' wires shorted to their respective lines...Once you have the 'on' wire connected to a switch...

You are pretty much done. +12v on the Yellow...+5v on the Red...Black is ground. Good to go.

Some PSUs will not function with out at least a little load on the system (despite all the sensors that we accounted for, actually pretty rare these days)...this unit has an LED wired in with a resistor that was included in the original design. If yours is one of these picky ones...an incandescent bulb from an old flashlight or an LED with a nice fat resistor can serve nicely here.



So now...a test...Notice the 5v leads just hanging out in the 'helping hands' LOL...moment of truth...




Looking good.


No sooner did I get it working than I noticed that the leads for the 12v were just a little smaller than those for the power lines going to my control board. Just for safety and piece of minds sake, I decided to use two leads for the 12v power and the 12v ground. I KNEW there was a reason I was saving those...Singles seemed plenty for the 5v for the Raspberry Pi.

A little shrink tubing, a  few left over connectors and a smidge of paint...

Good as new.



Now...where was I...?  ;)

https://i.imgur.com/6tCeWDE.gif
« Last Edit: June 30, 2017, 09:01:15 AM by Gingerbread Man »

Offline ch3rn0byl

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #1 on: August 15, 2016, 09:33:28 PM »
Whaaaaa!! This was pretty sweet! I've been tased before, voluntarily...hehe So I would be pretty hesitant to play with electricity. The gif looked like you were being careful like...please dont shock me please dont shock me lol
This is actually pretty sick! Keep them coming man!
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Offline Gingerbread Man

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #2 on: August 15, 2016, 09:59:14 PM »
LOL...You recognize the "Please don't shock me" look eh?

I knew I liked you... 8)

Offline Malachai

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #3 on: August 21, 2016, 12:45:08 AM »
That's pretty awesome layout... Now can you make me a lower for a 308 ...  8)
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Offline Amonsec

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #4 on: August 21, 2016, 03:13:47 AM »
Really nice work dude.  It makes me want to get into electronic.
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Offline c0ldg0ld

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #5 on: August 23, 2016, 05:44:19 AM »
That's pretty awesome layout... Now can you make me a lower for a 308 ...  8)

Need to look in to sintering to build any kind of reliable (in my eyes anyway) receiver.  https://en.wikipedia.org/wiki/Solid_Concepts_1911_DMLS
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Offline Gingerbread Man

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #6 on: August 23, 2016, 10:31:27 AM »
Need to look in to sintering to build any kind of reliable (in my eyes anyway) receiver...

Missed my talk in Vegas eh? ;)

There are SEVERAL receiver designs that have been through four-digit torture tests, and a few full firearms that have had at least double-digit tests.

This shit is moving along quickly...we have come a long way from the single shot blocks of ABS that were the early efforts...

Recording of a version of my Vegas talk coming soon...stay tuned...

Offline c0ldg0ld

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #7 on: August 24, 2016, 07:15:39 PM »
Yeah man, I've been waiting for the talk... I'll probably never convince the wife to let me go to vegas for one of those cons (though she is "surprising me" with a trip in December apparently)!  I haven't seen much more than the original designs and knowing how much my AR-15 kicks I wouldn't doubt being able to build a lower for one of those I just wonder about the AR-10... .308 is a helluva lot bigger round than 5.56.

For those of you who live in the US though, go buy yourself a stripped lower for about $60-$80 and build from there.  The rest of the parts require nothing special and can be shipped right to your door.  That's how I built mine, just like Johnny Cash... One piece at a time.
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Offline Gingerbread Man

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #8 on: August 24, 2016, 08:40:19 PM »
Yeah....308 is a different animal entirely :P

I am thinking that I will go down to Denhac this/next week to film the 'archival' version of this talk. Just doing a screen cap and a voice over does not allow me the 'energy' that makes one of these talks so fun.

I will have to see if anyone wants to come on down...

Offline c0ldg0ld

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #9 on: August 25, 2016, 09:27:58 PM »
So you mention that you wouldn't suggest this particular kit for someone to buy, do you have a recommendation?  I have an ultimaker 2 at work but would like something for the house and don't wanna spend a shit ton.
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Offline Gingerbread Man

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #10 on: August 25, 2016, 10:39:46 PM »
For one of us? Yeah, I *DO* recommend you pick one up.

But if you are not the 'handy' type...then it can leave you stuck at a few points.


Decent quality parts...
Great design...(Prusa i3)
Shitty engineering of the knock-off of a knock-off (FAR too many fastener types and sizes, and some pieces were actually mis-engineered so as to make them non functional.)
Terrible documentation...and I mean fucked.

But as far as designs go...the only real unfixable issue is the fact that it has an acrylic frame. And if you are careful, even that is not a big issue.

If I were feeling frisky I would opt for a commercially made frame kit and a pile of parts...15USD for a frame kit, ~50USD on steppers, ~40 on  a control board, 20 for a build plate...and about 100USD of rods and belts and couplings and wire...

Short of that, I would pick up an i3 clone from a reputable manufacturer...saves the hassle of all the calculations...and in the end, that warm-blanket of knowing that if you follow all the steps, it should just WORK, is worth a hell of a lot if this is your first build like this.

There are quite a few shops out there. I can PERSONALLY recommend a few:

Prusa of course...What?! Too expensive?!...moving on...

Folger Tech makes a VERY affordable printer kit (~300USD) that is quite similar to the i3 featured above. They also make one from 2020 extrusions which is very nice. Stuffed in boxes in the USA!

In Asia we have:

Anet
Hesine
Hictop
Alunar (a real one)
Omni

All of the above make decent i3 clones...some better than others...All feature 1.75mm filament...all have Melzi knock-off boards under the hood.

Just be warned: plenty of places will use pictures from other vendors and sell you an approximation of what you thought you were ordering. Cheaper steppers, shitty boards...it pays to only use reputable shops...preferably ones that handle more than just 3d printing...IMO of course ;)

When evaluating designs, again IMO, look for rigidity. If you remember the old MendelMax...you will remember just how irritating having the actual structure of the machine being made out of rods can be. Opt for a solid frame, preferably with as few individual pieces as possible...Choose materials not likely to warp...choose materials that fail gracefully instead of just suddenly giving out...acrylic falls short on both points.

I like solid metal frames. The Prusa i3-steel variant is very nice in this regard, and the Mendel90s and Prusas made with 2020 extrusions are a VERY affordable way to get the rigidity and modularity of design that you want.

A point to look for is to make sure that the TOP of the Z axis rods are supported. The different manufacturers have different takes on how to handle this portion of the machine, and their decisions make a significant impact to the need for tweaking and adjusting to get a decent print. A full bearing at the top, with an accompanying attachment to the support rod is ideal. Some pieces of shit just have them completely free-floating in the air...Z-wobble city.

The Acrylic Alunar is actually EXTREMELY nice in this respect...The water-cut acrylic is very accurate in its shape...When assembled correctly there is VERY little play in the position the guide rods and the individual pieces of the frame. In the particular kit above, the rods are trapped in the acrylic frame itself, and they are retained with small flaps that sit attached to the top with screws. When things are aligned properly, there is neither any gap nor any excess rod protruding from the top of the frame. The little flap will ONLY push over the opening in the frame if the rod is 100% beneath the threshold of the opening. And so by making sure that the rod is absolutely flush with the frame you can be assured that there is not any 'cant' or 'skew' to your frame and the rods inside. Very nice design.

In addition to this, this particular kit has the threaded rods ALSO sitting inside of the frame. However, these are NOT held tightly, they are just sitting inside some slightly oversized openings. Some manufactures us bearings here, and that really is the idea situation...But in a move that gives me the tingles in my cyberpunk region...the Alunar folks have instead just slightly offset the holes in the upper portion of the frame so that instead of the rods positioning themselves up the center of the cavity, they rest pressed up against one of the sides. This has the effect of keeping the rod under slight but definite tension along its whole length and remarkably reduces the z-wobble in all (and especially tall) prints.

There is a similar situation with the y-axis frame...VERY little allowance for misalignment of the y-axis with the rest of the frame. Good stuff. 10 Internets to those guys...they did not get it all wrong eh?

Now...if you wanna get hardcore about it...there are a few 'shortcomings' of the i3 design that, once you get to that level, leave some irreducible play in your prints that may at one point become bothersome. Most never get to that point :)

Namely, the use of an extruder directly above the hot-end, on the printing carriage, induces a bit of backlash that is difficult to account for...the same design also allows for uneven tension on the filament as the print is deposited at different points on the build plate. This can cause inconsistencies...

Then there is the issue of the build plate handling the Y-axis motion in addition to the Z-axis...this is not ideal as the print itself must be moved, and in addition to the adhesion problems this can cause with larger prints, the extra weight again contributes to backlash, a situation made all the worse but the Prusa designs use of tensioned belts on the Y- and X axes.

An idealized design, as far as the current understanding of FDM goes, incorporates remote (Bowden) extruder setups, and hot ends that are responsible for both the X and Y-axis motion, with the built platform merely moving downward as the print grows.

But again...few even get to the point where the give a fuck, or can see where that makes any difference...

Prusa i3 all the way brother... 8)
« Last Edit: August 25, 2016, 11:57:16 PM by Gingerbread Man »

Offline c0ldg0ld

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #11 on: August 26, 2016, 05:56:03 AM »
Wow, that was a detailed response!  The ultimaker2 actually sounds like it stacks up pretty decent with those guidelines.  I'm certainly not going to pay what they paid for one though and the feed has always been an issue with this one, takes some finesse.  Boss has basically printed 90% of a lulzbot taz for himself at home on the ultimaker, but at this point with the quality prints we are getting out of the ultimaker and running out of ideas to fix it I don't think I'll be doing the same.  Will start looking at some of the options you mentioned.
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Offline Gingerbread Man

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #12 on: August 26, 2016, 09:52:34 AM »
The TAZ is probably the best printer currently available i the under 3000USD category.

From the use of wiring harnesses, to the electrical contact-based self leveling system, to the nozzle wipe routine, to the premium parts. The only complaint I have against it would be the use of 3mm...but that is really just personal...and in a commercial environment...actually preferable.

Taz from Aleph Objects is second to none.

https://www.youtube.com/watch?v=lojprD2KvnU


Offline Malachai

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #13 on: August 28, 2016, 01:04:49 PM »
I would not mind having one of these in my office. lol...
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Offline c0ldg0ld

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Re: If it ain't broke...Fix it until it is!! ATX PSU for 3D Printers
« Reply #14 on: August 29, 2016, 04:53:14 PM »
Yeah maybe once we get the ultimaker back up and running I'll just print one of those too, I'll have him already working the bugs out!  Should come in much cheaper than $2500 if I print most of the parts!  UM2 uses 3mm as well, we're having some feeding issues (always been a little fussy about that) so the prints have suffered.  Need to get it sorted, I'm thinking about just snagging a new hot end for it and then working on clearing the blockages (thinking maybe soak in acetone) because we've got some ABS in there I guess that just aint coming out.  May go back to printing with PLA for a while.
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