3D Printer Component Questions

[James Denier]

Hey guys,

I'm having a bit of trouble figuring a few things out with regards to the 3D Printer I'm building. I'm only up to the 'buying of components' stage and was hoping to get some recommendations.

I'm building a Delta-style printer that uses a Bowden extruder so that factors into my decisions somewhat.

I've done a fair bit of reading across all of these areas and there's so many conflicting accounts that I thought I'd go with the people I know (that I can pester to help me in person if I'm struggling!).

Regarding hot ends, the printer I'm building was originally designed for an anUbis hotend. Other people have used J-Heads on them, with a slight tweak to the design. None of that should be an issue, I'm just wondering if anyone has any personal preferences or recommendations. What do you like?

I'm aiming to mostly print PLA but I want flexibility enough to print HIPS, Nylon, Laywood/brick and some of the more novel filaments coming out. ABS is also important but not as much as PLA. With that in mind, I've been looking at the E3D v6, it looks pretty good. I also found a local Melbourne guy who was making hot-ends a few years ago (http://extrude3d.com/store/index.php?route=common/home) but his website doesn't have any obvious activity in almost 12 months now.

A friend at Uni also may have mentioned that he'd heard a rumour regarding a few CCHS members looking to release a hot-end/extruder soon. Yay/nay/hush-hush?

After the hot-end the two biggest sticking points for me are Power Supplies and Electronics. The range of choice for the electronics is intimidating to say the least.

What would you recommend from the major/'big' players in the controller field? I've read mixed reviews about RAMPS and Sanguinololu and the 'Melzi' board seems to be popping up more frequently. For my needs, any of those would suffice but/and ideally I'd like to be able to include an LCD panel and SD card reader. Cost and local accessibility are my two major concerns but it being user-friendly and more idiot-tolerant would help immensely too I suspect. I'd rather spend $20 more on a board that can handle me being inexperienced with electronics than save the $20 but fry the board two months down the track. Same as Stepper Motor Drivers.

Power supplies are just as confusing. I've been doing a lot of reading and, as always, mixed reviews. Some (majority) seem to use PC ATX supplies but I recall a lot of discussion about how they're rather rubbish and have a habit of killing boards (due to voltage spikes, etc.). As a result I've been looking at power supplies more specifically built for 3D Printers and CNCs but really don't have the knowledge or experience to separate the chaff from the seed in that regard. From what I can tell, the printer should be fairly standard in terms of power requirements (heated bed, 4 stepper motors, driver boards and controller. Plus the hot-end) The power supplies I've seen others use for the same design sit around 20 Amps at 12V (so roughly 240 watts). Any recommendations in regards to what to look for and what to avoid there would be very appreciated too! This is the one I've been eyeing off so far (http://www.ebay.com.au/itm/200979000937?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648) even though it's a bit of overkill.

The other thing that isn't so much of an issue/problem and more of a value-for-money thing.. I've got all the plastic parts and all of the fixings on the way but no stepper motors, drivers, boards, print bed or any of the rest. Are there any places that are recommended as better to shop for those than others? There's a million websites that I can order this stuff from so it isn't any real concern, just figured it's worth asking if anyone has any favourites.

Thanks for any answers that come up and your time involved. It's very appreciated. I aim to bring what I have into a Monday meeting sooner rather than later, just need to wait until I have some stuff to put together!

Cheers,
Jamie.

[Rob Gannon]

Add far as hot ends go, you will have trouble with just about every hot end on the market when it comes to printing in all filament types.  The best/only option is to wait for the new one to be launched soon by John and Michael. I'm using one of their beta versions and it's pretty good.

For electronics,  RAMPS is good for beginners because it is a bunch of separate parts that you can swap out if you do blow something up, and everyone at the hackerspace knows everything there is to know about it.   Get a kit from reprapdiscounts.com that can handle 24 volts.

For the power supply,  an ATX will often struggle if you have a heated bed, so will that 240watt one you are looking at.  Get a 24 volt 500 watt power supply for around $30 from aliexpress.com. Use a 24 volt ceramic heater cartridge for your hot end,  and a 12 volt bed heater running at 24 volts for quick heat up.

I would also get 2.5amp nema 17s, not just the standard 1.2 or 1.8 amp ones, and the 8825 drivers rather than the 4988 drivers because a bit more power in your motors is always good.

Rob.

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[Stuart Young]

Regarding RAMPS:

The guys in the German RepRap Foundation did a version with blade fuses instead of the PTC's. Google GRRF Ramps 1.4.2 and you should find it.

Would post a link, but currently a passenger in a car, on my phone.

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[Nick Fryer]

Hi Jamie,

I got my power supply from ebay works great!

[pete...@gmail.com]

Lears cnc power supply is very good. Its adjustable >12 volts which is good as beds take forever to heat up at 12 v if your doing abs.
I used a 600 watt pc power supply. It went bank and blew my rumba! Thas why I got lears one.
His service also good. Used his budda hotend. A nightmare unless you can get the fan in the exact spot etc. Jams intermittently due to heat creep
Ive pulled my hair out on 2 hot ends, but have beta tested ...the one in the pipleline and it rocks.

lcd sd card reader was much much cheaper on ebay. (search on entire world )

Rumba has lots of room for expansion...and I like it.
I have a spare one with blown usb fddi chip I can sell a bit cheaper

Peter Zwag

[Darren Freeman]

On Thu, 2014-06-26 at 09:31 +1000, Rob Gannon wrote:
> For the power supply, an ATX will often struggle if you have a heated
> bed, so will that 240watt one you are looking at. Get a 24 volt 500
> watt power supply for around $30 from aliexpress.com.

The selection of power supplies for 3D printing has been quite a
contentious issue.

On the one hand, you can buy a lab supply that meets the Australian
standards, is safe to use, and is reliable. But these tend to run up to
(and over) $300 depending on power output.

Or, as you suggest, you can import one yourself from an unknown overseas
vendor. At this point, you assume full legal liability for what happens
next. I'm guessing almost everyone reading this lacks the capability to
evaluate and test whether the supply meets the standards and is
electrically safe. Often, they simply don't and aren't.

There have been incidents in the space, where people had power supplies
that either actually blew up in front of witnesses, or became so
hazardous in operation that they had to be removed from the space.

And even though the local supplier is legally required to ensure that
they meet the standards, this is sometimes not the case. I have some
dead units that were supplied in Australia by a reputable store, even
though they didn't meet the standard. (They are no longer available for
sale.) The mains voltage literally flashed over to the DC output and
blew tracks off the board, probably during a voltage spike.

I note that these units don't carry any markings to say that they have
been approved for sale in Australia. (They are required to carry an RMC
mark.) They do carry a CE mark, but frankly that is as useless as a
bottle of vitamins that have "scientifically tested" written on the
side. Nobody has actually checked whether these supplies meet the
various CE directives. (There is no "notified body" number alongside the
CE mark.)

I can only imagine what would happen to a 3D printer or a user, should a
power supply explode in this way with a printer connected, possibly with
a user touching part of the circuit, maybe with a laptop connected,
maybe with headphones on.

Just because the authorities aren't chasing people who import dodgy
power supplies, it doesn't mean that you are immune to losing your
expensive equipment, or your life, due to dodgy products that you can
get for next to nothing, partly because they haven't done the required
minimum amount of design and testing in order to ensure that they are
safe to use.

I just contacted a local testing company and got some general advice on
the issue of power supplies. They are *required* to carry an RMC mark,
and the compliance certificate that goes along with it, and they are
*required* to be registered with your state electrical body. If you
import a power supply and then allow it to be used here without meeting
these two conditions, then you could be committing a crime.

I am not a lawyer, and I am a little vague on what this all means,
having always relied on the local supplier to do this for me. But you
need to know that if you import a power supply yourself, then you also
need to know all of this.

I would rather that you all survive your curious encounters with
electricity, so my advice is not to personally import mains-connected
power supplies. If you only knew what goes on inside some of these
units, you'd be horrified.

Have fun,
Darren

[James Denier]

Hi guys,

Thanks for the feedback so far. The German RepRap Foundation provide a fairly complete kit, it seems (including an ATX power supply) but it weighs in at $300. Although for the entire electronics that sees like a reasonable price to me. RepRapDiscount doesn't offer any kits with the 8825 drivers so I've sent them an email asking for the cost to have them included in a kit instead of 4988's. Hopefully hear back from them soon. A 24v kit from them with 4988's is $209, a bit cheaper than the Germans but without the power supply.

I wonder, does anyone have a rough time-line or any idea when John and Michael's hot-end will be available to the general public? I would certainly rather use something manufactured locally, any issues I may encounter will be significantly easier to get resolved that way.

Darren:

Thank you for the detail regarding power supplies. I've investigated lab desktop supplies and for these needs they'll definitely weigh in at $300+ dollars. Safety for myself, others and my electronics is very important to me, I just need to figure out whether I can fit that kind of money into the budget at this point (or whether the project gets delayed until I'm able to).

If I were to go with an imported power supply, do you have any recommendations on what to specifically look for or avoid? And how hard are they to make safe(r) for people that have the knowledge/experience with them?

I appreciate all the suggestions and warnings thus far, thank you all.

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[Darren Freeman]

On Fri, 2014-06-27 at 00:00 +1000, James Denier wrote:
> If I were to go with an imported power supply, do you have any
> recommendations on what to specifically look for or avoid? And how
> hard are they to make safe(r) for people that have the
> knowledge/experience with them?

I have recommended NOT to import one. You'll only find out what to avoid
once it's exploded and killed your printer. (Note that in the last day
or two, someone else posted to the list mentioning that this happened to
their printer.)

It's not really worth starting with unsafe junk and trying to "make it
safer". This has to be designed in from the beginning. If you had to pay
a suitably qualified person to fix someone else's mistakes, not only
would it be far more expensive overall, but they wouldn't be very
comfortable with not knowing what else may be lurking, that they didn't
find and correct. (You really need all of the design documents and a lot
of time to go over them.)

Ultimately you'd still have to pay thousands of dollars in testing if
you wanted to avoid committing a crime. I don't know if this always
applies to one person using their own gear that they imported, say a
phone charger that came here in hand luggage. But if we're talking about
an OEM component like an open frame power supply that you have to wire
up yourself, I don't think you'd be okay. I certainly wouldn't want to
be implicated in it by trying to "make it safer" for you.

There is an economy of scale in getting a model approved for sale and
then recouping that over hundreds of units, especially where that model
is already approved overseas. It's just not worth it for one unknown
unit.

Have a look in the Jaycar, Element 14, RS Components, Mouser, and
Digi-Key catalogues. All of their gear should be safe and reliable.

There is a reason that people usually use ATX power supplies. They are
much more affordable, and if you can buy it in a reputable local
computer shop, it ought to be reasonably safe to start with, even if you
decide to change the DC output wiring to suit your project.

Having said that, I've seen some pretty terrible things come out of
otherwise reputable places, so remember to spend the money on a good
brand, too.

Have fun,
Darren

[Stuart Young]

FWIW: Expect some crackdown on PSU's and USB-style chargers, as a woman in NSW appears to have been electrocuted by a cheap after-market laptop PSU (presumably) while wearing headphones.

Article: http://www.theage.com.au/nsw/warning-over-usb-chargers-after-woman-dies-from-apparent-electrocution-20140626-zsngd.html

Have fun,
Darren

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[Robert Powers]

Oh, that's terrible!

Anyone with an interest in the *very* nitty-gritty of electronics power design, particularly USB chargers and older ICs, should know about Ken Shirriff's blog: http://www.righto.com

He's done comparison teardowns and efficiency benchmarking on all sorts of consumer power supplies. This is just an example of his incredible work and very much highlights some of the points Darren was making about the shortcuts you'd be amazed (and terrified) to hear about: http://www.righto.com/2014/05/a-look-inside-ipad-chargers-pricey.html

Cheers,

Bob

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[Gareth Pye]

"People should also not use any electrical devices while they are plugged in and charging." - the Age article above

If that was sane advice laptops, tablets, etc would turn off when charging.

Also how would you ever put songs onto an iPod Shuffle? Hack up a USB cable without the +5V line?

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[Clifford Heath]

I sometimes think Darren is too cautious, but not this time. I also have personally torn down 2 cheap USB chargers, and 2 Apple made dongles (one mine, one donated to the cause of science)  :-).

The Apple stuff is quite simply a work of engineering beauty, with massive dedication - I even once  thought excessive - to long-term reliability. VGA connector with full metal trapezoidal case hand-soldered shut on all 12 edges,  enclosing all wiring up to the external strain relief, for example. I have several in daily use, often under significant stress, for upwards of three years, the only failure being one, at the 5 year mark. I will never again begrudge them the price of such quality. ASUS I have similar respect for, though slightly less.

The cheap USB devices OTOH, were not able to survive even one month of careful gentle usage at 240v, and although both filed safely, that was pure luck -  both had likely failure modes that could kill me.

Never again will I buy off-brand 240v devices. I was also going to mention the Gosford woman's death. If you can't afford to play this game safely, just stay away until you can. And that's advice from a die-hard risk taker.

Clifford Heath.

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[Luke Weston]

I have a Meanwell 24V SMPS module here that bears an Australian C-tick and TUV/UL/CE type approvals and conformance marks.
But people will often just buy the cheapest thing from some Chinese supplier, and at first glance the outer chassis probably looks quite similar, unless you're reading the tiny sticker or studying the quality of the internal electronics with a trained eye, and a more reputable vendor like Meanwell or Manson would be dismissed because it's economically uncompetitive with generic cheap junk. Price that is "too good to be true" for a system with a certain rated power output can be a good indicator.

And compliance marks can be largely meaningless, since shonky vendors can print whatever the hell they please on the label, it is about as well regulated as homeopathy in many cases. Sometimes the comical broken English is a give away, like the famous "Designed by Abble in California" and things like that, but sometimes they do a more professional job of copying the label of a real Apple (or whoever) power supply. Anything that tries to copy the product appearance of a well-known brand such as Apple is generally a dodgy sign, and there's usually dodgy engineering inside if they are dodgy enough to try it.

Unfortunately I don't think there's an Australian database for publicly looking up conformance numbers, like an Australian equivalent of looking up the FCC IDs on the website. There should be.

In the era of growing international e-commerce, the requirements that apply to products being sold by businesses in Australia for the quality/safety/approval of the products they sell are increasingly irrelevant.
Who regulates the quality or safety of a product sent into the country from an international seller? If anybody, it's a Customs job. And they don't have the resources to open every box and carefully study every electrical device to check whether it is up to scratch technically, and check whether any marks from testing/standards agencies are honest or fake.

Also, it's worth noting that a device such as a Meanwell open-frame SMPS, or similar, is not a consumer product ready to be on the shelves at Dick Smith the same way as a smartphone for example. The requirements and standards that apply to it are different to the requirements that apply to a consumer product such as a smartphone. It's a component, a part that is assembled into a larger product. Component parts such as power supply modules often carry certain levels of component certification from the various testing and standards labs and organisations such as TUV, UL, etc, and this is done because it can make it easier for the manufacturer using that component to perform the testing/certification/standards process for their entire assembled system when there is pre-testing of some parts and components - but it does not eliminate the need. It is still the responsibility of the people building and marketing the assembled consumer product to ensure appropriate testing/standards/certification for compliance with the markets where the product is sold.

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[Clifford Heath]

On 27 Jun 2014 12:35, "Gareth Pye" <gar...@cerberos.id.au> wrote:
> "People should also not use any electrical devices while they are plugged in and charging." - the Age article above

It should say, while charging from any mains adapter. Charging from a good computer's USB with branded power supply (not cheap ATX) adds enough layers of safety, even if the computer is on the mains - I believe.

Clifford Heath

[Darren Freeman]

On Fri, 2014-06-27 at 11:34 +1000, Stuart Young wrote:
> FWIW: Expect some crackdown on PSU's and USB-style chargers, as a
> woman in NSW appears to have been electrocuted by a cheap after-market
> laptop PSU (presumably) while wearing headphones.

The timing on this is just terrible. It's pretty much the exact scenario
that I thought was purely hypothetical yesterday.

An example of where it pays to think about the absolute worst case
scenario rather than a more likely one. (I mean, really, what are the
odds that you're wearing headphones at that moment when your PS blows
up? And that their insulation breaks down?)

Had we not received this chilling confirmation today, we could now go on
to debate the likelihood of this happening, the merits of saving money
while on a poor student's budget, etc. etc. Maybe some people would be
convinced that I'm just trying to scare people for the sake of it, or
that I'm deeply in love with government regulation. (I'm not.)

But some innocent person, who was probably never cautioned about
checking for compliance marks, has lost their life to prove a point.
That we have no effective regulatory system in place to prevent dodgy
products from entering this country, and that consumers have close to
zero understanding of the seriousness of the issue, and they don't know
how to perform even basic checks for themselves.

We have outsourced almost all manufacturing to places where people are
much more loose with safety, and all we have left is testing the
products for ourselves before selling them. But that costs money, and in
a competitive marketplace, those who spend money that others can avoid
spending, tend to go out of business first. Consumers have to demand
this or it won't happen.

So it is up to all of us to be vigilant in what we personally do, and to
pass on the message to those who trust our judgment. Because the
government appears too busy to be engaged in anything proactive, and I
don't want someone I know to die for this cause.

Darren

[Robert Powers]

Just following links from my earlier message, doesn't look to be an isolated case by any stretch:

http://news.xinhuanet.com/english/china/2013-07/14/c_132540098.htm

http://appleinsider.com/articles/13/11/27/thai-man-dies-after-alleged-electrocution-from-charging-iphone-4s-

http://appleinsider.com/articles/13/07/15/woman-dies-using-a-charging-iphone-5-apple-vows-to-aid-in-investigation

http://appleinsider.com/articles/13/07/19/chinese-man-reportedly-electrocuted-by-iphone-4-and-third-party-charger

Jeez'em-crow.

-Bob

Darren

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[Rob Gannon]

"People should also not use any electrical devices while they are plugged in and charging."

I've made sure my electrical devices are unplugged while I'm using them but my cup of tea is cold,  my toast is white and my microwave popcorn is very crunchy!

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[Luke Weston]

If the device is honestly double-insulated (i.e. within a plastic box without external connectors or exposed metal coming out) then it won't bite you, even if there is a breakdown between the mains side and the ELV side. (In fact, many consumer appliances like plug-in energy meters often use transformerless power supplies where there is no attempt at any galvanic isolation on the board at all.) Similarly, if a device has a metal case or exposed metal but this is connected to mains earth on a 3-pin plug then this won't bite you either, even if it becomes exposed to high voltage as a result of a creepage or component failure, and the current leak to earth will trip the RCD (which you really must have if you have a very old building which doesn't already have one installed.)

It's worth nothing that the dodgy phone chargers are dangerous because they have a 2-pin mains plug with no mains earth connection, and they have exposed external metal, i.e. the USB connector shell. This means that if the galvanic isolation breaks down (eg. due to dodgy transformer construction, or inappropriate PCB creepage distance) between the 340V side and the ELV side then 340V DC is potentially exposed on the metal connector shell where you can touch it. It shouldn't be in that state, and if that was rectified the product wouldn't kill people even if the low quality of the internal electronics was maintained as is.

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[Luke Weston]

The moral of the story is not to get your engineering advice from a politician.

And, just like with drugs, the politician's answer will probably just be "ban ban ban" without any education or anything else, which is not a completely good answer in and of itself, although regulation is of course likely to play a real part in a good overall answer.

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[Scott Penrose]

I have seen tear down of the cheap USB charges,showing the low voltage line a half mmm from the mains line ! 

My mum has had a shock from a cheap charger (which I had bought her) while using her phone plugged in. We obviously chucked it ! 

Scott

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[Darren Freeman]

On Fri, 2014-06-27 at 12:55 +1000, Clifford Heath wrote:
> I sometimes think Darren is too cautious, but not this time.

Only sometimes? :)

When I was younger, my default position used to be "why not? what's the
worst that can happen?"

I still love to void warranties (using thermite, if necessary).. so long
as nobody gets hurt.

Problem is, after a while, you accumulate enough near-misses to think
twice about it next time. And for others with less experience, it still
looks like "why not?". You're not the life of the party if you keep
telling people that there's a 0.1% chance they could lose an eye if they
keep having fun.

Maybe it's just part of growing older and wiser. (And sober.) But even a
small chance of a horrible outcome just doesn't seem worth it, when the
benefits are so small. Saving a few dollars is nothing. Your funeral
will cost thousands.

Darren

[Clifford Heath]

+1 on the RCD. No matter the failure it would have saved this lady.

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[Clifford Heath]

On 27 Jun 2014 13:26, "Darren Freeman" <dar...@freemaninstruments.com> wrote:

>... even a

> small chance of a horrible outcome just doesn't seem worth it, when the
> benefits are so small.

That's the same reason I'm participating in this discussion from a hospital bed this morning. No, no electrical devices were involved. Diagnosis of gout attack in right hand is now in doubt.

Clifford Heath

[James Denier]

Thanks for all the feedback guys. That's quite sad news regarding the posted deaths, especially since they're 'consumer-level' products as opposed to the hobby/DIY area most of us are working in at the moment. It just goes to show that even 'safe' or commercial goods are worth being mindful of and watching out for.

Darren, in one of your earlier posts you mentioned that an ATX supply isn't a terrible idea. If one were to go down that route, what changes are required to the unit to make it suitable? Various friends who build sensitive electronics have advised me to steer clear of ATX supplies as they can have voltage spikes (particularly on start-up) sufficient to wipe out sensitive microcontrollers (which is something I've seen discussed here on the CCHS lists). Are there aftermarket changes that are required/can be performed to help minimize or eliminate that, or is it a case of buying from a reputable brand and keeping your fingers crossed?

As you've said, you have supplies purchased from reputable Australian dealers that have still failed, it seems quite difficult to know where to start in avoiding bad quality and finding good.

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Earlier also it was mentioned that John and Michael have a hot-end on the way out. Does anyone have a rough timeframe for that? I would, as stated, much rather something locally produced and locally supported than to pick up something from who knows where and never hear from the supplier when it fails under normal operation.

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[Luke Weston]

"If one were to go down that route, what changes are required to the unit to make it suitable? Various friends who build sensitive electronics have advised me to steer clear of ATX supplies as they can have voltage spikes (particularly on start-up) sufficient to wipe out sensitive microcontrollers (which is something I've seen discussed here on the CCHS lists)."

I'm not really convinced that that's really true.

After all, there are millions of the things in use around the world, offices full of them, and the failure rate is sufficiently small for the market to accept it - even for the cheap generic ones.
And the PCs that are used in the thousands in offices and average home users don't generally use expensive UberNinjaSuperFragDragon10000Titanium power supplies, they just use the generic cheap ones that, whilst relatively crap, are good enough to run a PC motherboard with an acceptably minute probability of killing it. Your average AVR is less "sensitive" than a PC - but then again there's a lot of regulation that goes on on the PC motherboard to regulate the lower voltage rails that actually power the CPU and what not.

Something like a RAMPS gets its 5V rail from the PC, or via 12 regulated down in the regulator on the Arduino, so even though there are a hundred reasons why RAMPS is shit, you can't blame it for any issues with the 5V regulation - crappy design or component choices on a cheap fake Arduino are more likely to come into play here if the 5V rail isn't behaving itself.

An ATX power supply can be modified for higher output voltages, a little bit higher, but there's no one-size-fits-all recipe that can be documented, and it requires skill and patience to trace out where the appropriate circuits and components actually are on that brand, so it's not trivial to do. And it defeats the whole point of having a pre-built thing where you don't have to mess with any internal wiring that is potentially exposed to high voltages.

As long as the heating elements (particularly the bed heater) are set up with a resistance that performs well at 12V, I see no reason why an ATX power supply can't perform well, as long as the rest of the electronics in the system is sensible and isn't complete crap.

One of the issues is that many heated beds don't rapidly heat up at 12V, and there's no option to go to a higher voltage

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[Darren Freeman]

On Sun, 2014-06-29 at 18:09 +1000, James Denier wrote:
> Thanks for all the feedback guys. That's quite sad news regarding the
> posted deaths, especially since they're 'consumer-level' products as
> opposed to the hobby/DIY area most of us are working in at the moment.
> It just goes to show that even 'safe' or commercial goods are worth
> being mindful of and watching out for.

Commercial has rarely equalled "safe" in this country. Nobody is
enforcing the law until after you're dead, and you won't get much
satisfaction out of that because, well, you're dead. (Same goes for
dodgy medical products and services.)

Some businesses value their reputation enough to get it right, but when
you're buying from some guy in the middle of a shopping mall or a
computer fair, I don't think this is a factor. So let the buyer beware.

> Darren, in one of your earlier posts you mentioned that an ATX supply
> isn't a terrible idea. If one were to go down that route, what changes
> are required to the unit to make it suitable? Various friends who
> build sensitive electronics have advised me to steer clear of ATX
> supplies as they can have voltage spikes (particularly on start-up)
> sufficient to wipe out sensitive microcontrollers (which is something
> I've seen discussed here on the CCHS lists). Are there aftermarket
> changes that are required/can be performed to help minimize or
> eliminate that, or is it a case of buying from a reputable brand and
> keeping your fingers crossed?

The "voltage spike" thing hasn't been true in my experience. I mean,
seriously, they power a computer. Computers tend to notice getting blown
up. And in this application, your microcontroller is fed from a linear
regulator that is fed from the ATX, so it's just not an issue. We've all
done it at some point and it works just fine.

But there are shocking ATX power supplies out there. (See what I did
there?) So it has to be a decent one. Ask yourself, "would I be happy
installing this in my brand new $2,000 gaming machine?" The one in my PC
wasn't very expensive, but it came with a 5 year warranty. That's
probably a good sign :)

Bear in mind that a basic ATX power supply doesn't independently
regulate the different outputs. It takes the average and regulates that.
So, you pull rated current from 12 V and nothing from 5 V, and you find
that 5 V has gone up to 7 V, and 12 V has gone down to 11 V or even 10
V. You have to seriously consider whether <11 V is fine for what you're
doing. For smaller printers like the Cupcake, or those without heated
beds, it's fine. It's not that bad if you're pulling a half or quarter
of rated load, as it droops as though there were a resistor in series
with the output. (Less current = less droop.)

There's nothing stopping you from finding or making a heated bed that
likes to run from 11 V (minus losses in your wiring and switching
circuitry), but if you're using the more-or-less standard Prusa style
PCB heated bed from Random Ebay Seller #372, you might need more than
that to get up to ABS temperatures. (It's a bit of a lottery depending
on the thickness of copper on the PCB, and the actual track widths.) But
if you're using PLA, again you're probably fine at 11 V.

So there's that. A basic ATX will give you about 10-11 V fully loaded,
although you can probably find a seriously nice and expensive one that's
got all outputs independently regulated. But before you fork out the
money, take a trip to a computer recycler and see if you can get a
s/hand server power supply. Look at the one on the printer in the space.
Just one 12 V output, so properly regulated.

As you get more advanced in your tinkerings, you'll probably want to
follow John B's advice and move to 18 V or 24 V. (Or you could do that
first, but..) I don't know of an affordable off-the-shelf option at this
voltage, so you'll just have to spend the money. Someone once asked if
you could wire them in series, and no, you can't. The black wires are
grounded, and it's not safe to try to change that.

In terms of after-market changes, anything that requires you to open it
up is going to require a certain level of competence around mains
voltages. Make sure you have it, or can get someone to help you. Most
commonly, people cut off the unwanted output wires, and replace the ten
or so remaining wires with just a couple of much heavier ones. So from
the outside, you just have two, plus the one that turns it on, if you
don't want it always on.

But even though this sounds simple, I've seen somebody do it in a way
that broke off a ground wire and left the whole chassis live. You're not
just working in one corner of the supply, you're working on all of it,
and you have to know what you're doing and properly test it afterwards.

Also be aware that these supplies don't have much, or any, strain relief
on the output wires. (These wires are internal to the computer, and
don't get yanked on.) If you're using it as a bench-top supply, make
sure you fasten the wires to the chassis somehow.

> As you've said, you have supplies purchased from reputable Australian
> dealers that have still failed, it seems quite difficult to know where
> to start in avoiding bad quality and finding good.

They didn't just fail, they failed spectacularly. They failed at the
design stage. They should never have been made, let alone sold. And,
very importantly, they don't have any approval markings to show that
they were ever legal to sell.

So I think the take-home message is, don't take it out of the shop
unless it's got an A-tick, a C-tick, or an RCM. And since these can be
faked, also don't buy it from some guy in a shopping mall, or on eBay.

And remember, if you import it, you're responsible for a whole lot of
testing and certification. Let's see what kind of penalties are given to
the dodgy sellers in Sydney who killed an innocent young mother.

Have fun,
Darren

[Rob Gannon]

If you use an ATX power supply make sure it is high enough output.  The average pc has a 300watt power supply which will struggle to heat your bed so go for at least 500 watt.

You need to connect the green wire to a black wire to turn it on.
You need to put a big resistor across the 5 volt, so the red and black,  which will stop the voltage drop across the 12 volt. Make sure you have a big heat sink on the resistor because it will get hot (I have the burn on my kitchen table to prove it).
There will usually be two 12 volt circuits (yellow),  one with more current than the other.  If you are using RAMPS as your electronics there are separate 12 volt inputs for the bed: 11amp minimum and for everything else 5amp minimum, so connect the higher current output to the higher current input.
Do all that and then apart from not being as neat as other options it will work fine.

Rob.

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[Gareth Pye]

On Mon, Jun 30, 2014 at 7:26 AM, Rob Gannon <robga...@gmail.com> wrote:

You need to put a big resistor across the 5 volt, so the red and black,  which will stop the voltage drop across the 12 volt. Make sure you have a big heat sink on the resistor because it will get hot (I have the burn on my kitchen table to prove it).

Am I nuts for thinking it'd be a good idea to use both 5v and 12v for the print bed heater? I know the efficiency of the 5V side would be low due to voltage dropped controlling it, but still better than dumping the power into something not used at all.

[Darren Freeman]

On Thu, 2014-06-26 at 16:07 +1000, Darren Freeman wrote:
> On the one hand, you can buy a lab supply that meets the Australian
> standards, is safe to use, and is reliable. But these tend to run up to
> (and over) $300 depending on power output.

> And even though the local supplier is legally required to ensure that
> they meet the standards, this is sometimes not the case. I have some
> dead units that were supplied in Australia by a reputable store, even
> though they didn't meet the standard. (They are no longer available for
> sale.) The mains voltage literally flashed over to the DC output and
> blew tracks off the board, probably during a voltage spike.

Well, I've discussed this with the general manager of the original
supplier of these units. What he said was - bench power supplies are not
prescribed articles, they are not required to be tested/certified, and
they are not required to meet any standards.

I think this is probably not correct, but I'm not a lawyer. I can say
that an engineer from Energy Safe Victoria just told me that all
equipment is required to be electrically safe, by complying with the
relevant standards. As for whether these units have to be certified,
that comes down to the exact wording of the regulation, and you could
argue either way.

In conclusion, these units were sold a long time ago, are not for sale
any more, and the supplier doesn't see it as an issue they'd like to
address. I suggested that they initiate a voluntary recall, but they
have decided not to.

I asked if it would be okay for me to post a warning to people who still
have these units, and he said that he "couldn't stop me" so long as it's
factual and it doesn't make any claims like such-and-such doesn't meet
the standards.

I'll post a reference to this list when I get it done.

Have fun,
Darren