ramps 1.4 wiring + psu

hi,

I would like to know which power supply I can use for the ramps 1.4 electronics.

I do plan to use a heated bed.
According to the wiki, I will need 5 + 11 A.

I found the SNT MW200-12 from MEANWELL for ~40€

It does 12 V and 16.7 A. Now I wonder if .7 A overhead is big enough if some peaks occur.

How much more than the bare minimum of 16 A should the psu be capable of?
What other psu would you recommend?

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The cables of my stepper motors are wrong.
Red and blue are swapped in the connector.

Would this also work? The connectors came wired up and I wonder why they are wrong.

Thanks for your help

Go for a 30A power supply -16.7A is totally inadequate.

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Waitaki 3D Printer

Ok, would you recommend one of those standardised switchmde psu or a ATX psu?

I'm not sure where the 5amp comes from, I've read it as well, but if you ask me, it's wrong. Or only applies to the Ramps board.
Steppers are rated at 1.2amp+, however you don't want them over about 1amp, 4 amps total.
Then you have the hot end, a resister uses almost 3.3amps and a cartridge I have been told is actually closer to 5 amps.
Then you have fans, which are about .3amps each.

Not everything runs at the same time, which explains how some people get away with only a 5amp power supply. However, Many people have unexplained glitches and this may be a part of it. I'm looking into my own power system for that reason.

Beds are also a bit optimistic at times in terms of power. I've seen GOOD 10 amp power supplies cut out on "10amp" beds.

Typically, you want your psu to be at least 20% more than you need, however in this case, since not everything runs all the time, maybe 10% is okay. If it's a Chinese power supply, add at least another 20% since they tend to exaggerate their capabilities.

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m
Ok, would you recommend one of those standardised switchmde psu or a ATX psu?

mmm, my personal choice would be an ATX.

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Waitaki 3D Printer

My personal choice would be Server PSU or a quality 30A unit. Stay away from ATX. However if you must do ATX, look up the latest corei7 specs for PSU and get an ATX psu that adheres to intel standard.

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Modicum V1 sold on e-bay user jaguarking11

What's the problem with ATX?
Why would I want a psu that adheres to intel standard?

To me, getting a server grade psu for a couple of stepper motors seems to be excessive and expensive.
Please elaborate on that.

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I'm still stuck as I'm not sure if the wiring of my motor cables should be changed or not.

Edited 2 time(s). Last edit at 07/01/2014 12:20PM by m.

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m
What's the problem with ATX?
Why would I want a psu that adheres to intel standard?

There are many threads about converting ATX power supplies for other uses, experiences with poor voltage regulation without base loads, etc. Here's one sample:

http://reprap.org/wiki/ATX#Base_Load

I have a nice, beefy ATX power supply that came out of a genuine IBM-branded "workstation" PC. It works fine, but the +12V rails are more like +11.3V rails even unloaded. Hence, the general advice to buy a better power supply (and not ATX) if purchasing new.....

So unless I want to brag about how accurately my psu can supply 12V, I'll be fine with an ATX.
Getting my printer together becomes increasingly tedious with contrary answers in this forum. =(

Any ideas on the motor cables?

Edited 1 time(s). Last edit at 07/01/2014 09:14PM by m.

Why do you ask if the wiki tells you the answer already? And if I answer the motor cabling question, will you add this to the wiki page?

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Well, the wiki also tells me that 16A are sufficient.
I think this thread proved so far that blindly following the wiki does not seem to be a good idea.

I'll add your information to the wiki. No problem.

@ Traumflug: If I add it to the wiki page, will you provide the information?

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m
So unless I want to brag about how accurately my psu can supply 12V, I'll be fine with an ATX.
Getting my printer together becomes increasingly tedious with contrary answers in this forum. =(

Any ideas on the motor cables?

You do realize voltage fluctuation can and will cause problems with movement and possible missed steps. Not to mention that if your psu droops to lets say 10v or so it will take ages for the heated bed to warm up. In any electronics, especially time sensitive electronics where real-time processing is being done noise in the power feed will cause issues. I said look for the latest intel standards because the newer generation psu's are designed to have primary load on the 12v rail vs the 5v or the 3.3v rail that the older units used, reducing the amount of resistance necessary to get them to operate within specs. Newer motherboards regulate voltage from down from 12v instead of 5v.... As for cost, I would rather buy a used psu from a server for $20bux shipped to my door than a new ATX psu.

Personally I feel that power delivery is way undervalued when considering these printer builds. People are reporting that they have had failed prints because they turned on their microwave that was in the same circuit because the cheap 30amp psu they bought from china drooped. A quality psu should be able to deal with those voltage droops on the input and still deliver the required voltage on the output.

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Modicum V1 sold on e-bay user jaguarking11

Biggest issue with generic PC power supplies is that manufacturers tend to over-state the current limits that they are capable of, even the big-names in the Gaming PC after-market have been known to do it. eg: A PSU might be capable of providing 20A on 12V, but only if it's drawing 1A on the 5V rail at the same time, and ONLY if it's on clean power.

Server power supplies usually work regardless of the load on other rails, and usually have a wide tolerance on their input voltages. Additionally, they usually don't have extra circuitry to generate rarely used voltages that are part of the ATX spec (such as -5V and -12V).

eg: An ex-IBM server AcBel brand PSU I have generates 12.2V @ 48A max and 5V @ 0.2A max ONLY - no other voltages. I've tested it and it definitely is capable of the amounts it claims.

Thanks for the information.
I got a tip from a friend who bought a reasonable priced switch mode supply that does 25A.

Now there's still the probably wrong wiring.

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Cefiar
Biggest issue with generic PC power supplies is that manufacturers tend to over-state the current limits that they are capable of, even the big-names in the Gaming PC after-market have been known to do it. eg: A PSU might be capable of providing 20A on 12V, but only if it's drawing 1A on the 5V rail at the same time, and ONLY if it's on clean power.

Server power supplies usually work regardless of the load on other rails, and usually have a wide tolerance on their input voltages. Additionally, they usually don't have extra circuitry to generate rarely used voltages that are part of the ATX spec (such as -5V and -12V).

eg: An ex-IBM server AcBel brand PSU I have generates 12.2V @ 48A max and 5V @ 0.2A max ONLY - no other voltages. I've tested it and it definitely is capable of the amounts it claims.

Not only are they capable of delivering said voltages and amperage, but they do it regardless if the wall socket is putting out dirty power or not. They do it for much longer periods of time with no thermal breakdown and they usually are under represented. Some of these units that are capabale of putting lets say 100amps @ 12v on a 220 line will hold over 110Amps nearly definitely. Most people do not know how harsh a data-center is compared to normal conditions, its susceptible to wild fluctuations in temperature as well as voltage and power quality. Some of these servers are running for years with their psu's at over 80c..... I had servers under my watch that were averaging nearly 100% cpu utilization for 6months +, believe you me a company will not put up with any server that has poor grade hardware as they will end the contract with the manufacturer quickly. IBM/HP are the very top of the heap when it comes to server stability in high workload environments, they would loose their shirt if their PSU's failed as often as ATX psu would fail under such conditions. Remember most of these environments have service contracts that last 5 years. IBM/HP is not interested in sending out staff out there every week at 200-1000bux a pop just for labor. A typical pc even a gaming rig spends its life in a fairly thermally stable environment as well as probably spends about 90-95% of its time idling, in the field I used to work in a server spends at least 40% of its time under full load, some are doing 95% of their time at full load due to the polling that is constantly happening when you want to send out low latency data around the globe.

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Modicum V1 sold on e-bay user jaguarking11

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jaguarking11
IBM/HP is not interested in sending out staff out there every week at 200-1000bux a pop just for labor.

Sounds like you are buying cheap servers. Every IBM server (and network switch, SAN, and similar rackmount equipment) that I've purchased in the past 25+ years has been configured with dual hot-swappable power supplies. When one fails, they FedEx out a replacement because it is a 15-second swap that they expect the customer to perform. To IBM's credit, I have only had one server power supply ever fail, and it was a crappy tower box that should have been labeled as a desktop.....

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vreihen

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jaguarking11
IBM/HP is not interested in sending out staff out there every week at 200-1000bux a pop just for labor.

Sounds like you are buying cheap servers. Every IBM server (and network switch, SAN, and similar rackmount equipment) that I've purchased in the past 25+ years has been configured with dual hot-swappable power supplies. When one fails, they FedEx out a replacement because it is a 15-second swap that they expect the customer to perform. To IBM's credit, I have only had one server power supply ever fail, and it was a crappy tower box that should have been labeled as a desktop.....

Most of the places I have worked for have either used colo or had huge datacenters (3 football fields worth in one case) They have no interest in paying anyone to man the environment. They use ILO/IMM to manage the servers remotely. When you have 3000+ servers, some sitting in a datacenter 2000miles away your going to have some issues at least once every two weeks. However the support contract with either one of those companies guarantees a certain amount of service. IE sla less than 6 hours from dead to operational. With HP we had a 4 hour turn around from dead to working, I have seen HP bring in a brand new server to replace an old machine, they dumped bios settings and swapped the disks over to the new box. They took the old box to analyse in lab due to the high service rate they had on it, it was worth over 100K at the time, custom 16GB dimms in it at the time, totaling somewhere in 1/2 terabyte of ram. With IBM however I can say that the xseries servers are great, as long as you don't move them or breathe on them. You look at them wrong and they will throw IMI errors, however most of the time those IMI errors were cleared on reboot, I suspect chassis rigidity was subpar on that generation of xseries servers. I can't say I have been in the field for 25 years, however I have been around the block once or twice.....

As for buying the servers. I do not buy servers. I manage them and their software, I build and maintain the health of the app and the os in the environment. I could care less what is going on with the hardware. If it does not work I fail over to another box. However in one of the smaller places I had to call in for support quite often. Having said that, I can say that psu issues are rare and far and few in between. Mostly disk/ram/mainboard goes dead at least 3 times before any PSU needed to be replaced. Hence why I chose to use one as they are proven.

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Modicum V1 sold on e-bay user jaguarking11

BTW: The IBM PSU I was referencing above is one of two that are actually in each server. They're both identical and you can run them independent easily. From what I understand, it's also possible to run them off completely different voltage levels (eg: one PSU @ 110V, the other @ 240V), as long as they support it.

What you say is very true about those PSU's in regard to dirty power. Also, many (not all) support DC input as well as AC (eg: The one I have supports 100-127VAC, 200-240VAC and 140-224VDC), which means if you've got a large DC battery bank (eg: for a large UPS or solar setup), you can run these direct off DC and totally avoid DC->AC conversion losses.

I know a few people that have been using server supplies like these to power 12V low-voltage lighting (halogen/LED) around their home, by using these supplies to down-convert the ~200V DC battery pack out of their solar setup, as they're simply more efficient (which means longer run-time).