Mesa 7i92 Installation, considering old ATX psu for I/O voltage source...

Hello all, and greetings from the USA. This week I finally got a working plan sorted out for a 4Axis desktop mill build after spending alot of time combing thru several data sources accross the web (primarily linuxcnc, much thanks for the years of good contributions from the folks here, this site has been very helpful). So, I will try to get to the point of this post and list the general harware information I have already got on hand then state what my current questions pertain to, and also I will note some additional build information to provide a better idea of the direction I intend to head with this project.

Hardware on hand:
Pc: Older Dell Vostro with intel i3cpu (quad-core), 4GB ram (generic matched set), native graphics, onboard ethernet port reserved for the Mesa OS: Fresh working install of Linuxcnc uspace(Debian Bookworm)
I/O: Mesa 7i92, 7i84, 7i85S (haven't connected any of these yet, but I do have cables)
PSU for I/O? Couple of different older ATX style computer PSU's, atypical 3.3v, 5v, and 12v outputs.

Hardware currently on the buylist:
Mill: Taig(Peatol) 5019 CNC ready with 5tpi ballscrews and extended bed
4thAxis: Sherline Rotary Table
Steppers: Presumably going to use the stock Taig(Lin Eng.?)DSLS 200oz-in steppers with encoders, probably around 4mH rating
Stepper Controllers: Either going to run Gecko G540 or G214s depending on what exact steppers I am able to source
Stepper PSU: Meanwell 1600w 110v/220v AC input, 48v-65v DC output. (again, the exact model depends on the stepper selection and Geck req.)

Alright, I believe that should cover most of the basic harware involved. A few items to note about the above listed hardware; As per the suggestions I noticed on the wiki and the forum I did go thru my bios bootmenu and turned off just about all the intel nonsense that was optional, I havent quite gotten deep enough into my config files or hal yet to really tune other settings as I only just got my Mesa cards a couple days ago. Currently I believe the cpu is still running on all 4 CORES but when I ran the base jitter tests they didn't look too bad ~26,000 max under moderate task loading if I really need to shut down to 1 core I will but wanted to ask for a little more clarity on why before doing so.
Mesa notes; I am hoping to utilize a G540 so I went for the 7i92f to have a more commonly implemented configuration there considering they were out of the 7i76 series when I looked. To support the encoders and additional I/O I picked up a 7i84 and 7i85S. I realize these two may require some hal work to get everything to play nice, but in light of availability this looked like a reasonable starting point.
Stepper notes; I am currently trying to get information from a couple of US retailers of TAIG equipment to see what options the have available without buying their control hardware/software as a package deal...(most of the taig controllers seem to perform rather poorly and are mach3/4 dependent). Hopefully, I can get a set of their 200oz/in DSLS steppers with encoders to be able to run a closed loop system, but I am not holding my breathe with current availabillity issues being what they are in that market here. I may have to outsource a different supplier for a 260oz/in low impedence dual shaft motor and figure out where in the blazes I can get an encoder from to tie it back into linuxcnc...

Main question at this time: I have a couple ATX psu's on hand I would like to repurpose IF they would be a good power source to drive various I/O thru the Mesa Cards, but a few hours of searching for clear information on the matter, I didn't have much luck. Biggest questions regarding that point being; would that power supply be a clean/stable power source that would work well with the mesa cards? This would be my first time repurposing one of these so is there any sense wires or psu regulation behaviour I should expect? And finally, just to get the mesa cards configured, would the ethernet line to the 7i92 be adequate to supply the other 2 cards until I start connection I/O lines, or would something like a split usb cable be a good choice from an extra motherboard port until I sort out my stepper motors and order a Meanwell for their drivers...

Sorry for the long-winded post, I seem to be compelled to be too thorough at times...

Sorry for the bad indentation/wraparound text on the first post, didn't realize the text input window was formatted at a wider width than the main forum. I tried to go back into that post and edit to adjust the spacing so it would be easier to follow, but other formatting started getting a little buggy so I cancelled the edit before it got worse... I will note the page width difference and try to keep things a little cleaner with that in mind next time.

Yes, you can use ATX power supplies for IO, and yes, a 1600W power supply for what you intend to use it is way to much, wayyyyy to much, i am sure you can get away with a 400W one, so get a 500W. Granted that same power supply is not going to also supply the spindle. For G540 even 200W is enough.
From experience, for G540 get the 36V, for G214 get the 48V.
To long to explain why.
And definitely, 4mH is to much inductance that will greatly limit the speed of the machine, get something under 2mH or thereabouts.
If you can afford it, get the LAM Technologies drives, in Germany they can be often found at a discount costing less than gecko, www.mechapro.de/shop/Schrittmotor-Steuer...ehaeuse:::22_49.html
I always get the DS1044 and DS1076. And do not forget the programmer at the bottom of that page for 28 Euro.

Thanks for the input on the ATX supply, I will start setting that up tomorrow when I go back out to my desktop.

I was aware the G540 is fused at something like 6A internally, guess I fudged the amp calc and accidentally
multiplied each axis by a transposed 5A figure when I was doing rough estimates, (720w just for 3Axis, lol)...

Main reason for the higher voltage on the psu is to be able to turn up my feedrates substantially to
make use of the ballscrews. I do really want to find some sub 2mH steppers (i did find some nice
german steppers under 1mH, but special order only...) but I was having a very hard time finding any
in stock over here with documentation and a dual shaft setup for encoders. So, it was looking
like I may need to run something like a common 4mH which would require alot of Volts to get
any appreciable rapids or torque, and with that higher impedance the G214 would come into play.
Do you think it is worth waiting on a 6week lead time to get a 1mH stepper? I really want to have
this thing running by about that time, and some lead times are 4months from now, hard to justify.

Are those german drivers similar to the ones kollmorgen markets? I had happened to notice
something about a programmer for theirs too but they didn't have alot of Amperage overhead
until you moved into the bigger industrial models and those looked REALLY expensive...
In any case, I will look into those drivers, 28euros on a programmer doesn't sound that bad if the
drivers don't add up to more than around 500euros...

Ok, so I just had a look at the mechapro site and it looks like the LAM drivers are completely different from
the ones I had noticed on the kellmorgen pdf. Probably a good thing tho, the smaller kellmorgen drivers were
more similar to the gecko and their larger ones were probably very pricey.


The LAM DS1076 does look like a higher quality unit compared to a gecko G214, now I have just got to get
my hands on some steppers to know what my supply voltage needs are going to be there...


Just to clarify for anybody reading from this point on, the 36V and 48V power supply's referenced in the last
few posts are referring to what I am going to power my STEPPER DRIVERS with, the ATX psu I primarily
started this thread to discuss is for 3.3V, 5V and possibly also 12V for other various I/O applications thru
the Mesa boards.

LAM Technologies specifies the nominal current for their drives so a 4A drive will do 5.6A peak, in practice setting one to 2A and wiring a china 2A motor will cook the motor pretty fast, some, some will be OK.
I have some set to 2A on Japanese 2.4A motors, they are hapilly working for several years.
As for power supplies, for servo systems you do need a bit more than the total drive/motor current/power, not with steppers, might have noticed the stepper voltage ratings are pretty low, single digit low.
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Did you consider getting the closed loop stppers/drives? Some can be found for nearly the same price as LAM with a good motor. No idea how good they are, but from reading here they are OK. But closed loop on drive only.
LAM have a nice feature called Boost, it can be programed to raise or to lower the current while working, so can be used to push more current while accelerating and less while at constant speed, or can be use to push more current when skipped steps/missed possition is detected when using encoders and loop closed in LinuxCNC.
Probably not helping much with all the options