PC hardware to run LinxCNC

Hello everyone,

I am finally in the process of assembling the bits and pieces that I acquired a few years ago the make a control box for my TAIG mill (see list below for components), and am trying to work out what a maximum sensible PC hardware selection might be given that the minimum requirements - and trying to buy them - for LinuxCNC seem to have been long-superseded. During the period that the CNC project was on hold, the linux box that was to run the control unit croaked (when the CPU daughterboard fell out of its slot).

I may be being overly cautious, but I don't want to fork out for some new hardware to find that the machine won't even pass the latency test. From my reading around the net, the following appear to be the things to watch out for:
CPU;
mainboard/chipset;
display adpater (embedded or otherwise)
Parport card controller

I've been searching for a list of probably-OK hardware items, but have only found the odd thing scattered through various forums - apart from the averred minimum, of course.

I can salvage the parport card from the defunct PC, along with case, PS, NIC, eSata card and HD, so I really only need mainboard with PCI slots, RAM, and display card.

Does anyone have any suggestions?

Here's my list of control box electronics, etc.:

Jaycar toroidal transformer 50V+50V 500 VA;
4 x "Vexta" PK268-01A 240/191 oz.in 6-wire NEMA23-spec stepper motors;
4 x Gecko 230V stepper drives;
Jaycar emergency power off (E-Stop) switch for cutting power to the Gecko drives;
Campbell Design's "Sound Logic Combo rev. 5" driver breakout board;
LED drive-status indicator daughterboard for Sound Logic breakout board;
PMDX-135-8020 PCB-456B "Power Prep Module";
PMDX-120 parallel-port test board for motors, drivers, etc. (PC not required for this particular item).

I will be very grateful for any advice.

Cheers,
Alex.

Hi
The D525MW Intel Atom board gets the vote of most people who have tried it.

www.linuxcnc.org/index.php/english/compo...imit=6&start=6#17727

It is small enough to build into a control box, low wattage, with a SSD almost completely silent and fast.
There is a PCI slot for either a parport card or Mesa IO card and latency is sub 10K.

Best of all it is cheap

regards

Hi ArcEye,

Many thanks for your suggestion: that sounds exactly what I need! I shall do some digging .

Cheers,
Alex.

As noted in other responses, there are boards based on the Intel ATOM pricessor that work perfectly. This is funny, really. All new Intel x86 processors except the ATOM are basically too good (i.e. too feature-rich) for LinuxCNC. but the ATOM accidentally works perfectly. (Well, almost perfectly: you do need to constrain Linux to using only one of the two CPU cores: this lets LinuxCNC use the other core by itself.)

You can build a computer around the ATOM motherboard. I will do this if my ancient Dell GX280 dies. My "perfect LinuxCNC computer" will be an ATOM mobo with an external power brick and a LAN connection, with no KVM and no disk. This system uses so little power that it does not need a fan and can therefore be sealed into the base of my machine, avoiding dust problems. My solution will cost about $200. I will use VNC or some other remote sreen system to control the computer from my "real" computer.

If you just want to get running and prefer to spend your time on machining instead of building a computer, you might want to consider the computer from Probotix. It costs about $265. They intend it for use with their CNC machines, and it ships with LinuxCNC installed. I seriously doubt that they intend for their computer to bre used for non-Probotix CNC machines, so they are not likely to be tremencously helpful if you have a strange problem, but they are good folks and will at least know what LinuxCNC is if you contact them.

For me: I bought a refurbished Dell GX280 for $100 from Tigerdirect. (Actually, I bought a GX260, but they shipped a GX280.) This machine just works for LinuxCNC. It's too big, and too hot. It has a fan, and will eventually die due to dust inhalation in the shop, but it just works.

BigJohnT wrote:

Once you find the D525 (hint newegg.com) working from that to the machine take a look at

Mesa 5i25/7i76 combo pci controller card and stepper interface card
Gecko 203v's or 251's depending on your power requirements.
Antek power supply if you want toroidal
www.kelinginc.net/ has geckos at a discount as well as power supplies. When looking at a power supply you want both stepper drive power 50-80vdc depending on needs and field power 24vdc and the Antek supply has that. Looks like keling also sells Antek power supplies so you might save some shipping if the price is the same.
An estop is nice to have!

John

Hi John - and everyone else,

I live in Sydney Australia so getting stuff from the US is prohibitively expensive on account of horrendous postage fees - even USPS. The exceptions are of course where things can't be sourced locally, like the Mesa cards. The kelinginc site was very informative, however, and has given me some stuff to think about.

Finding the Atom board is a bit tricky here too as production appears to have been halted ("due to lack of demand" according to the Wikipedia article on Atom processors ), although I have tracked down a supplier who does have them in stock.

As to driver power, the toroid transformer/PMDX-135 should give me filtered unregulated 70Vdc (50V * 1.4) on the Gecko side - I have 4 203Vs in hand. The Campbell "Sound Logic" BOB (made by James Cullen) takes mains 240V fed into its own onboard transformer to give 24V/12V/5V and has 4 drive connections, 4 home/limit connectors and 4 relays onboard (it also does spindle control but I will cross that bridge when I come to it: the TAIG mill currently has a Sherline motor/var-speed box on it). The Campbell/James Cullen board also has an E-stop connector. I am, however, digging about for a slightly higher output voltage toroid - the 50V that I have was the biggest that I could find locally - and kelinginc may yet get some custom form me .

As the Campbell/Cullen board has the drive signal outputs, I won't need the Mesa 7i76 - or at least not at the moment!

Finding PSUs for the Atom in this country is likewise a bit difficult, the main problem finding one whose specs explicitly state that they have 2x12 + 2x2 12V power connecters (since the Atom CPU apparently requires its own 2x2 connector). I have found a few psus that claim to be "SFX"-type, but unless I can actually view the connectors I'm not coughing up for one!

So I've now got something of a shopping list:
1 x BOXD525MW;
2 x 2 GB SO-DIMM3s;
1 x SDD drive;
1 x Mesa 5i25;
1 x psu for Atom board;
1 x 80Vdc toroid (possibly);
1 x 2-PCI riser board in case I need to nuke the onboard video.

The most critical of these is the Atom board as they appear to be in short supply: I can acquire the other bits and pieces at my leisure.

For reference, here's a link to my collection of hardware on my Flickr account. Also one of the TAIG mill/motor setup as it current stands (or sits). The entire "CNC conversion set is here but this set is mostly involving flanging up of a 4th axis device for the mill, from a design by Tony Jeffree which appeared in "Model Engineer's Workshop" magazine some years ago.

Cheers,
Alex.

arch dude wrote:

As noted in other responses, there are boards based on the Intel ATOM pricessor that work perfectly. This is funny, really. All new Intel x86 processors except the ATOM are basically too good (i.e. too feature-rich) for LinuxCNC. but the ATOM accidentally works perfectly. (Well, almost perfectly: you do need to constrain Linux to using only one of the two CPU cores: this lets LinuxCNC use the other core by itself.)

You can build a computer around the ATOM motherboard. I will do this if my ancient Dell GX280 dies. My "perfect LinuxCNC computer" will be an ATOM mobo with an external power brick and a LAN connection, with no KVM and no disk. This system uses so little power that it does not need a fan and can therefore be sealed into the base of my machine, avoiding dust problems. My solution will cost about $200. I will use VNC or some other remote sreen system to control the computer from my "real" computer.

If you just want to get running and prefer to spend your time on machining instead of building a computer, you might want to consider the computer from Probotix. It costs about $265. They intend it for use with their CNC machines, and it ships with LinuxCNC installed. I seriously doubt that they intend for their computer to bre used for non-Probotix CNC machines, so they are not likely to be tremencously helpful if you have a strange problem, but they are good folks and will at least know what LinuxCNC is if you contact them.

For me: I bought a refurbished Dell GX280 for $100 from Tigerdirect. (Actually, I bought a GX260, but they shipped a GX280.) This machine just works for LinuxCNC. It's too big, and too hot. It has a fan, and will eventually die due to dust inhalation in the shop, but it just works.

Hi arch_dude,

Thanks for our input . It certainly looks as though the Atom board is the way to go, especially in the light of, e.g., a secondhand machine being an unknown quantity (this was one of my considered options but it is looking less and less likely). I have a workshop dust problem too, even with a filtration unit, and I've been considering a filtered fan unit for the box, even though they care a bit pricey.

Since I have yet to build the control box, acquiring a simple Atom board is more appealing than coughing up for a Probotix solution given freight charges to Oz, etc., (see my reply to BigJohnT above), but thanks for the idea.

Cheers,
Alex.

Hi John,

I meant to put in where I was from in my initial post, but got distracted and forgot . My apologies!

I'm inclined to use Campbell board since I have it already, although i can't remember what I paid for it; however, five or so years ago the $Oz was a lot lower wrt the $US than it is currently (that appears to be changing again, though).

I did in fact order a BOX525DW from a crowd here in Sydney this afternoon, for AU$90 + postage, having been seduced by the idea of having the computer in the same box as the CNC controls - and had in fact been recenlty, albeit vaguely toying with the idea of doing just that, although I didn't then quite know how I was going to go about. Thanks to you people, I now do .

That just leaves a few things like memory and psu that I will take my time over. Likewise, i'll read throughthe 5i25's manual, which I downloaded from Mesa's website and have a bit of a think. My current impression is that it might be better at handling sigal timing than the onboard lpt1, but I could be wrong there.

Cheers,
Alex.