Best Computer for LinuxCNC and Connecting to Stepper Drivers

Discussion of linuxCNC (formerly knows as EMC2)
levlandau2
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Best Computer for LinuxCNC and Connecting to Stepper Drivers

Post by levlandau2 » Tue Sep 25, 2012 5:08 pm

Hello,

After much success with GRBL, I want to try LinuxCNC. I have seen Edward using a Dell D620 type laptop for running it. Is this ok to use, or do I need a Desktop? I am looking for "known good" computers, that I can buy cheap used on Ebay.

I know I need a parallel port, but was wondering if there were any other critical requirements for the PC..?

Also, is there a guide somewhere on how to connect LinuxCNC to the Buildlog stepper shield???

Thanks much.

levlandau2
Posts: 187
Joined: Tue Apr 17, 2012 1:52 am
Location: Minneapolis, MN, USA

Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by levlandau2 » Tue Sep 25, 2012 5:16 pm

I have an old Dell C600 laptop (700 Mhz Pentium III, 512 MB RAM) which I could try using, but am thinking that it would be too crappy and cause performance problems, so any guidance is appreciated. Probably better to use something more newer and robust....?

edwardrford
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Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by edwardrford » Tue Sep 25, 2012 5:54 pm

Because you already have it in your posession, and the C600 has a built in LPT, I say go for it! Download the iso, boot from CD-ROM, install linux CNC 2.5.x, and give it a spin! Can't hurt anything.

My guess is that the C600 will work, but may take a while to both boot up and Load linuxcnc. Although, once loaded you could always turn off toolpath visualization and use the simple DRO screen to save resources.

-Edward
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

levlandau2
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Location: Minneapolis, MN, USA

Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by levlandau2 » Tue Sep 25, 2012 6:00 pm

Ok, I will try that. I was kinda worried about using it since the LinuxCNC documentation says that laptops are notoriously bad for the real-time kernel....

So what would be the symptoms of the computer being too slow??

edwardrford
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Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by edwardrford » Tue Sep 25, 2012 8:56 pm

In my (not limited but not extensive) experience with EMC2/linuxCNC : If you can successfully install it on the machine, it will be sufficient. I sometimes get RTK errors when I startup linuxCNC, but have never seen any side effects from them. I just dismiss and carry on with what I was doing. They've never happened during a job...

-Edward
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

jsbannis
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Location: Chicago, IL

Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by jsbannis » Tue Sep 25, 2012 9:55 pm

I know that USB->Parallel adapters are almost always rubbish, but I'm not certain why you need a PC with the port on the motherboard? Monoprice has PCI cards with either single or double parallel ports for < $10. If you already have a desktop computer you could use, that's lacking a port, you could probably go that route.

*edit: You'd think with a background in computer science, years of pc building experience, yadda yadda I wouldn't confuse parallel and serial ports :D To be completely accurate they only have one parallel card that is < $10, and it only has one port. Still ought to suffice.
shapeoko #0057

zimmer62
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Location: Lansing, MI

Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by zimmer62 » Wed Sep 26, 2012 8:39 pm

talking to some people at the Michigan CNC conference, parallel port cards do make a difference. I'd research the card before buying it. If people on CNCzone.com have had luck with it, you should be fine. I've had a laptop that "kind of worked" but that's just not good enough for CNC work.

I have two old laptops that didn't work well enough for this, something to do with how the laptops LPT port is implemented at the bios level.

USB to LPT almost never works right for CNC from what I've found.

I'm using and old Dell 400SC and it seems to work great. I actually have two more of them, I might be interested in selling if anyone is interested. Shipping might be high unless you can meet mid-michigan area.

calica
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Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by calica » Mon Sep 02, 2013 10:05 am

I'm using a PCI card on my Shapeoko with LinuxCNC. Works fine. Biggest problem is it runs at 3.3V rather than 5V. The relay for my spindle needs 5-30v.

You do need to find the address assigned to the card with lspci.

zerblatt007
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Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by zerblatt007 » Mon Sep 02, 2013 2:55 pm

So a PCMCIA card could also be used then?
http://www.amazon.com/StarTech-Parallel ... B000SR2H4W

But then again, PCMCIA is kind of old too.. :-/

Maybe Express Cards could be used in the same success on newer laptops?
http://www.amazon.com/StarTech-com-Expr ... B001Q7X0W6
Shapeoko #958: Dual-Y drive, Double-X, Belt on outside, 1m Y-Axis, Acme Z, Opened up and boxed in. Kress 1050 Spindle.

calica
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Re: Best Computer for LinuxCNC and Connecting to Stepper Dri

Post by calica » Mon Sep 02, 2013 10:49 pm

In theory they should work. The big issue with laptops and LinuxCNC is laptops have more ACPI and APM layers running underneath than desktops. At least in years past. Modern systems I'd imagine would be pretty close. This shows itself in higher jitter values during latency-test and then higher base-period. This forces LinuxCNC to have lower step rates and lower resolution for software generated PWM. Not a real problem on the Shapeoko. A belt driven machine doesn't need a high step rate compared to a leadscrew.

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