[kiwichris]

Hi-ho,

I'm planning a conversion from an embedded controller to LinuxCNC and wondering what Breakout board folks are using?

I'll need three axis step+dir, three limit inputs, e-stop, single bit spindle control and tool height sensor input.

Wanting some thing opto-isolated, parallel or USB, not fussy if it works with EMC/LinuxCNC.

Cheers, Chris H.

[svenakela]

You don't specify if you're servo or step motor based.
I use servo systems only. I buy everything I need from CNCdrive - motion controls and they make really reliable and secure hardware. You'll get what you're looking for and a bunch of very good security features.
I've updated the timing table with my preferences and hardware.

[kiwichris]

Good point. :-)

The machine is stepper based.

Runs 320 steps per mm at the moment, max speed of 6m/min so 32khz max step rate, 40khz with some margin.

I used to run a small home made machine on an early version of EMC2, hence why I decided to go down this path rather than mach etc. That and the embedded controller has some limitations, and I believe a software bug or two that is just downright annoying!

I'll check out that site. The only one I'd looked at so far was the CNC4PC one.

I need to check the voltage/signal requirements for the stepper drivers and proximity limit switches soon as well. I'm not sure what they are but the logic supply is 24V.

Cheers, Chris H.

[whateg01]

I'm not making use of all of the inputs on the BOB I got from CNC4PC, but Arturo there seems good to work with, and I think he'd steer you in the right direction.

[109jb]

I am using the cheapo BOB linked below. It has worked well and would be able to do all you listed. All you would have to do is map the 4th axis limit input as your tool setter and you have everything on your list.


http://pages.ebay.com/link/?nav=item...obalID=EBAY-US

[whateg01]

109, I don't think that board is opto-isolated. Neither is the one I use on my machine, but the OP did say he wanted it. I keep thinking if I make any changes to my machine, I'll probably upgrade to opto-isolation. Does that seller have other boards that are?

[109jb]

Yep. I missed the OP request for opto isolation. I'm not sure if tgey have any that are opto isolated. My stepper drivers have opto isolation. I figure that is good enough for me since everything else is just switches anyway ( limits, touch probe. etc. )

[svenakela]

And as a reminder, if you have a board that's not listed in the timing table please add it with your working config.

[kiwichris]

Hi folks...

Just a follow up on this, after much reading and scratching of head I decided to go with a C11 breakout board from cnc4pc.

FYI, the machine is a K6100A from Jinan Quick CNC. Up till now I've been using the supplied DSP pendant controller and it's never been a 100% solution for me as it has some odd features.

Now the DSP has developed an intermittent fault so I've decided to switch to emc.

FYI: the fault in the DSP is no indication of quality on their part, I may have dropped it a few times.

I'll be ordering the BOB later on today and will create a thread for the conversion to EMC here..

Cheers, Chris H.

[andypugh]

Runs 320 steps per mm at the moment, max speed of 6m/min so 32khz max step rate, 40khz with some margin.

I can't help feeling that 40kHz is pushing it a bit for software stepgen.
Would a PCI solution be possible? I am a huge fan of the Mesa 5i25/7i76 combo ($200) which gives you MHz stepgens and lots of IO (all isolated) along with a specific VFD drive channel.
Not as cheap a parport+BoB, but you get a lot more IO and much faster stepgen.

[kiwichris]

I can't help feeling that 40kHz is pushing it a bit for software stepgen.
Would a PCI solution be possible? I am a huge fan of the Mesa 5i25/7i76 combo ($200) which gives you MHz stepgens and lots of IO (all isolated) along with a specific VFD drive channel.
Not as cheap a parport+BoB, but you get a lot more IO and much faster stepgen.

Hi-ho,

You're probably right that 40khz is pushing it. The mesa solution looks good, but for the moment I need the machine running reliably as I'm going to start loosing customers if I can't get the machine reliable again. Currently it's stopping mid-job on a regular basis and although it can recover it's taking ages to make anything.

Parallel BOB + LinuxCNC is familiar ground for me as my first machine was on the old EMC2/Ubuntu 8.04 platform and a home-brew BOB/Driver so I know I can get productive quickly.

The machine I've got for the purpose is a dual core 2.2Ghz 64bit AMD thing so confident it will cope with the cutting speeds I need which are only up to 2.5m/min (100ipm) which in this setup is 13khz. Currently I rapid at 5m/min (200ipm ish), which is the 26khz.

I'll run the jitter test on the PC tonight and put the figures into the stepconf wizard to see what it thinks. I'm pretty confident it'll be OK. My old machine running EMC2 was running 10Khz on a Celeron 1.7 without any issues

The BOB is on it's way Priority express mail and I picked up the cables / power supply I need this morning. I expect to be making dust again by the end of the weekend. In theory. Hopefully.

Cheers, Chris H.

[svenakela]

Chris, Don't count with the PC being super-faster just because it has more CPU. My experience is that many modern motherboards and peripherals causes bad latency figures. If you happen to have a good setup you might get good figures, you could also end up pretty crappy.
If you see figures less than expected, enter BIOS and disable Hyper Threading (if the PC supports it) and add "isolcpus=n" to the boot options where n is [number of cores]-1. You can add it to the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub, then run sudo update-grub.
You find more info about it here.

[kiwichris]

Chris, Don't count with the PC being super-faster just because it has more CPU. My experience is that many modern motherboards and peripherals causes bad latency figures. If you happen to have a good setup you might get good figures, you could also end up pretty crappy.

Hi...

Yeah, modern motherboards with everything embedded do not play well with the RT components, I had problems with my previous EMC2 install when I replaced a failed motherboard with a 'better' one and it was terrible. Disabling the onboard video and most of the embedded I/O and putting in a PCI parallel card and Decent video card fixed it...

I ran the latency tool on the machine last night with default settings and opened up 50 odd firefox windows, plus all the other apps the default linuxcnc package has and got a max jitter figure of 11200. I set the wizard config to be 15000 to be safe, and with the settings from the list for my stepper drivers (Leadshine MA680's) I got a max figure of 40 somethign khz.

I might be slightly wrong on those figures, that's from memory and I'm at work now (Day job, the CNC is the 'other' work ) In any case there seems to be a fair amount of overheard to get the cutting speeds I need, and rapids might be slightly slower to maintain margin but I can live with that.

I also had a play with axis and nothing much has changed so it all felt quite comfortable. home setting, G54 offset etc is all familiar ground, and I test-ran some existing G-code from vectric and the post-processor seems to be correct but I'll obviously have to cut some air before I trust it.

I just need to understand how I'll run the tool height sensor/probe as my previous machine was the 'paper underneath the tool' method but with a vacuum table that's not practical as we run a 0.05mm clearance above the table and resurfacing the table wastes a lot of time.

Onwards and upwards.