Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
the allocation of computing resources seems to be a recurring theme with pc based machine controllers. while i have wished for an accesible pocket calculator gui more than one time while standing in front of a machining center console, i have almost never wanted to surf the web or send emails while doing so. the enhanced machine controller spans a disparity between its intended function and the common usage of it's supporting hardware. maybe there is a workaround? when i installed linux cnc packages, one of the steps was drive partitioning, in case there was another OS already there, with some kind of neutral zone for exchange of data when switching the pc from one dedication of control to a different dedication of control. why not do the same thing with an enhanced machine controller? in one mode, the pc has the sole function of machine control and user interface for machine control. in the other mode, the pc has the common functions like internet and anything else in an OS's routine employ. i only have a very basic understanding of pc construction, so there might be some sort of fatal flaw in the idea of a dedicated machine control operating mode for a pc. however, my suspicion is that such operation has not been pursued for reasons of convenience of having a do-it-all pc operation mode. this may not always be advantagious. for example, imagine waking up in the morning, turning on the coffee maker, showering, and then finding that the coffee pot is empty because the coffee machine had a problem downloading the most recent bean roast sensing algorithm. --- On Mon, 2/20/12, Jon Elson el...@pico-systems.com wrote: From: Jon Elson el...@pico-systems.com Subject: Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC? To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Date: Monday, February 20, 2012, 9:54 AM Roland Jollivet wrote: My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? You have to figure this out for each case. What is the maximum encoder RPM at the desired rapid feed rate? (Don't forget belt reduction.) What is the base thread rate? For example, 60 IPM, 1000 cycle/rev encoder and a 2:1 belt reduction to a 5 TPI ballscrew. So, that is 60 * 5 * 2 * 1000 * 4 (encoder quadrature) / 60 secs/min = 40,000 counts/second. Well, that is a bit iffy, a count every 25 us. And, remember that if the encoder exceeds the rate at which the computer can count the pulses, you get a servo runaway, which is a lot worse than just losing position with a stepper. Now, if 30 IPM is OK, and you have 250 cycle/rev encoders directly coupled to the 5TPI screws, it should work fine, but that is a lot of compromises to avoid a better interface. I generally think that running steppers via software step generation is not a great thing to do, and running servos via software encoder counting is far WORSE! So, now you are suggesting using TWO computers instead of using purpose-built hardware to interface to the motion system! Now, you have to have TWO hard drives to back up, and TWO computers to boot and shut down cleanly. There may be times such an arrangement is desirable, but I really think it is the wrong approach. Jon -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
Although this is off topic by now, I agree with Charles. A CNC machine should be just that, and have a reliable stand alone PC at its core. A coffee machine makes coffee, and a CNC cuts metal. The thing I love about LinuxCNC is that when paired with Pico or Mesa hardware it provides an affordable alternative for machine builders. By remaining compatible with standard g-code a LinuxCNC control has capabilities close to that of a Fanuc or Haas. This, in itself, is amazing! All the other complaints about what it doesn't do, or what it's called for that matter, don't even bother me. Thanks to the developers of LinuxCNC, I can cut metal with the accuracy of a $40,000 machine on a $4000 machine. How can you not love that? -Original Message- From: charles green [mailto:xxzzb...@yahoo.com] Sent: Tuesday, February 21, 2012 5:47 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC? the allocation of computing resources seems to be a recurring theme with pc based machine controllers. while i have wished for an accesible pocket calculator gui more than one time while standing in front of a machining center console, i have almost never wanted to surf the web or send emails while doing so. the enhanced machine controller spans a disparity between its intended function and the common usage of it's supporting hardware. maybe there is a workaround? when i installed linux cnc packages, one of the steps was drive partitioning, in case there was another OS already there, with some kind of neutral zone for exchange of data when switching the pc from one dedication of control to a different dedication of control. why not do the same thing with an enhanced machine controller? in one mode, the pc has the sole function of machine control and user interface for machine control. in the other mode, the pc has the common functions like internet and anything else in an OS's routine employ. i only have a very basic understanding of pc construction, so there might be some sort of fatal flaw in the idea of a dedicated machine control operating mode for a pc. however, my suspicion is that such operation has not been pursued for reasons of convenience of having a do-it-all pc operation mode. this may not always be advantagious. for example, imagine waking up in the morning, turning on the coffee maker, showering, and then finding that the coffee pot is empty because the coffee machine had a problem downloading the most recent bean roast sensing algorithm. --- On Mon, 2/20/12, Jon Elson el...@pico-systems.com wrote: From: Jon Elson el...@pico-systems.com Subject: Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC? To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Date: Monday, February 20, 2012, 9:54 AM Roland Jollivet wrote: My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? You have to figure this out for each case. What is the maximum encoder RPM at the desired rapid feed rate? (Don't forget belt reduction.) What is the base thread rate? For example, 60 IPM, 1000 cycle/rev encoder and a 2:1 belt reduction to a 5 TPI ballscrew. So, that is 60 * 5 * 2 * 1000 * 4 (encoder quadrature) / 60 secs/min = 40,000 counts/second. Well, that is a bit iffy, a count every 25 us. And, remember that if the encoder exceeds the rate at which the computer can count the pulses, you get a servo runaway, which is a lot worse than just losing position with a stepper. Now, if 30 IPM is OK, and you have 250 cycle/rev encoders directly coupled to the 5TPI screws, it should work fine, but that is a lot of compromises to avoid a better interface. I generally think that running steppers via software step generation is not a great thing to do, and running servos via software encoder counting is far WORSE! So, now you are suggesting using TWO computers instead of using purpose-built hardware to interface to the motion system! Now, you have to have TWO hard drives to back up, and TWO computers to boot and shut down cleanly. There may be times such an arrangement is desirable, but I really think it is the wrong approach. Jon -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Keep Your
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
On Tue, 2012-02-21 at 03:47 -0800, charles green wrote: the allocation of computing resources seems to be a recurring theme with pc based machine controllers. while i have wished for an accesible pocket calculator gui more than one time while standing in front of a machining center console, i have almost never wanted to surf the web or send emails while doing so. the enhanced machine controller spans a disparity between its intended function and the common usage of it's supporting hardware. I tend to think the CNC PC should only have CNC software on it, it seems more grown up to have a purpose built machine that requires a certain amount of discipline to join the club, but the more I use my LinuxCNC PC's the more I also find I use the generic programs. While tuning, I need to access the Net to find what I or FF does. While setting up a new piece of hardware, I need to find a pin-out or spec., or download grpn so I can calculate a component value. (By the way, I've found the default gcalctool has a better Hex-Dec feature, so I usually have both on the screen.) I often have my VFD PDF manual on the screen. Inkscape and gEdit are often running for documentation purposes. gFTP is up too, so I can store and share my work. It all comes in handy, and in reality, none of it detracts from the core LinuxCNC function. My biggest frustration now is in finding PC hardware that plays well with Ubuntu and doesn't kill latency. The choice here is, develop new purpose built hardware and maybe rebuild LinuxCNC, or spend a day or two swapping out hardware until I get something that works well. Aimlessly fiddling with PC hardware for a couple days is painful, but months and months of development is not one of my options. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
It would be nice to know enough to debug latency issues, instead it feels like kludging around with no idea what is the cause. I suppose rtai has some tools if you know what you are doing. On Tue, Feb 21, 2012 at 1:12 PM, Kirk Wallace kwall...@wallacecompany.comwrote: On Tue, 2012-02-21 at 03:47 -0800, charles green wrote: the allocation of computing resources seems to be a recurring theme with pc based machine controllers. while i have wished for an accesible pocket calculator gui more than one time while standing in front of a machining center console, i have almost never wanted to surf the web or send emails while doing so. the enhanced machine controller spans a disparity between its intended function and the common usage of it's supporting hardware. I tend to think the CNC PC should only have CNC software on it, it seems more grown up to have a purpose built machine that requires a certain amount of discipline to join the club, but the more I use my LinuxCNC PC's the more I also find I use the generic programs. While tuning, I need to access the Net to find what I or FF does. While setting up a new piece of hardware, I need to find a pin-out or spec., or download grpn so I can calculate a component value. (By the way, I've found the default gcalctool has a better Hex-Dec feature, so I usually have both on the screen.) I often have my VFD PDF manual on the screen. Inkscape and gEdit are often running for documentation purposes. gFTP is up too, so I can store and share my work. It all comes in handy, and in reality, none of it detracts from the core LinuxCNC function. My biggest frustration now is in finding PC hardware that plays well with Ubuntu and doesn't kill latency. The choice here is, develop new purpose built hardware and maybe rebuild LinuxCNC, or spend a day or two swapping out hardware until I get something that works well. Aimlessly fiddling with PC hardware for a couple days is painful, but months and months of development is not one of my options. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
On Tue, Feb 21, 2012 at 1:26 PM, Erik Friesen e...@aercon.net wrote: It would be nice to know enough to debug latency issues, instead it feels like kludging around with no idea what is the cause. I suppose rtai has some tools if you know what you are doing. Do they? It's been a while since I have followed development, but I had never seen any information about that kind of tool. While tracking down latency problems is tricky, and sometimes impossible, it is deterministic enough that you can feel confident you fixed things when you are done. Eric -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
On 20 February 2012 06:14, Jon Elson el...@pico-systems.com wrote: Dropout wrote: A quick question, does latency matter for servo drives? Yes, absolutely. But, it is not as critical. For software stepping, the base thread is typically around 20 us, and so a jitter of even 5 us is more than noticeable. But, on a typical servo system (or a stepper with external step generating hardware) there is no base thread and the servo thread runs at 1000 us, so the effect of a 5us jitter is insignificant. As long as the worst-case jitter never exceeds 20 us, servos should run flawlessly. Jon So the norm is that a stepper system can run off the parallel port, but for DC servo's, extra hardware is required to sample the encoders. My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? Regards Roland -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
2012/2/20 Roland Jollivet roland.jolli...@gmail.com So the norm is that a stepper system can run off the parallel port, but for DC servo's, extra hardware is required to sample the encoders. My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? It is possible of course. But with low speed and/or low accuracy. It depends on your requirements. With 100ppr encoders at 3000rpm it's 50 kHz, might be too much even for very low latency. And common 2500ppr encoders are hardly compatible at all. Andrew -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
2012/2/20 Roland Jollivet roland.jolli...@gmail.com: My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? As Andrew mentioned, for normal speed with normal resolution encoders it is not going to work. I do not know prices for Pico Systems products (more info here: http://pico-systems.com/motion.html), but prices for Mesa FPGA cards start at 80-90$, which I find affordable. Even more - if You are thining about headless PC for realtime tasks and another PC for operator, I am sure that also Pico's solutions would be less cost than second PC. And FPGA card will provide also a lot more I/O pins than You have in 1 or even 2 parports. Viesturs -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
Roland Jollivet wrote: My question is; if one built a headless system(no video) and disabled drivers wherever possible, would such a system be fast enough to run DC servo's and read the encoders on the parallel port? You have to figure this out for each case. What is the maximum encoder RPM at the desired rapid feed rate? (Don't forget belt reduction.) What is the base thread rate? For example, 60 IPM, 1000 cycle/rev encoder and a 2:1 belt reduction to a 5 TPI ballscrew. So, that is 60 * 5 * 2 * 1000 * 4 (encoder quadrature) / 60 secs/min = 40,000 counts/second. Well, that is a bit iffy, a count every 25 us. And, remember that if the encoder exceeds the rate at which the computer can count the pulses, you get a servo runaway, which is a lot worse than just losing position with a stepper. Now, if 30 IPM is OK, and you have 250 cycle/rev encoders directly coupled to the 5TPI screws, it should work fine, but that is a lot of compromises to avoid a better interface. I generally think that running steppers via software step generation is not a great thing to do, and running servos via software encoder counting is far WORSE! So, now you are suggesting using TWO computers instead of using purpose-built hardware to interface to the motion system! Now, you have to have TWO hard drives to back up, and TWO computers to boot and shut down cleanly. There may be times such an arrangement is desirable, but I really think it is the wrong approach. Jon -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
A quick question, does latency matter for servo drives? Dropout. On 2/19/2012 1:36 PM, Viesturs Lācis wrote: 2012/2/19 Alan Browningajbrowning2...@yahoo.com: Thanks for the quick response. So you build your machines from the ground up with new componenets? Due to budget limitations I have to build things on the cheap. 2 of those machines were completely new builds, 2 were retrofits, one of the retrofits is my own machine, remaining are commercial services for customers. I prefer new components, where possible, but I am also very concerned about being as cost-effective as possible (that is why I delivered used monitor with one of those newly built machines). And that is why D525 is so attractive - for70 EUR (100 USD) it has mainboard with 2-core CPU and also built-in video card. Add RAM, HDD and PSU to get working PC. Of course, if You already have unused PC and are building machine for Your own use, it is obvious to use existing hardware for multitasking - not only collect dust in its case, but also drive a cnc machine. I think that best thing to do at the moment is installing Ubuntu + LinuxCNC on that PC and runing latency test to find out, how is Your particular PC behaving and what realtime performance You can get out of it. Viesturs -- Virtualization Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Virtualization Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
On Sun, 19 Feb 2012, Dropout wrote: Date: Sun, 19 Feb 2012 13:45:41 -0500 From: Dropout drop...@sympatico.ca Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC? A quick question, does latency matter for servo drives? Dropout. Well at some amount of latency it matters but servo systems will tolerate a lot more latency than software step generation will. 50 - 100 uSec of latency on a servo system will do little more than add a little (less than .0002 at normal cutting speeds) noise to the control loop, but the same latency on a system using software step generation will likely cause stalls during rapids. Peter Wallace Mesa Electronics -- Virtualization Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
Thanks. On 2/19/2012 2:51 PM, Peter C. Wallace wrote: On Sun, 19 Feb 2012, Dropout wrote: Date: Sun, 19 Feb 2012 13:45:41 -0500 From: Dropoutdrop...@sympatico.ca Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC)emc-users@lists.sourceforge.net Subject: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC? A quick question, does latency matter for servo drives? Dropout. Well at some amount of latency it matters but servo systems will tolerate a lot more latency than software step generation will. 50 - 100 uSec of latency on a servo system will do little more than add a little (less than .0002 at normal cutting speeds) noise to the control loop, but the same latency on a system using software step generation will likely cause stalls during rapids. Peter Wallace Mesa Electronics -- Virtualization Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Virtualization Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Latency - was Re: Which video card/driver for LinuxCNC?
Dropout wrote: A quick question, does latency matter for servo drives? Yes, absolutely. But, it is not as critical. For software stepping, the base thread is typically around 20 us, and so a jitter of even 5 us is more than noticeable. But, on a typical servo system (or a stepper with external step generating hardware) there is no base thread and the servo thread runs at 1000 us, so the effect of a 5us jitter is insignificant. As long as the worst-case jitter never exceeds 20 us, servos should run flawlessly. Jon -- Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
