Re: [Emc-users] US Digital encoders?
On Thu, 2012-02-02 at 22:21 -0500, gene heskett wrote: what can he use for an exciting signal? It seems I'm missing something obvious. I thought the idea was to move the motor back forth while comparing the commanded (presumably, the actual) position with the encoder's (also, presumably, the actual) position to see if there's any lag / jitter / instability between the two. Using freqgen (plus stepgen or whatever the motor might require) to drive the motor should accomplish the first part. Triggering halscope on (some part of) the output signal, then displaying both output and input traces will reveal their relation. Then use siggen to ramp / sawtooth freqgen and you'll see how the relation varies with speed acceleration. Yes? -- Ed http://softsolder.com -- 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] US Digital encoders?
On Thu, 2 Feb 2012, Viesturs L?cis wrote: Date: Thu, 2 Feb 2012 22:50:52 +0200 From: [UTF-8] Viesturs L?cis viesturs.la...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: Re: [Emc-users] US Digital encoders? 2012/2/2 andy pugh bodge...@gmail.com: On 2 February 2012 15:09, Viesturs L??cis viesturs.la...@gmail.com wrote: Could it be anything else, but the encoder problem? It could be an unfortunate resonance between the mechanical frequency of the machine frame and the servo loop. This might be why increasing the servo frequency was helpful. Increasing servo servo period frequency from 1 kHz to 2kHz helped. But any further increase up to 5 kHz did not provide any additional improvement. Even more, with 5kHz (and RTAI errors) I actually have returned at starting point. I had some courses, covering resonances, and the conclusion is that there should have been additional changes in behavior, when further changes in servo update rate were made. And it should not had gone back to the initial behavior. But that theory... Is it possible that you have some binding or tracking issues? The 7I39L has a current limit of 15A/phase If you exceed ths current, you will suddenly have a drastic change in your tuning as you will lose the inherent damping of a voltage mode drive. The current limit should never be reached in a properly tuned system but it may be happening when you have the oscillation. The way to check for this is look for the red overcurrent light on the 7I39 when you execute rapid accelerations (or perhaps due to resonance or binding) 2012/2/2 Sven Wesley svenne.d...@gmail.com: Did you try my suggestion to ground the encoder, as written in my previous mail? Sorry, I forgot. The thing is that I did not find that there was not an issue with lost encoder pulses anyway... Viesturs -- 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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] US Digital encoders?
2012/2/3 Peter C. Wallace p...@mesanet.com: Is it possible that you have some binding or tracking issues? The 7I39L has a current limit of 15A/phase If you exceed ths current, you will suddenly have a drastic change in your tuning as you will lose the inherent damping of a voltage mode drive. The current limit should never be reached in a properly tuned system but it may be happening when you have the oscillation. The way to check for this is look for the red overcurrent light on the 7I39 when you execute rapid accelerations (or perhaps due to resonance or binding) Thank You for the tip! The thing is that the oscillation occurs, when the speed of the jog has already been reached, not during acceleration. But I will pay attention to the LEDs. 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] US Digital encoders?
On Friday, February 03, 2012 10:33:35 PM Ed Nisley did opine: On Thu, 2012-02-02 at 22:21 -0500, gene heskett wrote: what can he use for an exciting signal? It seems I'm missing something obvious. I thought the idea was to move the motor back forth while comparing the commanded (presumably, the actual) position with the encoder's (also, presumably, the actual) position to see if there's any lag / jitter / instability between the two. Using freqgen (plus stepgen or whatever the motor might require) to drive the motor should accomplish the first part. Triggering halscope on (some part of) the output signal, then displaying both output and input traces will reveal their relation. Then use siggen to ramp / sawtooth freqgen and you'll see how the relation varies with speed acceleration. Yes? That, Ed, is essentially what I was asking for. And I had forgotten about freqgen. I used to have a memory... Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) My web page: http://coyoteden.dyndns-free.com:85/gene If you don't go to other men's funerals they won't go to yours. -- Clarence Day -- 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] US Digital encoders?
2012/1/31 Peter C. Wallace p...@mesanet.com: This can be mitigated by putting a common mode choke (Big ferrite bead) over the three motor leads (DO NOT include the ground lead) 1) I wrapped each of 3 power wires for motor around a separate ferrite bead. 2) I connected machine frame to common earth ground. Please try the encoder sample rate lowering example I provided. This will quickly help to see if there is a noise problem. Noise piked up by the encoder wires either inductively or capacitively tends to be short pulses. By lowering the input bandwidth a lot of this kind of noise can be filtered out. 3) Edited INI file, so that firmware load line is this: CONFIG=firmware=hm2/5i23/SVSTTP6_6_7I39.BIT num_encoders=3 num_3pwmgens=3 num_stepgens=2 enable_raw 4) Added to HAL file these lines: setp hm2_[HOSTMOT2](BOARD).0.raw.write_address 13312 # = 0x3400 = encoder Sample Rate Register setp hm2_[HOSTMOT2](BOARD).0.raw.write_data 14 # sample rate is clocklow (48 MHz)/SRR+2 # so divide by 16 = 3 Mhz setp hm2_[HOSTMOT2](BOARD).0.raw.write_strobe 1 # do write 5) In Show machine config I additionally ran: setp hm2_5i23.0.raw.write_strobe 1 Here's one way to check for lost encoder counts: Mark the shaft and the stator with a pencil/scribe at DRO reading of 0. Move around a lot or until you have the stall problem, turn off motor power and hand crank back to DRO 0 and check pencil mark alignment. This should get you to within a few 10s of counts 6) Scratched a mark in pulley and straight line in motor mounting plate. Aligned so that mark was on the line. Started up Emc. In Hal Meter I opened encoder.0.rawcounts pin, which had a value of 0. Jogged the joint, motor stalled at least 10 times, each time I stopped it with F2, then pressed F2 again, jogged again until it stopped and started to oscillate, so I stopped again with F2 and so on. After a while I turned off motor power (encoder power remained) and aligned the mark and the line (I could not see the screen while doing that). Rawcounts pin had a value -1 7) I tested - jogging bare motor works just fine, which, in case of acceleration lag in encoder, is obvious. The first 5 points were implemented so that all of them were in effect, when last point was conducted. The observed impact of first 5 points - NONE. So my conclusion is - machine is not losing encoder counts, there is no significant noise in encoder signal. Could it be anything else, but the encoder problem? Viesturs -- 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] US Digital encoders?
On Thursday, February 02, 2012 08:51:35 AM Viesturs Lācis did opine: 2012/1/31 Peter C. Wallace p...@mesanet.com: This can be mitigated by putting a common mode choke (Big ferrite bead) over the three motor leads (DO NOT include the ground lead) 1) I wrapped each of 3 power wires for motor around a separate ferrite bead. 2) I connected machine frame to common earth ground. That isn't the ideal method, although at 50 or 60 hz, not terribly important. We normally use the chokes as common items, where all leads are wound on the same toroid form. The latter doesn't block load surge noises because those will generally result in magnetic cancellation. The general idea is to block the longitudinal noise, keeping that soundly choked off in the motor itself. Brush arcing noises etc. I have not personally noted a problem in my lashup, but I've tried to maintain a star grounding and shield connection scheme too. But when I hooked up a probe a few days ago, I did find that I had to ground the probes shield to the machine frame, else when the probe circuit was closed to ground, halscope was showing quite a bit of noise that seemed to be related to the powerline frequency. Please try the encoder sample rate lowering example I provided. This will quickly help to see if there is a noise problem. Noise piked up by the encoder wires either inductively or capacitively tends to be short pulses. By lowering the input bandwidth a lot of this kind of noise can be filtered out. It also delays things, making stable setups harder to achieve because of the lag in the feedback. although if you've limited it to 3mhz with the code below, I can't bring myself to pointing a finger at it. You still have far more effective bandwidth at 3mhz than any modification of the servo drive, the rotational inertia of the motors armature mass likely limits its rate of change to well below 50 kilohertz even in an ironless motor. Ed: Is there some method he could use, using halscope, that could characterize a mechanical resonance from torsion in the drive and/or this questionable encoder prove there is an instability causing lag someplace. The only thing I can think of ATM would need a function generator to supply a low amplitude, enough to move the machine 20 thousandths back and forth, varying this drive frequency from about 0.1hz up. If its the lag in the encoder, the lag should be both visible in halscope, and varying the frequency of the function generator might make it resonate go crazy at a relatively low frequency. But that would require a function generator which I doubt Viesters has access to. Is there some other tool such as another pwmgen cobbled up out of hal stuff in linuxcnc's bag of tricks that could do this? Just thinking out loud, YMMV. 3) Edited INI file, so that firmware load line is this: CONFIG=firmware=hm2/5i23/SVSTTP6_6_7I39.BIT num_encoders=3 num_3pwmgens=3 num_stepgens=2 enable_raw 4) Added to HAL file these lines: setp hm2_[HOSTMOT2](BOARD).0.raw.write_address 13312 # = 0x3400 = encoder Sample Rate Register setp hm2_[HOSTMOT2](BOARD).0.raw.write_data 14 # sample rate is clocklow (48 MHz)/SRR+2 # so divide by 16 = 3 Mhz setp hm2_[HOSTMOT2](BOARD).0.raw.write_strobe 1 # do write 5) In Show machine config I additionally ran: setp hm2_5i23.0.raw.write_strobe 1 Here's one way to check for lost encoder counts: Mark the shaft and the stator with a pencil/scribe at DRO reading of 0. Move around a lot or until you have the stall problem, turn off motor power and hand crank back to DRO 0 and check pencil mark alignment. This should get you to within a few 10s of counts 6) Scratched a mark in pulley and straight line in motor mounting plate. Aligned so that mark was on the line. Started up Emc. In Hal Meter I opened encoder.0.rawcounts pin, which had a value of 0. Jogged the joint, motor stalled at least 10 times, each time I stopped it with F2, then pressed F2 again, jogged again until it stopped and started to oscillate, so I stopped again with F2 and so on. After a while I turned off motor power (encoder power remained) and aligned the mark and the line (I could not see the screen while doing that). Rawcounts pin had a value -1 7) I tested - jogging bare motor works just fine, which, in case of acceleration lag in encoder, is obvious. The first 5 points were implemented so that all of them were in effect, when last point was conducted. The observed impact of first 5 points - NONE. So my conclusion is - machine is not losing encoder counts, there is no significant noise in encoder signal. Could it be anything else, but the encoder problem? Viesturs -- Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99!
Re: [Emc-users] US Digital encoders?
On 2 February 2012 15:09, Viesturs Lācis viesturs.la...@gmail.com wrote: Could it be anything else, but the encoder problem? It could be an unfortunate resonance between the mechanical frequency of the machine frame and the servo loop. This might be why increasing the servo frequency was helpful. Adding some mass to the gantry temporarily, and seeing if that makes it worse, might be informative, but working from there to a solution is less easy. -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- 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] US Digital encoders?
2012/2/2 Viesturs Lācis viesturs.la...@gmail.com ... So my conclusion is - machine is not losing encoder counts, there is no significant noise in encoder signal. Could it be anything else, but the encoder problem? ... Did you try my suggestion to ground the encoder, as written in my previous mail? /Sven -- 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] US Digital encoders?
2012/2/2 andy pugh bodge...@gmail.com: On 2 February 2012 15:09, Viesturs Lācis viesturs.la...@gmail.com wrote: Could it be anything else, but the encoder problem? It could be an unfortunate resonance between the mechanical frequency of the machine frame and the servo loop. This might be why increasing the servo frequency was helpful. Increasing servo servo period frequency from 1 kHz to 2kHz helped. But any further increase up to 5 kHz did not provide any additional improvement. Even more, with 5kHz (and RTAI errors) I actually have returned at starting point. I had some courses, covering resonances, and the conclusion is that there should have been additional changes in behavior, when further changes in servo update rate were made. And it should not had gone back to the initial behavior. But that theory... 2012/2/2 Sven Wesley svenne.d...@gmail.com: Did you try my suggestion to ground the encoder, as written in my previous mail? Sorry, I forgot. The thing is that I did not find that there was not an issue with lost encoder pulses anyway... Viesturs -- 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] US Digital encoders?
On Thu, 2012-02-02 at 09:36 -0500, gene heskett wrote: that would require a function generator Perhaps gimmicking up a HAL circuit with siggen or freqgen to drive the stepper, then compare the encoder input with the motor output? You probably don't need a sine wave, just drive the motor back and forth at a variable rate: siggen providing a sawtooth wave to freqgen? Surely it'd be more complex than that, but triggering on one edge of the motor output and looking at the corresponding encoder edges should be revealing... -- Ed http://softsolder.com -- 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] US Digital encoders?
On Thursday, February 02, 2012 10:20:56 PM Ed Nisley did opine: On Thu, 2012-02-02 at 09:36 -0500, gene heskett wrote: that would require a function generator Perhaps gimmicking up a HAL circuit with siggen or freqgen to drive the stepper, then compare the encoder input with the motor output? You probably don't need a sine wave, just drive the motor back and forth at a variable rate: siggen providing a sawtooth wave to freqgen? Surely it'd be more complex than that, but triggering on one edge of the motor output and looking at the corresponding encoder edges should be revealing... In violent agreement Ed, but what can he use for an exciting signal? Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) My web page: http://coyoteden.dyndns-free.com:85/gene You have a strong desire for a home and your family interests come first. -- 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] US Digital encoders?
2012/1/31 Tom Easterday tom-...@bgp.nu: Do you have differential drivers for the encoders or are you running them single ended? Single ended. I would put the encoder signals on an oscilloscope and see what they look like to the controller. Since I do not have oscilloscope, it seems like HAL Scope would be the only option. But can I see A and B inputs of encoder module on 5i23 card? Or, it could be noise introduced into your signal driving the motors (rather than the encoders). That was an issue we ran into on the Plasma gantry table and had to design some custom filters to deal with it. I have retrofitted plasma table and IMHO in terms of generating noise the plasma is from totally different league. Client wanted to control the machine - jog the table and run/pause/stop g-code file - with usb joypad. I set them up with that option, but I know that pretty soon they removed the joypad, because plasma was disturbing the joypad. There are 4 wire leads for each motor - 3 phases and GND. I have packed leads for each motor in a separate socket. I do have power cable for spindle running along other cables, wrapped in aluminum foil and grounded at one end , plus the spindle was not turned on, when I tried to tune servos. So I do not see any source for noise in motor power cables. Plus I suppose the oscilloscope is the only way to check it. 2012/1/31 dave dengv...@charter.net: I also assume you use a star grounding system for your encoder and signal cables. Yes. 2012/1/31 Roland Jollivet roland.jolli...@gmail.com: Most CAT5 cable is solid single strand, not good for installing on machines or in vibrating environment. But maybe yours is multi-strand? Yes - they are multi-strand, but I called them flexible as I did not know the right word :) It took me some time to find those cables, because I was looking for shielded multistrand cables with at least 6 leads. I do have diy converters from single ended to differential signal. It was used to convert step and dir signals for 3 drives to differential signal. I could use them to get differential signal. But would it make sense not to have differential to single ended signal decoder and feed in 7i39 only half of the differential signal? Viesturs -- 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] US Digital encoders?
On Tue, 31 Jan 2012, Viesturs L?cis wrote: Date: Tue, 31 Jan 2012 19:51:37 +0200 From: [UTF-8] Viesturs L?cis viesturs.la...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: Re: [Emc-users] US Digital encoders? 2012/1/31 Tom Easterday tom-...@bgp.nu: Do you have differential drivers for the encoders or are you running them single ended? Single ended. I would put the encoder signals on an oscilloscope and see what they look like to the controller. Since I do not have oscilloscope, it seems like HAL Scope would be the only option. But can I see A and B inputs of encoder module on 5i23 card? Or, it could be noise introduced into your signal driving the motors (rather than the encoders). That was an issue we ran into on the Plasma gantry table and had to design some custom filters to deal with it. I have retrofitted plasma table and IMHO in terms of generating noise the plasma is from totally different league. Client wanted to control the machine - jog the table and run/pause/stop g-code file - with usb joypad. I set them up with that option, but I know that pretty soon they removed the joypad, because plasma was disturbing the joypad. There are 4 wire leads for each motor - 3 phases and GND. I have packed leads for each motor in a separate socket. I do have power cable for spindle running along other cables, wrapped in aluminum foil and grounded at one end , plus the spindle was not turned on, when I tried to tune servos. So I do not see any source for noise in motor power cables. Plus I suppose the oscilloscope is the only way to check it. The three phase PWM is a fair noise source. Not just capacitively coupled noise from the three motor wires but inductively coupled noise due to current spikes from the 28V PWM driving into the motors winding/frame capacitance. This can be mitigated by putting a common mode choke (Big ferrite bead) over the three motor leads (DO NOT include the ground lead) Please try the encoder sample rate lowering example I provided. This will quickly help to see if there is a noise problem. Noise piked up by the encoder wires either inductively or capacitively tends to be short pulses. By lowering the input bandwidth a lot of this kind of noise can be filtered out. 2012/1/31 dave dengv...@charter.net: I also assume you use a star grounding system for your encoder and signal cables. Yes. 2012/1/31 Roland Jollivet roland.jolli...@gmail.com: Most CAT5 cable is solid single strand, not good for installing on machines or in vibrating environment. But maybe yours is multi-strand? Yes - they are multi-strand, but I called them flexible as I did not know the right word :) It took me some time to find those cables, because I was looking for shielded multistrand cables with at least 6 leads. I do have diy converters from single ended to differential signal. It was used to convert step and dir signals for 3 drives to differential signal. I could use them to get differential signal. But would it make sense not to have differential to single ended signal decoder and feed in 7i39 only half of the differential signal? Viesturs -- 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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] US Digital encoders?
2012/1/31 Peter C. Wallace p...@mesanet.com: The three phase PWM is a fair noise source. Not just capacitively coupled noise from the three motor wires but inductively coupled noise due to current spikes from the 28V PWM driving into the motors winding/frame capacitance. This can be mitigated by putting a common mode choke (Big ferrite bead) over the three motor leads (DO NOT include the ground lead) Please try the encoder sample rate lowering example I provided. This will quickly help to see if there is a noise problem. Noise piked up by the encoder wires either inductively or capacitively tends to be short pulses. By lowering the input bandwidth a lot of this kind of noise can be filtered out. Thank You, Peter and guys! I am really starting to think that I should do some additional testing, before spending any additional funds. Viesturs -- 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] US Digital encoders?
2012/1/31 Viesturs Lācis viesturs.la...@gmail.com 2012/1/31 Peter C. Wallace p...@mesanet.com: The three phase PWM is a fair noise source. Not just capacitively coupled noise from the three motor wires but inductively coupled noise due to current spikes from the 28V PWM driving into the motors winding/frame capacitance. This can be mitigated by putting a common mode choke (Big ferrite bead) over the three motor leads (DO NOT include the ground lead) Please try the encoder sample rate lowering example I provided. This will quickly help to see if there is a noise problem. Noise piked up by the encoder wires either inductively or capacitively tends to be short pulses. By lowering the input bandwidth a lot of this kind of noise can be filtered out. Thank You, Peter and guys! I am really starting to think that I should do some additional testing, before spending any additional funds. Viesturs I'm jumping in here, without reading the entire discussion, but you need to ground the encoder housing as well. The Ethernet ground is not connected to the chassi of the encoder. I have been using AMT's for years with great success but had a tiny but very irritating lost-step-syndrome that a Ukrainian guy (Balazs at CNCDrive) solved in a split second: Add another ground cable to the encoder chassi. I did, know I'm leaving the machine for hours without a doubt. Diff.line driver's GND terminal --- Machine metal frame Machine metal frame --- PE (Protective earth grounding point) I could take a picture if you need to see what I mean. Regards, Sven -- 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] US Digital encoders?
2012/2/1 Sven Wesley svenne.d...@gmail.com I'm jumping in here, without reading the entire discussion, but you need to ground the encoder housing as well. The Ethernet ground is not connected to the chassi of the encoder. I have been using AMT's for years with great success but had a tiny but very irritating lost-step-syndrome that a Ukrainian guy (Balazs at CNCDrive) solved in a split second: Add another ground cable to the encoder chassi. I did, know I'm leaving the machine for hours without a doubt. Diff.line driver's GND terminal --- Machine metal frame Machine metal frame --- PE (Protective earth grounding point) I could take a picture if you need to see what I mean. Regards, Sven ...and to quickly correct myself. Balazs is HUNGARIAN nothing else. -- 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] US Digital encoders?
I would like to ask, if anyone could provide some recommendations for US Digital encoders - I chose them, because they seem to be next in the line in terms of affordability. I was particularly looking at E7P. I have Keling KL23BLS_115 Nema 23 servo motors: http://kelinginc.net/KL23BLS_115.pdf This image shows US Digital E5MD encoders (keling? DC brush motors via Dan Mauch) http://www.anderswallin.net/2006/12/dc-servos-for-cnc-mill/ They have been in use since 2006 and work well. Most of the videos over here are with this machine (not the most recent ones where you see a white enclosure with a red door, that is another machine) http://www.youtube.com/user/JMI80/videos Anders -- 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] US Digital encoders?
On Mon, 30 Jan 2012, Viesturs L?cis wrote: Date: Mon, 30 Jan 2012 12:18:51 +0200 From: [UTF-8] Viesturs L?cis viesturs.la...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: [Emc-users] US Digital encoders? Hello! The conclusion of my struggle with tuning servo motors is that I shall change encoders. I based it on Jon's findings, when testing AMT 102 encoders and I also got a feedback from a local guy, who also had used them on a cnc machine. Sorry, Peter, I could not figure out, how to precisely stop machine at the same spot to check for lost/gained encoder counts. With 3277 pulses per 1 mm I do not see a way to detect any deviance of less than thousand pulses. Here's one way: Mark the shaft and the stator with a pencil/scribe at DRO reading of 0. Move around a lot or until you have the stall problem, turn off motor power and hand crank back to DRO 0 and check pencil mark alignment. This should get you to within a few 10s of counts I would like to ask, if anyone could provide some recommendations for US Digital encoders - I chose them, because they seem to be next in the line in terms of affordability. I was particularly looking at E7P. I have Keling KL23BLS_115 Nema 23 servo motors: http://kelinginc.net/KL23BLS_115.pdf 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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] US Digital encoders?
On Mon, 30 Jan 2012, Viesturs L?cis wrote: Date: Mon, 30 Jan 2012 12:18:51 +0200 From: [UTF-8] Viesturs L?cis viesturs.la...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: [Emc-users] US Digital encoders? Hello! The conclusion of my struggle with tuning servo motors is that I shall change encoders. I based it on Jon's findings, when testing AMT 102 encoders and I also got a feedback from a local guy, who also had used them on a cnc machine. Sorry, Peter, I could not figure out, how to precisely stop machine at the same spot to check for lost/gained encoder counts. With 3277 pulses per 1 mm I do not see a way to detect any deviance of less than thousand pulses. I would like to ask, if anyone could provide some recommendations for US Digital encoders - I chose them, because they seem to be next in the line in terms of affordability. I was particularly looking at E7P. I have Keling KL23BLS_115 Nema 23 servo motors: http://kelinginc.net/KL23BLS_115.pdf Viesturs Before you change encoders, and noting that others have used the CUI/AMT encoders with success, can you try a little experiment to make sure this is not a noise -- losing count/commutation issue? The CUI/AMT encoders may have some problems that would affect final tuning but these would not cause oscillation with low gains nor would they cause a change in behaviour at high speeds. A little background first: HostMots2s encoder counters on the 5I23 have a input sample rate of 48 MHz. you have the input filter enabled which means that the A/B/I inputs need to be steady for 15 clocks before being recognized as a high or low. This is ~300 ns and allows count rate up to about 6 MHz. This is much faster than you need. Input noise immunity can be improved by lowering the input sample frequency so that the (typically short) noise pulses are rejected. For example if we set the input sample frequency to ~3 Mhz, we can still count up to 400 KHz or so but now an input pulse less than 5 uSec in width will be rejected. The encoder sample frequency is a settable parameter in the HostMot2 firmware but there is no direct HAL access to this parameter. To set it you must enable the raw mode. This is done by adding the enable_raw keyword to the firmware load line in your .INI file. See the raw mode section of the hostmot2 manual page. Once this has been done you need to setp write_address 13312 # = 0x3400 = encoder Sample Rate Register setp write_data 14 # sample rate is clocklow (48 MHz)/SRR+2 # so divide by 16 = 3 Mhz setp write_strobe true# do write This can be done by hand in the show hal configuration window -- 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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] US Digital encoders?
Viesturs Lācis wrote: I would like to ask, if anyone could provide some recommendations for US Digital encoders - I chose them, because they seem to be next in the line in terms of affordability. US Digital may not be the greatest. At least, at one time, you had to add capacitors to the encoder to make it work with longer signal cables. Avago and Renco make some nice, affordable encoders. I get the Avago units from Avnet, not sure about Renco distributors in EU, but they are now owned by Heidenhain. 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
Re: [Emc-users] US Digital encoders?
2012/1/30 Peter C. Wallace p...@mesanet.com: Before you change encoders, and noting that others have used the CUI/AMT encoders with success, can you try a little experiment to make sure this is not a noise -- losing count/commutation issue? Thank You for the explanation! I really appreciate that! And this kind of test with marking a spot on motor's pulley and frame is neat! Unfortunately I left yesterday after spending 4 days at client's site. And it is several hours to drive there. So I do not have access to machine and it would be way too expensive just to go there and test it. And there is nobody whom I could ask to do it for me :( I do agree that I should gather as much information as possible, before making any decisions, but I find the associated cost to be too high. I have flexible CAT5 cable with shielding used for encoder and hall sensor signals, shield is connected to GND only in the PC end, so I do not think that it could pick up some noise in the cable. I used a superglue to eliminate any chance of slip between motor shaft and encoder wheel. Jon Elson did very good comparison and analysis on these encoders and their poor performance. It is not only machine for my own use, but I also have to provide 2 year warranty, so I do not want to risk of getting encoders working now and then solving this issue again in few months or so. Based on these points I think that I have enough grounding to change the encoders, although that also is adding extra cost. I have no doubts that there are users who are happy with their CUI encoders. But there are also many cases, when CUI has let their customers down. Unfortunately I have heard opinions only from that second group. 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] US Digital encoders?
On Mon, 30 Jan 2012, Viesturs L?cis wrote: Date: Mon, 30 Jan 2012 22:33:57 +0200 From: [UTF-8] Viesturs L?cis viesturs.la...@gmail.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: Re: [Emc-users] US Digital encoders? 2012/1/30 Peter C. Wallace p...@mesanet.com: Before you change encoders, and noting that others have used the CUI/AMT encoders with success, can you try a little experiment to make sure this is not a noise -- losing count/commutation issue? Thank You for the explanation! I really appreciate that! And this kind of test with marking a spot on motor's pulley and frame is neat! Unfortunately I left yesterday after spending 4 days at client's site. And it is several hours to drive there. So I do not have access to machine and it would be way too expensive just to go there and test it. And there is nobody whom I could ask to do it for me :( I do agree that I should gather as much information as possible, before making any decisions, but I find the associated cost to be too high. I have flexible CAT5 cable with shielding used for encoder and hall sensor signals, shield is connected to GND only in the PC end, so I do not think that it could pick up some noise in the cable. I used a superglue to eliminate any chance of slip between motor shaft and encoder wheel. Jon Elson did very good comparison and analysis on these encoders and their poor performance. It is not only machine for my own use, but I also have to provide 2 year warranty, so I do not want to risk of getting encoders working now and then solving this issue again in few months or so. Based on these points I think that I have enough grounding to change the encoders, although that also is adding extra cost. I have no doubts that there are users who are happy with their CUI encoders. But there are also many cases, when CUI has let their customers down. Unfortunately I have heard opinions only from that second group. Viesturs I am suggesting this test because if there is a noise problem, different encoders may not help. A possible noise source is the PWM signals. This can couple into the encoder if the motor frame ground is not returned to system ground -- 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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] US Digital encoders?
2012/1/30 Peter C. Wallace p...@mesanet.com: I am suggesting this test because if there is a noise problem, different encoders may not help. Of course, I totally agree, but I just did not see a reason for noise by now. A possible noise source is the PWM signals. This can couple into the encoder if the motor frame ground is not returned to system ground Motor GND comes from transformator + rectifier bridge, so it is isolated from encoder power supply. Motor GND is connected to motor frame, so basically - to machine frame. I have not yet connected machine frame to earth ground, but I am planning on doing so for safety purposes. So it means that in that case mains supply and motor supply will not be isolated any more. Does Your suggestion imply doing this kind of connection or should I connect motor GND and encoder GND? 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] US Digital encoders?
On Jan 30, 2012, at 3:56 PM, Viesturs Lācis wrote: 2012/1/30 Peter C. Wallace p...@mesanet.com: I am suggesting this test because if there is a noise problem, different encoders may not help. Of course, I totally agree, but I just did not see a reason for noise by now. A possible noise source is the PWM signals. This can couple into the encoder if the motor frame ground is not returned to system ground Motor GND comes from transformator + rectifier bridge, so it is isolated from encoder power supply. Motor GND is connected to motor frame, so basically - to machine frame. I have not yet connected machine frame to earth ground, but I am planning on doing so for safety purposes. So it means that in that case mains supply and motor supply will not be isolated any more. Does Your suggestion imply doing this kind of connection or should I connect motor GND and encoder GND? Do you have differential drivers for the encoders or are you running them single ended? For reliability (your two year warranty) I would certainly run them with differential drivers. Also, I am with Peter, I think that you aren't going to magically fix the problem with new encoders. The issue that Jon found is very subtle and (may - or may not) help to get the last little bit of error out of the system but it isn't going to help with gross movement. Sounds like something else is at fault currently. It is so easy to pick up noise even when you think you have taken all precautions. It took me weeks to find out I had two simultaneous issues where solving one at time didn't look like it helped, finally, solving them both and my issue went away. I had re-route wires that I thought were out of the way even further out of the way of some Gecko stepper drivers AND add a decoupling capacitor to my single input to a spindle motor driver. I would put the encoder signals on an oscilloscope and see what they look like to the controller. You may discover a lot of crap that shouldn't be there... Or, it could be noise introduced into your signal driving the motors (rather than the encoders). That was an issue we ran into on the Plasma gantry table and had to design some custom filters to deal with it. -Tom -- 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] US Digital encoders?
are you using the ttl - differential converter/transmitters that you can get for the CUI/AMT encoders? (they are $10 US) we had issues with ttl encoders above about 15ft. (shielded cable) We have used them on our conversion and they work great (even for non cui/amt encoders) sam On 01/30/2012 02:56 PM, Viesturs Lācis wrote: 2012/1/30 Peter C. Wallacep...@mesanet.com: I am suggesting this test because if there is a noise problem, different encoders may not help. Of course, I totally agree, but I just did not see a reason for noise by now. A possible noise source is the PWM signals. This can couple into the encoder if the motor frame ground is not returned to system ground Motor GND comes from transformator + rectifier bridge, so it is isolated from encoder power supply. Motor GND is connected to motor frame, so basically - to machine frame. I have not yet connected machine frame to earth ground, but I am planning on doing so for safety purposes. So it means that in that case mains supply and motor supply will not be isolated any more. Does Your suggestion imply doing this kind of connection or should I connect motor GND and encoder GND? 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 -- 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] US Digital encoders?
On Mon, 30 Jan 2012 11:22:36 -0600 Jon Elson el...@pico-systems.com wrote: Viesturs Lācis wrote: I would like to ask, if anyone could provide some recommendations for US Digital encoders - I chose them, because they seem to be next in the line in terms of affordability. US Digital may not be the greatest. At least, at one time, you had to add capacitors to the encoder to make it work with longer signal cables. Avago and Renco make some nice, affordable encoders. I get the Avago units from Avnet, not sure about Renco distributors in EU, but they are now owned by Heidenhain. Viesturs, I've had good luck with Koyo encoders from Automation Direct. I use the TRD-2500-VD. differential, 2500 lpr, light duty ... dust sealed and have had no trouble with them. They are more expensive than the USD but still, I think, available at a good price. I also assume you use a star grounding system for your encoder and signal cables. On my Mazak all the cables have a section of bare shielding braid that is clamped to a grounding bar. I've monitored an encoder line for 24 hours and not had a single hit. :-) Dave 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
