From: gene h. <ghe...@wd...> - 2011-10-09 15:02:45
|
On Sunday, October 09, 2011 10:00:38 AM Bruce Klawiter did opine: > Jon Elson <elson@...> writes: > > Yeah, actually, I'd like to see one of these spikes zoomed in on the > > time scale so it is > > See image 9 here: https://sites.google.com/site/bmklawt/home/pid-tuning > > > Bruce says he has run it back > > and forth for > > a half hour, and it was within one encoder count of proper position > > (.0005") It seems VERY > > unlikely it could do that without errors accumulating. > > I am not following this, why can't it do this without errors > accumulating. If his position feedback is entirely from the encoders, these are generally digital and less subject to noise pickup. So each time it is disturbed, the position feedback corrects it. It could run for days that way with no accumulated error. > > I think Bruce has an oscilloscope, > > I do not have one, wouldn't have a clue how to use it if I did. The interpretation is similar to what you see with the halscope. Time is the horizontal axis, voltage (or whatever you are measuring) is the vertical axis. > I unhooked the Y and Z axis amps and only had the X axis plugged into > the DAC board and when running the X axis it still had random jerks. This looks as if something is disturbing the D/A output to the motor driver. The position feedback is then correcting it. > Here are two videos of the jitter I get in the Z and Y axis. > The > first one showing the Z axis jitter when the X axis is moving back and > forth. The knob is on the end of the servo motor. > http://www.youtube.com/watch?v=7wZQwee8bec > > The second one is of the Y axis while the X axis is homing, as soon as > the X axis stop so does the Y jitter > http://www.youtube.com/watch?v=O66oefYwhp0 Now, this is a small clue. And I would read that as meaning that somewhere, it appears the ground connection from the D/A might be sharing a path with some motor current. A ground loop maybe that defeats the intention of the star topology? With the power removed, you should be able to lift each circuits ground conductor from the 'star' connection point, and measure between the star point and the lifted connection without finding there is still a low resistance path between them. Low being defined as below 20 ohms generally but this isn't a hard and fast rule. Basically, each circuits common point, and each servo _is_ likely 2 circuits, one for power & one for control in which case each should be connected to this star point with no connection between them except at the 'star' point, and a path to earth ground then is nothing more than another wire leaving this 'star' common point. It is there for your safety, or should be, but the rest of the system shouldn't care. If you are using shielded cables, don't use the shield for ground currents, tie it to the 'star' and cut it loose and back for insulation at the other end. Any grounds in that cable also get connected to the star point. The idea being that if there is only one common point, then any noise on this common point is impressed equally on all connections common to this 'star' point, thus becoming 'longitudinal' noise that because all the circuitry works on differences, is not seen and has no effect. I hope this helps. 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) Your heart is pure, and your mind clear, and your soul devout. |
From: Bruce K. <bm...@ya...> - 2011-10-09 19:16:47
|
--- On Sun, 10/9/11, gene heskett <ghe...@wd...> wrote: >Now, this is a small clue. And I would read that as meaning that >somewhere, it appears the ground connection from the D/A might be sharing a >path with some motor current. A ground loop maybe that defeats the >intention of the star topology? >"star point" What is the "star point"? |
From: gene h. <ghe...@wd...> - 2011-10-10 01:59:08
|
On Sunday, October 09, 2011 09:37:58 PM Bruce Klawiter did opine: > --- On Sun, 10/9/11, gene heskett <ghe...@wd...> wrote: > >Now, this is a small clue. And I would read that as meaning that > >somewhere, it appears the ground connection from the D/A might be > >sharing a path with some motor current. A ground loop maybe that > >defeats the intention of the star topology? > >"star point" > > What is the "star point"? Sorry, I probably should have elaborated on that. Imagine that someplace in this equipment, you have a long bolt whose head is spot welded to the frame. This is the only ground point in the system and all other signal and power supply commons are stacked up on this one bolt, reaching out to the rest of the circuit with individual wires for each circuit that needs a ground reference. So it would resemble a star, where the bolt is the center of the star with the wires leaving it in all directions. No other ground connections are allowed because that would make a ground loop with currents flowing around the loop between the two grounds. The idea of a single point ground is just that, one common ground for the whole system. However even the use of 'ground' in the sense that it is connected to an earth ground, is generally not all that important. What is important is having one, and only one, point in the system where all the commons come together. So when you see 'star point' think of this one single long bolt, it is the 'star' point. 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) "Life is too important to take seriously." -- Corky Siegel |
From: Bruce K. <bm...@ya...> - 2011-10-10 04:03:34
|
--- On Sun, 10/9/11, gene heskett <ghe...@wd...> wrote: >The idea of a single point ground is just that, one common ground for the >whole system. However even the use of 'ground' in the sense that it is >connected to an earth ground, is generally not all that important. What is >important is having one, and only one, point in the system where all the >commons come together. Thanks I understand that |
From: gene h. <ghe...@wd...> - 2011-10-10 04:40:39
|
On Monday, October 10, 2011 12:34:15 AM Bruce Klawiter did opine: > --- On Sun, 10/9/11, gene heskett <ghe...@wd...> wrote: > >The idea of a single point ground is just that, one common ground for > >the whole system. However even the use of 'ground' in the sense that > >it is connected to an earth ground, is generally not all that > >important. What is important is having one, and only one, point in > >the system where all the commons come together. > > Thanks I understand that You are welcome. But when you find it, we all want to know what you found so that one of us is vindicated. No secrets here and no big ego's either. ;-) It wouldn't be the first time I was wrong in 77 years, but I am a C.E.T. (Certified Electronics Technician) now retired from the CE chair at one of the local TV stations, where since 1984, I have (alone about half the time) kept them on the air, and still help out occasionally. 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) The rule on staying alive as a program manager is to give 'em a number or give 'em a date, but never give 'em both at once. |
From: Bruce K. <bm...@ya...> - 2011-10-15 14:18:51
|
Trying to get rid of spikes, see image 8 here: https://sites.google.com/site/bmklawt/home/pid-tuning See the jitter here: http://www.youtube.com/user/bmklawt >Probably not the root cause of the problem, but you might try commenting >out all the backlash statements in your ini file. < Tried this, no change < >OK, well, this is looking like there is a problem in the servo amps. >Maybe you need to check the + and - 15 Volts, or whatever the servo amps use >as the supply for their op-amps. Capacitors may have deteriorated and there is >noise on these supplies.. > I checked this it has +15 volts and -15.2 volts, I don't know how to check for noise < >Possibly you have grounded a circuit that should not be grounded to the >machine's common ground. > Grounding problem has been mentioned a lot, I always assumed ground was ground, everything in the control is grounded to the chassis. It is pretty much as it was originally. I have a crude schematic here, maybe someone can find the problem: https://sites.google.com/site/bmklawt/home/control-schematic > >Another thought is that the logic signal that enables the servo amps is not being >held at the right voltage, so the servo amps are right on the edge of >enabling/disabling. This can cause a transient every time the amp enables that >causes it to jump.. > How would I check this? > >polarity of the signals is important. The command input "SIG" is on J1 Pin 2. >The signal common, for tach, command and anything else is J1 Pin 4. J1 Pin 4 >needs to be connected to the ground of the DAC board. > Well I am sure this is right if it is backwards the servos run away > >If the connections are right, then I'd suggest running a big ground wire from the >servo amp chassis to the PPMC. > Did this, no change > >On the power supply that feeds the amps, is its output common grounded >to something? And does the motor return line come back directly to the >power supply common, without connecting to anything else along the way? > Well there is two power supplies going to the amps so I am confused, please see the schematic here https://sites.google.com/site/bmklawt/home/control-schematic I don't know were the motor return line is > Your help is greatly appreciate |
From: gene h. <ghe...@wd...> - 2011-10-15 16:21:09
|
On Saturday, October 15, 2011 12:12:40 PM Bruce Klawiter did opine: > Trying to get rid of spikes, see image 8 here: > https://sites.google.com/site/bmklawt/home/pid-tuning > > See the jitter here: http://www.youtube.com/user/bmklawt > > >Probably not the root cause of the problem, but you might try > >commenting out all the backlash statements in your ini file. > > < > Tried this, no change > < > > >OK, well, this is looking like there is a problem in the servo amps. > >Maybe > > you need to check the + and - 15 Volts, or whatever the servo amps use > > >as the supply for their op-amps. Capacitors may have > > deteriorated and there is >noise on these supplies.. > > I checked this it has +15 volts and -15.2 volts, I don't know how to > check for noise < > > >Possibly you have grounded a circuit that should not be grounded to the > >>machine's common ground. > > Grounding > problem has been mentioned a lot, I always assumed ground was ground, > everything in the control is grounded to the chassis. It is pretty much > as it was originally. I have a crude schematic here, maybe someone can > find the problem: > https://sites.google.com/site/bmklawt/home/control-schematic > > >Another > > thought is that the logic signal that enables the servo amps is not > being >held at the right voltage, so the servo amps are right on the > edge of >enabling/disabling. This can cause a transient every time > the amp enables that >causes it to jump.. > > How would I check this? > > >polarity of the signals is important. The command input "SIG" is on J1 > >Pin 2. The > > signal common, for tach, command and anything else is J1 Pin 4. J1 Pin > 4 >needs to be connected to the ground of the DAC board. > > Well I am sure this is right if it is backwards the servos run away > > >If the connections are right, then I'd suggest running a big ground > >wire from the >servo amp chassis to the PPMC. > > Did this, no change > > >On the power supply that feeds the amps, is its output common grounded > >to something? And does the motor return line come back directly to the > >power supply common, without connecting to anything else along the way? > > Well there is two power supplies going to the amps so I am > confused, please see the schematic here > https://sites.google.com/site/bmklawt/home/control-schematic > I don't know were the motor return line is > I think you will have to find it. There has been a discussion of grounding here on this list just in the last 2 weeks or so, which your drawing isn't complete enough to tell if its right or wrong. Basically, everyplace your drawing shows as going to ground should go there on its own wire, and they should meet at one common bolt. There shouldn't be a measurable path to this bolt from any wire that has been disconnected from this bolt, it is the center of the 'star'. Any other ground will make a 'ground loop' and the circulating currents will develop voltages that can mess with the servo's. This could even call for remounting power supplies so they are isolated from the mounting if they are internally grounded. > Your help is greatly appreciate > ------------------------------------------------------------------------ > ------ All the data continuously generated in your IT infrastructure > contains a definitive record of customers, application performance, > security threats, fraudulent activity and more. Splunk takes this data > and makes sense of it. Business sense. IT sense. Common sense. > http://p.sf.net/sfu/splunk-d2d-oct > _______________________________________________ > Emc-users mailing list > Emc...@li... > https://lists.sourceforge.net/lists/listinfo/emc-users 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) Pilfering Treasury property is paticularly dangerous: big thieves are ruthless in punishing little thieves. -- Diogenes |
From: Jon E. <el...@pi...> - 2011-10-15 21:27:55
|
gene heskett wrote: >> Well there is two power supplies going to the amps so I am >> confused, please see the schematic here >> https://sites.google.com/site/bmklawt/home/control-schematic >> I don't know were the motor return line is >> > I think you will have to find it. There has been a discussion of grounding > here on this list just in the last 2 weeks or so, which your drawing isn't > complete enough to tell if its right or wrong. Basically, everyplace your > drawing shows as going to ground should go there on its own wire, and they > should meet at one common bolt. The Westamp servo amps in question appear to have a full isolation barrier between control circuits and power circuits. If that is true, it is not necessary, and may be undesirable to tie these two power supplies common. > There shouldn't be a measurable path to > this bolt from any wire that has been disconnected from this bolt, it is > the center of the 'star'. Any other ground will make a 'ground loop' and > the circulating currents will develop voltages that can mess with the > servo's. This could even call for remounting power supplies so they are > isolated from the mounting if they are internally grounded. > Yup, that is a concern. The fact that his Z axis appears to have abnormal transients even when disconnected from any command input at the same time the X has similar transients seems to indicate a ground loop **IS** to blame for this. There should be NO WAY that two amplifiers should have this kind of transient at the same time. When disconnected from the command source (the PPMC DAC board in this case) then the only connections I see are the +/- 15 V analog supply to the servo amps and the motor power supply, and the system ground. Somehow, something is being communicated between the X and Z amp that shouldn't be. Jon |
From: Bruce K. <bm...@ya...> - 2011-10-16 03:53:07
|
>Yup, that is a concern. The fact that his Z axis appears to have >abnormal transients even when disconnected from any command input at the >same time the X has similar transients seems to indicate a ground loop **IS** to >blame for this. There should be NO WAY that two amplifiers should have this >kind of transient at the same time. When disconnected from the command >source (the PPMC DAC board in this case) then the only connections I see are >the +/- 15 V analog supply to the servo amps and the motor power supply, and >the system ground. Somehow, something is being communicated between the >X and Z amp that shouldn't be. > >Jon > I may not be understanding this, when you say the "The fact that his Z axis appears to have abnormal transients even when disconnected from any command input" are you saying I unplugged something or just that there is no code telling the Z axis to move. I guess the next thing to do is run all the grounds to one common location. Should they all go to the ground coming in from the 120 volt supply? Do I need to isolate the the power supplies from the chassis and also ground those to the common ground? I will run all the test and do all the other suggestion that have been mention, that I am able to do and report back. Just out of curiosity what more do need in the schematic to make it complete. https://sites.google.com/site/bmklawt/home/control-schematic Much appreciated, Bruce |
From: Jon E. <el...@pi...> - 2011-10-16 05:04:58
|
Bruce Klawiter wrote: >> > I may not be understanding this, when you say the "The fact that his Z axis appears to have abnormal transients even when > disconnected from any command input" are you saying I unplugged something or just that there is no code telling the Z axis to move. > My understanding from a message about a week ago was that you had disconnected the DAC board from the Z axis amp, and still saw a twitch on the Z at the same time as the X twitched. If I got that wrong, sorry, but I was pretty sure that was what you said was the setup when you posted Image 8. If you just disconnected the DAC by removing HAL lines in the config files, then that is a very different thing, and doesn't prove that the spikes are not coming from the DAC. If that is what you did, I would disconnect the DAC from Z amp and see if you can still get these spikes in X and Z at the same time. And, if you mean by "no code telling Z to move" that there was no G01 Z1.234 line in the G-code program, that is not correct, as the PID component is normally controlling ALL axes ALL the time, even if that control is to keep them in the same place. The encoder moves a count this way or that, and the servo loop is responsible for moving them back to the commanded position. > I guess the next thing to do is run all the grounds to one common location. Should they all go to the ground coming in from the 120 volt supply? > Do I need to isolate the the power supplies from the chassis and also ground those to the common ground? > I will run all the test and do all the other suggestion that have been mention, that I am able to do and report back. > I'd really advise against major electrical modifications without understanding what is wrong and why. Jon |
From: Bruce K. <bm...@ya...> - 2011-10-16 19:50:33
|
>My understanding from a message about a week ago was that >you had disconnected the DAC board from the Z axis amp, and >still saw a twitch on the Z at the same time as the X twitched. I must have not have been very clear on that, what I said or meant to say is, I disconnected the Z and Y axis from the DAC and disconnected all the connectors from the Y and Z amps. With the Y and Z axis disconnected the X axis still twitches. I have disconnected the X axis and the Y and Z still twitch. If all the axes are connected and I run any one axis I get the twitching on all the axes, 99% of the time. Once in a blue moon one axis will twitch by itself, if that means anything. I did just unplug the Z axis from the DAC and the twitching went away on the Z axis. |
From: Jon E. <el...@pi...> - 2011-10-17 04:34:07
|
Bruce Klawiter wrote: > > >> My understanding from a message about a week ago was that >> you had disconnected the DAC board from the Z axis amp, and >> still saw a twitch on the Z at the same time as the X twitched. >> > > I must have not have been very clear on that, what I said or meant to say is, I disconnected the Z and Y axis from the DAC and disconnected all the connectors from the Y and Z amps. With the Y and Z axis disconnected the X axis still twitches. > I have disconnected the X axis and the Y and Z still twitch. > To ME, "disconnect" means removing wires. Do you mean you removed the HAL net command lines in one of the config files? That really does not do much, the driver is still writing the last value, or zero, to the DAC channel, every servo cycle. > If all the axes are connected and I run any one axis I get the twitching on all the axes, 99% of the time. Once in a blue moon one axis will twitch by itself, if that means anything. > > I did just unplug the Z axis from the DAC and the twitching went away on the Z axis. > OK, so unplug is physical, and "disconnect" is software, is that right? If so, this now indicates the completely opposite situation. It might still be a ground loop, but is looking more and more like there is a communication error between the PPMC and the computer. There is a DAC communication test, but it can give misleading results, that's why I did not mention it before. Can you run the ppmcdiags with the "dactest" option, otherwise exactly the same as the commtest and other options? If you get error messages it may not mean a lot, as the DAC is normally a write-only device, and the test writes and reads back the values. Writing has always been fine, but reading back has some timing problems and so gives errors on some parallel ports. Errors in reading back won't affect the motion system, but the test can't distinguish between write errors and read errors. Oh, VERY IMPORTANT, do not have the servo amps enabled when running this test! It writes random values to the DAC, and would drive the servos wild. If this doesn't turn up any useful info, then you may have to find a friend with an oscilloscope to check if there are pulses coming out of the DAC analog outputs. If there are such pulses, then we will have to find out what is causing them. Jon |
From: Bruce K. <bm...@ya...> - 2011-10-17 05:14:22
|
> I must have not have been very clear on that, what I said or >meant to say is, I disconnected the Z and Y axis from the >DAC and disconnected all the connectors from the Y and Z > >amps. With the Y and Z axis disconnected the X axis still twitches. >I have disconnected the X axis and the Y and Z still twitch. > >To ME, "disconnect" means removing wires. > Jon, sorry this is so confusing, when I say unplugged or disconnected I mean the same thing, I am removing the wires from the DAC or amp. I don't have the smarts to know how to disconnect things through the hal file. Bruce |
From: Jon E. <el...@pi...> - 2011-10-17 17:25:22
|
Bruce Klawiter wrote: >> I must have not have been very clear on that, what I said or >> meant to say is, I disconnected the Z and Y axis from the >> DAC and disconnected all the connectors from the Y and Z > >> amps. With the Y and Z axis disconnected the X axis still twitches. >> I have disconnected the X axis and the Y and Z still twitch. >> >> To ME, "disconnect" means removing wires. >> >> > Jon, sorry this is so confusing, when I say unplugged or disconnected > I mean the same thing, I am removing the wires from the DAC or amp. > > I don't have the smarts to know how to disconnect things through the > hal file. > Well, now then, I am really confused! One time you said that the jerks were still there on the Z axis with it "disconnected", now lately you seem to say the Z axis twitch was gone when you unplugged the Z axis cable. I think we have to step back and be very careful to say exactly what we are doing and what happened. But, if you still get twitches on the Y or Z axis with the DAC disconnected, then it is clear there is some problem in the servo amps. Jon |
From: Bruce K. <bm...@ya...> - 2011-10-17 19:46:29
|
Problem solved. Well I hope it is solved and I don't even know how I did it. Here is what I did today, Jon said "You may be able to use the AC range on a DVM, and check while the machine is moving, that might have an effect. The AC range of the meter should show just about zero, anything over 0.1 V AC is highly suspicious that there is ripple on the supply due to failed capacitors." I did this while the X axis was moving and all the axes were twitching, I got a steady reading on the meter. These are the readings DC volts -15.02 on AC range .101, DC volts 15.19 on AC range .001 I think I remember Jon saying the PPMC motherboard is not grounded but could be, by grounding the D-sub body, I checked and it was grounded to the chassis so I thought I would find out how. I unplugged everything from the PPMC boards and found if the amps where plugged into the DAC or the parallel cable was plugged in, the D-sub connector was a dead short to the chassis. Don't know what that means but I made a not of it and put everything back together. With all this talk of grounding I thought I would unscrew the the PPMC motherboard from the chassis and just let it float in mid air. I did this and ran the mill again and the twitching went away, I thought cool I found it, but to make sure I knew I had pinpointed the problem, I remounted the PPMC motherboard back were it was and the twitching has not returned so I don't know what I did. You can see the PPMC boards mounted here:https://sites.google.com/site/bmklawt/home/pictures Any idea what I did that corrected the twitching. Bruce |
From: Jon E. <el...@pi...> - 2011-10-18 02:39:22
|
Bruce Klawiter wrote: > Problem solved. > > Well I hope it is solved and I don't even know how I did it. OHHHhhh NOOooooo! That's the worst kind, as it can come BACK! > Here is what I did today, > Jon said "You may be able to use the AC range on a DVM, and check while the machine is moving, that might have an effect. The AC range of the meter should > show just about zero, anything over 0.1 V AC is highly suspicious that there is > ripple on the supply due to failed capacitors." > > I did this while the X axis was moving and all the axes were twitching, I got a steady reading on the meter. > These are the readings DC volts -15.02 on AC range .101, DC volts 15.19 on AC range .001 > Well, this is NOT OK! .1 V AC on the minus power supply to the op amps in the servo amp is a real problem. And, it isn't your meter, as the + side is reading .001, which is fine. > I think I remember Jon saying the PPMC motherboard is not grounded but could be, by grounding the D-sub body, I checked and it was grounded to the chassis so I thought I would find out how. I unplugged everything from the PPMC boards and found if the amps where plugged into the DAC or the parallel cable was plugged in, the D-sub connector was a dead short to the chassis. > Don't know what that means but I made a not of it and put everything back together. > > Yes, the DAC outputs have a signal pin and a ground pin. The encoder board also has a ground pin for each encoder. > With all this talk of grounding I thought I would unscrew the the PPMC motherboard from the chassis and just let it float in mid air. I did this and ran the mill again and the twitching went away, I thought cool I found it, but to make sure I knew I had pinpointed the problem, I remounted the PPMC motherboard back were it was and the twitching has not returned so I don't know what I did. > > > Any idea what I did that corrected the twitching You had a bad electrical connection. It may have been that the PPMC card cage was NOT grounded to the chassis, and noise was coming from the computer through the parallel port to the PPMC. Anyway, somewhere in this mess, there must have been a bad connection, and in the process of taking it apart and reassembling, a loose screw got put in tighter, paint that was insulating something got scraped away, or something that wasn't plugged in securely got reconnected better. Unfortunately, with older CNC equipment, some of the connectors on them start out being of dubious quality, like tin-plated Molex and AMP connectors, and as they age the connections get more and more flaky. If it comes back, start wiggling and reseating connectors one at a time until you find the exact culprit, and then you'll know what to repair. Make sure the PC power supply is properly grounded to the panel. Another thing might be to run a short ground strap directly from the DB-25 on the PPMC motherboard to one of the mounting screws of the PC motherboard. They look to be only a couple inches apart in the photo. The bad news is this sort of stuff is REALLY common, depending a bit on the environment the equipment has lived in. But, I'm sure glad you got it solved, at least temporarily. (I'm not trying to jinx you!) This proves it is not a fundamental problem, but is almost certainly in the bad connection category. Those can STILL be maddening. Jon |
From: Bruce K. <bm...@ya...> - 2011-10-18 03:33:29
|
>> Well I hope it is solved and I don't even know how I did it. >OHHHhhh NOOooooo! That's the worst kind, as it can come BACK! I know, I spent the rest of the day trying to get the twitching to come back so I would know what the problem was, but I can't. >Well, this is NOT OK! .1 V AC on the minus power supply to the op >amps in the servo amp is a real problem. And, it isn't your meter, >as the + side is reading .001, which is fine. Well then I will have to find a new power supply. >Yes, the DAC outputs have a signal pin and a ground pin. >The encoder board also has a ground pin for each encoder. With only the encoders plugged into the PPMC boards the D-sub connector does not show ground. OK let make sure I am saying this right with only the encoder plugged in and my meter set to ohms, one lead on the D-sub connector and on on the chassis it shows an open circuit. If I plug in the amp to the DAC or the parallel cable my meter shows a dead short. Not that this helps of changes anything I just want to make sure I am explaining it rigth Would there be any benefit to moving all the grounds to one one point, this would be fairly easy to do. Thanks Jon and everyone else for the help |
From: gene h. <ghe...@wd...> - 2011-10-18 03:53:06
|
On Monday, October 17, 2011 11:46:15 PM Bruce Klawiter did opine: > >> Well I hope it is solved and I don't even know how I did it. > > > >OHHHhhh NOOooooo! That's the worst kind, as it can come BACK! > > I know, I spent the rest of the day trying to get the twitching to come > back so I would know what the problem was, but I can't. > > >Well, this is NOT OK! .1 V AC on the minus power supply to the op > >amps in the servo amp is a real problem. And, it isn't your meter, > >as the + side is reading .001, which is fine. > > Well then I will have to find a new power supply. > > >Yes, the DAC outputs have a signal pin and a ground pin. > >The encoder board also has a ground pin for each encoder. > > With only the encoders plugged into the PPMC boards the D-sub > connector does not show ground. > OK let make sure I am saying this right with only the encoder > plugged in and my meter set to ohms, one lead on the D-sub > connector and on on the chassis it shows an open circuit. If I plug > in the amp to the DAC or the parallel cable my meter shows a dead short. > Not that this helps of changes anything I just want to make sure I > am explaining it rigth I would go to the far end of this cable and opern up the dsub shell and break the connection there. It is making a ground loop. > Would there be any benefit to moving all the grounds to one one point, > this would be fairly easy to do. I would certainly try it. I have had no problems, but that is how I have always done it. With my 60 years of chasing electrons for a living, that is a lesson I learned about the first time I ever built an audio amplifier at about 15 YO. A Williamson circuit, using KT-66 vacuum tubes. > Thanks Jon and everyone else for the help > ------------------------------------------------------------------------ > ------ All the data continuously generated in your IT infrastructure > contains a definitive record of customers, application performance, > security threats, fraudulent activity and more. Splunk takes this data > and makes sense of it. Business sense. IT sense. Common sense. > http://p.sf.net/sfu/splunk-d2d-oct > _______________________________________________ > Emc-users mailing list > Emc...@li... > https://lists.sourceforge.net/lists/listinfo/emc-users 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) Classical music is the kind we keep thinking will turn into a tune. -- Kin Hubbard, "Abe Martin's Sayings" |
From: Bruce K. <bm...@ya...> - 2013-06-26 03:03:21
|
I need help to get me started on this. The winch is to drop and raise a chandelier for the local high school doing Phantom of the opera, I am building the chandelier and would like to build the winch also. The chandelier I'm guessing will weight 200 pound and the winch can be 120 volts I would like to drop, free fall the chandelier 16 to 25 feet then in the last foot or so arrest its fall so it crumples on the stage without actually crashing into the stage floor, then raise it back up slowly. I'm thinking I could just attach a spool to a servo motor and unwind the cable really fast, some question I have would be what motor, how do I size the motor, what controller that's easy to program, how do you guarantee the cable does not get tangled up, how do you make the cable wind up side to side on the spool. Any help or ideas I can get on this project or if you can point me where i can go to learn or get help will be greatly appreciated. Regards, Bruce |
From: John K. <jmk...@fa...> - 2013-06-26 04:28:51
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Priority number one needs to be safety. Lifting 200 lbs is not a big deal. Lifting 200 lbs when people might be underneath is a very big deal. If something breaks and it drops 16 to 25 feet it could kill somebody. Maybe you already know all this stuff - in that case, please don't be offended. Better safe than sorry. Does the stage already have a fly system? Even if it is manual, having the pulleys and counterweight system in place simplifies things a lot. In any case, I would strongly recommend counterweighting the chandelier. Hang two strong pulleys in the fly loft, one where you want the chandelier, and one backstage or in the wings. Run a cable from the chandelier to the first pulley, then the second, then the counterweight. Make the counter weight maybe 10-20 lbs heavier than the chandelier, so the chandelier will naturally want to go up. Then to drop it, use the motor to lift the counterweight. That way, if the motor fails, the chandelier goes up. The counterweight will fall, but you can locate it in a spot where it can't hit anyone. Everything should be ridiculously strong and overbuilt if there is any chance of people under the load. Breaking strength of all cable, fittings, pulleys, and rigging should be at least ten times the maximum expected load. Use as much redundancy as possible. Pulleys should be hung from the ceiling from strong structural members, using two independent methods of attachment. One that bears the load under normal conditions, and a backup (such as a loop of chain or steel cable) in case the first one breaks or comes loose or slips. The backup loop probably should pass below the actual lifting cable, so even if something crazy happens (like the pulley axle failing), the cable will still be caught by the safety line. Ideally you would never let it be above people at all. Perhaps you can drop it at the very front edge of the stage, and instruct the cast to never enter or cross that spot. Be very cautious about lifting and especially holding any significant weight with a servo. If the drive shuts down or trips out for any reason, the weight will drop unless the motor has a brake, AND the brake is properly interlocked with the drive, AND it works correctly. Holding a weight stationary is typically harder on the drive and the motor than making the same torque while spinning - that just increases the risk that the drive might overheat and shut down. My gut tells me that it will be very difficult to slow the "falling" chandelier without it being very obvious. The mind knows what a falling object should do, and is pretty good at detecting "unnatural" behavior. The control can be done in HAL if you want. It isn't hard to set up a servo loop with a PID controller. The position command could come from hal-streamer, which would let you define a position vs time profile using something as simple as a spreadsheet, and play it back exactly as many times as you want. You could experiment with different profiles to try to get something that looks as natural as possible. Making the cable wind evenly side to side can be done with a level wind mechanism. If the cable is short and thin and the drum is wide it can be a simple threaded rod 6 inches or so in front of the drum that is belted or geared to the drum, and moves a guide across the drum. For example, assume you are using a 1/4" cable, and your drum is 4" in diameter. One turn of the drum means 4 times pi = 12.56 inches. Call it a foot. To handle 25 feet of line, you will have 25 wraps on the drum. If each wrap is 1/4" and you want to have a single neat layer, then the total width of the drum needs to be at least 25 times 1/4" = 6.25 inches. If your level wind uses 3/8-16 threaded rod, it will take four turns of the rod to move the cable guide 1/4". So the threaded rod needs to turn four times for every revolution of the drum. Small timing belt pulleys would work for that. A couple years ago I built a system somewhat like this. I was lifting a much smaller load - a prop that weighed less than 10 lbs and was bulky and rather soft - so I didn't have the same safety concerns. I used three winches with a kinematics module in HAL so I could control the prop in three dimensions over a fairly large working envelope. I was using kevlar line that was about 0.035" in diameter. I used 1/4-20 threaded rod for the level wind, geared roughly 4:5 with the drum. So the 0.035" line wound onto the drum at about 0.040" per turn. The drum was over a foot long, so I could fit at least 300 turns on it. The drums were made from 4" schedule 80 PVC pipe with plugs for the motor shaft on one end and a bearing on the other. The OD of the pipe was about 4.5", so when completely wound up I had over 350 feet of line on the drum. The motors were some beefy NEMA 42 steppers with microstepping drives. Even with my much lighter load, powering down the stepper drive would allow the string to unwind and the load to drop, Here is some testing of that system: http://www.youtube.com/watch?v=uVdXyU4W5dQ On Tue, Jun 25, 2013, at 11:03 PM, Bruce Klawiter wrote: > I need help to get me started on this. > The winch is to drop and raise a chandelier for the local high school doing Phantom of the opera, I am building the chandelier and would like to build the winch also. > The chandelier I'm guessing will weight 200 pound and the winch can be 120 volts > I would like to drop, free fall the chandelier 16 to 25 feet then in the last foot or so arrest its fall so it crumples on the stage without actually crashing into the stage floor, then raise it back up slowly. > I'm thinking I could just attach a spool to a servo motor and unwind the cable really fast, some question I have would be what motor, how do I size the motor, what controller that's easy to program, how do you guarantee the cable does not get tangled up, how do you make the cable wind up side to side on the spool. > Any help or ideas I can get on this project or if you can point me where i can go to learn or get help will be greatly appreciated. > > Regards, > Bruce > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by Windows: > > Build for Windows Store. > > http://p.sf.net/sfu/windows-dev2dev > _______________________________________________ > Emc-users mailing list > Emc...@li... > https://lists.sourceforge.net/lists/listinfo/emc-users -- John Kasunich jmk...@fa... |
From: Bruce K. <bm...@ya...> - 2013-10-15 22:37:52
|
I need help First let me say i know zero about controllers. I am building the chandelier for the high schools performance of Phantom of the Opera. I need to remotely control the lights, two actuators and some spark emitters. The chandelier will sit on the stage all crumpled up as the play starts it will slowly raise and the lights will flicker and all come to life as the chandelier reaches is apex. Later in the play we will lower the chandelier a few feet and shake it with the actuators, flicker some of the lights and set off the spark emitters. Everything need to run off a 12 volt battery. There are: 48 LED globes. Some types of spark emitters, not sure what I am using yet, don't want to set of the smoke alarms Some type of linear actuator to pull two tiers of the chandelier together to shake it. Open to suggestions. Run everything but the winch, remotely. I'm told I need a pic controller for this and the engineer where I work says he'll put it all together and program it, but I need to find it and buy it first. Any help I can get on this will be greatly appreciated. Bruce |
From: Dave C. <lin...@gm...> - 2013-10-16 05:03:20
|
When you say remote.. do you mean via wireless ?? If you can run some wire which is obviously needed for the power anyway.. then this can be very simple via some switches and a multi- conductor cable. I'd run the wire down along with the winch line. Surpluscenter.com has some cheap 12 volt actuators.. Don't over think this.. Personally I think a PIC is WAY over thinking this.. a cheap PLC with relay outputs would be easier to work with and more cost effective for a one off like this..(if it is even required) Automation Direct has relay output PLCs for less than $100. The programming software is free. Dave On 10/15/2013 6:34 PM, Bruce Klawiter wrote: > I need help > > First let me say i know zero about controllers. > > I am building the chandelier for the high schools performance of Phantom of the Opera. > I need to remotely control the lights, two actuators and some spark emitters. > The chandelier will sit on the stage all crumpled up as the play starts it will slowly raise and the lights will flicker and all come to life as the chandelier reaches is apex. > Later in the play we will lower the chandelier a few feet and shake it with the actuators, flicker some of the lights and set off the spark emitters. > > Everything need to run off a 12 volt battery. > There are: > 48 LED globes. > Some types of spark emitters, not sure what I am using yet, don't want to set of the smoke alarms > Some type of linear actuator to pull two tiers of the chandelier together to shake it. Open to suggestions. > Run everything but the winch, remotely. > > I'm told I need a pic controller for this and the engineer where I work says he'll put it all together and program it, but I need to find it and buy it first. > > Any help I can get on this will be greatly appreciated. > Bruce > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60135031&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc...@li... > https://lists.sourceforge.net/lists/listinfo/emc-users |
From: Robert S. <rob...@ho...> - 2013-10-16 07:15:12
|
I would disagree with getting a Plc versus getting a pic micro controller . I use picaxe chips which come preloaded with a boot loader and there is a free programmer available. Picaxe chips come in various sizes. The one I use the most is the 18m2 which are as cheap as 4.95 each. https://www.sparkfun.com/products/10187. If you are looking for a pic chip that does not have a boot loader pre-loaded, they are usually a tad cheaper but they will need a special programmers which run around 80.00 or so. Sent from my iPhone > On Oct 16, 2013, at 1:05 AM, "Dave Cole" <lin...@gm...> wrote: > > When you say remote.. do you mean via wireless ?? > > If you can run some wire which is obviously needed for the power > anyway.. then this can be very simple via some switches and a multi- > conductor cable. I'd run the wire down along with the winch line. > > Surpluscenter.com has some cheap 12 volt actuators.. > > Don't over think this.. Personally I think a PIC is WAY over thinking > this.. a cheap PLC with relay outputs would be easier to work with > and more cost effective for a one off like this..(if it is even > required) Automation Direct has relay output PLCs for less than $100. > The programming software is free. > > Dave > >> On 10/15/2013 6:34 PM, Bruce Klawiter wrote: >> I need help >> >> First let me say i know zero about controllers. >> >> I am building the chandelier for the high schools performance of Phantom of the Opera. >> I need to remotely control the lights, two actuators and some spark emitters. >> The chandelier will sit on the stage all crumpled up as the play starts it will slowly raise and the lights will flicker and all come to life as the chandelier reaches is apex. >> Later in the play we will lower the chandelier a few feet and shake it with the actuators, flicker some of the lights and set off the spark emitters. >> >> Everything need to run off a 12 volt battery. >> There are: >> 48 LED globes. >> Some types of spark emitters, not sure what I am using yet, don't want to set of the smoke alarms >> Some type of linear actuator to pull two tiers of the chandelier together to shake it. Open to suggestions. >> Run everything but the winch, remotely. >> >> I'm told I need a pic controller for this and the engineer where I work says he'll put it all together and program it, but I need to find it and buy it first. >> >> Any help I can get on this will be greatly appreciated. >> Bruce >> >> ------------------------------------------------------------------------------ >> October Webinars: Code for Performance >> Free Intel webinars can help you accelerate application performance. >> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from >> the latest Intel processors and coprocessors. See abstracts and register > >> http://pubads.g.doubleclick.net/gampad/clk?id=60135031&iu=/4140/ostg.clktrk >> _______________________________________________ >> Emc-users mailing list >> Emc...@li... >> https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60135031&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc...@li... > https://lists.sourceforge.net/lists/listinfo/emc-users |
From: Erik C. <dv...@in...> - 2013-10-16 10:19:46
|
On 16.10.13 01:04, Dave Cole wrote: > Don't over think this.. Personally I think a PIC is WAY over thinking > this.. a cheap PLC with relay outputs would be easier to work with > and more cost effective for a one off like this..(if it is even > required) Automation Direct has relay output PLCs for less than $100. > The programming software is free. +1 Something that is ready to go, and programmable in the problem domain (i.e. already has commands which deal with the real world; controlling outputs and timing, as well as sense inputs), will give much quicker results. Having spent 30 years designing with microcontrollers (in telecommunications R&D), I'll offer these thoughts: 1) Both AVR and PIC have their fans, leaving other good contenders such as the MSP430 less popular. Beware of fans pushing their mascot, without fully considering your design issues. Any of them will do your job - after many weeks of learning, design, implementation, and debugging. Heck, even an AT89C2051 has the advantage of eliminating a lot of confusing on-chip hardware from one's first effort. 2) Availability of a bootloader is useful if you need to update the firmware in the field. Otherwise, it adds zero so long as you have a programmer for the device. These are dirt cheap, can be DIY, and can be as little as a few wires from a PC parallel port, in the case of AVR. If tackling a project which _must_work_flawlessly_on_the_night_, without some years of experience with 'C' and assembler programming, then please add a month or two to the project. The other big hurdle is mastering the on-chip hardware on an unfamiliar microcontroller - definitely non-trivial if it's your first. (On one project, I remember the hardware design team sending one of their guys to Australia from Tokyo, with the populated first system prototype under his arm, because it wouldn't do anything. I had chosen the micro, so my team had to help work out which clause of over 300 pages of manual had been overlooked in the circuit design. With perhaps 50 man-years of experience on tap, it was solved in a couple of hours.) A beginner under time pressure may struggle with a series of such device familiarisation experiences. 3) Hand-knitted prototypes can be less than robust. Wires soldered onto pins of devices stuck through matrix board don't endure tumbling around on a stage. If the solution must involve a microcontroller, then grab something like an Arduino, and build the IO on a plug-in daughterboard, which they insist on calling a "shield". 4) If it's DIY, build at _least_ two, and make all connection plug-in. Standing there on the night saying "I think the relay driver's futzed", with no plan B, is not a winning hand for the "man of the night" award. 5) The one essential ingredient in such a design project is time; time to learn, time to make mistakes, time to find them in the code, and time to fix and test and test. But plays don't run to split second schedules. Since remote control is needed anyway for initiation of one or more sequences, is there need for more automation than a PLC can readily provide? Erik -- Harrisberger's Fourth Law of the Lab: Experience is directly proportional to the amount of equipment ruined. |
From: John P. \(FS\) <jo...@ca...> - 2013-10-16 09:54:58
|
Greetings >I'm told I need a pic controller for this and the engineer where I work says he'll put it all together and program it, but I need to find it and buy it first. >Any help I can get on this will be greatly appreciated. I suspect there is a misunderstanding as what you say sounds high risk. Choosing the hardware certainly requires a detailed understanding of the interfaces to your lights, spark generators and actuators. As an EE, I would not like to be given an arbitrary PIC (chip or development board), and driver boards and try to put them together for a one-off project. I too vote for a small PLC - I have not done a detailed search but you might need 24 volts (two batteries) to have the widest choice. John Prentice |