Re: [Emc-users] Where to put controllers?
2009/10/6 Ian W. Wright watchma...@talktalk.net: One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors If you really had enough energy coupling from the spindle motor wires to the stepper wires to create false steps then something really quite scary was going on. The several amps at several volts that flows in the stepper motor cables should be immune to all interference short of a nuclear EMP, whereas the logic-level signals are very easily swamped by RFI (see the discussions on pull-ups in the encoder thread) I am no expert, and we do seem to have one who will probably give you chapter and verse later in the day, but I would say that moving the drivers to the motors was quite a bad idea. -- atp -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
Hi Ian, The signal lines are FAR more sensitive to noise than the stepper lines. It is virtually impossible to pick up enough noise on the motor lines to affect the motor. I don't think your Z axis problem was directly related to pickup on the motor wires. It is possible that there was some noise picked up and it was re-radiated in your control cabinet. I always try to keep the signal lines as short as possible, especially in noisy environments. Les Ian W. Wright wrote: HI, I'm in the process of building a second little mill - this time a stepper-driven gantry type and I'm wondering what the pros and cons might be of different driver locations. On the first mill I had all the controls in a big box under the bench with heavy wires going to each motor but I'm wondering now whether any advantage might be gained in this project by positioning the driver cards adjacent to each motor. This would shorten the cables carrying power to the motor but would mean carrying signal cables from the parallel port around the machine together with DC power wires to each card. One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors and so I had to change to a 'universal' AC motor drive for the spindle which was heavy and limited in speed. I tried various methods of screening the Z-axis motor leads and put ferrite beads over them but nothing seemed to work. As I'd like to use a high speed spindle based on a DC motor on this mill, I wondered if it might be easier to shield the 'signal-in' wires rather than the power wires to the motor. Any thoughts? Ian _ Ian W. Wright Sheffield UK -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, Ian W. Wright wrote: HI, I'm in the process of building a second little mill - this time a stepper-driven gantry type and I'm wondering what the pros and cons might be of different driver locations. On the first mill I had all the controls in a big box under the bench with heavy wires going to each motor but I'm wondering now whether any advantage might be gained in this project by positioning the driver cards adjacent to each motor. This would shorten the cables carrying power to the motor but would mean carrying signal cables from the parallel port around the machine together with DC power wires to each card. One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors and so I had to change to a 'universal' AC motor drive for the spindle which was heavy and limited in speed. I tried various methods of screening the Z-axis motor leads and put ferrite beads over them but nothing seemed to work. As I'd like to use a high speed spindle based on a DC motor on this mill, I wondered if it might be easier to shield the 'signal-in' wires rather than the power wires to the motor. Any thoughts? Ian I may sound like a broken record Ian, but the 'star' grounding configuration, and running all signal and motor drive circuits through a cable similar to Belden Star-Quad with all the shielding for even the motors output drive tied to the central point of this star, where the central point where it all comes together is at the common point. The cumputers ground line from the parport, and the minus rail of the motor power psu are all connected, possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge bare copper that goes from the motor - terminal on the xylotex, around to the side of the box I made for the xylotex board, so that the shields of the motor cables were tied to it. My motor cables are about 6 feet long, and the shields stop short of the motor, no connection on that end. The machines ground is also connected there via a rather circuitous route going through the spindle motors power cable, the one cable that is not shielded, via the PMDX-106 and the interconnecting cable back to the breakout strip on the xylotex. I have not had any noise problems. Belden's search facilities can be confusing. Another supplier might be Canare http://www.canare.com/UploadedDocuments/Cat11_p35.pdf -- 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 NRA is offering FREE Associate memberships to anyone who wants them. https://www.nrahq.org/nrabonus/accept-membership.asp It's a dog-eat-dog world out there, and I'm wearing Milkbone underware. -- Norm, from _Cheers_ -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote: On Tuesday 06 October 2009, Ian W. Wright wrote: HI, I'm in the process of building a second little mill - this time a stepper-driven gantry type and I'm wondering what the pros and cons might be of different driver locations. On the first mill I had all the controls in a big box under the bench with heavy wires going to each motor but I'm wondering now whether any advantage might be gained in this project by positioning the driver cards adjacent to each motor. This would shorten the cables carrying power to the motor but would mean carrying signal cables from the parallel port around the machine together with DC power wires to each card. One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors and so I had to change to a 'universal' AC motor drive for the spindle which was heavy and limited in speed. I tried various methods of screening the Z-axis motor leads and put ferrite beads over them but nothing seemed to work. As I'd like to use a high speed spindle based on a DC motor on this mill, I wondered if it might be easier to shield the 'signal-in' wires rather than the power wires to the motor. Any thoughts? Ian I may sound like a broken record Ian, but the 'star' grounding configuration, and running all signal and motor drive circuits through a cable similar to Belden Star-Quad with all the shielding for even the motors output drive tied to the central point of this star, where the central point where it all comes together is at the common point. The cumputers ground line from the parport, and the minus rail of the motor power psu are all connected, possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge bare copper that goes from the motor - terminal on the xylotex, around to the side of the box I made for the xylotex board, so that the shields of the motor cables were tied to it. My motor cables are about 6 feet long, and the shields stop short of the motor, no connection on that end. The machines ground is also connected there via a rather circuitous route going through the spindle motors power cable, the one cable that is not shielded, via the PMDX-106 and the interconnecting cable back to the breakout strip on the xylotex. I have not had any noise problems. Belden's search facilities can be confusing. Another supplier might be Canare http://www.canare.com/UploadedDocuments/Cat11_p35.pdf I've been known go to Home Depot and buy a Cutler-Hammer neutral bar; and tie everything to that. Seems to work. Dave -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
I've been known go to Home Depot and buy a Cutler-Hammer neutral bar; and tie everything to that. Seems to work. I've done the same thing, it works well. Screw the bar to the steel backplane and make that the center of the star ground. Best thing you can do for CNC components is to put everything into a steel box and use a star ground. Position the box to minimize wiring distances. Put the PC into the same box if you can. That will allow signal wires to be very short minimizing the chances for noise pickup. If you have a spindle VFD, consider putting it in a separate box or put a filter on the front end and the motor leads. Some VFDs are incredible noise makers. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemrd=1item=160367025737ssPageName=STRK:MESE:IT The guy selling these is extremely reputable.. (a shameless plug) ;-) I have other versions of the same PC with PCI slots also for Mesa boards etc. You can actually mount something like this on the inside of the panel door saving space on the backplane for the drives, power supply etc. Automationdirect.com has some decent prices on enclosures, but surplus electrical houses also sell used enclosures usually very cheaply. Dave dave wrote: On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote: On Tuesday 06 October 2009, Ian W. Wright wrote: HI, I'm in the process of building a second little mill - this time a stepper-driven gantry type and I'm wondering what the pros and cons might be of different driver locations. On the first mill I had all the controls in a big box under the bench with heavy wires going to each motor but I'm wondering now whether any advantage might be gained in this project by positioning the driver cards adjacent to each motor. This would shorten the cables carrying power to the motor but would mean carrying signal cables from the parallel port around the machine together with DC power wires to each card. One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors and so I had to change to a 'universal' AC motor drive for the spindle which was heavy and limited in speed. I tried various methods of screening the Z-axis motor leads and put ferrite beads over them but nothing seemed to work. As I'd like to use a high speed spindle based on a DC motor on this mill, I wondered if it might be easier to shield the 'signal-in' wires rather than the power wires to the motor. Any thoughts? Ian I may sound like a broken record Ian, but the 'star' grounding configuration, and running all signal and motor drive circuits through a cable similar to Belden Star-Quad with all the shielding for even the motors output drive tied to the central point of this star, where the central point where it all comes together is at the common point. The cumputers ground line from the parport, and the minus rail of the motor power psu are all connected, possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge bare copper that goes from the motor - terminal on the xylotex, around to the side of the box I made for the xylotex board, so that the shields of the motor cables were tied to it. My motor cables are about 6 feet long, and the shields stop short of the motor, no connection on that end. The machines ground is also connected there via a rather circuitous route going through the spindle motors power cable, the one cable that is not shielded, via the PMDX-106 and the interconnecting cable back to the breakout strip on the xylotex. I have not had any noise problems. Belden's search facilities can be confusing. Another supplier might be Canare http://www.canare.com/UploadedDocuments/Cat11_p35.pdf I've been known go to Home Depot and buy a Cutler-Hammer neutral bar; and tie everything to that. Seems to work. Dave -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, dave wrote: On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote: On Tuesday 06 October 2009, Ian W. Wright wrote: HI, I'm in the process of building a second little mill - this time a stepper-driven gantry type and I'm wondering what the pros and cons might be of different driver locations. On the first mill I had all the controls in a big box under the bench with heavy wires going to each motor but I'm wondering now whether any advantage might be gained in this project by positioning the driver cards adjacent to each motor. This would shorten the cables carrying power to the motor but would mean carrying signal cables from the parallel port around the machine together with DC power wires to each card. One reason for considering this is that, on my previous machine, I had a problem with the Z-axis stepper picking up interference from brushed spindle motors and so I had to change to a 'universal' AC motor drive for the spindle which was heavy and limited in speed. I tried various methods of screening the Z-axis motor leads and put ferrite beads over them but nothing seemed to work. As I'd like to use a high speed spindle based on a DC motor on this mill, I wondered if it might be easier to shield the 'signal-in' wires rather than the power wires to the motor. Any thoughts? Ian I may sound like a broken record Ian, but the 'star' grounding configuration, and running all signal and motor drive circuits through a cable similar to Belden Star-Quad with all the shielding for even the motors output drive tied to the central point of this star, where the central point where it all comes together is at the common point. The cumputers ground line from the parport, and the minus rail of the motor power psu are all connected, possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge bare copper that goes from the motor - terminal on the xylotex, around to the side of the box I made for the xylotex board, so that the shields of the motor cables were tied to it. My motor cables are about 6 feet long, and the shields stop short of the motor, no connection on that end. The machines ground is also connected there via a rather circuitous route going through the spindle motors power cable, the one cable that is not shielded, via the PMDX-106 and the interconnecting cable back to the breakout strip on the xylotex. I have not had any noise problems. Belden's search facilities can be confusing. Another supplier might be Canare http://www.canare.com/UploadedDocuments/Cat11_p35.pdf I've been known go to Home Depot and buy a Cutler-Hammer neutral bar; and tie everything to that. Seems to work. That, and no place else for each branch that leaves it. Same idea as by piece of 12 gauge and a hot soldering iron. Either will work provided the screws are tight enough to present a gas tight joint for extended amounts of time. You cannot do that with alu conductors of course as they cold flow at 20x the rate of copper. This relaxes the joint pressure, air gets in, and alu does what it normally does when exposed to the oxygen in the air, form an insulating film with 100% coverage, and a 30-50 volt breakdown in about one millisecond. Alu is great, in its place, but inside an electrical box of any kind its just a damned fire starter with a long fuse timing. Dave --- --- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net 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) The NRA is offering FREE Associate memberships to anyone who wants them. https://www.nrahq.org/nrabonus/accept-membership.asp The opulence of the front office door varies inversely with the fundamental solvency of the firm. -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
Thanks guys, That's that then, controllers in a cabinet again! Gene, Having worked on installing mainframe computers for many years I do normally use star earths for anything electronic and my previous controller cabinet certainly has this - a central bolt - for all the stepper control stuff and the wiring for each stepper was done in shielded cable with the shielding tied to the star point and the shielding extended right up to, but not tied to the motors.. The spindle - a mains high speed brush motor, however was separately fed via a thyristor speed control board from a relay in the control cabinet. The motor has suppressors across the brushes and to earth and all the earths on this side of things were tied to an earthing point on the machine and so I suppose that there is a vague possibility that interference could have tracked back through the mains wiring although here again, the mains to both parts was fed from the same wall socket. However, I am skeptical of this as the only axis that was affected was the Z-axis - the one nearest the spindle motor. I tried several spindle motors without curing the problem ( the axis would very slowly feed down into the work ) and only solved it when I changed to a synchronous-type of motor. Maybe there was something amiss with the stepper which made it susceptible to interference - I don't know. Ian ___ Ian W. Wright Sheffield UK -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
This relaxes the joint pressure, air gets in, and alu does what it normally does when exposed to the oxygen in the air, form an insulating film with 100% coverage, and a 30-50 volt breakdown in about one millisecond. Alu is great, in its place, but inside an electrical box of any kind its just a damned fire starter with a long fuse timing. While I agree that copper is much superior to alum. and alum wiring when used in places like house wiring didn't turn out so well, however alum power cable is pretty much the standard for service entrances. Also many panel power components are made of alum - often with plating to prevent the oxidatation problems. It's like everything else, if you do it the right way, no problems, ignore the rules and they will come back and bite you. Most alum terminal blocks and even the grounding/neutral bars you can buy at home depot etc are either tin plated copper or tin plated alum. The ones I have used before are tin plated copper. They work great and they are cheap. Dave -- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, Ian W. Wright wrote: Thanks guys, That's that then, controllers in a cabinet again! Gene, Having worked on installing mainframe computers for many years I do normally use star earths for anything electronic and my previous controller cabinet certainly has this - a central bolt - for all the stepper control stuff and the wiring for each stepper was done in shielded cable with the shielding tied to the star point and the shielding extended right up to, but not tied to the motors.. 100% right so far. The spindle - a mains high speed brush motor, however was separately fed via a thyristor speed control board from a relay in the control cabinet. The motor has suppressors across the brushes Ouch! If the motor is being fed by an HF switching VSD, like mine is, that would put a heavier than normal stress on the HexFet such a speed controller uses to control the motor. The problem with the noise filters is that they contain capacitors used as bypasses to shunt the noise to ground, and the charge they absorb at the instant either the thyristor in your control, or the HexFet in mine, are turned on. Then those capacitance's need to be recharged to operating voltage and can absorb 10 of amps for a microsecond or so. That sure can telegraph back through the mains wiring for that drive. I had the top cap off of my spindle motor once because I was curious as to how much trouble it might be to renew the brushes in my PM field universal motor. I did not find any noise suppression in mine. So in my case, all I have is the relatively square wave at about 150 volts peak, at about 25 khz, which _should_ be at least as noisy as the brush arcing. However there is not another power load on the machine, so the green wire in the motors power cord, which now goes back to the VSD I took out of the gear head and put into the same box as the PMDX-106, that ground carries on to the PMDX-106, and on through the control signal cable running the PMDX-106, and hence eventually to my central 'star' point. The only theory I can come up with quickly is that while the machine itself may be grounded via whatever it might have for a power cord, lighting maybe, but that the Z might not be tied to the frame very well due to the lube on the ways. Any number of scenarios can be imagined depending on the machine configuration. In my case, the whole Z drive is bolted solidly to the top of the z post, so that is fairly well grounded. But the Z sled and gibs could lead to some isolation of the noise, again due to the lube on the ways. If you have a decent scope, float its power cord with a 3 to 2 adapter, and ground the probes to a heavier wire that is tied to the star point, and just go poking around to see where the noise is coming from. Bear in mind that long ground will be a good antenna, picking up quite a bit of noise all by itself, but after a while, you get the feel for what is different. Because we're looking for something that is pretty noisy, I'd turn up the gain and just go look for maximum noise that is not the chopper of the axis drives. Just for grins, I'm going to haul my scope out there and see what I find, and I'll report back. Curiosity bumps need rubbed and scratched you know. and to earth and all the earths on this side of things were tied to an earthing point on the machine and so I suppose that there is a vague possibility that interference could have tracked back through the mains wiring although here again, the mains to both parts was fed from the same wall socket. However, I am skeptical of this as the only axis that was affected was the Z-axis - the one nearest the spindle motor. And that, to me, is the puzzling part. There can be borderline situations where just one axis is sensitive enough to be effected, but the instances of it being the z are all out of proportion. I tried several spindle motors without curing the problem ( the axis would very slowly feed down into the work ) and only solved it when I changed to a synchronous-type of motor. Maybe there was something amiss with the stepper which made it susceptible to interference - I don't know. Ian ___ Ian W. Wright Sheffield UK --- --- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net 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) The NRA is offering FREE Associate
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, Dave wrote: This relaxes the joint pressure, air gets in, and alu does what it normally does when exposed to the oxygen in the air, form an insulating film with 100% coverage, and a 30-50 volt breakdown in about one millisecond. Alu is great, in its place, but inside an electrical box of any kind its just a damned fire starter with a long fuse timing. While I agree that copper is much superior to alum. and alum wiring when used in places like house wiring didn't turn out so well, however alum power cable is pretty much the standard for service entrances. Also many panel power components are made of alum - often with plating to prevent the oxidatation problems. Even for power drops they are a fire starter. In my 25 years of being the CE at WDTV, we were knocked off the air and had to replace all the 750mcm cable from the substation pole to the tx building twice due to grand and glorious fireworks from a Burndy Hy-Press installed alu sleeve failing just outside the weather head. Twice. The last time the fire went largely un-noticed by the operator on duty in the building, and the heat telegraphed down our copper 750mcm so well that when we laid the weather head on the ground and pulled it apart, the insulation was cooked for about 3 feet into the weather head. The power guys wanted to run alu into the weather head and into the meter base inside the building, but I scrounged up enough 750mcm in copper that we could rebuild it in copper. But they refused, claiming they didn't have any copper that heavy, to string anything but alu from the weather head to the substation pole. And only 600mcm to boot. I was seen as grumbling about it when I walked away, defeated cuz that run wasn't ours. My house is all copper, but the service drop they replaced with a heavier cable when I added a 200 amp service 4 years ago, is alu.. And every time I'm on the roof, I 'cop a feel' of each crimp sleeve to make sure there's no heat. So far, so good, like the guy that plans to live forever said. I bought a house in Nebraska that had alu jumpers from the meter head outside, to the service box inside, about an 8 inch run. I put out 2 fires in the middle of the night in that box or in the meter head, the 2nd time they got replaced with some 000 I had at the transmitter, color code be damned. And its a felony to break the seal on a meter head in Nebraska. I called Ron, the line super at Wayne County Public power the next morning both times and told him to send somebody by with a new seal. He already knew me well, so the next question was what the hell were you doing in there? knowing the answer was related to alu wire before he asked it. It's like everything else, if you do it the right way, no problems, ignore the rules and they will come back and bite you. If one goes around and inspects it, tightening loose connections, it can be pretty good. The average home owner cannot do that and has no clue that it needs to be done from time to time. He gets his wake up call when his insurance denies his claim because there was alu wire found in the ashes of what was a $350k home.. Most alum terminal blocks and even the grounding/neutral bars you can buy at home depot etc are either tin plated copper or tin plated alum. Even tin plated alu would scare me, cuz that tin plate can't have a continuous metal to metal connection to the alu. Cleanly cut alu will form an oxide coating in a millisecond that is good for 40 volts, and if it lays around a day between machining and plating, it will be good for 400 volts. alu oxide is two things, first the second hardest substance commonly available, and second, a good enough insulator that it has been used as a replacement for the mica or silicon rubber insulators between power transistors and their heat sinks. I've actually seen it use in older transistorized tv's under the horizontal output transistor, which may have as much as 1600 volts on it at the instant its turned off at anywhere from 15 to 120 khz. The ones I have used before are tin plated copper. They work great and they are cheap. Chuckle, with suitable emphasis on the cheap part Dave. Copper is plumb outta sight now. Dave --- --- Come build with us! The BlackBerryreg; Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9#45;12, 2009. Register now#33; http://p.sf.net/sfu/devconf ___ Emc-users mailing list Emc-users@lists.sourceforge.net 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) The
Re: [Emc-users] Where to put controllers?
If I had my druthers, aluminum wire and terminal blocks would not be used also But cheapness pervades.. I've been doing control and power engineering work for about 30 years now and I have only seen a few instances where alum entrance cable has screwed up. Usually because it wasn't prepped properly. But you are right, if you want bullet proof reliability you don't use alum in electrical installation. I am sure that the space shuttle does not have any aluminum terminal blocks in it! Still, try and find a heavy junction power block for industrial use that is not alum It is pretty much impossible. That is also pretty much all the power company will run any longer. I have some new 15KV lines on the poles in front of my place and they are all twisted alum cable. Chuckle, with suitable emphasis on the cheap part Dave. Copper is plumb outta sight now. Actually it has come down a lot. A 500 ft roll of THHN 10 gauge stranded was over a hundred bucks a roll for a while. The last I checked it is about $55 now. It is sort of like gas at $2.30 a gallon, it is cheap compared with $4.50! ;-) The copper ground/neutral bus bars I bought at the local home store recently for a star ground central point were about $6.50 each. Cheap by industrial prices ... I was talking with a customer of mine today... They were talking about some slide mechanisms that had to be replaced on a machine I helped install last year.. The replacement parts being discussed were only about $10K they said So everything is relative. :-) Dave Gene Heskett wrote: On Tuesday 06 October 2009, Dave wrote: This relaxes the joint pressure, air gets in, and alu does what it normally does when exposed to the oxygen in the air, form an insulating film with 100% coverage, and a 30-50 volt breakdown in about one millisecond. Alu is great, in its place, but inside an electrical box of any kind its just a damned fire starter with a long fuse timing. While I agree that copper is much superior to alum. and alum wiring when used in places like house wiring didn't turn out so well, however alum power cable is pretty much the standard for service entrances. Also many panel power components are made of alum - often with plating to prevent the oxidatation problems. Even for power drops they are a fire starter. In my 25 years of being the CE at WDTV, we were knocked off the air and had to replace all the 750mcm cable from the substation pole to the tx building twice due to grand and glorious fireworks from a Burndy Hy-Press installed alu sleeve failing just outside the weather head. Twice. The last time the fire went largely un-noticed by the operator on duty in the building, and the heat telegraphed down our copper 750mcm so well that when we laid the weather head on the ground and pulled it apart, the insulation was cooked for about 3 feet into the weather head. The power guys wanted to run alu into the weather head and into the meter base inside the building, but I scrounged up enough 750mcm in copper that we could rebuild it in copper. But they refused, claiming they didn't have any copper that heavy, to string anything but alu from the weather head to the substation pole. And only 600mcm to boot. I was seen as grumbling about it when I walked away, defeated cuz that run wasn't ours. My house is all copper, but the service drop they replaced with a heavier cable when I added a 200 amp service 4 years ago, is alu.. And every time I'm on the roof, I 'cop a feel' of each crimp sleeve to make sure there's no heat. So far, so good, like the guy that plans to live forever said. I bought a house in Nebraska that had alu jumpers from the meter head outside, to the service box inside, about an 8 inch run. I put out 2 fires in the middle of the night in that box or in the meter head, the 2nd time they got replaced with some 000 I had at the transmitter, color code be damned. And its a felony to break the seal on a meter head in Nebraska. I called Ron, the line super at Wayne County Public power the next morning both times and told him to send somebody by with a new seal. He already knew me well, so the next question was what the hell were you doing in there? knowing the answer was related to alu wire before he asked it. It's like everything else, if you do it the right way, no problems, ignore the rules and they will come back and bite you. If one goes around and inspects it, tightening loose connections, it can be pretty good. The average home owner cannot do that and has no clue that it needs to be done from time to time. He gets his wake up call when his insurance denies his claim because there was alu wire found in the ashes of what was a $350k home.. Most alum terminal blocks and even the grounding/neutral bars you can buy at home depot etc are either tin plated copper or
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, Gene Heskett wrote: [huge snip about strange noises] Just for grins, I'm going to haul my scope out there and see what I find, and I'll report back. Curiosity bumps need rubbed and scratched you know. Back from the shop. I wasn't able to get a extension lead to that star point in my lashup, the closest I could get was the chassis of the stepper motors psu, about 30 of 14 gauge wire away. Just waving the probe around I was able to find the short un-shielded sections between where the shielding of the motor cables stops and the motors, a fair amount of noise that was pretty much gone by the time I was 6 of air away. And my running spindle has about 250 volts of combined noise and power when connected directly to it. The best pickup I could get without connection was about 15 volts with the probe laying against the cable for about 3. That seems fairly noisy, but I can't hear it but very faintly on an AM radio 7 feet away, listening to our local AM'er after daytime hours when he has to reduce to 50 watts at sundown. He plays a mix of county and bluegrass that time of the night. Other neighborhood noises are worse than the spindle motor. Hooked onto the z sled, or to the machine frame, was all the same, and about 4.5 volts of noise was generated by the xylotex, but it was very fast, all settled and quiet well within a microsecond, the majority of it in the first 15 nanoseconds. I am inclined to think that I was looking at the 3 foot ground lead acting as an antenna because I got an identical display when checking the chassis of the psu. Long ground leads can do some real funkity stuff in the less than a microsecond time frames. Noise that you can see, and which lasts much longer than a microsecond, probably should be run down and fixed. But I didn't see anything to worry about. I should probably shield the spindle motor lead but haven't found a shielded cable rated for line voltages and up. Haven't looked all that hard either TBT. -- 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 NRA is offering FREE Associate memberships to anyone who wants them. https://www.nrahq.org/nrabonus/accept-membership.asp Nothing can be done in one trip. -- Snider -- Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Where to put controllers?
On Tuesday 06 October 2009, Dave wrote: If I had my druthers, aluminum wire and terminal blocks would not be used also But cheapness pervades.. I've been doing control and power engineering work for about 30 years now and I have only seen a few instances where alum entrance cable has screwed up. Usually because it wasn't prepped properly. But you are right, if you want bullet proof reliability you don't use alum in electrical installation. I am sure that the space shuttle does not have any aluminum terminal blocks in it! Still, try and find a heavy junction power block for industrial use that is not alum It is pretty much impossible. Yes, a box I put in to service a standby tx about 5 years ago was all alu for its buss bars. Needless to say, all the connections have been re-snugged, several times although its actually wired with copper. That is also pretty much all the power company will run any longer. I have some new 15KV lines on the poles in front of my place and they are all twisted alum cable. And you would be wise to cop a feel of the crimp sleeves at your weather head occasionally. Chuckle, with suitable emphasis on the cheap part Dave. Copper is plumb outta sight now. Actually it has come down a lot. A 500 ft roll of THHN 10 gauge stranded was over a hundred bucks a roll for a while. Ouch! The last I checked it is about $55 now. It is sort of like gas at $2.30 a gallon, it is cheap compared with $4.50! ;-) Sound like I better go stock up on a box of 12-2/wg then, I'm getting low. The copper ground/neutral bus bars I bought at the local home store recently for a star ground central point were about $6.50 each. Cheap by industrial prices ... Yup, considering there is more machine work in making it than there is material in it, that 'work' is what we pay for at the end of the day. I was talking with a customer of mine today... They were talking about some slide mechanisms that had to be replaced on a machine I helped install last year.. The replacement parts being discussed were only about $10K they said So everything is relative. :-) Only eh? But you are correct. In broadcasting, I am constantly amazed at how somebody can take 75 pounds of sheet alu, heliarc weld it into a specific shape for an RF mask filter, and get nearly $20k for the finished product. Until you realize that every dimension in it, is calculated to a tolerance of maybe .005, and it still has adjustment screws they tune once and locktite forever, or until it gets abused and dented. Since this stuff is usually installed on the tx output lines, its normally about ceiling high, catches more hell from the errant stepladder while replacing lamps than anything else. The cost of something is always relative to the cost of the something it goes with. A basic truism. [...] -- 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 NRA is offering FREE Associate memberships to anyone who wants them. https://www.nrahq.org/nrabonus/accept-membership.asp All phone calls are obscene. -- Karen Elizabeth Gordon -- Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
