Hal Eckhart wrote: > > Thanks for responding, Jon. > > I don't really know what a commercial-grade noise filter is, > but I do have a fancy surge supressor. It never helped with > the old system much. > Hal,
Sola is a company that manufactures higher end isolation transformers, surge suppressors and constant voltage transformers. I have acquired some of these from older equipment that was getting scrapped. A constant voltage transformer takes in a wide voltage range like 95-150VAC and outputs a constant 118VAC output. This is good for power line fluctuation where there are brownouts and overages from motors that brake and dump the kinetic energy back into the power lines. Just do a search on ebay. Sola's surge suppressors are going to be in the $100 range on ebay as opposed to a $20 fancy plastic one. Protecting from a one-time event ($20 unit) is different than a constant environment of transient abuse. It has been a while but I used to frequent the 3M surplus store in Minneapolis and they had all kinds of industrial surplus. I'm sure they had some Sola products. I am using a rotary phase converter on my Bridgeport VMC. I had a problem when the spindle quickly ramped down to zero during a stop spindle or a tool change. The kinetic energy in the spindle dumped back through the spindle driver and back into the power lines. Since the rotary phase converter was not as rigid as the power lines my voltage at the rotary phase converter would jump more than 15% or so. When the Bridgeport saw the voltage kick up too high it would fault and require a reset. It was a hard fault and the Z axis would fall about 0.050". A constant voltage transformer would have been a band-aid and probably would have worked in my case. Instead I decided to put a 1.5 second RC filter in the analog spindle command (0-10Vdc) line. This accomplished a couple of things for me. Spindle ramp up and down became smoother providing less wear on the spindle and drive and power fluctuations went away. > Once upon a time, I fired the plasma is the air 5 feet away > from a short piece of zip cord with a digital VOM on it. It > registered 1000 volts, which is the limit. Like you said, the energy from a plasma spark alone can radiate as electromagnetic noise and be picked up in a loop of wire some distance away. If this were my setup I would put the PC in a Faraday cage (a metal box with adequate cooling but shielded much the same way a microwave oven is). I think the Dell GX270s are mostly plastic so they are inviting EMI directly into the motherboard and I/O cards. The problem with replacing a PC whenever it dies is that the PC may issue a rapid servo command before it gives out. You can monitor EMI noise and transients by connecting a neon bulb and an LED in series. If the voltage is high enough to get the neon to ionize the neon will blip but the LED will have a brighter flash. I would connect 2 LEDs back to back and in opposite directions to detect any positive and negative transients. You can take an old PC and connect the neon bulb & LED setup from any input or output you want to monitor and ground of the PC. If enough voltage is induced in an encoder line, etc. the neon bulb and one of the LEDs should blip. The transients may also be too fast or too low in energy to see anything but just enough to cause damage. If transients are getting into the PC through I/O lines, the Faraday cage won't help much. In a super noisy environment I would personally run fiber optic transceivers between the PC in a Faraday cage and the machine. Now that optical S/PDIF cables are a couple of bucks on ebay you can run 15' of plastic fiber between your PC and the rest of the world. The trick is to find a S/PDIF transceiver board with enough I/O to completely pass all the I/O back and forth to the PC. You might have to make a pair of custom isolation PC boards. Dennis J. Deyen Product Design Mgr. Pedersen Power Products 3900 Dahlman Ave. Omaha NE 68107 ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
