Bingo! I found the issue! So follow along with me here. In this pic, the yellow arrow on the right points to my 12V-to-5V buck converter, for the opto supply. Purple wire out of it is 5V to the IM483s. The black ground wire out of it was connected (follow the yellow dots) to the ground of the motor power supply (34V) !!! It has been at least a few years since this was put together, so I'm not sure why. http://orlandorobotbuilders.com/rw/2015-03-08-Elec-04-GroundIssue.jpg
With this wire, I had 1.8Vp-p noise on the 3.3V (actually 3.1V measured) step/dir lines. Once I removed this, I got 3.1V ~300mVp-p noise. I put back my optoisolator board and got 4.2V +/- 300mVp-p noise. Then I switched to shielded wire (USB wire) and still got 300mVp-p noise. I changed to using the 5.0V from the USB header on the mobo and still got 300mV. I'll keep that, but will need to put my 12V-5V switching converter as I need the power for other things that will be on the board. When I get time again, I'm going to try tighter twisted pair. Thanks for all the help! Cheers, -Neil. On 3/8/2015 11:25 PM, Dave Cole wrote: > Andy is right. Bag the 5V power supply and do a port steal from the > USB port for a 5V supply. > > You can get nice tight twisted wire pairs from a Cat 5 patch cable. > > Dave > > On 3/8/2015 6:58 PM, Neil wrote: >> Oops... I should've sent this to the list. Also, I'll add that that >> black ground wire test did not make a difference. >> >> Cheers, >> -Neil. >> >> >> On 3/8/2015 7:53 PM, Neil wrote: >>> Ah yes... let me clarify that part. If you look at the far right in >>> the pic, just below the plug going into the PC power supply is my >>> 12V-5V buck switching PS that provides the opto supply. It's wrapped >>> in heatshrink tubing, but you can see purple & black wires coming out >>> of it. It takes 12V from the PC PS, and puts out 5V on the purple >>> wires. You can see the purple wires going into the IM483s (on the >>> right side). FWIW, the right side of the IM483s in my pic is the >>> input side, the left is the motor side, with the orange/black wire >>> pairs being the motor power. >>> >>> In the quick reference here ( >>> http://motion.schneider-electric.com/downloads/quickreference/QR_IM483_805.pdf >>> ), the bottom left of the second page shows the opto wiring. My >>> ground reference is essentially it's referenced back to the PC PS ground. >>> >>> As I was experimenting with this, I added that black wire from the >>> DB25 ground on the parport to see if a better ground would help -- the >>> wire goes up, but then comes back down on the right in the pic (you'll >>> see it blocking the PC PS fan) and into the 2 pin white amp connector >>> just above the right-most IM483. You'll see it as a crimped pin w/o a >>> housing. Those 2-pin white connectors are just a bunch of connectors >>> I had wired up to supply 12V around the board as needed. It's 12V >>> from the PC PS. >>> >>> I'll check my 5V with a scope and also try using the 5V USB power. But >>> I suspect shielding will help it a lot. >>> >>> Cheers, >>> -Neil. >>> >>> >>> >>> On 3/8/2015 7:23 PM, andy pugh wrote: >>>> It isn't clear from that what the signals are referenced to. You >>>> appear to only have a single wire from the parport GND to somewhere >>>> out-of-shot. Rather than use a separate supply for the opto 5V you >>>> could steal 5V from a USB port. (Or from a convenient header on the >>>> motherboard) If you take 5V to Opto+ and wire the Opto- to the >>>> parport, then invert the sense of the signals in the config then I >>>> suspect you might have better results. >>> >> ------------------------------------------------------------------------------ >> Dive into the World of Parallel Programming The Go Parallel Website, >> sponsored >> by Intel and developed in partnership with Slashdot Media, is your hub for >> all >> things parallel software development, from weekly thought leadership blogs to >> news, videos, case studies, tutorials and more. Take a look and join the >> conversation now. http://goparallel.sourceforge.net/ >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > --- > This email has been checked for viruses by Avast antivirus software. > http://www.avast.com > > > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming The Go Parallel Website, sponsored > by Intel and developed in partnership with Slashdot Media, is your hub for all > things parallel software development, from weekly thought leadership blogs to > news, videos, case studies, tutorials and more. Take a look and join the > conversation now. http://goparallel.sourceforge.net/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
