On Saturday 31 March 2018 11:52:01 Chris Albertson wrote: > On Fri, Mar 30, 2018 at 8:20 PM, Gene Heskett <ghesk...@shentel.net> wrote: > > On Friday 30 March 2018 20:34:52 Chris Albertson wrote: > > > > > > Just one question? Can you build this for less than you can buy it > > from Mesa? Or Pico? If you time is worth a buck an hour, its a slim > > chance of yes. Very slim. Otherwise get it from a supplier that > > supports us. > > The arm is not going to use MK or LCNC. I'm using that on the > machine tools > but this arm needs more flexibility than offered by any of the machine > tool controllers. This is the high level control software I'll use > if you are interested: > https://moveit.ros.org/documentation/concepts/ > This pulse generator will be part of the blue box called "robot > controllers" > > The trouble with Mesa in this case is that I'd have to write a whole > bunch of FPGA code to make it into what they call a "joint trajectory > action server" > > I thought about using G-code for the robots but they need to do things > like notice you have set a beer can on the table then plan motion > around the can. This has to happen in real time, you can't code the > motion in advance > > There is not much to build. A need to buy an ARM-M based board and > than add a buffer chip to convert 3.3 volts to 5 volt TTL. Cot should > be <$20 total but if one of these works I can build it for under $5 > .ebay.com/itm/STM32F103C8T6 > <https://www.ebay.com/itm/STM32F103C8T6-ARM-STM32-Minimum-System-Devel >opment-Board-Module-For-Arduino/162247218933?epid=532038167&hash=item25 >c6b016f5:g:ZXMAAOSwA3dYCJJd> > > > Back to steps per second. If the carriage moves at 90ipm, that is 38 > mm/sec, with a 5mm screw that means 8 turns per second. or 1600 > full steps per second but perhaps you are doing 1/4 steps so it is > 6400 steps/second. Your machine with software steps is doing about > 8X slower? with no more then 800 steps/second. It looks like there > is no need for more than 10K steps per second and half that might > work.
I think its running 1/8 step. But my hand isn't anywhere near the good book on that. That machine also threw a drive fault, so got rebooted when amanda screamed about a read-only drive this morning. I've a 60GB SSD to put in it if its not the cable, which IIRC is red=trouble after some time, copper and that bright red insulation dye do not tolerate each other at all well. If the data cable is red, and a tail on the log blows up when its touched, that dye has struck again. Its beat me to a pulp for the last 40 years starting with the J.A.Pan Co 2 way radio microphone cables back in the early 70's. Use any other color but red for a sata data cable. > About jitter, if 3% of the period reduces torque and the fastest rate > is 10KHz then only 3 uSec of jitter can be tolerated. > Since it regularly tolerates more than that with the speed limits configured, I should have emphasized "bleeding edge" speeds. 10 ipm isn't bleeding edge by any definition. 70+, maybe but its out of torque from low motor voltage long before it gets up to that speed. I also have homemade dampers on the rear shaft which on that machine helps a lot. Right now, running latency-histogram on that machine, with a 25 us base thread, the max deviation in about a ten minute run is -8.0 us to +8.5us, but those wide times were maybe once in that 10 minutes. It might exceed 3 us once a minute. > > How many motors in your arm? The 7i90HD at less than $70, + 3 > > 7i42TA's at about 45$ ea, about $200, can handle 8 steppers. And > > have plenty of gpio left to do lots of other things. Limited only by > > your imagination. > > > > -- > > Cheers, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ---------------------------------------------------------------------- >-------- > > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
