1. I have a chosen a DRV8824 for stepper while you use DRV8825 and I think only maximum current is different. 2. You talk about TS-4900 or BBB with Cortex-A* CPU there I had chosen an ordinary computer. 3. Instead of FPGA I have chosen cheap STM32 micro controllers.
I work with electronic development so it is important for me to familiar with these micro controllers while you just want to get machine running. I tested timer output switching at around 4MHz with DMA update of compare value a few hours ago. I also use same micro controller for servo motors, it is more or less built for this purpose. Regards Nicklas Karlsson On Wed, 23 Mar 2016 14:28:44 -0500 <ceen...@in-front.com> wrote: > I second the point about not using a PC. Most of the CNC reliability issues > I see are with backplane card edge connectors for DC servo drives and > connectors subject to vibration/chafing of gold plating and oxidation of tin > plating. A consumer grade PC motherboard is not meant for machine vibration. > USB keyboard, PCI slot and SATA connectors seem to be a weak point as their > insertion lifetimes are on the order of 50 or so. I would prefer a 1 or 2 > PCB solution with tightly coupled interconnects (possibly soldered) board to > board just to eliminate potential sources of connector failure. > > My still functional 29 year old Bridgeport Interact 412 uses a Heidenhain 151 > CNC controller. It's 12MHz TMS9995 microprocessor is surrounded with TTL > counters for encoder position and associated logic that generates 0-10V > spindle and brush DC servo command data. Any single core 1GHz A9 would run > circles around what I have now. The cost of a PC versus a purpose-built > embedded CNC controller is not an issue for me as long as the controller does > not creep into the thousands of $$. Machine reliability and up time come > first but safety is right up there as well. You can imagine what servo > runaway is like when an encoder cable is broken. In my case mouse chewed. > > I've been following the BBB discussions and think the BBB would work for the > networking & GUI and any RT servo timing should be handled by a FPGA. The > BBB's 200MHz PRUs are OK for a simple 3D machine but my 6 head pick and place > has X & Y axes, (12) Nema 11 stepper motors and 112 pneumatic feeders. A > little beyond a BBB's I/O count. > > We developed a FPGA based stepper algorithm using the popular DRV8825 Reprap > microstepping driver. The 8825 phase current is dynamically varied based on > RPM and these tables are stored in the FPGA. Changing phase current vs. RPM > allows us to tune around motor and carriage resonance points. We took a Nema > 17 stepper and had it spinning at 3000RPM with 40-bit speed resolution. At > full speed the 32x microstepping clock was 320kHz. Probably something a PRU > could do in assembly language but is more flexible with VHDL. > > I'm considering the BBB and a Spartan-6 cape for ~$100 and the Zynq-based > Snickerdoodle for $62-$157. The TS-4900 also looks appealing. > > > Dennis > > > On Wed, Mar 23, 2016 at 6:27 AM, Erik Friesen < > e...@aercon.net> wrote: > > > > I don't want bang for my buck. What I want is a control board I can drop > > into my haas, and doing it with x86 isn't very feasible. Dropping a > > embeddedarm ts4900 on a custom baseboard would be real slick, and it seems > > that it could surely compete with the 1990's era motorola running at 40mhz. > > ------------------------------------------------------------------------------ > Transform Data into Opportunity. > Accelerate data analysis in your applications with > Intel Data Analytics Acceleration Library. > Click to learn more. > http://pubads.g.doubleclick.net/gampad/clk?id=278785351&iu=/4140 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785351&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
