Thanks for all of the extra information, Gene. I really appreciate it. The Xylotex board I'm talking about is actually just a DB25 interface card for the Beaglebone Black. It's not their driver board. I'm using a Gecko G540 to drive my steppers. The router itself will be a ShapeOKO2 hardware kit that I'll modify to take NEMA23 steppers. It's really just a starting point for me. It'll be a way to get an, in theory, working router relatively quickly on a budget. I'm sure I'll run into things that don't work ideally and/or that I just don't like. That's also part of the reason I went with a different electronics system than the ShapeOKO2 kit usually uses. I want my electronics to be useable regardless of the mechanical setup I decide to use. Most of the design work for this first build was done for me by the ShapeOKO people and I'm hoping that the change to NEMA23 and a real CNC software setup won't introduce too many problems with their design.
Thanks, Russ On Sun, Jul 27, 2014 at 4:28 AM, Gene Heskett <[email protected]> wrote: > On Sunday 27 July 2014 01:27:48 Russel Ingram did opine > And Gene did reply: > > Yeah, I know I could hardwire it to work. I would rather not. > > Especially since the software is capable of doing what I want, at > > least with other drivers. If I can do it in software, the cabling is > > much simpler. Thanks for the suggestion, though. > > > I tend to have an urge to "simplicate" things. :) The only other comment > I'd make is that with the torsion springiness of having two motors whose > resonances might add up at certain speeds, would make dampers on the rear > of the motors seem like a good idea. With single 225 oz motors on the XY > of my mill, I doubled its speeds with some dampers I made. They are > visible in some of the pix in the emc link on my web page in the sig. > However, if I make any more of that type, I will use alu for the spool. > In a pinch, the rubber disks could be made from a truck tire inner-tube, > but somehow, about the time I was contemplating making those, I stumbled > over a flat sheet of 1/8" rubber at a yard sale in a neighboring town. > The steel washers are the biggest fender washers I could find at Tractor > Supply, and I turned the spools shank to just fit them. I'd go alu for the > spools next time because the weight of the steel probably has an effect on > how much accel I can use without a stall. Stepper motors are fickle beasts > in that regard. > > I also blew several of the xylotex boards, and went shopping on ebay, > buying 7 of the 2M542 drivers, 4 for the mill and 2 for the lathe & one > spare, still in its box 3 or 4 years later. About $50 a copy at the time, > and seemingly bulletproof. I had one shut itself down to protect itself > in that time. Took a powerdown to reset it. Otherwise they've Just > Worked(TM). Rated 4.2 amps and 50 volts, not recommended below a 24 volt > supply as lower voltages = more heat. 28 volts on the mill, and about 37 > volts for the lathe. Those on the lathe run noticeably cooler. Surplus > iron for the power tranny is hard to find in that voltage/current range. > > All of these drivers, including the xylotex need a goodly amount of > capacitance in the psu output circuit because they recycle the current > regulating chopper currents back into the psu, and poor capacitors can let > that result in a ripple voltage at the chopper frequency that can easily > exceed the a3977's voltage ratings, and that lets the smoke out instantly. > So my last home made psu for the lathe has a choke input filter, and > around 30,000 uf as output filter in the form of a triplet of 10,000 uf, > 35 volt cans whose tops are gooped to the floor of the box its all in. The > choke input lashup results in a much more stable output voltage as the > loads vary, unlike using a huge input cap in a pi section filtering scheme > would. The power transformer runs cooler too because those huge current > peaks that charge the cap input filter aren't there. > > Yeah, I'm an old fart now, looking at 80 yo in October, but in my working > years I was/am a C.E.T., and a tv station Chief Engineer who didn't send > anything I could get docs for, out to be repaired. So electronics are > generally not a huge problem for me. Switching power supplies are quite > efficient too, but not all of them on the market can tolerate a stepper > motors back currents, as they will see the over voltage and shut down. > > One I tried to add enough output capacitance to, to alleviate that, then > wouldn't start, seeing the charging surge of a 10,000 uf cap and shutting > down thinking its output was shorted. BBLB stuff (big sigh). Built By > Lowest Bidder. :) > > Have fun Russell, thats what this is all about to me, keeps me out of the > bars! > > 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> > US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS > > > ------------------------------------------------------------------------------ > Want fast and easy access to all the code in your enterprise? Index and > search up to 200,000 lines of code with a free copy of Black Duck > Code Sight - the same software that powers the world's largest code > search on Ohloh, the Black Duck Open Hub! Try it now. > http://p.sf.net/sfu/bds > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
