On Monday 24 October 2016 00:41:02 Danny Miller wrote: > > Sounds like its the -H I'd want too. More conserving of horizontal > > real estate. And while I'm not going to add yet another potential > > loose connection to the home switch setup, these bobs I have have > > such poor terminals that I will cobble up a distribution point for > > all the stuff that needs 5 volts. 2 bobs and 2 points on the opto so > > far as 5 volt loads. As for home/limits, these cheap bobs, intended > > for a Mach system, already have pullups so all they'll have to do is > > pull to ground with a microswitch. > > > > Thanks Danny, for calling that board to my attention. > > > > Cheers, Gene Heskett > > Some FYI- > > Mesa cards use a 3.3v FPGA, but you can enable a bidirectional bus > switch which can convert to "mostly" 5v IO, but it's not a true 5v. > > Also ALL IO has pullup resistors on the Mesa, which only have an > effect as inputs. Outputs are not open-collector, they're driven, but > a bus switch's driven "high" is less than the 5v Vdd. > > This worked quite well for me. The AM882H has 5v opto-isolated IO, > with integral resistors (so it's gotta be 5v to generate specified > opto drive current), and they didn't common the anode or cathode. The > step/dir/enable I fed by tying the anodes to 5v and the cathodes to > the Mesa IO pin because drive-low is definitely 0v but drive-high > isn't quite 5v. > > And the IO is just pulldown. My board's got a bunch of optoisolators > and their outputs are just pulldowns against the Mesa inputs' built-in > pullups- which is simple. > > BTW, about "loose connectors"- this ferrule stuff CHANGED MY LIFE on > clamp-down-on-stranded-wire: > > https://www.amazon.com/uxcell-AWG10-Insulated-Ferrule-Terminal/dp/B00U >BUR6E2/ref=sr_1_6?ie=UTF8&qid=1477283614&sr=8-6&keywords=ferrule > > https://www.amazon.com/Signstek-Adjusting-Ratcheting-Crimping-AWG23-10 >/dp/B00HPRYIL8/ref=sr_1_5?ie=UTF8&qid=1477283614&sr=8-5&keywords=ferrul >e&th=1 > > Seriously, it's amazing. I learned not to trust stranded-on-clamps. > Strands fray and short, they break, they work out strand-by-strand. > And having to rework it damages the wire. I've tinned stranded wire in > the past, only to have it get loose later and wires fell out, and > Googled this- most people say "never tin, it's too soft and gets loose > and your wire falls out". Oh. Kay.
Tinning should be limited to about 1/16" on the end of the stripped wire, so that is inserted beyond the clamping screw. Its real reason is to bind the tips of all strands together so there's no flyers sticking out. Solder cold flows a lot worse than copper, so you have to go back annually and tighten the screw another 20 degrees for several years if the screw is bearing on the solder. This problem with cold flow is 50x worse with alu wire. Use it under a roof you don't mind burning down in 20 or less years. > This stuff is cheap and quick, it makes a 100% solid strain-relieved > bond. Phoenix connectors hold them easily and they never let go. > > Use that 4-jaw tool, NOT the 6, if they're going in clamp connectors. > Only 2 surfaces get used, so square maximizes the surface area that > gets used. > > I showed this stuff to my hacker buds and they were all "OMG where has > this been all my life???" Looks like a great idea. The square means that the screw pressure is on the two flats, and any cold flow will be longer to occur because the pressure per sq/in is less. The reason I was bitching about these bobs is that the screw is pushing on a thin leaf of metal that comes down on the wire, and once tightened, its bent such that a wire once removed, needs a double viagra pill to be stiff enough to push the leaf up and re-enter the terminal. Common 24ga hookup wire just bends double and will not go back in without a hell of a fight. Needs to be 18ga to be stiff enough to force its way under the leaf, and its not big enough to take two of them in the same terminal. PIMA, but the electronics are good, no laggy opto's to distort a pwm signal, and they give a rail to rail output, sourceing or sinking 24 milliamps. Opto's on the bob are a waste of protection with modern stepper drivers as they all have their own optos for all inputs. Properly driven, a 2M542 driver can exceed 350 kilohertz step rates. Put an opto on the bob and it will often fall over, stalling the motor at half that. One of them in series with a 10 kilohertz pwm signal and the control linearity error over powers the PID's ability to keep the motor within 20% of the requested speed. I found which one it was, pulled it and bridged the 2 pins to bypass it, and now I get within 5% of the requested speed without a lincurve module in the signal path, and the PID handles that nicely. FWIW Danny, I am a Certified Electronics Technician with at least 65 years of chasing electrons for a living. I may ask questions of these kind people, but its generally a quest for the latest knowledge on exotic subjects like the recent thread on glues, which you and Bruce explained quite well. Thank you. 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
