On Saturday 01 December 2018 14:32:54 Thaddeus Waldner wrote: > I do have plenty of isolated inputs and outputs for that and my plan > was to use those. But as I got to wiring it up, I thought it would be > really neat to hook up all wires from each motor cable to their > respective stepgen headers. This isn’t possible, I see… so back to the > initial plan. > > As a related question, what is the prevailing wisdom on working with > multiple power supplies? Is it OK or advisable, for example, to tie > the ground at the stepgen on header to the common pin on the isolated > inputs, together with the ground for my 24v power supply?
Good question but you aren't quite ready to ask it yet. I'll answer though, to see if I can head trouble off. So set it up with a single ground bolt, and run individual insulated ground wires to this bolt and make sure that is the only ground. Do NOT succumb to the temptation of running a ground bus with stuff tied to it at arbitrary points along this "ground buss", you WILL have noise problems if you do. And this single point could bounce 100's of volts without bothering the circuits because everything is getting the same ground reference. This is called a "star" ground because all grounds come from a single point, and this is the only point connected back to the buildings static ground, possibly by one power supplies earth terminal still connected to the 3rd pin of THAT power plug. In the case of power supplies fed with 3 wire cable, disconnect the green wire from the psu at its ground terminal, and run a grounding wire from that terminal to your single ground bolt. Any ground to ground short circuit constitutes a ground loop, which is an excellent antenna to pick up noise enough to destroy your logic circuitry because you'll then have all the stepper and vfd noise supered into the other controls. It would be a good idea to splice that static ground wire and connect it to the single point bolt, but only from one static ground wire in the whole bunch. In my case, each stepgen of the 4 I am using of the 8 a 7i76 has, has its own enable input. But if you want to shut down the stepgen motors drivers, which I don't because you may need to rehome them on re-enabling, you would have at arrange a gpio output pin to do that. As for power savings, I've always settled for enabling the drivers half power mode with the dip switch when its stopped. The motors stay comfortable to the touch even when they're fairly busy. This half power mode is probably responsible for the axis minimum speed setting. I could see a potential positioning error if the steps are at a slow enough rate that it might jump a whole step at a certain slow speed and heavy load with the current being bounced between full and half. It hasn't happened to me though, and my little HF mill has done quite a bit of EDM at feeds in the 5 thou to 20 thou a minute range. Plenty slow enough to activate the half current mode. OTOH, EDM doesn't need any force, so that may be my salvation. > And a related question… > > I need to have individual enable and drive feedback signals because I > am using the hard stop homing feature of the Clearpath drive (drive > backs the axis into a hard stop and sets that as home) This is not the most accurate way to do that when microstepping the drives. So do use switches, located enough full steps from any hard stop that it never touches the hard stop. > and I need to > control the order in which homing happens. The way it works is, when > configured to use hard stop homing, the drive will home when power is > applied and the enable signal is high. Once motion stops, the feedback > signal goes high, at which point I would home the next axis in the > order. LCNC does that automaticly normally, just set the HOME_SEQUENCE numericly in the order desired, starting with zero. But its a manually performed operation from the gui. It skips any axis if that axis is set to a -1. > I suppose I could simply wire the feedback signal into the home switch > to take care of the inputs. Is there a HAL signal that I can wire to > the enable pins, perhaps with some sort of latching device? > > Thanks! > > > On Dec 1, 2018, at 8:40 AM, Peter C. Wallace <[email protected]> > > wrote: > > > > On Sat, 1 Dec 2018, Thaddeus Waldner wrote: > >> Date: Sat, 1 Dec 2018 03:52:12 +0000 > >> From: Thaddeus Waldner <[email protected]> > >> Reply-To: "Enhanced Machine Controller (EMC)" > >> <[email protected]> > >> To: "Enhanced Machine Controller (EMC)" > >> <[email protected]> Subject: [Emc-users] 7i96 > >> step-direction headers > >> I am using TTL step-direction outputs on the 7i96 I/O board to > >> drive a Teknic ClearPath motor. With the board set to TTL mode, is > >> it possible to address the step- and dir- pins. I would like to use > >> one for an enable output for the motor and the other for the > >> feedback from the motor (input). > >> > >> Thaddeus Waldner > > > > No, the + and - step and direction pins are inverted copies of the > > same signal. You can as Andy suggests limit the number of active > > stepgens in the hal file and then use the freed step/dir pins as > > outputs (they can not be used as inputs) > > > > You should also be able to use one of the 7I96s isolated outputs to > > drive the enable (one output could perhaps drive all enables) > > > > Likewise you should be able to use the isolated inputs for drive > > feedback (and if these are used to signal a drive fault you can also > > parallel them if they are normally off or series connect then if > > they are normally on so be able to use a single input to monitor all > > drives) -- 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> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
