On Saturday 01 December 2018 21:11:52 Thaddeus Waldner wrote: > While I see that I need to get better at asking questions because I > didn’t quite get an answer to what I was really asking, I do > appreciate your insight into “Star grounding.” I have made a mental > note of it and actually, all of my components installed thus far are > grounded at a single point. Thank you. > > Now what I really want to know is, in the case of multiple DC power > supplies, is it advisable to connect the negative terminals of each, > and are there any pitfalls in doing that? For example, can I connect > the negative terminals of the 5vDC supply and the 24vDC supply to the > 7i96 isolated input common terminal? I believe I incorrectly called > the negative terminal the ground earlier. > > I agree with your point on not homing stepper motors by banging them > against a hard stop. However ... The Teknic ClearPath are not stepper > motors. They are brushless DC servo motors with an integrated motor > driver and encoder. They have a controller that can auto-tune the > motor to the mechanical system ... . The SK models are designed to be > drop-in replacements for stepper motors, complete with step/direction > input signals and programmable steps per revolution setting. They also > have sensorless homing. This feature drives the axis at user-defined > speed and torque limit against an axis end stop. The home position is > repeatable to within one count of the internal encoder (11,500CPR, I > believe). The motor controller stays alive and tracks the encoder, > even when the main DC supply (75v) is cut. It does this via an > auxiliary 24v supply.
I see. > My machine does have end limit switches installed. I just think the > way the ClearPath does homing ought to be more repeatable. > > Now, is there a “home command” signal that I can connect to the enable > signals of my ClearPath motors in order to sequence the homing > routine? > See "man 9 motion", as I'm sure it has both a home command and a home in progress tally for each axis. You may even find a home input that you could drive with a one shot timing out after the power supplies are up and stable to make it automatic on power up. But I'd have to worry about the safety aspects too, like what happens if somebody gets hurt by the unexpected machine motion. I wouldn't look for a home command signal, but a "home completed" from each axis. For that I expect you would have to ask the drive maker. I expect it exists but they may have a different name. Be sure and get the location of that terminal on the drive. Better yet the complete manual for the drives, so you'd have it next time there is a question. > Thaddeus Waldner > > ________________________________ > From: Gene Heskett <[email protected]> > Sent: Saturday, December 1, 2018 3:52 PM > To: [email protected] > Subject: Re: [Emc-users] 7i96 step-direction headers > > 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 > > _______________________________________________ > Emc-users mailing list > [email protected] > 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> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
