What represents, or what should I expect from, a well tuned servo system?

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16 Apr 2018 15:24 #109127 by PCW
AFAIK signals are only created by net commands in hal files, (or via halcmd) though there can be
many hal files in a particular configuration
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20 Apr 2018 23:25 - 20 Apr 2018 23:26 #109360 by DeckelHead
Things are really picking up (finally) and going both well and smoothly. I am almost done with my HAL files, I think. I am down to just a few nits that I don't know how to handle...

One of these is how to handle something like my air pressure sensor. I want it to prevent my control from turning on. I think I can do that fairly easily, but there is a catch... When you have a motion error (like a following error) you get TWO experiences. The first is that the control shuts off. The second is that you get an error message. I'd like the same type of thing with my air pressure switch. I don't need an 'LED' on the control panel because I really don't care about the sensor. But if there is no pressure and I try to start the machine, *then* I want to know why.

How does one create an error message associated with a pin?

Another use case, by the way, is the fault line being returned by my VFD. Ordinarily,I don't really care about it (why waste the real estate for something that is always green?). But if there is a VFD fault, *then* that error message is important.
Last edit: 20 Apr 2018 23:26 by DeckelHead.
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21 Apr 2018 02:15 #109366 by rodw
Try this.
linuxcnc.org/docs/html/man/man9/message.9.html

Also, you can create an estop chain in software using estop_latch to include a seperate input that triggers an e-stop. Its not well documented anywhere but I did work it out and share an example here somewhere.
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01 May 2018 21:14 #109942 by andypugh

DeckelHead wrote: I think I may have solved the index problem... If I'm right, then you were correct and it was a connection issue. While the wire was snug in the terminal block, I think it was actually pushed in too far. The terminal is of the type that pulls up on a U-bar to provide the clamping pressure. I think the clamp may actually have been on the insulated portion and not the stripped copper. As such, there could be a poor connection.


It is possible to have the screw nice and tight, but have the wire below the U. But in that case the wire pulls out easily.

I like to use ferrules to prevent the problem you describe.
As seen here (though you can't see them in the DIN terminal blocks, you can elsewhere).

Cheapest source I know is the local electrical factor: but I prefer this style crimping tool to theirs.
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01 May 2018 21:44 #109952 by DeckelHead
Its a good suggestion, Andy, and one that I thought about too late. When I had this problem I started to think about it and found a set of crimpers just like you show on eBay. The problem now is whether or not I want to go back and redo all of my connections. I'm already 'behind' and I want to make some chips. Also, the particular crimper I got still has a fairly large diameter for the smallest ferrule. It may work but I have to try it out. Also, I have some concerns that the ferrules will be a bit big for use on the 7i77 terminals. Those blocks are fairly close to one another.

I think my longer term plan is to get the machine working and to then possibly go back and put ferrules everywhere. Oh, there was one downside on a few terminals. I really tried hard to avoid any pairing of wires on a single terminal but, alas, I do have a few. Because the ferrules are circular, however, I don't know how well they'll work in those cases.

On a slightly different topic... After I posted that I had 'fixed' the machine, I had the issue again. I knew I where to look, however. I quickly found that there was one screw that *somehow* managed to avoid being tightened. Needless to say, it worked fine after that... All of this was, in the end, self-inflicted. I still worry about the initial thought of having pushed a wire too far in though (what you alluded to), but that ended up *not* being the actual fault in my case... Just a dumb screw that was not tight. (rolling eyes).... Yes, I checked the others. :)
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01 May 2018 21:50 #109956 by andypugh
My pictures shows a bunch of orange crimps populating a 7i84 board, which is the same pitch as a 7i77.
You have to use quite small wire, but that is fine for signal-level stuff. I think those orange are 0.5mm2
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01 May 2018 21:56 #109958 by DeckelHead
Yeah, I have some fine wires but most are a little bigger. The fine ones are a PITA, frankly. They don't have any lineal stability so they just bend around almost by blowing on them.

I'll likely go back and install ferrules later. I do prefer that... Much cleaner.

In my console, I plan on installing ferrules from the get go. I have a 7i84 actually arriving today in the mail. I debated taking all those little wires back to the 7i77 because I have room there. But, in the end, I decided that was a waste of energy! A local 7i84 makes a lot more sense.
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