Getting HALscope to trigger on axis motion

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26 Sep 2019 23:59 #146305 by Scot
Okay folks,

So I've gotten a single axis to move, jog, be commanded in the MDI of AXIS, and I've gotten my home/limit switches configured to trip properly if axis motion goes past the soft limits, accidentally. And now I'm getting ready to tune that servo.

Jon at Pico Systems has been an amazing help for most of this, but he's often busy when I'm working and need advise. So I'm here to see if any of you bright and experienced people can help me figure out one sticking point in the tuning process. Although I think I have the basic idea for the process of tuning using the HALscope, I cannot for the life of me, figure out the direct path to make get HALscope to trigger when I move the axis. I understand a bit about oscilloscopes, but until a couple days ago, I've never used one. In this instance of tuning, the way that Jon advises, part of the easier way to reach the numbers for optimal tuning is to make the HALscope trigger when the axis is jogged.

Can anyone explain an easy way to get this to happen? I can see the position movement of one of the trace HALpins triggers the scope, but even though it's set up as close as I can get it to the example that Jon put out on the wiki, I cannot seem to find that sweet spot for putting the traces in position to make it work.

Thanks,

Scot

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27 Sep 2019 02:06 #146313 by Todd Zuercher
I usually set Halscope to monitor the joint's velocity command, and set Halscope to trigger off of that.

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27 Sep 2019 02:56 #146319 by Scot
Well, I guess that's my trouble, Todd. I know how to set the scope to see the trace to follow and to determine what to adjust. But the question was how do I get the scope to trigger when I jog the axis?

From what I know and what I've accidentally done, after doing my best to follow what Jon Elson laid out in his section of the wiki on tuning, the scope triggers when the axis moves if it's set up correctly. I just don't know what I'm doing wrong. Because I can't seem to make the scope trigger when I hit the jog move button on the Manual control tab of AXIS. The tutorial lays out what the screens look like, but it doesn't give a process to make the scope trigger when the axis moves. I've seen it work because I've done it accidentally.

The scope reacts to the move when it's set properly. I don't know how to get the trigger to occur when the jog button is depressed. Basically when I make the move on the axis, it will not trigger.

Take into consideration that I'm sort of a green horn on the use of an oscilloscope. I've actually never used one in any way, shape or form until 2 days ago. And it's sort of a steep learning curve, even for a guy like me with a decent machining background and some basic electronics experience. This is my first servo system and I chose brushless servos due to the space constraints of the brush motors and their brush points sticking out into an area where they can be damaged.

Does that make sense? Thanks for the insight, though.

Scot

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27 Sep 2019 06:54 #146337 by pl7i92
halscope is more to see interactions between pins
and find out if there are missledings in signal flow
or spikes to pin signal that got hardware confusing

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27 Sep 2019 07:02 #146341 by Scot
Yes, I understand what the tool is for. I've actually had it working and I even figured out the problem after scouring the details of what I was doing.

But thank you, anyway for the reply. The hard part for me in this endeavor is that although I've built stepper systems before, I chose to do a brushless servo system. And it's a hell of a learning curve.

Thanks again,

Scot

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27 Sep 2019 07:06 #146343 by pl7i92
you will get PRO soon
its always a challenge to chance technologies Upwards

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27 Sep 2019 07:18 #146346 by Scot
Many thanks.

I'm in deep right now. I've been doing 12 hour days for about a month now. I did a 30 hour run the other night when I couldn't sleep. I have that tendency to go hard core, sometimes.

Linux CNC has come a long way since I first played with EMC. I think it was 1999 or 2000 when I first got into it. It's a hell of a system, now.

I can't wait to see this machine turn parts.

Scot

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27 Sep 2019 11:03 #146366 by pl7i92
you will see them
take your time and sleep well ;-)

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27 Sep 2019 12:28 #146373 by Todd Zuercher
Many forget that people new to Linuxcnc may have no experience using an o-scope. But there is a very good tutorial in the Linuxcnc documentation about learning to use Linuxcnc's built in o-scope program Halscope.
You need to select a source for Hal-scope to trigger off (button at lower right corner of the window)
Here is a link to the the triggering section of the tutorial.
linuxcnc.org/docs/html/hal/tutorial.html#_triggering
The following user(s) said Thank You: Scot

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27 Sep 2019 13:46 - 27 Sep 2019 13:46 #146385 by bevins
I usually put it on roll and change settings until I can see what I need then I trigger.

just my 2cents
Last edit: 27 Sep 2019 13:46 by bevins.
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