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Author Topic: Losing steps or something?  (Read 53884 times)

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Re: Losing steps or something?
« Reply #110 on: November 07, 2010, 10:39:04 PM »
The photos, I hope.

Offline Dan13

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Re: Losing steps or something?
« Reply #111 on: November 08, 2010, 04:45:50 AM »
Hi Don,

That is a nice debugging feature of the PMDX that you discovered. It proved what we had already been guessing - that everything after the Geckos outputs was fine. The problem is somewhere between Mach3 and Geckos inputs.

So are you saying that the offsetting disappears at higher acceleration rates? Interesting... if so you have the solution now, but don't know the cause yet.

Anyway, I really don't like your pictures of the signals. Something is surely wrong there. Can you connect the scope in exactly the same manner to the PMDX outputs while it's set to demo mode? Would be interesting to see the signals. For some reason, I am thinking your scope is not set right. Can you just use one channel and look at the direction signal? Just set the scope to DC mode and jog each side. I am pretty much sure that the direction is a state and should look like a DC line on the scope.

Dan
Re: Losing steps or something?
« Reply #112 on: November 08, 2010, 03:09:01 PM »
Hi, Again.  First, Duh!  The 1Volt O'scope readings are my fault.  The variable gain on the scope was set.  Now the traces show 3V logic for everything.  I've moved the pins around in Mach and the stepped direction signal is always there.  The wierd thing is that the steps lag the dir pulses sometimes and sometimes not... 
2 Questions that come to my mind are: 1) Why is the Direction signal a pulse?  2) Why is the timing of the pulses changing?
I'll post a picture of the driver test, showing tha it is acceptable...  I think.

Dan.  I'll hook up the Breakout board and try to hook up the scope to its outputs.  However, I didn't see any change recently going from direct connection from Mach to the Geckos vs. Mach, BOB, Geckos.  It is worth a try, though.  I suspect something in the computer is the problem.  But what?  Only Windows XP and Mach 3 are on it.
Re: Losing steps or something?
« Reply #113 on: November 08, 2010, 03:10:16 PM »
Driver test.
Re: Losing steps or something?
« Reply #114 on: November 08, 2010, 03:17:35 PM »
Hi, again Dan.  It appeared after I installed the dwell in the program that the offsetting went away except at the extremely slow acceleration rate of 0.5...  Why would very slow accel. cause the steps/direction signals to malfunction?  The fact that sometimes the pulses are leading vs. lagging bothers me a lot.  I would expect that the direction pulses ( if they are supposed to be pulses) wouls stay in the proper timing sequence.  The two O'scope pictures show clearly a timing difference, sometimes during the same line  of code execution. 
Thanks for the help, Don
Re: Losing steps or something?
« Reply #115 on: November 08, 2010, 03:34:44 PM »
I just tried the jog mode.  Set the Dir Pin to Pin 2 hooked up the scope to pin 2 and ground, terminated the pin with a 4.7k resistor to ground, and set the jog rate to 30% feedrate.  Note that the little ticks on the lower part of the trace are the screen reticle.  The timing of the direction "Pulses" seems to be varying, even across the screen.  When I ran jog at 100%, the trace was jittering and flickering.  Not steady.  It is definitely not setting a steady state!

Offline Dan13

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Re: Losing steps or something?
« Reply #116 on: November 09, 2010, 12:51:08 AM »
Hi, Again.  First, Duh!  The 1Volt O'scope readings are my fault.  The variable gain on the scope was set.  Now the traces show 3V logic for everything. 

Glad you discovered it, Don. Was actually hoping you'd find a similar fault of yours with the direction pulsing issue ;)

Hi, again Dan.  It appeared after I installed the dwell in the program that the offsetting went away except at the extremely slow acceleration rate of 0.5...  Why would very slow accel. cause the steps/direction signals to malfunction?

Have got no explanation to this at this point.

The fact that sometimes the pulses are leading vs. lagging bothers me a lot.  I would expect that the direction pulses ( if they are supposed to be pulses) wouls stay in the proper timing sequence.  The two O'scope pictures show clearly a timing difference, sometimes during the same line  of code execution. 
Thanks for the help, Don

This is something to be worried about indeed. Absolutely not the way it was meant to be.


I just tried the jog mode.  Set the Dir Pin to Pin 2 hooked up the scope to pin 2 and ground, terminated the pin with a 4.7k resistor to ground, and set the jog rate to 30% feedrate.  Note that the little ticks on the lower part of the trace are the screen reticle.  The timing of the direction "Pulses" seems to be varying, even across the screen.

Again, this needs to be investigated. Have never tried to look at the Mach signals with a scope, but I do know that I can measure the direction state with a voltmeter and it would show 5V or 0V depending on the direction. Could be Brian has changed something in last versions...? Don't think so. But would be nice of him to chime in here and confirm this.

When I ran jog at 100%, the trace was jittering and flickering.  Not steady.  It is definitely not setting a steady state!

A symptom of a not perfect driver test, though yours looks good (if the picture shows the worst case).

Dan
Re: Losing steps or something?
« Reply #117 on: November 17, 2010, 04:38:48 AM »
Hi, Guys.  I ordered a SmoothStepper last Thursday, and it arrived Monday.  I've installed it and I will post pictures of its outputs.  It looks promising.  No more jittering and the Direction signal is a STEADY! state.  Steps are stable also.
Don

Offline Dan13

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Re: Losing steps or something?
« Reply #118 on: November 17, 2010, 04:44:16 AM »
Hi Don,

Good news! And the signals look like they should be. I still wonder though why you were seeing those odd signals with the PP...

Dan
Re: Losing steps or something?
« Reply #119 on: November 17, 2010, 04:47:32 AM »
Don't know...  I'll try putting the whole machine though trial runs tomorrow, though.  I hope this is the solution...   Don