Messages

21

FAQs / Re: Losing steps or something?

« on: November 05, 2010, 04:14:18 AM »

Hi, I'm pretty sure the scope is set up correctly.  I swapped the leads and channels to verify this.  I will check on Roger's suggestion of loading the port and seeing if the voltages and signals change.  It would be interesting to see if a problem is in the PP.  The dir pulse is changing a couple of uS before the step rises, but they fall together.  Thus the direction pulse is still "setup" when the step pulse falls.  It should work this way, but I would be worried about stray induced steps getting into other lines, or something.  Hmmm.  Maybe that is part of my problem...  Thanks.
Don

22

FAQs / Re: Losing steps or something?

« on: November 04, 2010, 06:18:39 AM »

By the way.  From the Geckodrive manual,  Minimum logic "0" time is 0.5 uS while the minimum logic "1" time is 4.5 uS.  Microstepping occurs on the falling edge of the step input.
Step pulse "0" time:  .5uS min.
Step pulse "1" time:  4.0uS min.
Direction Setup:  1uS min.

23

FAQs / Re: Losing steps or something?

« on: November 04, 2010, 06:13:42 AM »

Hi, Roger, Have a nice vacation.  Yeah, I couldn't believe it either.  Something seems very wrong.
All that is attached to the parallel port is my cheater cable to which I have hooked the probe leads to the outer end.  Nothing else.  The 1V pulses concern me too.  I even swapped channels, then cables, to verify it was NOT coming from the testleads or Scope.  I'm going to drag out the other computer and hook up the scope to see if it exhbits similar behavior.  Also, I have recieved another PCI parallel port card from Ebay, I might install in the current computer.  Might be interesting to see what voltages it puts out.  I'll try to keep things orderly, and take notes so you can see when you get back.  Thankyou for the help.  At least we are finding something.

Don

24

FAQs / Re: Losing steps or something?

« on: November 04, 2010, 05:46:08 AM »

Continued,  The next pair of screen shots is time base set to 5uS/div.  Starts out with Direction pulses- oh, yeah - Pulses, not steady state.  Is this a clue?  Step pulse is delayed about 2-3 uS on rise from Dir pulse.  Both fall together. 

I changed the Dir in Motor Tuning from 0 to 5uS and the delay changed to 5uS - a full division on the scope.  Both still fall together.
Changed Dir to 0 and Step to 5uS and step is delayed 2-3 us from Dir.
I didn't take pics of those traces.

25

FAQs / Re: Losing steps or something?

« on: November 04, 2010, 05:33:03 AM »

Land of the strange anomalies, here.  I hooked up the O'scope.  It works.  I think.  First the program I am running that gives me enough time to observe the traces.  I found that slowing the feedrate too much gives either to short blips instead of pulses, or trace scans that are very hard to watch...
Program: F10
G20G90
M98P1234L100
M30
O1234
G1X1.0
G1X0.
M99

Scope settings:  Channel 1 hooked to pin 2  (step) Lower Trace in Pictures.    Channel 2 is hooked to pin 3 (Dir) upper trace in pictures.
External trigger is hooked on the Dir pin.  Coupling is DC for all.  Amplitude is set to 1 Volt per division for both channels, Triggering is set Ext., DC, Auto level, Normal mode.

First observation was that the upper trace is only showing a 1 volt signal...  lower trace is showing 3 volts.  That is unusual.  Both signals are set to Low Active in the motor outputs
The first 2 pictures show going out, and going back .1mS per division time.

26

FAQs / Re: Losing steps or something?

« on: November 03, 2010, 03:37:38 PM »

Hi, Roger.  Thanks for the info.  I'll try to get to it tomorrow as I'm shor on time today.  Don

27

FAQs / Re: Losing steps or something?

« on: November 03, 2010, 05:13:07 AM »

Hi, All.  Good reading your input.
I have tried different step and Dir numbers ranging from 0us to 15 us with no change.  I would have expected something...  Currently have step set to 2 us per Gecko suggestion.
Question...  Does the Direction act as a pulse for each step? or does it change state for reversals of motion direction only, ie. steady state for duration of move in that direction?
My steps are set to "Low Active" in the Motor Outputs.  The Direction s are set to what ever makes the axis move the correct direction.
I'm running 25Khz clock on this setup since more than 50 inch per minute gets dangerously fast and toward stall speed of the steppers.  I don't make a living off this machine so I want accuracy and reliability more than speed.

I would like setup instruction on using an O'scope as I do have a BK Precision 1530  30mhz scope.  If it could be hooked up to see the timing differences between step and direction it would be nice.  It is a simple dual trace scope, not a storage type.  About 20 years old.  If you think it might be helpful, tell me how to set it up on the machine and I'll try it.  Most of my advanced electronics has been repair of old tube amps... Very basic.
Rich, good to hear from you,  I don't know if my scope is good enough for this application, but if you think it might be, I'm open to suggestion.  I have never seen a pulse counter, although it would seem such a device must exist.
The servo motor isn't hooked up and with the iterative tests it is quite obvious that it doesn't return to zero.  Also, the stepper motor for the X axis is shown in the picture or more correctly the belt and pulleys.  Changing the acceleration doesn't seem to have any effect at this time...  I'm sure the problem is not mechanical. 
Oscope settings would be helpful. 
Don

28

FAQs / Re: Losing steps or something?

« on: November 02, 2010, 04:28:31 AM »

Hi, again...  The repeatability test is on page 5-15 of the Using Mach3 Manual.  I changed the feedrate and distance to go to suit my impatient time constraints.  I just wish there was some way to "count" the step pulses as they came out of the parallel port.  Then I could have proof positive if the problem was really inside the computer.
The XML was cleaned out when I did the fresh install this weekend.  I uninstalled Mach3, then went searching through the computer and deleted the Mach3 folder.  Then I emptied the recycle bin.  Then I downloaded a fresh copy of the lockdown version to my Studio 17 laptop and burned a cd from that file.  That is all I installed.  No license file yet.  I was hoping the license file was somehow causing the problem but it was a long stretch. 

As you can see from the pictures, The servo motor is not hooked to the table.  It still offsets (rotates) around as I run the test program...
Roger, please instruct me as to how you set up and conducted the incremental jog test.  It might be interesting to try. 

Also I too would be very interested in details of your SmoothStepper offsetting odessy, and how you solved it.  I have been wondering if, should this be a pp issue(unlikely on 3 computers), a Smooth Stepper might be in the works for a test... 

If I could do it I would try to post a video clip of the "stuttering" behavior.  Any suggestions?
Don

29

FAQs / Re: Losing steps or something?

« on: November 01, 2010, 04:51:19 PM »

current setup with Viper drive in system.

30

FAQs / Re: Losing steps or something?

« on: November 01, 2010, 04:49:29 PM »

H, Dan.  Obviously the signals to the driver are corrupted.  The drivers only send the motors where they are told.
Considering that the base program I'm running is in the Mach manual, it would seem that if it were a common problem, everyone would see it.  It is not subtle if you are checking repeatability.
I've actually used 3+ different PCs.  1) PC Chips mobo, AMD Athlon proc. etc.  2) ASUS P5QL/EPU with Intel E6500 proc. etc. and 3) My current setup: Asus A7N8XE-Delux Mobo with AMD Sempron 2500+, etc.  This Computer has the smoothest OCX Driver test I've seen.  All have exhibited this offsetting behavior.  I also have tried it with a Dell Inspiron 8200 Laptop but had the same results.
I've used at least 3 different PP cables plus my cheater.  Replaced the cables from BOB to Geckos, etc. 
The Larken Viper servo system is just clamped to the top of the mill table, since It is a different form factor than my steppers.  Making precise angular offset measurements is not practical but with an indicator wire and a mark on the pulley on the motor, it is quite obvious that it is doing the same thing the stepper system does.  I don't think the table/leadscrew system has anything to do with what we are observing here.
I believe I saw a reference somewhere on the forum to using EPP Mode with the parallel port. It is the mode I'm using, after having tried all the options in the Bios previously to no effect.

The tests I did today seem to show the same results with the servo as with the Geckos.  I also set to Exact stop mode but other than running slower on the tests, The offsetting was the same.
I did notice that when running the test with G1X+.005 the machine stutters near the beginning of the test about 3 times and then runs smoothly for the remaining 2/3 to 3/4 of the test.  the BOB activity LED flickers accordingly.
OCX Driver test:  CPU Mhz: 1837  Shortest time: about 32.___ us,  Longest time: about 38.___ us.  APIC timing constant: 11910.  Max Variation 2.3___ us  The tallest spike on my 19" LCD monitor in the graphic display was less than a quarter inch tall.
I'll post a pic of the setup.