weird behavior on Z homing

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26 Nov 2012 02:13 #26942 by BigJohnT
Replied by BigJohnT on topic weird behavior on Z homing

I only see the home switch true once. I assume the stepper is stalled out and because the control has no idea if that is the case it keeps searching for the home switch again.

John


at that speed cannot stall, you can see that home seach is done much faster, in ini its 3 for homing and 1 for latch
Also, switching back to the lpt port with old config works normal.


By the way, thanks to everybody for helping me!


Must have something to do with the slow speed... a stepper can stall at any speed for many reasons. As Peter said if you on the bleeding edge of timings it may break. Try both search and latch at the same speed. The stepper is not turning so that tells me it is stalled for what ever reason.

John

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26 Nov 2012 02:23 #26943 by BigJohnT
Replied by BigJohnT on topic weird behavior on Z homing
To add to the problem it is the Z axis and it is going up and fighting gravity. Try supporting the Z to see if the weight is the issue at that speed. Also are you using a marginal power supply for your steppers?

John

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26 Nov 2012 02:29 #26944 by PCW
Replied by PCW on topic weird behavior on Z homing
You should be able to see what the stepgen is being told and what it is actually doing
by monitoring the stepgens command and feedback positions:

z-pos-cmd
z-pos-fb

plotting (via HALScope) these along with the Z home switch might be helpful

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26 Nov 2012 06:18 #26945 by cncbasher
you also have in your ini file

HOME_SEQUENCE = 1
HOME_USE_INDEX = NO
HOME_SEQUENCE = 2

i.e home sequence entry is duplicated ...

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26 Nov 2012 07:49 - 26 Nov 2012 07:50 #26946 by Psykhon
Replied by Psykhon on topic weird behavior on Z homing

I wonder is this is an electrical/timing issue
Is it possible that your timing is marginal? (looks like it)
You have all the timings set to the G540 minimums,
that is, just on the edge of not working

I would set steplen to 1500, stepspace to 2500
and both dir setup and hold to say 700. These settings cannot
hurt anything (they still allow the maximum G540 step rate)
but they give you some 500 ns timing margin (instead of 0)


And that did the trick :laugh:
everything works as espected :)

Side note:
-those values where generated by pncconf
-I did try increasing steplen and space but not setup or hold
-Those values work flawesly for X and Y
-Same values that been using on LPT, without problem

anyway, LOTS of thanks to everibody :laugh:

Now, PCW, just tryed the charge pump config you wrote earlier but no sucess, where is the NET that tells to that stepgen in wich port.pin should output?
setp hm2_5i25.0.stepgen.04.dirsetup 100
setp hm2_5i25.0.stepgen.04.dirhold 100
setp hm2_5i25.0.stepgen.04.steplen 100
setp hm2_5i25.0.stepgen.04.stepspace 100
setp hm2_5i25.0.stepgen.04.position-scale 16000 # 16000 steps per machine unit
setp hm2_5i25.0.stepgen.04.step_type 2 # quadrature for square wave output
setp hm2_5i25.0.stepgen.04.control-type 1 # velocity mode
setp hm2_5i25.0.stepgen.04.maxaccel 0
setp hm2_5i25.0.stepgen.04.maxvel 0
setp hm2_5i25.0.stepgen.04.velocity-cmd 1 # one machine unit per second so 16KHz

net machine-is-enabled hm2_5i25.0.stepgen.04.enable


For g540 should be on LPT 16, wich is IO 5 on 5I25

thanks again!
Last edit: 26 Nov 2012 07:50 by Psykhon.

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26 Nov 2012 10:30 #26947 by PCW
Replied by PCW on topic weird behavior on Z homing
Pinouts are hardwired into each configuration. Stepgen 4 step output should be on LPT16 but you may need to update the 5I25 to the latest G540 firmware to get this feature. You can see if your firmware is correct by looking at the kernel log file with dmesg after running LinuxCNC

Its quite likely that timing that works on a LPT port will not work on a 5I25 stepgen. This is because the LPT timing is determined by software and LPT access time so even if you use the reset mode to generate short step pulses, if you specify 1000 ns, the actual step time will be 1000 ns plus the LPT access time (so more like 2000 ns actual step pulse time). The 5I25 has 30 ns resolution on its stepgen timings so if you specify 1000 ns you will actually get 990 ns, that is the, closest selectable time to 1000 ns
The following user(s) said Thank You: Psykhon

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27 Nov 2012 20:38 #26988 by Psykhon
Replied by Psykhon on topic weird behavior on Z homing
this seems to be the lowest safe values, in case anyone finds himself in the same situation
DIRSETUP   = 300
DIRHOLD    = 300
STEPLEN    = 1200
STEPSPACE  = 2200


Where is the proper place to make a suggestion to modify pncconf default values for 5i25+G540?

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27 Nov 2012 21:35 #26990 by BigJohnT
Replied by BigJohnT on topic weird behavior on Z homing
The pncconf part of the forum.

What voltage are you using to drive your steppers?

John

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27 Nov 2012 21:42 #26991 by Psykhon
Replied by Psykhon on topic weird behavior on Z homing
This are 3.1nm steppers and Im fedding 36V 2.8A, been working very nice on LPT, hope to improve speed with the 5i25

with the 5i25, can I enable acpi now? nothing important but would be nice if the computer turns itself off after linux shuts down

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27 Nov 2012 22:16 - 27 Nov 2012 22:18 #26993 by Psykhon
Replied by Psykhon on topic weird behavior on Z homing
got charge pump working, had to change this line:


net machine-is-enabled hm2_5i25.0.stepgen.04.enable
with:
net estop-out hm2_5i25.0.stepgen.04.enable iocontrol.0.user-enable-out

Dont know if this is the most "elegant" or accurate way, sure someone understand this better

Anyway, for future reference, this makes the charge pump work

It needs a 5th stepgen:
loadrt hm2_pci config=" num_encoders=0 num_pwmgens=0 num_3pwmgens=0 num_stepgens=5" 

and this segmet sets the 5th stepgen as a charge pump as pointed out by PCW
setp hm2_5i25.0.stepgen.04.dirsetup 100
setp hm2_5i25.0.stepgen.04.dirhold 100
setp hm2_5i25.0.stepgen.04.steplen 100
setp hm2_5i25.0.stepgen.04.stepspace 100
setp hm2_5i25.0.stepgen.04.position-scale 16000 # 16000 steps per machine unit
setp hm2_5i25.0.stepgen.04.step_type 2 # quadrature for square wave output
setp hm2_5i25.0.stepgen.04.control-type 1 # velocity mode
setp hm2_5i25.0.stepgen.04.maxaccel 0
setp hm2_5i25.0.stepgen.04.maxvel 0
setp hm2_5i25.0.stepgen.04.velocity-cmd 1 # one machine unit per second so 16KHz

net estop-out hm2_5i25.0.stepgen.04.enable iocontrol.0.user-enable-out
Last edit: 27 Nov 2012 22:18 by Psykhon.

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