Slew speed weirdness


Martin Chapman
 
Edited

Morning all, I need the help of the team please.
I built a system using the MKS Gen 2 board TMC2160 drivers and 400 step motors, to convert my G11
Everything seemed to be going well but I have not had much chance to use it. When I put my bigger scope on, occasionally the motors would be noisy, after a while I figured it might be a power issue so I switched to 24V,(two old leisure batts.) This seemed to work okay but for other reasons I switched back to my WO Z71. Everything seemed okay until the first time I tried to use it at night. When I start to align, the DEC motor would make a horrible noise and stop moving, RA would be fine. Much checking of worm engagement etc. later I swopped the leads over and this time it was RA that played up. Okay I thought, maybe I have damaged the driver when I increased the load with my bigger scope. Not  having the funds to replace the driver just now, I spent some time yesterday fiddling around with it and discovered something odd. It will work okay, as long as select the lowest slew rate, (1 deg/sec), anything over that causes the fault, now, just from curiosity yesterday I discovered that I can do the star alignment, at the slowest slew rate, but, once the alignment is done, I can turn the slew rate back up, all the way to it's max, (4 deg/sec). no joy until alignment is complete, but works as it should once alignment is complete. i guess I have something wrong somewhere, but cannot imagine what it could be, especially as it all seemed to be fine when I first built it.
On Another matter, I have seen that spiral search is available, on version 4.7 onwards, I cannot find any links to anything later than V 4.3, any clues please.
Any help is much appreciated.








Howard Dutton
 

1. You really should be using the latest release of OnStep: https://github.com/hjd1964/OnStep

2. Sounds like the motors are stalling (suddenly stop with vibration/whining noise,) and as expected slowing down helps. Be sure Vref is set at about 50% of the motors rating as a starting point and feel free to experiment with about +/- 25% from there to see if slews are faster.  Make sure the worms are not binding and axes of mount move freely.  Make sure your balance is decent.  Use 24V not 12V if possible.

3. There is really no difference between being aligned or not as far as moving the motors.  I expect it's just randomness being misinterpreted.


Martin Chapman
 

Thanks Howard, Vref is not adjustable on these drivers. Balance is okay, everything seems to move freely and I'm using 24V. I'm baffled by why I can only do the alignment at the slowest setting but after that can crank it right up with no problems?
Can I use the same config file for the latest version?
Thanks again.
Mart.


Howard Dutton
 

On Tue, Oct 12, 2021 at 06:14 AM, Martin Chapman wrote:
Can I use the same config file for the latest version?
Probably but not 100% sure, I just don't keep exact tabs on every minor change to development versions.

Best to make a new one.


Howard Dutton
 

On Tue, Oct 12, 2021 at 06:14 AM, Martin Chapman wrote:
Thanks Howard, Vref is not adjustable on these drivers.
Either you're setting the current with Vref or in software.  If in software change it there.


Martin Chapman
 

Er, okay, where would that be then, if it's not too much trouble to ask?
KR.
Mart.


Howard Dutton
 

On Tue, Oct 12, 2021 at 06:42 AM, Martin Chapman wrote:
Er, okay, where would that be then, if it's not too much trouble to ask?
Stepper Driver Adjustment


Martin Chapman
 

Thanks, Howard, I will look into this.
KR.
Mart.


Dave Schwartz
 

Those are 5160 drivers - I can see the discrete MOSFETs under the bottom end of the heatsink on the upper module. These modules come with that long heatsink that sticks onto the MOSFETs at either end because that is where the heat is produced, not in the 5160 chip itself. These modules have no Vref trimpot, as stated in the 'adjustment' link Howard provided, and must be done using the configuration settings (AXIS[1|2]_DRIVER_IRUN, AXIS[1|2]_DRIVER_IGOTO, AXIS[1|2]_DRIVER_IHOLD). Also use the correct AXIS[1|2]_DRIVER_MODEL.

On 2021-10-12 9:14 a.m., Martin Chapman wrote:
Thanks Howard, Vref is not adjustable on these drivers. Balance is okay, everything seems to move freely and I'm using 24V. I'm baffled by why I can only do the alignment at the slowest setting but after that can crank it right up with no problems?
Can I use the same config file for the latest version?
Thanks again.
Mart.
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Martin Chapman
 

Thanks, Dave, yes, my bad, Typo on my end, they are indeed Bigtreetech TMC 5160s
Thanks for pointing that out.
KR.
Mart.


Khalid Baheyeldin
 

Any easy way to generate a new Config.h, is using the OCG.
After you do this, change the IRUN and IGOTO per the formula on the stepper adjustment page that Howard linked to.
Then test and see how it goes.


Martin Chapman
 

Thanks, Khalid, didn't make any difference really, other than my Max slew speed has dropped from 4 deg/sec to 3. beginning to suspect I may have a damaged driver after all. I will upload the latest Onstep version and try again, might try putting my original S2209 drivers back in. 
KR.
Mart.


Khalid Baheyeldin
 

Looks like your suspect driver works well with low speeds.
That tells me it is not damaged.

Let us have some specifics.

What are the motors you are using?
Are they 1.8 (200 step) or 0.9 degrees (400 steps per rotation)?
What is their max current rating?
Did you use a different microstepping for GOTOs? That is one way of speeding up slewing.

Attach the config file that you used last.


Eric Esch
 

It may also be prudent to voltage drop / ohm test the wiring from driver to motors, and possibly power supply to make sure we aren’t having any issues there. Also, are both axis suffering from reduced slew speed or just a single axis? If both are suffering, I doubt it is a driver issue and more then likely a software, or power supply issue. 

if you believe it to be a driver issue, swap the position of the drivers and see if the reduced speed follows the “suspect” driver. 


Also remember that electrical Gremlins generally live in the grounds. Ie a bad ground can cause some really weird crap to happen in seemingly unrelated parks of the system.


Martin Chapman
 

Hi Khalid, 4oo step motors, max current 1.68 A
I have attached a config file that I tried yesterday.
What baffles me is that I can do a star alignment at 1 deg/sec, and no higher, once the star alignment is done, I can push the slew up to it's max of 4 deg/sec and it works fine, makes no sense to me, that bit.
I do remember that when I first had this problem, I touched the dec motor to see if it was working and it was too hot to touch, haven't had this problem since. I have swapped the leads over and then the problem shifts to the RA axis, which is what lead me to suspect the driver.
Take care and stay safe.
Mart.


On Wed, Oct 13, 2021 at 4:48 PM Khalid Baheyeldin <kbahey@...> wrote:
Looks like your suspect driver works well with low speeds.
That tells me it is not damaged.

Let us have some specifics.

What are the motors you are using?
Are they 1.8 (200 step) or 0.9 degrees (400 steps per rotation)?
What is their max current rating?
Did you use a different microstepping for GOTOs? That is one way of speeding up slewing.

Attach the config file that you used last.


Martin Chapman
 

Hi Eric, just the Dec playing up, yes, I swapped the leads over and the problem followed onto the RA, which is why I suspected the driver. 
What baffles me is that I can do a star alignment at 1 deg/sec, and no higher, once the star alignment is done, I can push the slew up to it's max of 4 deg/sec and it works fine!

Take care and stay safe.
Mart.


On Wed, Oct 13, 2021 at 5:15 PM Eric Esch <ericesch85@...> wrote:

It may also be prudent to voltage drop / ohm test the wiring from driver to motors, and possibly power supply to make sure we aren’t having any issues there. Also, are both axis suffering from reduced slew speed or just a single axis? If both are suffering, I doubt it is a driver issue and more then likely a software, or power supply issue. 

if you believe it to be a driver issue, swap the position of the drivers and see if the reduced speed follows the “suspect” driver. 


Also remember that electrical Gremlins generally live in the grounds. Ie a bad ground can cause some really weird crap to happen in seemingly unrelated parks of the system.


Khalid Baheyeldin
 

Your current settings in Config.h are too high.

1.68 X 1.41 X 0.35 = 829 mA

That is for IRUN

Try 1050 for IGOTO

Change IHOLD OFF

#define AXIS1_DRIVER_IHOLD           OFF
#define AXIS1_DRIVER_IRUN             830
#define AXIS1_DRIVER_IGOTO           1050

Same thing for AXIS2

Let us know what that does.


Martin Chapman
 

Thanks Khalid, I will let you know as soon as I can figure out how to get the Wifi working again, hasn't worked since I installed the latest Onstep version. Incidentally, up until someone told me about this the other day, irun, Ihold and Igoto were all set to off. still worked.
Take care and stay safe.
Mart.


On Wed, Oct 13, 2021 at 6:48 PM Khalid Baheyeldin <kbahey@...> wrote:
Your current settings in Config.h are too high.

1.68 X 1.41 X 0.35 = 829 mA

That is for IRUN

Try 1050 for IGOTO

Change IHOLD OFF

#define AXIS1_DRIVER_IHOLD           OFF
#define AXIS1_DRIVER_IRUN             830
#define AXIS1_DRIVER_IGOTO           1050

Same thing for AXIS2

Let us know what that does.


Khalid Baheyeldin
 

On Wed, Oct 13, 2021 at 02:32 PM, Martin Chapman wrote:
Incidentally, up until someone told me about this the other day, irun, Ihold and Igoto were all set to off. still worked.
That is quite odd.
The TMC5160 require a value at least for IRUN.


Martin Chapman
 

Apparently not, I was blissfully unaware of any of these values until I asked a question earlier this week. Knowing what the values do though, I am rather surprised anything happened at all.
Take care and stay safe.
Mart.


On Wed, Oct 13, 2021 at 7:39 PM Khalid Baheyeldin <kbahey@...> wrote:
On Wed, Oct 13, 2021 at 02:32 PM, Martin Chapman wrote:
Incidentally, up until someone told me about this the other day, irun, Ihold and Igoto were all set to off. still worked.
That is quite odd.
The TMC5160 require a value at least for IRUN.