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Microsteps slewing with ramps1.4 A4988

julianporter5@...
 

When using the Goto function the scope does not point in the correct direction. 
I must have something wrong in the configuration.
I’m using a Ramps 1.4 board with A4988 drivers. I have jumpers under the drivers which set the microsteps to 16.
I have MICROSTEPS_GOTO set to off in the configuration generator.
Should it be set to 16?
If I set it to 16 the compilation fails with the error “Comfiguration: AXIS1_MICROSTEPS_GOTO should be less than AXIS1_MICROSTEPS or _OFF”

Khalid Baheyeldin
 

On Thu, Nov 28, 2019 at 03:55 PM, <julianporter5@...> wrote:
When using the Goto function the scope does not point in the correct direction. 
Not enough information here.
Does it do a short or long slew (i.e. ends up before or after the object)? This means steps per degrees are wrong (too small or too large)
Does it point to the wrong area in the sky (e.g. east instead of west)? This is a axis reverse problem (either it is set when it should not, or needs to be set but is not so).

I must have something wrong in the configuration.
What are the parameters that you used on the spreadsheet?
What steps per degree did you end up using in the configuration?

I’m using a Ramps 1.4 board with A4988 drivers. I have jumpers under the drivers which set the microsteps to 16.

I have MICROSTEPS_GOTO set to off in the configuration generator.
Should it be set to 16?
If I set it to 16 the compilation fails with the error “Comfiguration: AXIS1_MICROSTEPS_GOTO should be less than AXIS1_MICROSTEPS or _OFF”
Ignore microsteps goto for now, until we figure out what is wrong and which problem it is ...

julianporter5@...
 

Like all good astronomers I have the scope set up in the kitchen!
I know there is a problem because I'm trying to do an alignment and find that the scope does not steer to the Az/El of the chosen star.
Both Onstep and Stellarium give the same position for the star so i don't think I have a time or location setup problem.
I would like to answer your question as to whether it does a long or short slew. Can I use the app directly to drive the mount in angular coordinates to answer that? 
Im sure I have the RA connected correctly as it is rotating in the right direction when tracking.

The spreadsheet and config files are here 





Here 

Khalid Baheyeldin
 

On Thu, Nov 28, 2019 at 05:14 PM, <julianporter5@...> wrote:
I know there is a problem because I'm trying to do an alignment and find that the scope does not steer to the Az/El of the chosen star.
Both Onstep and Stellarium give the same position for the star so i don't think I have a time or location setup problem.
If you set the location and time from the Android app, then it should be correct, no need to worry about any of them being wrong.

When you say "same position", you mean same RA or DE or Alt and Az? If the former, then it does not mean anything. If the latter, then it means they match.

I would like to answer your question as to whether it does a long or short slew. Can I use the app directly to drive the mount in angular coordinates to answer that? 
No, the OnStep App does not offer the option to enter Alt/Az coordinates.

But you can open the Arduino IDE's serial monitor and enter the commands that are at the very end of this page.
They move the scope to a certain Alt and Az.

See if this gives the same location in the sky as Stellarium.

Im sure I have the RA connected correctly as it is rotating in the right direction when tracking.
Good.

The spreadsheet and config files are here 
This is the CG-4 / EQ3-2, which Pete recently said was problematic.

julianporter5@...
 

The serial monitor is really useful for testing, Ive confirmed that the RA axis is moving by the correct amount.

The pointing error in RA was due to the following:

1) One gear was slipping on its spindle which was easily fixed.  

2) The RA worm gear is loose in its housing allowing the belt drive to slip. I might be able to change the motor mounting to help but mechanically the mount isn’t very good. 

Khalid Baheyeldin
 

On Fri, Nov 29, 2019 at 02:14 PM, <julianporter5@...> wrote:
I might be able to change the motor mounting to help but mechanically the mount isn’t very good.
Which is what Pete found out the hard way: after converting a CG-4, and lots of issues, he moved the motors to a CG-5 and all the issues went away.

You may want to consider this option down the road.

julianporter5@...
 

I’ve been on the lookout for an Eq5 at a good price for sometime. I was happy to start with the eq3-2 as a prototype. It would be nice to see if I can overcome some of the mechanical issues then change to use the MKS gen-L board before switching to a different mount.

tnut55
 

I did an EXOS1 which (I think) is equivalent to a cg4.  The EXOS2 appears to be equivalent to cg5.

It works for visual.  I wouldn't spend time or money on the former for AP unless you just put a camera on the mount for constellation shots unguided and kept the exposures relative short.

Mark


On Fri, Nov 29, 2019 at 3:34 PM, julianporter5@...
<julianporter5@...> wrote:
I’ve been on the lookout for an Eq5 at a good price for sometime. I was happy to start with the eq3-2 as a prototype. It would be nice to see if I can overcome some of the mechanical issues then change to use the MKS gen-L board before switching to a different mount.

julianporter5@...
 
Edited

I've been using the serial monitor.

What exactly are the Sa and Sz values? They aren't the angle set by the stepper motors around each axis. 

I did confirm with the declination motor disconnected  Sz did set angle of rotation around the RA axis. 
So I'm happy that I have put the right values into the configuration generator.

I was not successful doing the same test with the other axis. Setting the angle of rotation was not repeatable. Powering off didn't work as a reset.

Despite all this, when I use the app to do a single star align the direction the scope points looks close to that shown in Stellarium. 
To stop the belts slipping I've had to make the worm gears run with very little resistance and the backlash now is very large.
 
It will be worth a go with a telephoto lens on a camera. The goto might be good enough. I just need reasonable tracking. 

I've got an RTC for RAMPS, the TMC2130 drivers and a MKS gen-L board.
Should I switch to the MKS gen-L board first then switch drivers and forget about the RTC?

And what about micro steps for slewing?

Khalid Baheyeldin
 

On Wed, Dec 4, 2019 at 12:48 PM, <julianporter5@...> wrote:
I've been using the serial monitor.

What exactly are the Sa and Sz values? They aren't the angle set by the stepper motors around each axis. 
No.

They are the alt and azimuth coordinates of an object.
OnStep translates those sky coordinates into motor steps based on motor and driver parameters, ...etc.

The use of Alt and Az in this test avoids the issue of incorrectly set (or never set) data/time/location/...etc.

You can read this reference of OnStep serial commands.

I did confirm with the declination motor disconnected  Sz did set angle of rotation around the RA axis.
I couldn't make out what this means.

 So I'm happy that I have put the right values into the configuration generator.

I was not successful doing the same test with the other axis. Setting the angle of rotation was not repeatable. Powering off didn't work as a reset.
The success of your test is when the mount is pointing in the correct azimuth and altitude that you told it to.
For example, if you set it to 90 Az, and +45 Alt, then it should point due east, and make a 45 degree relative to the horizon.

Despite all this, when I use the app to do a single star align the direction the scope points looks close to that shown in Stellarium. 
So it seems to be working then?

To stop the belts slipping I've had to make the worm gears run with very little resistance and the backlash now is very large.
 
It will be worth a go with a telephoto lens on a camera. The goto might be good enough. I just need reasonable tracking. 

I've got an RTC for RAMPS, the TMC2130 drivers and a MKS gen-L board.
Should I switch to the MKS gen-L board first then switch drivers and forget about the RTC?
If you have an Arduino Mega2560 and a RAMPS board, then go ahead and try that with the RTC before buying anything else.
The TMC2130 must be the SPI variant with upward pointing pins.

Don't switch to the MKS Gen-L unless you find a real tangible issue with the RAMPS board.

And what about micro steps for slewing?
Microsteps for slewing is only relevant to speed up slewing if it is too slow without it.
If you can slew at anything above 1.5 deg/sec, then you can live without it.

Another restriction is that the type of board and driver can dictate whether microstep slewing is possible at all or not.
Don't worry about it for now, until you test slewing speed and find it too slow.