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Re: Celestron CGE

tnut55
 

Yes, there are 3 CGE conversions in the showcase.  All use belt drive but I don't think any are 1:1.

A 5:1 planetary reducer, a 1:1 belt with the native 1:180 worm wheel reduction seems reasonable to me.


On Tue, Dec 24, 2019 at 10:13 AM, fetoma
<fetoma@...> wrote:
Alex and John, have you seen the showcase page with the already belt driven converted CGE's?


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 

There is now a Wiki page that covers this topic, I welcome comments and corrections, this is my best understanding of the subject:
https://onstep.groups.io/g/main/wiki/Stepper-Motor-Accuracy

I am not done testing motors but have finished with the 1.7A 0.9° NEMA17 for now I think.  Next will be the 0.85A 0.9° NEMA17 PKP244MD08 which is really more interesting to me since that's what my G11 uses.


Re: Celestron CGE

fetoma
 

Alex and John, have you seen the showcase page with the already belt driven converted CGE's?


Re: Introduction and some help

Grant Baxter
 

Hi Dave

Thanks for the info, really appreciate it. If I understand it correctly, the RJ45 connector is an 8 pin, and in this instance, bridged to essentially a 4 pin. 

In terms of wiring, my stepper motors have 4 wires: red, black, blue and green - which wire goes to which pin pairing?

Regards

Grant


Re: Introduction and some help

Dave Schwartz
 

The sockets on the STM32 PCB are RJ45, with each pair of pins (1-2, 3-4, 5-6, 7-8) connected by the PCB. The interconnection is done to increase both current carrying capacity and robustness of the connection. What I have done is use an inexpensive RJ45 breakout board, with RJ45 socket on it, and connect the motor wires into it - bridging the same wires that are doubled at the PCB end. The breakout board then gets hot-glued somewhere on the mount or motor bracket and I use standard RJ45 ethernet cables.

Some people do not use the RJ45 on the PCB and wire 4-pin aviation connectors directly to the header by the drivers (that's what they are there for) and use another aviation connector at the motor end. Then you get to make your own cables.

Pictures of both are available in the message history through a search.

On 2019-12-24 8:47 a.m., Grant Baxter wrote:
The motorizing of the mount is progressing, albeit slowly. The stepper motors have arrived (Nema 17 400 step, 0.9 degree, 0.9 A) and I have ordered the onstep STM32 unit. Am now want to sort out the cabling from the controllers to the motors - as I understand it, the cable connectors on the STM32 are RJ45 connectors and the motor end of the cable is RJ11, so 2 questions please:

firstly - can I connect a male RJ45 connector to a male RJ11 connector? If so, what is the wiring diagram?  Secondly, what type of cable should I be using? Am assuming it will be a 4 core cable sufficient to carry the 0.9A? Or are there other considerations - for example - maximum length of the cable etc?

Thanks for the guidance

Regards

Grant


Re: Buying an EQ5

Prasad
 
Edited

 
Vixen worm shaft extended on both sides and so, it may be broken only on one end. Since it is a Dec shaft you may still be able to use the mount. RA shaft damage may give you excessive PEC but Dec shaft damage is not consequential IMO.

Added during edit:
A Vixen GP mount is greatly superior in quality to Bresser (or any China made) mount. I have both Vixen GP & SP as well as Bresser EXOS2 and I am stating my experience. 
 
 
 

On Tuesday, December 24, 2019, 08:14:43 AM EST, julianporter5@... <julianporter5@...> wrote:
 
 

[Edited Message Follows]

What is the quality like of a Bresser Mon2 eq Mount

I've seen a Vixen Great Polaris but the end of the declination worm gear shaft has sheared. This begs the question whether there is other damage to the gear. Where would I find a replacement worm gear?


Re: Introduction and some help

Grant Baxter
 

The motorizing of the mount is progressing, albeit slowly. The stepper motors have arrived (Nema 17 400 step, 0.9 degree, 0.9 A) and I have ordered the onstep STM32 unit. Am now want to sort out the cabling from the controllers to the motors - as I understand it, the cable connectors on the STM32 are RJ45 connectors and the motor end of the cable is RJ11, so 2 questions please: 

firstly - can I connect a male RJ45 connector to a male RJ11 connector? If so, what is the wiring diagram?  Secondly, what type of cable should I be using? Am assuming it will be a 4 core cable sufficient to carry the 0.9A? Or are there other considerations - for example - maximum length of the cable etc?

Thanks for the guidance

Regards

Grant


Re: Buying an EQ5

julianporter5@...
 
Edited

What is the quality like of a Bresser Mon2 eq Mount

I've seen a Vixen Great Polaris but the end of the declination worm gear shaft has sheared. This begs the question whether there is other damage to the gear. Where would I find a replacement worm gear?


Re: Celestron CGE

John Scherer
 
Edited

While I don’t own a CGE Mount, I wouldn’t exclude belt drive without some testing. You gain torque and by not using a gearbox, you reduce the likelihood of backlash, which can be significant depending on how lucky you get with the motor/gearbox purchase.   I'm doing a 4:1 belt drive with my Losmandy GM-8.


Re: Celestron CGE

Alexander Varakin
 

I am getting a CGE too with the purpose of converting it to Onstep.
I believe that belt drive provides better accuracy so I think that planetary gears would work for visual work, but for AP it is worth the effort to have a belt drive.

Alex


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 

And the last (for tonight) is the S109 running the motor at 2.32A:


Re: how enter telescope position manually

Khalid Baheyeldin
 

On Mon, Dec 23, 2019 at 06:38 PM, Dan Sawyer wrote:
Is it possible to enter onstep scope Dec and RA coordinates manually?
Do you mean ask it to slew to an RA/DEC combo, or tell it that it is pointing to a certain RA/DEC combo?

Both are possible, though I assume that you mean the latter, so you can polar align indirectly.

For the first (slew to coordinates), you can use the Android App, select Enter Coordinates, then fill in the values, and OnStep will slew to that place.

For the latter (set coordinates manually), Sync is the function you need, but it is tricky in that to Sync, you need an object to sync on.
If you use a planetarium, you can go to the zenith, then Sync on that point.

I am able to do it from KStars, though other planetariums probably can do the same.

I tried Stellarium Mobile Plus, and it does not have this function when I click the nearest star to the zenith, only Goto. Maybe Sky Safari can do it?

Since your goal is polar alignment, checkout the Refine PA function, which is documented under the Advanced page on the Wiki. Maybe it is all you need.


Re: SkyWatcher14- Debug help please

DaveGee
 

G'day,

I did a couple of things
- corrected an error in my StepsPerDegree (oops!)
- changed MaxAzm to 360
- reversed the direction of the Az motor
uploaded the code to the Teensy

And rebooted my phone and... Sensible slews achieved.  Yay!

Now all I need for all this smoke to disappear and try it out under some stars.

I have a video of the rig slewing on by FB profile...
https://www.facebook.com/profile.php?id=100011497001381

--
Regards
DaveGee
www.kuriwaobservatory.com


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 
Edited

Now the LV8729 at 0.96A (40% power,) I will not test above this setting for this motor since the driver can't reach 1.7A  My plan is to test at 40%, 70.7%, and 100% power where possible.


how enter telescope position manually

Dan Sawyer
 

Is it possible to enter onstep scope Dec and RA coordinates manually?

I would like to point the scope to the zenith using a precision level for both Dec and RA; and set onstep azimuth to the current latitude and RA to the current sidereal time. Both of these can be known to a reasonable starting precision.

Based on the above OnStep and the mount will be in a known position relative to its current polar adjustment. If it then 'moved' to a known star the difference between the star and center of field should accurately reflect mount Polar misalignment.

I am interested in experimenting with this.

Dan


Re: Stepper motor mount for Losmandy GM-8

John Scherer
 

I should add, my plan is to machine both the plate and the cover from aluminum.   3D printing just allows for rapid prototyping and iterations in the design.   


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 

And here's the same motor/test except stealthChop and 0.96A (40% power) instead of 1.7A (70.7% power), I expected a very different outcome here with less accuracy.


Re: Stepper motor mount for Losmandy GM-8

John Scherer
 

Hey Chris, it’s PETG and prints @ 240-260c and has great thermal properties and should be fine with the heat from
the stepper.  If your stepper ever got hot enough to soften PETG, you’d have other problems ;-)


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 
Edited

Note that in theory the TMC2130/TMC5160 microstep current table can be programmed to improve on this performance and I now have the data to do so for this motor.


Re: Characterizing NEMA17 stepper motor/driver micro-stepping accuracy

Howard Dutton
 

Here's another chart.  Same motor/same test except spreadCycle instead of stealthChop.  The stealtChop mode came out slightly on top with better accuracy and less variance.