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Re: My DIY Friction Drive Mount #maxesp3 #cnc #diy #mount #esp32

johnwashington1978@...
 

Wow, think of beauty made with a homebrew cnc!

I've been aiming to build a mount to replace mine, given the current prices of the higher end skywatcher mounts you could submit the whole job to a machine shop for less than new skywatcher prices.  I work a fair amount with Teknic professionally so I've intended to use their clearpath servos and friction - but its nice to see you've successfully implemented a stepper setup!  Drive torque isn't really a huge issue with a balanced scope - you do however need gearing to keep the stepper RPM up to a sensible speed, which isn't an issue with a servo.

I note mesu mounts appear to use a relatively tiny encoded servo and get a massive gear ratio by having a motor shaft with a small diameter.


Skywatcher EQ3-2 BluePill STM32 Goto moves way to much #EQ3

Frank
 

Hello and gooooood evening from Germany ;-)

First of all, again! Thank you for this project. I have got a Skywatcher 150/750 Newtonian telescope on a EQ3-2 mount. I moved from a MKS Gen L to BluePill STM board. But now I am facing an issue, which I can not explain.

I am currently in testing stage and my mount is pointing to Polaris and so on. I uploaded my site coordinates using an old android phone with OnStep app on it and synced the time.

On my iPhone with different apps like Stellarium or sky safari on it I can control the telescope over wifi. The issue now if I am doing a goto to Kochab or to Capella for testing, the telescope moves to much. For example the degree from Polaris to capella should be for example 40 degree to west. The telescope moves to west but it points down, lets say it moves 200 degree. 

My hardware setup for OnStep is:
BluePill Board
TMC2130 SPI (bigtreetech)

With the MKS Board it was working and I don't have got any clue which I made different.

My XLSX Calculations:


Attached also my config.

Can someone have a look on this and help me, please?

Maybe the

#define AXIS2_DRIVER_MICROSTEPS_GOTO  2 //  

Setting does not work on the bluepill board?

Thank you :-)


Re: Occasional error in guide speed - massive overcorrections

Howard Dutton
 
Edited

On Thu, May 27, 2021 at 11:32 AM, GuitsBoy wrote:
I was under the assumption that any guide speed was retained, be it .25x .5x or 1x.   I use .5x for guiding, but its quite possible that somethings was slewing at 1x.   However, the PHD over-corrections appear to be guiding at something like 4x or 8x, while the calibration was expecting 0.5x.  It does not appear to simply be double.  But I'll certainly keep this in mind.  Thanks.
I agree this seems like a bug.  Not sure if I want to fix it or not, for fear of breaking something in release-4.24 but the following is likely to be a low risk fix (untested.)

In the file Guide.ino add the following line just before enableGuideRate(guideRate); near lines 184 and 200.

if (pulseGuide) { guideTimerCustomRateAxis1=0.0; guideTimerCustomRateAxis2=0.0; activeGuideRate=-1; }

Let me know once you've checked it out.

For some background this is similar to the known issue with guide rates being wrong after spiral searches.  Easier to fix though, I think.

OnStepX has a guide subsystem design that should effectively address these annoying behaviors with custom guide rates (by virtue of its design.)


Re: Occasional error in guide speed - massive overcorrections

Howard Dutton
 

On Thu, May 27, 2021 at 07:48 AM, GuitsBoy wrote:
Also, a quick side question that doesn't warrant it's own thread.  Is there any way to issue a Find/Home command or a Home/Reset command from ASCOM (device hub, poth, or any clients using the ASCOM driver)? 
ASCOM's FindHome() is implemented and this can be done.  I use my own software so not really sure about what others support it.


Re: Occasional error in guide speed - massive overcorrections

Howard Dutton
 
Edited

On Thu, May 27, 2021 at 07:48 AM, GuitsBoy wrote:
I know you don't use APT, but it seems I cannot use a slew rate slower than 2x sidereal, or 0.00835654 degrees/sec.  Anything lower than this results in an error.  I notice that the ASCOM device hub, under capabilities, it shows primary and secondary axis rates as .00833 - 2.00000.  Perhaps this is connected to the reason APT cant move slower than 2x?  Any way to adjust this?
No.


Re: My DIY Friction Drive Mount #maxesp3 #cnc #diy #mount #esp32

Rafael Barberá Córdoba
 

Really impressive work Luca! When you have time and resolve all the remaining issues it will be very interesting know how precise the RA tracking will be.

I mean “blind” tracking without guiding of course ;). I hope that this kind of mount will not suffer from PE

Regards


Re: Occasional error in guide speed - massive overcorrections

GuitsBoy
 

I was under the assumption that any guide speed was retained, be it .25x .5x or 1x.   I use .5x for guiding, but its quite possible that somethings was slewing at 1x.   However, the PHD over-corrections appear to be guiding at something like 4x or 8x, while the calibration was expecting 0.5x.  It does not appear to simply be double.  But I'll certainly keep this in mind.  Thanks.

On 5/27/2021 2:26 PM, Khalid Baheyeldin wrote:
OnStep has a specific behaviour that people should keep in mind.
If you set the guide speed to anything less than 1X (i.e. 0.5X or 0.25X), it stays at what you selected.
But if you go and select 1X for any other reason, then 1X overrides 0.5X or 0.25X.

So mentally, I have to remember this, and do one of two workarounds:
- Never use 1X for any reason. That way the 0.5X I used for guiding 'sticks'.
- If I use 1X for whatever reason, then I go again and manually change the guiding speed to 0.5X again.


Re: Occasional error in guide speed - massive overcorrections

Khalid Baheyeldin
 

OnStep has a specific behaviour that people should keep in mind.
If you set the guide speed to anything less than 1X (i.e. 0.5X or 0.25X), it stays at what you selected.
But if you go and select 1X for any other reason, then 1X overrides 0.5X or 0.25X.

So mentally, I have to remember this, and do one of two workarounds:
- Never use 1X for any reason. That way the 0.5X I used for guiding 'sticks'.
- If I use 1X for whatever reason, then I go again and manually change the guiding speed to 0.5X again.


Re: Home sensors

Martin Bonfiore
 

Howard,

Thanks for the idea about adding the goHome(true)...I will give it a try..  I totally agree that an un-commanded rapid motion on startup should not be added and is not something I was looking for.  


Re: Occasional error in guide speed - massive overcorrections

GuitsBoy
 

While you're here, Howard, I was wondering if you might have any idea about a couple of things.

I know you don't use APT, but it seems I cannot use a slew rate slower than 2x sidereal, or 0.00835654 degrees/sec.  Anything lower than this results in an error.  I notice that the ASCOM device hub, under capabilities, it shows primary and secondary axis rates as .00833 - 2.00000.  Perhaps this is connected to the reason APT cant move slower than 2x?  Any way to adjust this?  I don't see anything obvious in the driver.  I assume this is a slew rate limitation and not a pulse guide rate limit, since I can manually pulse guide in PHD2 at 0.5x just fine.  However, confusingly, this seems to be what changes the pulse guide rate resulting in my wild overshoots while guiding.  I'm scratching my head trying to make sense of it.

Also, a quick side question that doesn't warrant it's own thread.  Is there any way to issue a Find/Home command or a Home/Reset command from ASCOM (device hub, poth, or any clients using the ASCOM driver)? 

Thanks for any insights,
-Tony



On 5/27/2021 10:37 AM, Howard Dutton wrote:
Thanks for the heads up, I'll keep this interaction in mind.


Re: MiniPCB v2 - Teensy 3.1 losing communication with wemos #wemos #wifi

Howard Dutton
 

Glad you seem to have it sorted.


Re: Occasional error in guide speed - massive overcorrections

Howard Dutton
 

Thanks for the heads up, I'll keep this interaction in mind.


Re: My DIY Friction Drive Mount #maxesp3 #cnc #diy #mount #esp32

tomofreno2000
 

Backlash was the reason I ask about the mechanism for applying normal force for the friction drives.  Looks like you did a great job! I would evaluate performance for a while before you consider adding encoders, as I expect slippage will not be an issue - but you know the mounts capability better than I.


Re: hello everyone, i have a new question. If I install a powerful servo motor with encoder instead of stepper motor, will the system work? #mount

Howard Dutton
 
Edited

The Step/Dir interface is an industry standard and is not limited to driving stepper motors.

There is no end to the options available, most of us use stepper motors with open loop control since it's cheap and effective.  I doubt the scale of whatever "larger telescope" is beyond something that can be handled by a stepper motor of some sort but nothing stopping you from using a servo.

Here's another source that's been mentioned here before:
https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/clearpath-sd-stepper-replacement/


Re: My DIY Friction Drive Mount #maxesp3 #cnc #diy #mount #esp32

Unluckyluke84
 

Thank you John for yor reply and suggestions. Yes, an encoder may be worth it , and I'll take it in consideration in the next "release" if there will be one....but It will be an High resolution one for sure. 


@Gildo I'm from Brescia 🙂


Zhumell Z8 Dobsonian accuracy troubleshooting/showcase #dob #backlash #maxesp3

Burton
 

Alright, so I've had a night out under the stars with my telescope! I had to increase stepper current to 1000 and decrease microsteps to 32 as I was running into stalling problems due to high RPMs on the stepper motors. I don't know if that was overkill, but I am pretty sure that solved the issue. 

Here's my build so far:
I used Nema 17 motors with 100:1 gearboxes, then going from a 40 tooth gear to a 320 tooth gear for an 8:1 ratio. I had to make belt tensioners in order to get things tight enough. I just bought a 5 meter length of GT2 belt from amazon, and used a 3D printed belt clamp on the altitude axis, and I sanded 2 inch sections and Gorilla Glued the belt together for the azimuth axis. So far after a week of being under tension, all seems good! 


So far, I've been having issues with figuring out backlash, which using the method layed out on the wiki, I am using 960 for the altitude, and 300 for the azimuth. Do these sound like they could be in the right range? After doing a 3 star alignment, here is the view that I get with my aligned laser when slewing to a star for reference. It is probably more than a moon's width away from the target star. Is this a good level of accuracy? 




Besides that, I just really don't understand how the backlash feature works.. Because even when I align it with the star, because of the backlash it doesn't track the star until it has moved around significantly in the eyepiece, usually leaving the view. 

I'll also link my config file and Excel spreadsheet.


Re: G11 Dual Axis & G8 Single Axis Configration #configuration

 

On Wed, May 12, 2021 at 04:07 AM, Dave Schwartz wrote:
CP2102

Final slove the issue..

CP2102 not able to detect or not able to upload error was fix... it was duel to board manufacture issue, connection RXT n TXD after solder both wire it able to connect just fine... ( i think the board trace line to thin or manufacture defect )

 


Re: hello everyone, i have a new question. If I install a powerful servo motor with encoder instead of stepper motor, will the system work? #mount

 

I find it worth a shot.
Because my goal is a bigger carrier. and connect and operate a larger telescope
 


Re: MiniPCB v2 - Teensy 3.1 losing communication with wemos #wemos #wifi

jarl_72@...
 

Hello Howard,

Thank you for replying.

I am, indeed, using release 4.24.

I tested the board using an HC05 without problem, and tested it through WiFi as well using the same cellphone (Samsung Galaxy S21) and SkySafari. It all seemed to be working fine.
...except OnStep app kept crashing.

I noticed the app kept getting worse, though. So I cleared the app cache and data, and I have not been able to make this thing crash anymore.
Not yet, at least :D

Now to do some testing using an actual telescope...

Thanks!!!


Re: SHC

Howard Dutton
 
Edited

On Tue, May 25, 2021 at 05:11 PM, Howard Dutton wrote:
  • The scroll rates when entering numbers are pretty fast.  The rates also change rather quickly.  It's easy to overshoot your mark and difficult to get within a minute of desired time.  Setting of coordinates (in goto) has the same issue.
A known issue, I'm busy with other stuff.
I added code to regulate the scroll speed when navigating the u8g2 interface, this includes the menus and also controls for setting values.

Rather than using a fixed scroll speed I implemented acceleration, so at first it moves slowly then after about 5 seconds it's very fast.  This is needed since some of the catalogs are quite large and would take forever to scroll through otherwise.

Seems to be working quite nicely here.

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