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Re: Worm gear adjustment EQ3-2

Dave Schwartz
 

Yes, it is. You have to dismount the motor to get at the adjustment push-pull screws and then rotate the shaft manually until you find, and adjust for, the tightest spot in the axis rotation. There will then be spots where the mesh is looser than ideal but at least the gears won't bind and stall the motor. Such is the price to be paid with this class of machining. There is no such thing as uniform backlash with budget mounts.

On 2019-12-17 2:53 a.m., julianporter5@... wrote:
I found one of the bronze bearings to be quite worn. I’ve put the best bearings on the RA axis.

The worm gear adjustment looks Identical on the Eq5. Is backlash adjustment also problematic with the Eq5?


Re: RTC init failed

Howard Dutton
 

I fixed this, both the master and beta were updated.


Re: Encoders

Howard Dutton
 

On Mon, Dec 16, 2019 at 08:18 PM, --Oz-- wrote:
I already have the servo motors mounted, the A4950 drivers and have one arduino pro mini, so cost wise will be two bucks for another pro mini to try it out.
If it were me and I had a pair of perfectly good servo's already mounted up and ready to go, I'd be doing the same.  I look forward to hearing about how it goes.


Re: Worm gear adjustment EQ3-2

julianporter5@...
 

I found one of the bronze bearings to be quite worn. I’ve put the best bearings on the RA axis.

The worm gear adjustment looks Identical on the Eq5. Is backlash adjustment also problematic with the Eq5?


Re: Encoders

--Oz--
 

Thanks Khalid, I have acknowledged that I have been thoroughly warned!  :)

I already have the servo motors mounted, the A4950 drivers and have one arduino pro mini, so cost wise will be two bucks for another pro mini to try it out.



Re: Encoders

Khalid Baheyeldin
 

On Mon, Dec 16, 2019 at 03:42 PM, --Oz-- wrote:

I routinely get 0.25arc/sec RMS guided on my G11 (PEC-OFF with good atmosphere), almost always under 0.5. I have used PemPro and uploaded to my mount, gut it seems my autoguiding maid it unnecessary.
Yeah, that is correct.
With autoguiding on a low PE mount, all the other tricks are not necessary: that includes PEC, Encoders for tracking rate, Fully Compensated Tracking, ....etc. They are all superceded by autoguiding.

That is one of the reasons I am recommending plain steppers, in addition to making it overall a simpler conversion.


Re: Encoders

--Oz--
 

Thanks for the replies!
That way, no backlash issues, and it can track Periodic Error, ...etc.And they usually use encoders with much higher resolution.
The RA should never stop or go backward when tracking (aka eastward weight bias keeps the slop in gear-train always in mesh, on the driving side), the 10,000 encoder would be 40,000 quadrature , where the G11/Gemini with 360t * 25(geaqrbox) * 250ppr * 4 (quadrature) equals 9,000,000, or 225x more resolution (in best case). I routinely get 0.25arc/sec RMS guided on my G11 (PEC-OFF with good atmosphere), almost always under 0.5. I have used PemPro and uploaded to my mount, gut it seems my autoguiding maid it unnecessary. I am not attempting to get my ci700 to do the same, but I would hope its around 1arc/sec rms. I bought the ci700 used, I cleaned it up, added the extra bearings, so really its in a unknown state at the moment. 

Regarding PID tuning, I have a couple decades worth tuning PID's, most recently on my quad's (me flying here https://www.youtube.com/watch?v=uHoFfpLSb2g )


RTC init failed

Alain K
 

Hello Howard,

I received this message when onstep start in the Wifi status page :
"RTC init failed"

OnStep 3.13b
OnESP 1.11h
I'm on a breadboard with the MaxESP3 pinmap.
Wemos D1 pro
DS3231 RTC module.

I know the RTC module is OK because the test with the library exemple work, with the same pinmap.

Regards.


Re: ci700

--Oz--
 

Wow! Fast and excellent replies, many thanks guys getting me up to speed quickly!!! On to more reading :)


Re: ci700

Khalid Baheyeldin
 
Edited

On Mon, Dec 16, 2019 at 12:35 AM, --Oz-- wrote:
I am looking to buy the stm32 Kit C to use on my ci700 that has Gemini servo motors with 250ppr encoders and the arduino pro mini (with https://github.com/misan/dcservo) with A4950 motor drivers. This setup would be 180t * 25 * 250 * 4 = 4,500,000 ticks for turn (half of the G11/Gemini setup), I am guessing that is ok.

Few questions:
1. for the arduino pro mini, should I order the 3V or 5V version to use with the bluepill stm32?
Retaining the servos is possible, but before you embark on this, consider the challenges:

1. Rarity: I only know of one person (German or Austrian?) who have made it work a few years back. There was possibly another person asking questions (Asia), but not sure if he actually implemented it or not. On the other hand, we have hundreds of people using stepper motor setups.

2. Complexity: you require two additional microcontrollers, one for each servo motor, and additional firmware on them.

3. Tuning: you need to do the PID thing described in dcservo's documentation and Youtube videos.

Based on the above, I think that you are better off with just stepper motors, like the vast majority of OnStep users. Ignore the encoders.

If I decide to use stepper motors, looks like one guy used nema 17 (17HS4401) and 16t/40t pulleys with belts, where do i find these parts (links):
2. Motors? 
Read the entire Construction page. It has lots of helpful links.
Use the spreadsheet on the construction page to run the numbers.

OMC Stepper, as simingx said. Also eBay and AliExpress.

Motors that are 0.9 degree are better, and they should have adequate holding torque (36 Ncm or more), and low inductance.

This 0.9 degree, 0.9A motor is popular with EQ5 mounts.
With sufficient reduction (3:1), it should be able to drive CI700 (G11 like mount)

An alternative approach is to get a motor with an integrated gearbox with more reduction (e.g. 10:1 to 15:1).
That way, you can use 1:1 pulleys with a lesser number of teeth (e.g. 25T to 25T), so they are easier to fit on the worm shaft side.
With the added benefit that the reduction increases resolution and torque at the same time.
Again, run the numbers in the spreadsheet.

3. belts/pulleys?
eBay or AliExpress. Also Amazon.
The Construction page has belt size calculators, ...etc.

4. What stepper motor driver is most recommended (LV8729)?
Depends on the motor current.
If it is low (1A or less) then LV8729 will work well, and the TMC2130.
If it is above 1A, then you need the S109 or the TMC5160.

Again available on AliExpress, eBay and Amazon.

5. If you dont have BHC or the SHC, how do you control the mount (align-stars/goto/etc)?
The STM32 kit C has a Wemos, which is an ESP8266 and allows full control from an Android App. Very convenient.


Re: ci700

Dave Schwartz
 

On 2019-12-16 12:35 a.m., --Oz-- via Groups.Io wrote:

6. Looks like the SHC PCB is not sold anymore, (https://baheyeldin.com/astronomy/onstep-esp32-smart-hand-controller-shc.html), Is there a schematic somewhere? <https://baheyeldin.com/astronomy/onstep-esp32-smart-hand-controller-shc.html>
https://easyeda.com/dschwartz/onstep-shc


Re: Encoders

Howard Dutton
 

On Sun, Dec 15, 2019 at 08:16 PM, --Oz-- wrote:
What is the reason to have the encoders goto the ESP32 and not the stm32? (sorry noob here)
It's usually an ESP8266 handling that.  STM32 and several other MCU's OnStep runs on really don't have enough pins.  This solution works for all OnStep's and only handles the pointing side of things, kind of like digital setting circles for OnStep (though there is experimental support for tracking correction if the RA encoder is up to that level.)


Re: ci700

simingx@...
 

I'll try:
2) https://www.omc-stepperonline.com/
3) Ebay / Aliexpress
4) TMC2130 et al, but read the FAQ
5) Android app, Kstars, Sky Planetarium, etc


ci700

--Oz--
 

I am looking to buy the stm32 Kit C to use on my ci700 that has Gemini servo motors with 250ppr encoders and the arduino pro mini (with https://github.com/misan/dcservo) with A4950 motor drivers. This setup would be 180t * 25 * 250 * 4 = 4,500,000 ticks for turn (half of the G11/Gemini setup), I am guessing that is ok.

Few questions:
1. for the arduino pro mini, should I order the 3V or 5V version to use with the bluepill stm32?

If I decide to use stepper motors, looks like one guy used nema 17 (17HS4401) and 16t/40t pulleys with belts, where do i find these parts (links):
2. Motors? 
3. belts/pulleys?

4. What stepper motor driver is most recommended (LV8729)?
5. If you dont have BHC or the SHC, how do you control the mount (align-stars/goto/etc)?

6. Looks like the SHC PCB is not sold anymore, (https://baheyeldin.com/astronomy/onstep-esp32-smart-hand-controller-shc.html),  Is there a schematic somewhere?

TIA!


Re: Encoders

Khalid Baheyeldin
 

On Sun, Dec 15, 2019 at 11:16 PM, --Oz-- wrote:
I just found Onstep a week ago, been reading/searching, project looks very impressive.
My ci700 currently has Gemini servo motors with 250ppr encoders and 25:1 gearbox (with 180t RA/DEC gears).
When people use encoders with OnStep, they mostly make them directly coupled to the axes, not after the gear reduction.
That way, no backlash issues, and it can track Periodic Error, ...etc.
And they usually use encoders with much higher resolution.

What is the reason to have the encoders goto the ESP32 and not the stm32? (sorry noob here)
Note that encoders are experimental. Read more here (near the bottom of page).

That is the way Howard designed it, my best guess it that it is due to:
  • lack of spare pins (OnStep STM32, Teensy 3.2, ...etc.)
  • To not interrupt the main microcontroller too often, specially with high resolution encoders

I came across this video showing a hardware method of connecting encoders, have you guys seen it? Seems to be quite a bit less bothering the main loop over the interrupt method.
Not applicable.
Yeah, encoders can be connected to any microcontoller, in theory, but OnStep does not do it that way (for the reasons above, possibly others).
And we don't have spare timers for the STM32 (OnStep uses them).
As well, we also do not want to have too much microcontroller specific stuff within OnStep.

My plan is to order Kit C and: 
1. use the arduino pro mini (with https://github.com/misan/dcservo) with A4950 motor driver to my servo motors.
2. test the method discussion in this thread.
You can drive servo motors from OnStep, and the dcservo project helps to do that.
One hard part is the PID tuning, which looked tricky to me when I last looked at dcservo. Since then I ripped the servos out and replaced them with steppers and all works well.

This is just my take on the question, Howard (and others who implemented encoders) will add more ...


Re: Encoders

--Oz--
 

I just found Onstep a week ago, been reading/searching, project looks very impressive.
My ci700 currently has Gemini servo motors with 250ppr encoders and 25:1 gearbox (with 180t RA/DEC gears).

What is the reason to have the encoders goto the ESP32 and not the stm32? (sorry noob here)

I came across this video showing a hardware method of connecting encoders, have you guys seen it? Seems to be quite a bit less bothering the main loop over the interrupt method.
https://www.youtube.com/watch?v=HunHtmiO2uo

My plan is to order Kit C and: 
1. use the arduino pro mini (with https://github.com/misan/dcservo) with A4950 motor driver to my servo motors.
2. test the method discussion in this thread.

Thanks for all the hard work guys!


Re: naive beginner question - How to compile OnStep on Arduino IDE

Dan Sawyer
 

Thank you. The instructions now make sense:

Use the following parameters when flashing OnStep to the board:
     Board: Generic STM32F103C8
     Variant: STM32F103CB (20K RAM, 128K Flash)
     Upload method: Serial

I apologize for my slowness; I appreciate the patience. The hardware kit is due to arrive tomorrow. That will be a whole new endeavor. 


Re: naive beginner question - How to compile OnStep on Arduino IDE

Khalid Baheyeldin
 

On Sun, Dec 15, 2019 at 07:42 PM, Dan Sawyer wrote:
Sketch uses 117960 bytes (179%) of program storage space. Maximum is 65536 bytes. 
This is covered in the documentation too, second link.

Please read the second link under "Flashing OnStep to the STM32"


Re: naive beginner question - How to compile OnStep on Arduino IDE

Dan Sawyer
 

Thank you again. The issue was a copying issue. I copied the whole directory instead of the single digitalWriteFast directory. 

OnStep now compiles, however it is getting an image too large error. I used the online configuration tool to generate the Config file. 

Arduino: 1.8.5 (Linux), Board: "Generic STM32F103C series, STM32F103C8 (20k RAM. 64k Flash), STM32duino bootloader, 72Mhz (Normal), Smallest (default)"
Sketch uses 117960 bytes (179%) of program storage space. Maximum is 65536 bytes. 
Global variables use 13160 bytes (64%) of dynamic memory, leaving 7320 bytes for local variables. Maximum is 20480 bytes.
Sketch too big; see http://www.arduino.cc/en/Guide/Troubleshooting#size for tips on reducing it.
Error compiling for board Generic STM32F103C series.
 
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
 


Re: naive beginner question - How to compile OnStep on Arduino IDE

Khalid Baheyeldin
 

In the second link I sent you, there is a section titled: Installing Arduino IDE.
At the end of that section, there are instructions and links on how to get digitalWriteFast.