Date   

Config.h modification

Dahle
 

‌Hello everyone,
I am new to the group, I am French and like any good French I do not have a good command of the English language so I trust Google Translate. I just bought a mount with an Onstep controller. I noticed that the RA motor is not turning in the right direction. I know the modification is done in config.h. Hence my questions: How to modify this parameter (AXIS1_DRIVER_REVERSE) if I understood correctly in config.h while I do not have the source (sketch?), And without modifying the other parameters? I'm trying to see how this programming works because I don't know anything about it.
For information, I do not have access to WiFi Onstep (ERR_CONNECTION_REFUSED)

Thank you
Alain


Re: Can't get less than 1" total RMS

Henk Aling
 

As an aside, I tried setting the microstepping first to 256x and 128x.  For some reason the goto becomes excruciatingly slow.  I went back to 64x and goto worked normal again.  I suppose the TMC2130 or Wemos does not like those values.  They work for others.


Re: Can't get less than 1" total RMS

Henk Aling
 

On Thu, Jul 22, 2021 at 07:10 PM, Alexander Varakin wrote:
Henk,
Can you share your guide graph for this session?
Are you getting most of error on RA or on DEC?
Can you share your unprocessed stack? I can measure the PSF for you.
I have the guide log, debug log and Autosave.tif are at

https://1drv.ms/t/s!At7g23ZLfniEogZzcmiOJVv7REFN
https://1drv.ms/t/s!At7g23ZLfniEogdzcmiOJVv7REFN
https://1drv.ms/u/s!At7g23ZLfniEogVzcmiOJVv7REFN

I tried to attach the logs but they show a cross so I think they failed.
The image of 14x60 subs is at Losmandy_users@groups.io | Photo and is at low res included below. 



There is a gradient, the neighbors still have the Christmas lights on outside.  
When you study the log, several things went wrong in the beginning.  DEC started to drift.  I loosened the clutches, still drift.  Later I found that a screw that had to be loose for the SLW was stuck.  After loosening it the SLW could work again and the rest was smooth.  Lots of bumps while I was doing that.  Eventually the clouds moved in.


Re: Newbie question #EQ5 #fysetc

Dave Schwartz
 

Yes, the BME280_SPI will work in place of the BMP280_SPI... Just change the P to E in the parameter name and you'll be going to go.


On July 23, 2021 7:00:03 p.m. EDT, marclloveras@... wrote:
Thanks a lot, Dave, Khalid and Drew.
After reading the threads posted by Khalid I realised that my wiring was not ok, 
After adding the line suggested by Dave in the config file, it worked fine.
I assume that the same wiring will work for the BME, just changing the “define WEATHER” line. I will buy one and substitute the BMP.

This the final configuration with BMP280:
 

config.h _______________________________________________________________

#define LED_STATUS2                OFF

#define WEATHER                       BMP280_SPI

#define BMP280_CS_PIN           PC7  

Wiring _______________________________________________________________

* SCL to SD-SCK 

* SDO to SP1-MISO 

* SDA to SD-MOSI 

* CSB to PC7 


--
Sent from my Android device with K-9 Mail. Please excuse my brevity.


Re: Newbie question #EQ5 #fysetc

marclloveras@...
 

Thanks a lot, Dave, Khalid and Drew.
After reading the threads posted by Khalid I realised that my wiring was not ok, 
After adding the line suggested by Dave in the config file, it worked fine.
I assume that the same wiring will work for the BME, just changing the “define WEATHER” line. I will buy one and substitute the BMP.

This the final configuration with BMP280:
 

config.h _______________________________________________________________

#define LED_STATUS2                OFF

#define WEATHER                       BMP280_SPI

#define BMP280_CS_PIN           PC7  

Wiring _______________________________________________________________

* SCL to SD-SCK 

* SDO to SP1-MISO 

* SDA to SD-MOSI 

* CSB to PC7 


Re: Can't get less than 1" total RMS

Henk Aling
 

I am wondering if I configured my system poorly for the given load and stepper characteristics.

My stepper is 0.9 degrees configured with 64 microsteps.  My gear reduction is 360.  When I am autoguiding at the magical 0.25" RMS it is reasonable to assume that the guider tries to squash errors of around 0.25".  The step size for this after gear reduction is 360*0.25"=90".  The step angle is 0.9*3600/64"=50.625".  The number of steps the stepper needs to take is therefore 90/50.625=1.8 steps.
 
For a well defined pulse clearly we need more than 1.8 steps.  If I guided at 256 microsteps this would be 4x that, 7.2 steps.  Not perfect but a lot better.  So maybe I should use 256 microsteps?  
 
Will the torque then still be good enough depending on the acceleration associated with the pulse ramp-up time?  If it is not we will miss steps, which leads to more error and control action.  
 
The incremental microstepping torque is Tmicro = Thold*sin((pi/2)/nMicro) where nMicro=256 in this case.
 
I found this torque calculation reference at Oriental motors:
 
https://www.orientalmotor.com/products/pdfs/2018-2019/technical-reference/Technical_Reference_Overview.pdf?hsCtaTracking=72ff05cd-3657-4344-9f9a-2e6973a004d1%7C65a4e02f-5779-4945-953a-1e14fe96003b
 
I ran the math for my system:
 
- An OTA of 48 lbs placed at 1 ft from the RA axis
- Counterweights for simplicity placed at 1 ft
- A stepper with a holding torque of 0.36 Nm
- A guide ratio of 0.25
- 256x microstepping
- A static load of 2 lbs at 2 feet (like Howard used in the static stepper analysis)
- An equal amount of friction added (ditto)
- A rotor inertia of 54 g cm^2
- A ramp-up/down time that is 0.1 times the total pulse time
- A safe factor of 2
- I have not accounted for reducing Vref of the TMC2130 to half
 
The outcome of this is that, during the ramp-up, a total torque of Tm=0.0079841 is achieved, with a Tmicro=0.0088348.  Apparently, with this configuration, we are right at the limit of what the stepper can achieve.  With 0.5x guiding I would not be able to step safely.  With 64x microstepping I would not be close enough in terms of accuracy.
 
If you want to check the math or just keep me honest, here's the Scilab script.  The variable names are similar to what is used in the above link, the math was taken from the horizontal rotating table example with 10 weights.
 
// Conversion constants
kg2oz = 35.2739619;
m2in = 39.3700787;
lb2oz = 16;
kg2lb = 2.20462262;
ft2in = 12;
m2ft = 3.2808399;
Nm2ozin = 141.61193227806;
rad2deg = 180/%pi;
rad2as = rad2deg*3600;
 
J0 = (54/1000)/100^2;               // Rotor inertia in kg/m^2
Tl = (2/kg2lb)*(2/m2ft);            // Load torque for 2 lbs at 2 feet
Tl = 2*Tl;                          // Add an equal amount for friction
gearRatio = 360;                    // Gear ratio
guideRatio = 0.25 ;                  // Guide rate
dTheta = 0.25/rad2as;               // Minimum step for control
r = 1/m2ft;                         // Masses (OTA, counterweights) are at 1 ft from RA axis
m = 2*48/kg2lb;                     // 48 lbs plus counterweights
Jw = m*r^2;                         // Moment of inertia in kg-m^2
omEarth = (15/rad2deg)/3600;        // Nominal angular velocity OTA at equator
dOmega = guideRatio*omEarth;        // Change in angular velocity
t0 = (dTheta/dOmega)/1.25;          // Total pulse time
t1 = 0.1*t0;                        // Time to ramp-up or ramp-down linearly, say 0.1*t0
                                    // (t0 + t1)*dOmega = dTheta, t1 = 0.25*t0
 
// After the gearing
Tl1 = Tl/gearRatio;
dPhi1 = dTheta*gearRatio;
Jw1 = Jw/gearRatio;
dOmega1 = dOmega/gearRatio;
 
micro = 64;
thetaStep = (0.9/micro)/rad2deg;    // Step angle
Sf = 2;                             // Safety factor
A = dPhi1/thetaStep;                // Number of pulses
f2 = A/(t0-t1);                     // Pulse speed
Nm = (thetaStep/(2*%pi))*A*60;      // Revolutions per minute
 
// Microstepping torque vs holding torque
Thold = 0.36;                       // Holding torque
Tmicro = Thold*sin((%pi/2)/micro);
 
Ta = ((J0 + Jw1)/9.55)*Nm/t1;       // Acceleration torque
Tm = (Tl1 + Ta)*Sf;                 // Required torque
 


Re: Can't get less than 1" total RMS

George Cushing
 

Ah, Losmandy rates the G11 at a 60 pound payload. Your average 12" f/4.5 Newt weighs about 45 pounds. CF may knock off a 2-3 pounds, but you are still pushing the mount's limits.

Additionally, as we say at the yacht club that boat has a a lot of windage. The 50"+ length and 14"+ height of the optical tube has to be considered when evaluating the capacity of a mount. 


Re: Focuser for MaxEsp3

Seven Jones
 

On Wed, Jul 21, 2021 at 09:26 PM, Ken Hunter wrote:
You can caarefully cut away the connecter, unsolder the pins 1 at a time and install the pins like I did in my build.

That's how I'm gonna do it.
What are the plug on your board? As far as I know also the small screw terminals also fit?


Re: Thanks OnStep - Results from a recent project using a G11 OnStep Mount

Chad Gray
 

WOW!  Beautiful!


On Fri, Jul 23, 2021 at 12:08 AM Rockmover <kruse@...> wrote:
I just wanted to post a recent project that was made possible by both OnStep, and all the help from these message boards.

Unfortunately, due to work, my astronomy time has been limited the last 6 months.  However, my buddy who shares our remote observatory has been taking great advantage of the G11 OnStep mount, and a small Stelavue 80 mm scope setup we have.  
 
https://www.astrobin.com/7381yd/

IC 2177 - Seagull Nebula, 






            StockCarMafia


Thanks OnStep - Results from a recent project using a G11 OnStep Mount

Rockmover
 

I just wanted to post a recent project that was made possible by both OnStep, and all the help from these message boards.

Unfortunately, due to work, my astronomy time has been limited the last 6 months.  However, my buddy who shares our remote observatory has been taking great advantage of the G11 OnStep mount, and a small Stelavue 80 mm scope setup we have.  
 
https://www.astrobin.com/7381yd/

IC 2177 - Seagull Nebula, 






            StockCarMafia


Re: Can't get less than 1" total RMS

Henk Aling
 

On Thu, Jul 22, 2021 at 09:06 PM, Mike Ahner wrote:
On Thu, Jul 22, 2021 at 07:13 PM, Henk Aling wrote:
I would like to understand the effect on tracking accuracy.
Maybe start here:
main@onstep.groups.io | Wiki
I know that link well, it doesn't say anything about Vref for the TMC2130.


Re: Can't get less than 1" total RMS

Mike Ahner
 

On Thu, Jul 22, 2021 at 07:13 PM, Henk Aling wrote:
I would like to understand the effect on tracking accuracy.
Maybe start here:
main@onstep.groups.io | Wiki


Re: Can't get less than 1" total RMS

Henk Aling
 

On Thu, Jul 22, 2021 at 07:10 PM, Alexander Varakin wrote:
Henk,
Can you share your guide graph for this session?
Not for this session but I will get a PHD2 log tonight.

Are you getting most of error on RA or on DEC?
This time about 50% more on RA but that was also because I did not counterweight much.  During my best run at 0.6" total RMS they were about equal.

Can you share your unprocessed stack? I can measure the PSF for you.
I will put an Autosave.tif on my cloud space and let you know.

One more question, I can't find good references for the TMC2130's Vref.  There was a calculator online that returned 1.27 V for my 0.9 Amps/phase (== Irms I think).  Howard said to turn it down to half that, which I did.  I would like to understand the effect on tracking accuracy.  I will experiment tonight.


Re: Can't get less than 1" total RMS

Alexander Varakin
 

Henk,
Can you share your guide graph for this session?
Are you getting most of error on RA or on DEC?
Can you share your unprocessed stack? I can measure the PSF for you.



Re: Can't get less than 1" total RMS

Henk Aling
 

Thanks Mark.  The numbers you mentioned are helpful.

I am very aware of the large weight especially now that I am getting more experience with it.  I will try imaging with my 6" Mak-Newt and see if it works better than the 12".

I am using DIY spring loaded worms that work great for goto.  For tracking I have turned them off sometimes and did not notice much difference.

I think my PA is very good as I do it using Ekos.  No drift unguided.  I am counterweighting in RA, not quite ready to misalign in DEC.


Re: Can't get less than 1" total RMS

Mark Christensen
 

Henk,

There are two variables you didn't consider: Your skies and the sheer weight (not to mention the moment of inertia) of your rig.

I used my G11 for several years with a 12" f/5 and it was hit or miss for imaging - sometimes I couldn't shoot longer than 120seconds, while other times I could go for 300sec. And of course it made a great sail in any breeze.

When I pulled in my horns and went back to my 8" f/5.5 everything was much more reliable, even if I stick a Barlow on it.

As to guide rate, 0.5X is the max I'd go. The only time I guide at 1X is when I am doing something like chasing a comet head.

Personally I shot 1 to 2 second guiding exposures. If I have done decent job of polar alignment and the skies are stable I get between 0.25 and 0.33". The reason why polar alignment is important is because the fewer corrections the mount makes in either axis the less chance there is that it will impact the other axis. But I don't do a perfect job of polar alignment since that way all corrections (aside from chasing seeing) will be in one direction on DEC. So backlash isn't a player there, and of course it isn't a player in RA either, if you bias the RA balance slightly eastward - that way the gear faces always stay in contact.

Stock G-11, high precision worms, old fashioned worm blocks carefully adjusted. And I don't try to get backlash out! That is overdone by most people and even the factories.

Mark Christensen


Re: ESP8266 ESP-01 and external antenna

 


Found here 
https://www.mentebinaria.com.br/forums/topic/764-lab-01-esp8266-esp-01-pigtail-antena/


Re: Calculations needed for spur gear drive

Tom Gideon
 

Great!!

Thanks,
Tom

On Jul 22, 2021, at 9:24 AM, Khalid Baheyeldin <kbahey@...> wrote:

Gear pitch is not important as long as both gears are the same.

The spreadsheet has two RATIOS since most mounts have two stages of reductions.
If your mount only has one gear reduction stage, then just enter 1 in the other.

If your mount has 13 teeth to 217 teeth, and nothing else, then use GR1 = 1,
and GR2 = 217/13 = 16.692.

This reduction is not enough even with a 400 step motor (0.9 deg), and 1/32 microsteps.
So you'd better use a geared motor, and enter that ratio in GR1.

For example with a 50:1 gearbox:

200, 32, 50, 16.692 = 14,837.333

If your goal is visual observing only, then less reduction may work.


Re: Calculations needed for spur gear drive

Khalid Baheyeldin
 

Gear pitch is not important as long as both gears are the same.

The spreadsheet has two RATIOS since most mounts have two stages of reductions.
If your mount only has one gear reduction stage, then just enter 1 in the other.

If your mount has 13 teeth to 217 teeth, and nothing else, then use GR1 = 1,
and GR2 = 217/13 = 16.692.

This reduction is not enough even with a 400 step motor (0.9 deg), and 1/32 microsteps.
So you'd better use a geared motor, and enter that ratio in GR1.

For example with a 50:1 gearbox:

200, 32, 50, 16.692 = 14,837.333

If your goal is visual observing only, then less reduction may work.


Re: Setting backlash Question

Henk Aling
 

On Wed, Jul 7, 2021 at 01:02 PM, Khalid Baheyeldin wrote:
There is a simpler way to adjust backlash than what is in the Wiki.
No calculations needed ...

Basically, during daylight, use a faraway stationary terrestrial object.
For example a communication tower, a nail on a neighbour's chimney, or something like that.

Start OnStep normally, then slew to that object.
Turn off tracking.
Now using trial and error, try to refine how the object is centered when you move E and W.
If it jumps, then the backlash value is too high, reduce it.
If it lags, then the backlash value is too low, increase it.
Keep doing this until you don't observe any jump or lag when you reverse direction.

Repeat with N and S buttons for the other axis.
I like that, and will try it myself.  However backlash may not be the same for each target.  Backlash due to a gearbox will likely be constant but backlash due to a non-round cog wheel or play in the RA and DEC axes, which every gear-based mount has, will depend on the position of the target in space and time.  It's best to just focus on the gearbox if possible and compensate for that part if you have a controller that allows it.  Or use stepper motors that don't require a gearbox.  But then you have to deal with noise as a result of the low torque, which I am looking into now.

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