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G11 RA motor is stalls when tracking but not when slewing

Erik Nordberg
 
Edited

Hi friends !
I have had a problem the last couple of years with the RA motor that stops working when tracking at star but when hitting the slew buttons on the hand controller it works as usual.
There is no stall warning in the display.
Often I can get it working again after pushing the buttons on the handcontroller but last night it did not work that way. I even shut down Gemini twice and after a restart the star was
OK and not drifting but when I center the star it immediatly starts drifting which means the RA motor has stopped. And never a stall warning in the display.
I know the that the stall warning does work when for example I adjust the wormwheel.
Is this a problem that any of you guys has encountered before ?
Rgds
Erik Nordberg
 

Hi Eric,

The most common reason is a loose Oldham coupler part.

Look at the drive metal parts of the RA Oldham coupler...see if one end is loose. They can get loose over time, and it might be temperature dependent.? If one of those ends gets loose, the motor will tell Gemini it is still turning (so no Lags message), but the worm will not be driven..so the axis will not move.

-----

I was going to say:

Try swapping the cables from RA to DEC (...the RA is shorter...might be difficult).

However, if the cable were faulty, I think the Gemini would say "Lags" or something like that.? I think the Oldham coupler is the most likely trouble.

Best wishes,
Michael


On Sun, Sep 22, 2019, 12:27 PM Erik Nordberg <tierozi@...> wrote:
Hi friends !
I have had a problem the last couple of years with the RA motor that stops working when tracking at star but when hitting the slew buttons on the hand controller the works as usual.
There is no stall warning in the display.
Often I can get it working again after pushing the buttons on the handcontroller but last night it did not work that way. I even shut down Gemini twice and after a restart the star was
OK and not drifting but when I center the star it immediatly starts drifting which means the RA motor has stopped. And never a stall warning in the display.
I know the that the stall warning does work when for example I adjust the wormwheel.
Is this a problem that any of you guys has encountered before ?
Rgds
Erik Nordberg

 
Edited

It¡¯s quote possible the motor is slightly bad for whatever reason. ?Try swapping motors Ra to Dec etc

the reason it¡¯s bad at sidereal (I¡¯m assuming it¡¯s a G1) is the motor drive energy delivered is low. ?At higher drive rates it¡¯s provided with more energy....it moves faster. it could be a bad ¡°H¡± bridge but I doubt it. ?So try swap the motors over.?

If the system is a G2, you can enter the WEB interface and select¡±servos¡± page:


In this you can increase the servo motor tracking percentage ( increase energy) to the motor. ?Try increasing it a little let¡¯s say 35%


it could also be as Michael said or a slipping motor pinion gear

If it is still failing....get back?

--
Brendan
 

Erik

i also should have said.....take that bad motor off and start run system like it¡¯s installed. ?You can run it on a bench (non installed) it¡¯s just the axes won¡¯t move. ?

So start it up.....if it¡¯s a Ra motor, it¡¯s pinion should feel tight on boot right up till the HC displays ¡°cold boot at xxxxxxx¡± ?At this point the pinion will start rotating at its specified sidereal rate. ?It will have resistance to your finger pressure on the pinion aka ¡°not weak¡±. If it¡¯s a DEC motor it won¡¯t move till you command it but from start it will feel tight and resist rotating by fingers.?

Don¡¯t worry if you¡¯re fiddling causes a stall warning they¡¯ll clear next boot.?

Test the above
--
Brendan
 

Brendan's point of "motor drive energy is low" made me also think of this to check:

Make sure you are using a >12v power source for the gemini. it is rated from 12-18v but ideally you want 15-18v. 12v isn't going to be enough

On Sun, Sep 22, 2019 at 4:16 PM Brendan Smith <brenatlilydale@...> wrote:

[Edited Message Follows]

It¡¯s quote possible the motor is slightly bad for whatever reason.? Try swapping motors Ra to Dec etc

the reason it¡¯s bad at sidereal (I¡¯m assuming it¡¯s a G1) is the motor drive energy delivered is low.? At higher drive rates it¡¯s provided with more energy....it moves faster. it could be a bad ¡°H¡± bridge but I doubt it.? So try swap the motors over.?

If the system is a G2, you can enter the WEB interface and select¡±servos¡± page:


In this you can increase the servo motor tracking percentage ( increase energy) to the motor.? Try increasing it a little let¡¯s say 35%


it could also be as Michael said or a slipping motor pinion gear

If it is still failing....get back?

--
Brendan



--
Brian?



Brian Valente
portfolio

Erik Nordberg
 

Thanks guys.
I?ll try your suggestions when I get home again.
I have to solve this cause it?s very irritating when it happens :)
I?ll let you know how it goes.
Cheers
Erik

Den s?n 22 sep. 2019 kl 21:27 skrev Erik Nordberg via Groups.Io <tierozi=[email protected]>:

Hi friends !
I have had a problem the last couple of years with the RA motor that stops working when tracking at star but when hitting the slew buttons on the hand controller the works as usual.
There is no stall warning in the display.
Often I can get it working again after pushing the buttons on the handcontroller but last night it did not work that way. I even shut down Gemini twice and after a restart the star was
OK and not drifting but when I center the star it immediatly starts drifting which means the RA motor has stopped. And never a stall warning in the display.
I know the that the stall warning does work when for example I adjust the wormwheel.
Is this a problem that any of you guys has encountered before ?
Rgds
Erik Nordberg

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