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G11 "click" and jump at end of slew

 

Several months ago I had my G11 motors tucked in and also upgraded to spring-loaded worm gears. ?Ever since then when I slew with the hand controller I hear a "click" at the end and the image jumps a bit. ?Has anyone else seen this behavior? ?I'm wondering if the springs aren't adjusted tight enough and the worm is riding up on the gear during the slew and then dropping in at the end. ?Happens on both axes at all speeds except "Centering". ?I can try to characterize it based upon slew speed if folks think that would matter. ?Scope is balanced in both axes with about 30lbs of payload.
Thanks in advance,
Dave
 

On Tue, Sep 24, 2024 at 09:59 AM, David Flynn wrote:
Several months ago I had my G11 motors tucked in and also upgraded to spring-loaded worm gears. ?Ever since then when I slew with the hand controller I hear a "click" at the end and the image jumps a bit. ?Has anyone else seen this behavior? ?I'm wondering if the springs aren't adjusted tight enough and the worm is riding up on the gear during the slew and then dropping in at the end. ?Happens on both axes at all speeds except "Centering". ?I can try to characterize it based upon slew speed if folks think that would matter. ?Scope is balanced in both axes with about 30lbs of payload.
Thanks in advance,
Dave
Hi Dave,
?
Did Losmamdy also update your Gemini 2 with the latest version firmware L6.02 and program the onboard PIC chips that control the servo motors?? Also verify that your PIC chips have version 3.0 code. Double check this and if in doubt download the current GFU and do a complete reflash your Gemini 2 firmware and hand controller.?
?
Some mounts even with the latest firmware can exhibit a slight click when stopping. Not sure what it is but some users have reported this.?
?
One other thing to check is that the servo motors are just snug enough to hold them in place and that they are positioned to have just the right gear engagement.? If it is right you'll know it as the mount will be much quieter when slewing when they are just right.??
?
Keep us posted.?
?
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric - South Pasadena, CA?
 

¿ªÔÆÌåÓý

Hi Chip, Dave,

To cite a big company, "It's not a bug, it's a feature". 8) In fact, after a move there often remained a little offset (servo lag) with the earlier PIC firmware, especially in the DEC axis. Typically the torque increases with the servo lag and if that remaining offset is very low, the torque may still be too low to move the very last steps. That happens not in RA when it's tracking, since there are many steps per second, but in the DEC axis the very last fine positioning steps are critical if DEC is a bit out of balance, the gear mesh is too tight or other problems (grease, ...) require a bit more torque. Of course it shows that the mount isn't moving perfectly smooth, for whatever reason.

To achieve the highest possible accuracy especially when guiding in DEC I asked David for this special feature in the pic software: If there persists a little offset after a move (slewing, guiding, ...) _and_ there are no further movements for? about a second in this axis please increase the torque somewhat shortly to overcome this and get the lag to zero. You can monitor that on the HC Balance screen. This aims at perfect guiding in DEC, especially avoiding some offset adding up until there is enough torque or a guiding program gets more aggressive. All the test were perfect.

So if you hear that click: In general it is O.K. and does no harm, it just indicate a final little movement was necessary. Up to a certain degree it is completely normal. If this "final move" gets easily visible and significant, please take care of the setup. In summary I would say that one servo curve is not enough for both smooth movements and accurate guiding, especially in DEC, but it is a good indicator that some fine tuning will help.

¸é±ð²Ô¨¦





Am 24.09.24 um 20:36 schrieb Chip Louie:

On Tue, Sep 24, 2024 at 09:59 AM, David Flynn wrote:
Several months ago I had my G11 motors tucked in and also upgraded to spring-loaded worm gears. ?Ever since then when I slew with the hand controller I hear a "click" at the end and the image jumps a bit. ?Has anyone else seen this behavior? ?I'm wondering if the springs aren't adjusted tight enough and the worm is riding up on the gear during the slew and then dropping in at the end. ?Happens on both axes at all speeds except "Centering". ?I can try to characterize it based upon slew speed if folks think that would matter. ?Scope is balanced in both axes with about 30lbs of payload.
Thanks in advance,
Dave
Hi Dave,
?
Did Losmamdy also update your Gemini 2 with the latest version firmware L6.02 and program the onboard PIC chips that control the servo motors?? Also verify that your PIC chips have version 3.0 code. Double check this and if in doubt download the current GFU and do a complete reflash your Gemini 2 firmware and hand controller.?
?
Some mounts even with the latest firmware can exhibit a slight click when stopping. Not sure what it is but some users have reported this.?
?
One other thing to check is that the servo motors are just snug enough to hold them in place and that they are positioned to have just the right gear engagement.? If it is right you'll know it as the mount will be much quieter when slewing when they are just right.??
?
Keep us posted.?
?
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric - South Pasadena, CA?
 

Rene,
?
Thank you for the update and first real explanation of why there can be a tic heard when the servos are coming to a stop. As you know the tic sound has been reported by some people but for some reason many other people don't have as loud a tic.?
?
So if I am understanding you correctly Gemini is reading the encoders and predicts where the encoders should end up for a given motion.? If there is inadequate motion to arrive at the desired end point an addition boost in torque may be applied? to ensure an completed move lands the encoders at the correct end point.??
?
I have two Gemini 2 powered mounts and initially I heard a tic sound after the L6 updates. It was not consistent and I thought? I was imagining it. So I reset my spring loaded worms as I always have since my first Gemini 1 by using a bench power supply. I run the mount 720 degrees in both directions observing where the right spot(s) are and adkust the spring load or in the old days work backlash so there is minimal rise in current use by the Gemini 2 all the way around the worm gear.?
?
Since doing this I have never heard the same pronounced tic others have recorded and reported come from my mounts. There can be a very faint tic but I can only hear it now with a mechanic's stethoscope, not anything as is heard in the videos posted.?
?
So you explanation may have clarified why some have the tic and some don't and why I did but no longer hear it after making adjustments to the worms. At least it seems.like an explanation and certainly in my sample of 2 mounts anyway.?
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric - South Pasadena, CA?
 

¿ªÔÆÌåÓý

Chip,

Running the worm gears in for some revolutions is a perfect way to smooth tracking and guiding. The pic firmware tries to reach the indicated position exactly and we went the extra mile to overcome some "stiction" once the movement stopped. If there is not too much resistance, the pointing will be perfect immediately (as recorded by the motor encoders), if the movement stopped but a lag persists, the torque will be increased to overcome it.

¸é±ð²Ô¨¦
?





Am 25.09.24 um 17:01 schrieb Chip Louie:

Rene,
?
Thank you for the update and first real explanation of why there can be a tic heard when the servos are coming to a stop. As you know the tic sound has been reported by some people but for some reason many other people don't have as loud a tic.?
?
So if I am understanding you correctly Gemini is reading the encoders and predicts where the encoders should end up for a given motion.? If there is inadequate motion to arrive at the desired end point an addition boost in torque may be applied? to ensure an completed move lands the encoders at the correct end point.??
?
I have two Gemini 2 powered mounts and initially I heard a tic sound after the L6 updates. It was not consistent and I thought? I was imagining it. So I reset my spring loaded worms as I always have since my first Gemini 1 by using a bench power supply. I run the mount 720 degrees in both directions observing where the right spot(s) are and adkust the spring load or in the old days work backlash so there is minimal rise in current use by the Gemini 2 all the way around the worm gear.?
?
Since doing this I have never heard the same pronounced tic others have recorded and reported come from my mounts. There can be a very faint tic but I can only hear it now with a mechanic's stethoscope, not anything as is heard in the videos posted.?
?
So you explanation may have clarified why some have the tic and some don't and why I did but no longer hear it after making adjustments to the worms. At least it seems.like an explanation and certainly in my sample of 2 mounts anyway.?
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric - South Pasadena, CA?
 

Thanks to both of you for all the info. ?Yes, I did have my pic firmware updated to level 6. ?I'm not too far from Burbank so stopping by Losmandy is no trouble so I just let them do the programming for me. ? I will admit I haven't updated the board firmware using the GFU in a while, I'm a Mac guy so it's kind of a pain for me to do it, but I'll take care of it. ?Currently I'm running 6.00 so not that far off. ?Thanks for the explanation of the final positioning nudge and that's probably what I'm hearing and seeing. ?I'll play with the Balance screen to see what that teaches me.
?
Thanks again for your quick and informative responses.
?
Dave.

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