|
Its funny..Mclennan lists its 25:1 gearbox as P5-G11
Had a laugh.......
--
Brendan
|
To check PEC, you could first confirm that the PEC index rolls over at 32000. You can verify that by going to the web interface, State page, and monitor the RA PEC Pointer while the mount tracks at sidereal rate. The RA PEC Pointer should increment and roll over at 32000 with the 125:1 gearbox (or 6400 with the regular gearbox).
You could also create a dummy PEC file during the day by simply training PEC with the hand controller, and send a guiding command periodically with the hand controller (both East and West commands). Then open the currpec.pec file in the PEC folder on the SD card and check that the header information matches your setup and the PEC data contains the correct divisors for the entire worm cycle.?
Eric
|
On Wed, Jun 16, 2021 at 04:52 PM, <pcboreland@...> wrote:
Eric,
Thank you for the information you have provided. I have a far better understanding of what is going on under the hood. A final question, which I'm sure has been asked here many times, how is the PE curve get synced with the worm?
Peter
The following description is my understanding for the regular gearbox, and will likely change for your 125:1 gearbox. The PEC index is not absolute and rolls over at every worm cycle (6400 steps), so a method is used to sync the PEC index to the RA axis index. The RA index is relative to the CWD position, where the RA index is 1152000. As the RA axis rotates, the RA index and PEC index decrement/increment by 1 for each encoder tick. At RA index 1152000 (CWD), the PEC index is 0 when you first boot up the Gemini. When training PEC, Gemini resets the PEC index to 0 and starts recording guiding commands for a full worm cycle (6400 PEC steps for the regular gearbox). Resetting the PEC index at an arbitrary RA index location would cause the PEC index to be out of sync with the RA index, so Gemini also calculates an offset as it resets the PEC index, aka PEC Worm Offset, which you can find in the currpec.pec header. You can calculate the PEC worm offset for any arbitrary RA index in Excel as follows: 6400 - MOD(PEC index + RA index - 1152000, 6400). Then, at the next boot up, at CWD the RA index is 1152000 and the PEC index is non zero as calculated by Gemini based on the PEC worm offset save in memory (PEC index + PEC worm offset = 6400 at RA index 1152000). Hopefully this all makes sense and you can figure out how to translate this for your 125:1 gearbox. Eric
|
As was pointed out by David Partridge, it is possible to change out the gear box on just RA if one uses the web interface to select the parameters. I installed the 125:1 gearbox earlier in the day, and have been able to gather some initial data. As might be expected there is good and bad.
The Good. Unmoded, my Ra guided on average 30% worse than the Dec axis looking back over 6 months of logs. With the limited short run tests done earlier this evening RA is now guiding 10 to 20% better than Dec. A huge shift in performance. A seeming improvement of greater than 0.6 arcsec on 10 min runs. I'll be imaging in 90 minute blocks later tonight so will hopefully get data worth sharing, and this improvement holds
The Bad. 1. Ra runs slow. Over a 3hr period it fell behind the object a noticable bit. This I assume is because the Ra tracking divisor is set to 89754 when it needs to be set 89754.2. I go not think this is a big deal as guiding ought to handle this problem. 2. Pec training runs for just 48s. 1/5th of a worm cycle. Not sure how to fix this? I do not see any parameters to lengthen the record time. Pec is turned off and I'm using Predictive Pec in PHD2, but hoping this can be fixed?
First Ha image of the Cygnus Wall just came in!
|
PCBoreland,
(What is your first name?)
I encountered the same?problem as you report: the Gemini-2 PEC training acquisition time is broken.? The internal PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC file.?
The PEC training in Gemini-1 does work.? You don't need PEMpro if you have a G-1. You can use PEMpro if you want of course.?
I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I did not have a CAT5 cable connection so I did not deliver the files requested.? Bottom line: G-2 PEC does not yet work.??
Meanwhile I am happy to read your detailed reports on the 125:1 gearbox.? I agree that PHD2 autoguiding will correct the DEC and RA.? It would be the same if tracking the sun or moon or a planet...you must use autoguiding.??
And yes. The 125:1 vs 25:1 means that slewing will be somewhere like 5x slower.? Yet it is the tracking perfection? that you are focussing on.??
Best, Michael
As was pointed out by David Partridge, it is possible to change out the gear box on just RA if one uses the web interface to select the parameters. I installed the 125:1 gearbox earlier in the day, and have been able to gather some initial data. As might be expected there is good and bad.
The Good. Unmoded, my Ra guided on average 30% worse than the Dec axis looking back over 6 months of logs. With the limited short run tests done earlier this evening RA is now guiding 10 to 20% better than Dec. A huge shift in performance. A seeming improvement of greater than 0.6 arcsec on 10 min runs. I'll be imaging in 90 minute blocks later tonight so will hopefully get data worth sharing, and this improvement holds
The Bad. 1. Ra runs slow. Over a 3hr period it fell behind the object a noticable bit. This I assume is because the Ra tracking divisor is set to 89754 when it needs to be set 89754.2. I go not think this is a big deal as guiding ought to handle this problem. 2. Pec training runs for just 48s. 1/5th of a worm cycle. Not sure how to fix this? I do not see any parameters to lengthen the record time. Pec is turned off and I'm using Predictive Pec in PHD2, but hoping this can be fixed?
First Ha image of the Cygnus Wall just came in!
|
I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken. The internal
PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC file. Michael, you obviously haven't used PEMPro, because you don't feed a PHD2 unguided log file into PEMPro to create a PEC curve. Maybe you are thinking of the PEMPro Log Viewer, which does accept PHD2 logs for analysis? I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I did not
have a CAT5 cable connection so I did not deliver the files requested. Bottom line: G-2 PEC does not yet work. You must mean recording PE via an autoguider doesn't work, right? PEMPro does work with the Gemini-2 PEC. BTW, recording via autoguider is likely to provide inferior results. In fact, this method doesn't work very well at all if there are any non-integer fundamental frequencies, which is not uncommon. I can explain why this is so, if this isn't obvious? -Ray -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Thursday, June 17, 2021 8:56 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
to do this?
PCBoreland,
(What is your first name?)
I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken. The internal
PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC file.
The PEC training in Gemini-1 does work. You don't need PEMpro if you have a G-1. You can use PEMpro if you
want of course.
I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I did not
have a CAT5 cable connection so I did not deliver the files requested. Bottom line: G-2 PEC does not yet work.
Meanwhile I am happy to read your detailed reports on the 125:1 gearbox. I agree that PHD2 autoguiding will
correct the DEC and RA. It would be the same if tracking the sun or moon or a planet...you must use autoguiding.
And yes. The 125:1 vs 25:1 means that slewing will be somewhere like 5x slower. Yet it is the tracking perfection
that you are focussing on.
Best,
Michael
On Thu, Jun 17, 2021, 8:10 PM pcboreland via groups.io <pcboreland@...> wrote:
As was pointed out by David Partridge, it is possible to change out the gear box on just RA if one uses the
web interface to select the parameters. I installed the 125:1 gearbox earlier in the day, and have been able to
gather some initial data. As might be expected there is good and bad.
The Good. Unmoded, my Ra guided on average 30% worse than the Dec axis looking back over 6 months
of logs. With the limited short run tests done earlier this evening RA is now guiding 10 to 20% better than Dec. A
huge shift in performance. A seeming improvement of greater than 0.6 arcsec on 10 min runs. I'll be imaging in 90
minute blocks later tonight so will hopefully get data worth sharing, and this improvement holds
The Bad. 1. Ra runs slow. Over a 3hr period it fell behind the object a noticable bit. This I assume is
because the Ra tracking divisor is set to 89754 when it needs to be set 89754.2. I go not think this is a big deal as
guiding ought to handle this problem. 2. Pec training runs for just 48s. 1/5th of a worm cycle. Not sure how to fix
this? I do not see any parameters to lengthen the record time. Pec is turned off and I'm using Predictive Pec in
PHD2, but hoping this can be fixed?
First Ha image of the Cygnus Wall just came in!
|
Ray,
I am speaking about trying to use the built in PEC recorder feature advertised as being internal to Gemini-2.? It does not work for the G11T.? It appears it does not work for the 125:1 gearbox either.? In both cases the G-2 quits taking data before a complete worm cycle period is complete.? Without using a complete worm cycle it cannot generate a correct PEC correction curve.?
You are right....I have not used PEMpro.? I have used Gemini-1 to generate it's internal PEC with good results.? ? I have used PECprep for PE analysis, not generate PEC for the Gemini system.? ?I only use non-guided star tracking to acquire PE data for analysis.? ??
Best regards, Michael?
On Thu, Jun 17, 2021, 10:37 PM Ray Gralak < iogroups@...> wrote: > I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken.? The internal
> PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
> purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC file.
Michael, you obviously haven't used PEMPro, because you don't feed a PHD2 unguided log file into PEMPro to create a PEC curve. Maybe you are thinking of the PEMPro Log Viewer, which does accept PHD2 logs for analysis?
> I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I did not
> have a CAT5 cable connection so I did not deliver the files requested.? Bottom line: G-2 PEC does not yet work.
You must mean recording PE via an autoguider doesn't work, right? PEMPro does work with the Gemini-2 PEC.
BTW, recording via autoguider is likely to provide inferior results. In fact, this method doesn't work very well at all if there are any non-integer fundamental frequencies, which is not uncommon. I can explain why this is so, if this isn't obvious?
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
> Sent: Thursday, June 17, 2021 8:56 PM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
> to do this?
>
> PCBoreland,
>
> (What is your first name?)
>
> I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken.? The internal
> PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
> purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC file.
>
> The PEC training in Gemini-1 does work.? You don't need PEMpro if you have a G-1. You can use PEMpro if you
> want of course.
>
> I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I did not
> have a CAT5 cable connection so I did not deliver the files requested.? Bottom line: G-2 PEC does not yet work.
>
> Meanwhile I am happy to read your detailed reports on the 125:1 gearbox.? I agree that PHD2 autoguiding will
> correct the DEC and RA.? It would be the same if tracking the sun or moon or a planet...you must use autoguiding.
>
> And yes. The 125:1 vs 25:1 means that slewing will be somewhere like 5x slower.? Yet it is the tracking perfection
> that you are focussing on.
>
> Best,
> Michael
>
>
>
>
>
> On Thu, Jun 17, 2021, 8:10 PM pcboreland via <pcboreland=[email protected]> wrote:
>
>
>? ? ? ?As was pointed out by David Partridge, it is possible to change out the gear box on just RA if one uses the
> web interface to select the parameters. I installed the 125:1 gearbox earlier in the day, and have been able to
> gather some initial data. As might be expected there is good and bad.
>
>? ? ? ?The Good. Unmoded, my Ra guided on average 30% worse than the Dec axis looking back over 6 months
> of logs. With the limited short run tests done earlier this evening RA is now guiding 10 to 20% better than Dec. A
> huge shift in performance. A seeming improvement of greater than 0.6 arcsec on 10 min runs. I'll be imaging in 90
> minute blocks later tonight so will hopefully get data worth sharing, and this improvement holds
>
>? ? ? ?The Bad. 1. Ra runs slow. Over a 3hr period it fell behind the object a noticable bit. This I assume is
> because the Ra tracking divisor is set to 89754 when it needs to be set 89754.2. I go not think this is a big deal as
> guiding ought to handle this problem. 2. Pec training runs for just 48s. 1/5th of a worm cycle. Not sure how to fix
> this? I do not see any parameters to lengthen the record time. Pec is turned off and I'm using Predictive Pec in
> PHD2, but hoping this can be fixed?
>
>? ? ? ?First Ha image of the Cygnus Wall just came in!
>
>
|
Peter,
The difference between 89754 and 89754.2 over 3 hours is about 0.4 arcsec; it is not likely the cause of the mount running slow.
Did you do the test I suggested in a previous post? Did the PEC index roll over at 32000? Is you RA index 5760000 at CWD position?
Michael,
The built in PEC training always runs the full 4 minutes on my G11 Gemini 2; I used it last time a few weeks ago for some testing without any issue. Which files did Rene ask you to download from the Gemini?
Eric
|
Hi Michael, I am speaking about trying to use the built in PEC recorder feature advertised as being internal to Gemini-2. It
does not work for the G11T. It appears it does not work for the 125:1 gearbox either. In both cases the G-2 quits
taking data before a complete worm cycle period is complete. Without using a complete worm cycle it cannot
generate a correct PEC correction curve. How are you determining that it is quitting early? And, how much earlier does is it quitting for you? And again, using an autoguider to create a PEC curve is not going to give the best result. Not only are the recorded values phase delayed, but the data is subject to random star scintillation. And, worse, if the mount has any non-integer fundamentals, the recorded PEC curve will not match every worm cycle because each worm cycle will vary. In this case, the only way to produce a useful PEC curve is to remove the non-integer frequencies, which PEMPro can do. -Ray -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Thursday, June 17, 2021 10:55 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
to do this?
Ray,
I am speaking about trying to use the built in PEC recorder feature advertised as being internal to Gemini-2. It
does not work for the G11T. It appears it does not work for the 125:1 gearbox either. In both cases the G-2 quits
taking data before a complete worm cycle period is complete. Without using a complete worm cycle it cannot
generate a correct PEC correction curve.
You are right....I have not used PEMpro. I have used Gemini-1 to generate it's internal PEC with good results. I
have used PECprep for PE analysis, not generate PEC for the Gemini system. I only use non-guided star
tracking to acquire PE data for analysis.
Best regards,
Michael
On Thu, Jun 17, 2021, 10:37 PM Ray Gralak <iogroups@...> wrote:
> I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken. The
internal
> PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
> purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC
file.
Michael, you obviously haven't used PEMPro, because you don't feed a PHD2 unguided log file into
PEMPro to create a PEC curve. Maybe you are thinking of the PEMPro Log Viewer, which does accept PHD2 logs
for analysis?
> I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I
did not
> have a CAT5 cable connection so I did not deliver the files requested. Bottom line: G-2 PEC does not yet
work.
You must mean recording PE via an autoguider doesn't work, right? PEMPro does work with the Gemini-2
PEC.
BTW, recording via autoguider is likely to provide inferior results. In fact, this method doesn't work very well
at all if there are any non-integer fundamental frequencies, which is not uncommon. I can explain why this is so, if
this isn't obvious?
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
> Sent: Thursday, June 17, 2021 8:56 PM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any
reason not
> to do this?
>
> PCBoreland,
>
> (What is your first name?)
>
> I encountered the same problem as you report: the Gemini-2 PEC training acquisition time is broken. The
internal
> PEC that is advertisef to work in G-2 does not work. The only way to get a working PEC at this time is by
> purchasing PEMpro, then use a PHD2 unguided log file fed into PEMpro to have it create the correct PEC
file.
>
> The PEC training in Gemini-1 does work. You don't need PEMpro if you have a G-1. You can use
PEMpro if you
> want of course.
>
> I reported the G-2 problem to Renew Goerlich who asked me to download certain files from the G-2, but I
did not
> have a CAT5 cable connection so I did not deliver the files requested. Bottom line: G-2 PEC does not yet
work.
>
> Meanwhile I am happy to read your detailed reports on the 125:1 gearbox. I agree that PHD2 autoguiding
will
> correct the DEC and RA. It would be the same if tracking the sun or moon or a planet...you must use
autoguiding.
>
> And yes. The 125:1 vs 25:1 means that slewing will be somewhere like 5x slower. Yet it is the tracking
perfection
> that you are focussing on.
>
> Best,
> Michael
>
>
>
>
>
> On Thu, Jun 17, 2021, 8:10 PM pcboreland via groups.io <pcboreland@...> wrote:
>
>
> As was pointed out by David Partridge, it is possible to change out the gear box on just RA if one uses
the
> web interface to select the parameters. I installed the 125:1 gearbox earlier in the day, and have been
able to
> gather some initial data. As might be expected there is good and bad.
>
> The Good. Unmoded, my Ra guided on average 30% worse than the Dec axis looking back over 6
months
> of logs. With the limited short run tests done earlier this evening RA is now guiding 10 to 20% better than
Dec. A
> huge shift in performance. A seeming improvement of greater than 0.6 arcsec on 10 min runs. I'll be
imaging in 90
> minute blocks later tonight so will hopefully get data worth sharing, and this improvement holds
>
> The Bad. 1. Ra runs slow. Over a 3hr period it fell behind the object a noticable bit. This I assume is
> because the Ra tracking divisor is set to 89754 when it needs to be set 89754.2. I go not think this is a big
deal as
> guiding ought to handle this problem. 2. Pec training runs for just 48s. 1/5th of a worm cycle. Not sure
how to fix
> this? I do not see any parameters to lengthen the record time. Pec is turned off and I'm using Predictive
Pec in
> PHD2, but hoping this can be fixed?
>
> First Ha image of the Cygnus Wall just came in!
>
>
|
Ray,
PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of 32000.?
Peter
|
PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
32000. 32000 is above the maximum number of ticks, which I think is 25600. The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle. -Ray -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via groups.io
Sent: Friday, June 18, 2021 6:22 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
to do this?
Ray,
PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
32000.
Peter
|
Nice catch, Ray.? That could explain the puzzle... and also my puzzle on my 1:2 belt drive G11T.??
(Please see my PEMpro question at the bottom of this email...)
Some thoughts...?
The number of data points recorded in the PEC run is very small.? For my 1:2 belt drive recorded at 1 sec intervals, the number of points is only 2*319 = 638 points.? Even recording at 0.1 sec intervals this is 6,380 points.? ?(There is a CPU RAM storage limit of 96 kbytes but there is also large external Flash available.)
Ray suggests that the optical encoder tick counts per worm rotation has to do with the puzzle.??
A worm rotation value in raw optical encoder ticks is: ? 256 ticks per motor rev x? 25 stock gearbox (or 50 for me, 125 for PCBoreland) gearbox rotation reduction.
At 25 you get 6400 At 50 you get 12800 At 125 you get 32000 (over 25,600 Ray mentions as a limit)
The stock 25:1 and 50:1 gearbox values are at or below 25,600 Ray mentions as a limit for encoder nominal ticks.? The 125:1 gearbox goes higher.??
However if the system is counting "quadruture"? ticks (and we know it can)? then the values become At 25 you get 6400 -> 25,600? At 50 you get 12800 -> 51,200 (>>25,600 or 32,767) At 125 you get 32000->128,000 (>>25,600 or 32,767)
I mention +/- 32,767 as the size of a C "int" 2 byte number.? You can double the "int" value using "uint" to go from 0 to 65535 still taking only 2 bytes.?
The question is: why is the tick count limit 25,600 or 32,000? ?Isn't there sufficient RAM or Flash memory? Spec sheet says there is 98kb of RAM on the LPC2388 ARM CPU chip.??Maybe using only on-CPU RAM is the limiting problem.? There should be huge room on the Flash drive for the data.??
An int size 2 bytes can go to +/- 32767 A uint size 2 bytes can go 0 to 65535? A long size 4 bytes can go to +/-? (huge)
This now seems like a firmware code or memory storage issue. It would need the memory to allocate for a larger tick number, or more PEC data collection numbers, or both.? ?If anyone can address it, it will be Rene.?
Ray:? will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve also fail if the problem is with the G-2 tick size data storage in the present firmware???
All the best, Michael
??
On Fri, Jun 18, 2021, 7:24 AM Ray Gralak < iogroups@...> wrote: > PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
32000 is above the maximum number of ticks, which I think is 25600.
The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle.
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via
> Sent: Friday, June 18, 2021 6:22 AM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
> to do this?
>
> Ray,
>
> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
>
> Peter
>
|
Hi Michael, Ray: will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve
also fail if the problem is with the G-2 tick size data storage in the present firmware? PEMPro will retrieve the count from the Gemini and use that to calculate the PEC curve. In this case, the number would be 6400, which would be wrong, so I suspect the resulting curve would be bad. Depending on the firmware implementation, other things might not work as expected, like GOTO's and autoguiding. Have you tried either? -Ray -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Friday, June 18, 2021 8:18 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
to do this?
Nice catch, Ray. That could explain the puzzle... and also my puzzle on my 1:2 belt drive G11T.
(Please see my PEMpro question at the bottom of this email...)
Some thoughts...
The number of data points recorded in the PEC run is very small. For my 1:2 belt drive recorded at 1 sec intervals,
the number of points is only 2*319 = 638 points. Even recording at 0.1 sec intervals this is 6,380 points. (There is
a CPU RAM storage limit of 96 kbytes but there is also large external Flash available.)
Ray suggests that the optical encoder tick counts per worm rotation has to do with the puzzle.
A worm rotation value in raw optical encoder ticks is:
256 ticks per motor rev
x 25 stock gearbox (or 50 for me, 125 for PCBoreland) gearbox rotation reduction.
At 25 you get 6400
At 50 you get 12800
At 125 you get 32000 (over 25,600 Ray mentions as a limit)
The stock 25:1 and 50:1 gearbox values are at or below 25,600 Ray mentions as a limit for encoder nominal ticks.
The 125:1 gearbox goes higher.
However if the system is counting "quadruture" ticks (and we know it can) then the values become
At 25 you get 6400 -> 25,600
At 50 you get 12800 -> 51,200 (>>25,600 or 32,767)
At 125 you get 32000->128,000 (>>25,600 or 32,767)
I mention +/- 32,767 as the size of a C "int" 2 byte number. You can double the "int" value using "uint" to go from 0
to 65535 still taking only 2 bytes.
The question is: why is the tick count limit 25,600 or 32,000?
Isn't there sufficient RAM or Flash memory? Spec sheet says there is 98kb of RAM on the LPC2388 ARM CPU
chip. Maybe using only on-CPU RAM is the limiting problem. There should be huge room on the Flash drive for
the data.
An int size 2 bytes can go to +/- 32767
A uint size 2 bytes can go 0 to 65535
A long size 4 bytes can go to +/- (huge)
This now seems like a firmware code or memory storage issue. It would need the memory to allocate for a larger
tick number, or more PEC data collection numbers, or both. If anyone can address it, it will be Rene.
Ray: will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve
also fail if the problem is with the G-2 tick size data storage in the present firmware?
All the best,
Michael
On Fri, Jun 18, 2021, 7:24 AM Ray Gralak <iogroups@...> wrote:
> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks
instead of
> 32000.
32000 is above the maximum number of ticks, which I think is 25600.
The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle.
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via
groups.io
> Sent: Friday, June 18, 2021 6:22 AM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any
reason not
> to do this?
>
> Ray,
>
> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks
instead of
> 32000.
>
> Peter
>
|
My Goto's with my G11T 1:2 belt drive and 25:1 McLennan gearbox are spot on.? That works fine.
And when I used a 50:1 McLennan and the stock 3 transfer gears on tucked Titan RA the GoTos also worked fine.? And PCBoreland's report on the 125:1 gearbox also said that worked fine.? Only PEC showed trouble.?
Those drive systems and gotos seem to have all been tested and debugged correctly.
It's the PEC that ... needs debugging and a solution for the non-stock gear ratios above 25:1.??
I'll hope Rene sees these notes and enters the fray!
It is also good that these issues are seeing the light of day so they can get resolved.? Any one person who observed a problem was considered an anomaly.? Nowit is clear that there is a consistent PEC issue and it comes about when the gear ratios are over 25:1.? ?
Best regards, Michael
On Fri, Jun 18, 2021, 9:10 AM Ray Gralak < iogroups@...> wrote: Hi Michael,
> Ray:? will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve
> also fail if the problem is with the G-2 tick size data storage in the present firmware?
PEMPro will retrieve the count from the Gemini and use that to calculate the PEC curve. In this case, the number would be 6400, which would be wrong, so I suspect the resulting curve would be bad.
Depending on the firmware implementation, other things might not work as expected, like GOTO's and autoguiding. Have you tried either?
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
> Sent: Friday, June 18, 2021 8:18 AM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
> to do this?
>
> Nice catch, Ray.? That could explain the puzzle... and also my puzzle on my 1:2 belt drive G11T.
>
> (Please see my PEMpro question at the bottom of this email...)
>
> Some thoughts...
>
> The number of data points recorded in the PEC run is very small.? For my 1:2 belt drive recorded at 1 sec intervals,
> the number of points is only 2*319 = 638 points.? Even recording at 0.1 sec intervals this is 6,380 points.? ?(There is
> a CPU RAM storage limit of 96 kbytes but there is also large external Flash available.)
>
> Ray suggests that the optical encoder tick counts per worm rotation has to do with the puzzle.
>
> A worm rotation value in raw optical encoder ticks is:
>? ?256 ticks per motor rev
> x? 25 stock gearbox (or 50 for me, 125 for PCBoreland) gearbox rotation reduction.
>
> At 25 you get 6400
> At 50 you get 12800
> At 125 you get 32000 (over 25,600 Ray mentions as a limit)
>
> The stock 25:1 and 50:1 gearbox values are at or below 25,600 Ray mentions as a limit for encoder nominal ticks.
> The 125:1 gearbox goes higher.
>
> However if the system is counting "quadruture"? ticks (and we know it can)? then the values become
> At 25 you get 6400 -> 25,600
> At 50 you get 12800 -> 51,200 (>>25,600 or 32,767)
> At 125 you get 32000->128,000 (>>25,600 or 32,767)
>
> I mention +/- 32,767 as the size of a C "int" 2 byte number.? You can double the "int" value using "uint" to go from 0
> to 65535 still taking only 2 bytes.
>
> The question is: why is the tick count limit 25,600 or 32,000?
>? Isn't there sufficient RAM or Flash memory? Spec sheet says there is 98kb of RAM on the LPC2388 ARM CPU
> chip.? Maybe using only on-CPU RAM is the limiting problem.? There should be huge room on the Flash drive for
> the data.
>
> An int size 2 bytes can go to +/- 32767
> A uint size 2 bytes can go 0 to 65535
> A long size 4 bytes can go to +/-? (huge)
>
> This now seems like a firmware code or memory storage issue. It would need the memory to allocate for a larger
> tick number, or more PEC data collection numbers, or both.? ?If anyone can address it, it will be Rene.
>
> Ray:? will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve
> also fail if the problem is with the G-2 tick size data storage in the present firmware?
>
> All the best,
> Michael
>
>
>
>
>
>
> On Fri, Jun 18, 2021, 7:24 AM Ray Gralak <iogroups@...> wrote:
>
>
>? ? ? ?> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks
> instead of
>? ? ? ?> 32000.
>
>? ? ? ?32000 is above the maximum number of ticks, which I think is 25600.
>
>? ? ? ?The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle.
>
>? ? ? ?-Ray
>
>? ? ? ?> -----Original Message-----
>? ? ? ?> From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via
>
>? ? ? ?> Sent: Friday, June 18, 2021 6:22 AM
>? ? ? ?> To: [email protected]
>? ? ? ?> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any
> reason not
>? ? ? ?> to do this?
>? ? ? ?>
>? ? ? ?> Ray,
>? ? ? ?>
>? ? ? ?> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks
> instead of
>? ? ? ?> 32000.
>? ? ? ?>
>? ? ? ?> Peter
>? ? ? ?>
>
>
>
>
>
>
>
>
>
|
And, worse, if the mount has any non-integer fundamentals, the recorded PEC curve will not match every worm cycle because each worm cycle will vary
Thankyou Ray. ?Explains quite the opposite effect to many are striving ?for?
cheers
--
Brendan
|
Michael
Is the pulse width to the motor fixed in duration such that it results in 256 tics per rev to match the optical encoder or can the pulse width vary. Since the quadriture can determine where the motor is at (0, pi/2, pi, 3pi/2, 2pi) with much finer resolution, it could vary but does it? When you see phd graphs of the RA axis trying to "catch up" on poorly aligned mounts, you see multiple pulses being sent, one after the other, resulting in overshoot, this appears to be constant duration pulses. Or am I missing something?
Chuck
On Friday, June 18, 2021, 08:18:43 AM PDT, Michael Herman <mherman346@...> wrote:
Nice catch, Ray.? That could explain the puzzle... and also my puzzle on my 1:2 belt drive G11T.??
(Please see my PEMpro question at the bottom of this email...)
Some thoughts...?
The number of data points recorded in the PEC run is very small.? For my 1:2 belt drive recorded at 1 sec intervals, the number of points is only 2*319 = 638 points.? Even recording at 0.1 sec intervals this is 6,380 points.? ?(There is a CPU RAM storage limit of 96 kbytes but there is also large external Flash available.)
Ray suggests that the optical encoder tick counts per worm rotation has to do with the puzzle.??
A worm rotation value in raw optical encoder ticks is: ? 256 ticks per motor rev x? 25 stock gearbox (or 50 for me, 125 for PCBoreland) gearbox rotation reduction.
At 25 you get 6400 At 50 you get 12800 At 125 you get 32000 (over 25,600 Ray mentions as a limit)
The stock 25:1 and 50:1 gearbox values are at or below 25,600 Ray mentions as a limit for encoder nominal ticks.? The 125:1 gearbox goes higher.??
However if the system is counting "quadruture"? ticks (and we know it can)? then the values become At 25 you get 6400 -> 25,600? At 50 you get 12800 -> 51,200 (>>25,600 or 32,767) At 125 you get 32000->128,000 (>>25,600 or 32,767)
I mention +/- 32,767 as the size of a C "int" 2 byte number.? You can double the "int" value using "uint" to go from 0 to 65535 still taking only 2 bytes.?
The question is: why is the tick count limit 25,600 or 32,000? ?Isn't there sufficient RAM or Flash memory? Spec sheet says there is 98kb of RAM on the LPC2388 ARM CPU chip.??Maybe using only on-CPU RAM is the limiting problem.? There should be huge room on the Flash drive for the data.??
An int size 2 bytes can go to +/- 32767 A uint size 2 bytes can go 0 to 65535? A long size 4 bytes can go to +/-? (huge)
This now seems like a firmware code or memory storage issue. It would need the memory to allocate for a larger tick number, or more PEC data collection numbers, or both.? ?If anyone can address it, it will be Rene.?
Ray:? will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve also fail if the problem is with the G-2 tick size data storage in the present firmware???
All the best, Michael
??
On Fri, Jun 18, 2021, 7:24 AM Ray Gralak < iogroups@...> wrote: > PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
32000 is above the maximum number of ticks, which I think is 25600.
The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle.
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via
> Sent: Friday, June 18, 2021 6:22 AM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
> to do this?
>
> Ray,
>
> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
>
> Peter
>
|
Good question, about pulse widths!, but ..I do not know the answer.? ?The pulse widths should be varied and capable of being quite short by the uP, but I have not scoped out the actual pulses to see how short they do go. ?? If Rene were listening in, he could tell you the answer immediately.? I emailed him this morning about the PEC riddle.??
Best, Michael
Michael
Is the pulse width to the motor fixed in duration such that it results in 256 tics per rev to match the optical encoder or can the pulse width vary. Since the quadriture can determine where the motor is at (0, pi/2, pi, 3pi/2, 2pi) with much finer resolution, it could vary but does it? When you see phd graphs of the RA axis trying to "catch up" on poorly aligned mounts, you see multiple pulses being sent, one after the other, resulting in overshoot, this appears to be constant duration pulses. Or am I missing something?
Chuck
On Friday, June 18, 2021, 08:18:43 AM PDT, Michael Herman < mherman346@...> wrote:
Nice catch, Ray.? That could explain the puzzle... and also my puzzle on my 1:2 belt drive G11T.??
(Please see my PEMpro question at the bottom of this email...)
Some thoughts...?
The number of data points recorded in the PEC run is very small.? For my 1:2 belt drive recorded at 1 sec intervals, the number of points is only 2*319 = 638 points.? Even recording at 0.1 sec intervals this is 6,380 points.? ?(There is a CPU RAM storage limit of 96 kbytes but there is also large external Flash available.)
Ray suggests that the optical encoder tick counts per worm rotation has to do with the puzzle.??
A worm rotation value in raw optical encoder ticks is: ? 256 ticks per motor rev x? 25 stock gearbox (or 50 for me, 125 for PCBoreland) gearbox rotation reduction.
At 25 you get 6400 At 50 you get 12800 At 125 you get 32000 (over 25,600 Ray mentions as a limit)
The stock 25:1 and 50:1 gearbox values are at or below 25,600 Ray mentions as a limit for encoder nominal ticks.? The 125:1 gearbox goes higher.??
However if the system is counting "quadruture"? ticks (and we know it can)? then the values become At 25 you get 6400 -> 25,600? At 50 you get 12800 -> 51,200 (>>25,600 or 32,767) At 125 you get 32000->128,000 (>>25,600 or 32,767)
I mention +/- 32,767 as the size of a C "int" 2 byte number.? You can double the "int" value using "uint" to go from 0 to 65535 still taking only 2 bytes.?
The question is: why is the tick count limit 25,600 or 32,000? ?Isn't there sufficient RAM or Flash memory? Spec sheet says there is 98kb of RAM on the LPC2388 ARM CPU chip.??Maybe using only on-CPU RAM is the limiting problem.? There should be huge room on the Flash drive for the data.??
An int size 2 bytes can go to +/- 32767 A uint size 2 bytes can go 0 to 65535? A long size 4 bytes can go to +/-? (huge)
This now seems like a firmware code or memory storage issue. It would need the memory to allocate for a larger tick number, or more PEC data collection numbers, or both.? ?If anyone can address it, it will be Rene.?
Ray:? will PEMpro generates a useable PEC curve for gearboxes above 25:1.....or ....will the PEMpro PEC curve also fail if the problem is with the G-2 tick size data storage in the present firmware???
All the best, Michael
??
On Fri, Jun 18, 2021, 7:24 AM Ray Gralak < iogroups@...> wrote: > PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
32000 is above the maximum number of ticks, which I think is 25600.
The tick count probably wraps at 25,600 so 32000-25600 = 6400, which would explain the 1/5 cycle.
-Ray
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of pcboreland via
> Sent: Friday, June 18, 2021 6:22 AM
> To: [email protected]
> Subject: Re: [Losmandy_users_io] Changing the servo motor encoders from 256 to 512 or 1024. Any reason not
> to do this?
>
> Ray,
>
> PEC training quits after 48s, 1/5th period of the worm. I think this has to do Pec working with 6400 ticks instead of
> 32000.
>
> Peter
>
|
On Fri, Jun 18, 2021 at 11:38 AM, Brendan Smith wrote:
And, worse, if the mount has any non-integer fundamentals, the recorded PEC curve will not match every worm cycle because each worm cycle will vary
Thankyou Ray. ?Explains quite the opposite effect to many are striving ?for?
I thought this too, but the mount (worn turn) does have integer multiples. It is defined by the steps per revolution (6400 for the 25:1 gearbox). I noticed in "configure PEC" a Set PEC Period selection and a drop down box. There are multiple options 1x6400, 2x6400 up to I think 4x6400. I had expected this to change to being indexed to 32000, but the pec recording only indexed up to 6400. I wonder what would happen if one created the PEC curve using third party software. How is that curve indexed? I have ordered. 50:1 gearbox. I can confirm the the small gear can be reamed out to 1/8th. I'm evermore convinced that upping the hear ratio is defiantly worth doing. There is the option of changing out the encoder too, but these PEC issues would still remain. I confident we can solve this as a group.
|
I took a look at the PEC file and ran a quick test to see if a curve with 3200 steps is possible and it seems to be so. The PEC process is very simple. I only changed out one gearbox, I wonder if PEC is getting the step information from the Dec axis by mistake which has 6400 steps?
|
Peter, The Gemini 2 serial commands document says:
| 27 |
? |
? |
2000..25600 |
Number of RA steps for one worm revolution (since is a product of spur ratio and motor encoder ratio,this command can only be used for reading out the maximum step count, not for setting it).
Note:?This product must not exceed 25600. If higher values are reported the combination of RA spur gear ratio and motor encoder is invalid. |
Therefore, the limit is 25600, and Gemini probably defaults to 6400 if the gear ratio and encoder combination is invalid. The 50:1 gearbox will result in a valid combination, so PEC should work. You can do the tests I suggested previously to confirm the PEC index will roll over at 12800 while you wait for your new gearbox. Eric
|
Michael Herman