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1
DIY AstroEQ / Re: WIFI Adapter build - working with SynScan Desktop and Mobile Apps
« on: November 21, 2023, 20:51:23 »
Hi Mike,
It has been more than 2 years since this post but I can confirm your code works. Thanks!
Exceptions:
1) Newer versions of SynScan Pro are not compatible and they reply with "Negative Response".
2) Version SynScan Pro 1.19.12 for Windows works perfectly once the timeout in the app settings is changed to 5000.
3) The newest SynScan Pro for Android returns the same "Negative Response" and you'll need a phone or tablet running an old version of Android to be able to install SynScan Pro 1.19.12.apk (I haven't try this yet).
4) The resistors mentioned in the code (50ohm and 100ohm) are not necessary. Direct connection to the TX and RX pins on the Arduino Mega should be enough.
5) If you are going to replace the Bluetooth module with the NodeMCU ESP8266, you'll need to bypass any resistors installed between the RX and TX lines. Connect directly.
I'll keep investigating the "Negative Response" issue and report back if a solution is found.
Cheers
Alex
It has been more than 2 years since this post but I can confirm your code works. Thanks!
Exceptions:
1) Newer versions of SynScan Pro are not compatible and they reply with "Negative Response".
2) Version SynScan Pro 1.19.12 for Windows works perfectly once the timeout in the app settings is changed to 5000.
3) The newest SynScan Pro for Android returns the same "Negative Response" and you'll need a phone or tablet running an old version of Android to be able to install SynScan Pro 1.19.12.apk (I haven't try this yet).
4) The resistors mentioned in the code (50ohm and 100ohm) are not necessary. Direct connection to the TX and RX pins on the Arduino Mega should be enough.
5) If you are going to replace the Bluetooth module with the NodeMCU ESP8266, you'll need to bypass any resistors installed between the RX and TX lines. Connect directly.
I'll keep investigating the "Negative Response" issue and report back if a solution is found.
Cheers
Alex
2
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: January 14, 2016, 00:08:47 »Hey Alex, which solution do you think is better diodes or fast decay? Have you had the chance to test your guiding?
Hi,
I haven't checked the guiding using the diode configuration but to tell the truth, I didn't noticed any substantial difference from the fast decay mode during the test on the bench. I'm pretty sure both will work fine but if you or a friend can do the soldering to accomplish fast decay on the driver, then stay with that. You will get something more compact.
I would also recommend to use pulleys and belts and get rid of the gears. You will always have tracking/guiding problems if you keep using gears.
Regards
Alex
3
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: December 01, 2015, 23:21:15 »
That's awesome news Tom!
Looking forward to knowing how things go with it.
Glad to bring some help to the forum.
Alex
Looking forward to knowing how things go with it.
Glad to bring some help to the forum.
Alex
4
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: November 30, 2015, 02:21:47 »
Hi,
For research sake and the will to help others with the jumping/missing steps problem, I decided to try the diode trick.
The good news is that it really worked!
As you can see in the pictures the circuit I made for the diodes was to simply solder their leads together in a loop, leaving
an overlap of about 7mm on each side for connection. Sorta looks like rabbit ears when connected to each phase of the motor.
Something much more elegant can be made using a project circuit board or somehow integrate the diodes in the AEQ circuit.
(Please ignore the resistors on the left side of the breadboard. They are from another project)
Although I used an Aduino Uno, a different motor and a different code for this test, the missing steps were still there at 1/32 microstepping.
After connecting the diodes the problem dissapeared but the sound coming from the stepper motor was similar. It ran smoothly but I didn't notice any difference
from the fast decay PIN 19 to PIN M2 soldering modification.
I was using 1N5408 diodes which have maximun continuous forward current rating of 3A. After having the motor running for about 40 minutes they never got hot not
even warm. The Supplied power to the DRV8825 was 12v - 2A and the Vref for the 2.6v and 1.2A rated Nema 17 stepper motor was 0.59v.
I wouldn't worry so much about the mount not going back south during the PHD calibration. Mine also does that and the guiding is excellent anyways. This glitch
also used to happen when my CG5 was stock. Maybe is a software problem.
Like Tom mentioned, guiding problems like overcorrection can be atenuated in EQMODs "ASCOM PulseGuide Settings" as well as "ASCOM PulseGuide Monitor".
Further information on how to use these settings can be found at the EQMODs website.
If you still haven't set the DRV8825s into fast decay mode or done the diode trick, I'm afraid that your guiding problems are related to the mix decay problems these drivers have.
Hope all these helps
Alex
For research sake and the will to help others with the jumping/missing steps problem, I decided to try the diode trick.
The good news is that it really worked!
As you can see in the pictures the circuit I made for the diodes was to simply solder their leads together in a loop, leaving
an overlap of about 7mm on each side for connection. Sorta looks like rabbit ears when connected to each phase of the motor.
Something much more elegant can be made using a project circuit board or somehow integrate the diodes in the AEQ circuit.
(Please ignore the resistors on the left side of the breadboard. They are from another project)
Although I used an Aduino Uno, a different motor and a different code for this test, the missing steps were still there at 1/32 microstepping.
After connecting the diodes the problem dissapeared but the sound coming from the stepper motor was similar. It ran smoothly but I didn't notice any difference
from the fast decay PIN 19 to PIN M2 soldering modification.
I was using 1N5408 diodes which have maximun continuous forward current rating of 3A. After having the motor running for about 40 minutes they never got hot not
even warm. The Supplied power to the DRV8825 was 12v - 2A and the Vref for the 2.6v and 1.2A rated Nema 17 stepper motor was 0.59v.
Quote
Although I have adjusted the worm and worm gear to be quite tight I have problems with phd calibration due to backlash. Star goes north but doesn't come back to its place.
I wouldn't worry so much about the mount not going back south during the PHD calibration. Mine also does that and the guiding is excellent anyways. This glitch
also used to happen when my CG5 was stock. Maybe is a software problem.
Quote
In guiding I still have similar problems of overcorrection on both sides.
Like Tom mentioned, guiding problems like overcorrection can be atenuated in EQMODs "ASCOM PulseGuide Settings" as well as "ASCOM PulseGuide Monitor".
Further information on how to use these settings can be found at the EQMODs website.
If you still haven't set the DRV8825s into fast decay mode or done the diode trick, I'm afraid that your guiding problems are related to the mix decay problems these drivers have.
Hope all these helps
Alex
5
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: October 07, 2015, 22:39:55 »Nice job with the soldering Alex. I'm glad you got yours going.
Thanks Tom. Was not easy but doing the second one I found that its easier to solder the wire to the M2 pin first (this will serve you as some kind of support) then make a thin line of solder come out of pin 19 and solder the other end of the wire to it. The picture can give you an idea of what I mean. I strongly recommend using a soldering helping hand tool.
At least with Astro it is only light you are trying to capture not sound!
True. The noise is not a big deal. Can't hear it unless I'm close to the mount.I'm tempted to ask Pololu if they would consider making a new revision of the board with the decay pin broken out - even if just to a pad (ideally an on-off-on surface mount switch) in light of this issue. Not sure that they would do it though.
I read of people trying to reach Pololu with the same suggestion but haven't seen any change yet. Hopefully they are considering it and the next version will have an option to facilitate this.
Wow 10 minutes! My setup is also around 10kgs and I would be more than happy to achieve that. Unfortunately I cannot do soldering that well so this is not an option for meYou could try with the diodes or the TO-220 as Tom suggested. I also recommend using the exact same motor model for both RA and DEC.
Btw I have disassembled the mount following the guides online but most of them are outdated for a new skywatcher eq5 mount. Both ra and dec axis have radial ball bearings and the grease isn't as bad as they've described (it is quite sticky though). After long search I couldn't find the suggested grease in my country(as always) so I ordered some on ebay. So my mount is sitting stripped waiting to be greased. I hope I can assemble it back without any problems, and not make it worse than before. I will post if it improves tracking and reduce periodic error.
I did the same to my mount about a year ago (disassemble, clean, regrease, assemble and adjust the worm gear mesh). I did see some improvement. Hope yours will run well too
Alex
6
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: October 07, 2015, 04:48:57 »
Hi everybody
My apologies for delay of my reply. Haven't checked the forum in a while.
Attached is a specification sheet of the motor I used for my Arduino Astro EQ.
Their rated voltage is 2.8v. Way below the supplied voltage which is 12v.
I immediately noticed the 1/32 microstep problem when I first set the mount to sidereal tracking using EQMOD and heard the motors doing the microstepping followed by a sudden jump. I later set a really slow custom tracking rate in EQMOD and by touching the RA motor pulley I counted 16 microsteps and a sudden big step. Days later I took the mount out for testing and I knew it was something really bad when I went to try to focus the telescope and saw through the live view of my camera that the star (Vega) was oscillating up and down. Then I thought that the autoguiding could fix it...wrong. The glitch was so bad that calibration went out of wack and so the guiding . The motors were ignoring most of the pulse commands because the drivers were forcing them to do the described glitch. 16 microsteps then a sudden big step. The problem is also present in the 1/16 and 1/8 configurations but goes away using 1/4 microstepping so I suspect that the sudden big jump is a 1/4 microstep.
I tried lower voltage power supplies but not luck. Googling here and there for what the problem could be with the DRV8825 I stumbled upon the page Cedric posted and later with the diodes solution. Lacking any of the mentioned diodes, I opted for the fast decay modification. It was really difficult to solder such a small thing! I used resistor leads instead of a wire which are thinner and more comfortable to work with.
The modification was a success. Now the motors run smoother but they make more noise. Not a big deal since my CG-5 was able to pull a 10 mnts exposure with round stars having about 22 pounds of load on it
Haven't tried the diodes trick yet but now I feel tempted.
Cheers
Alex
My apologies for delay of my reply. Haven't checked the forum in a while.
Attached is a specification sheet of the motor I used for my Arduino Astro EQ.
Their rated voltage is 2.8v. Way below the supplied voltage which is 12v.
I immediately noticed the 1/32 microstep problem when I first set the mount to sidereal tracking using EQMOD and heard the motors doing the microstepping followed by a sudden jump. I later set a really slow custom tracking rate in EQMOD and by touching the RA motor pulley I counted 16 microsteps and a sudden big step. Days later I took the mount out for testing and I knew it was something really bad when I went to try to focus the telescope and saw through the live view of my camera that the star (Vega) was oscillating up and down. Then I thought that the autoguiding could fix it...wrong. The glitch was so bad that calibration went out of wack and so the guiding . The motors were ignoring most of the pulse commands because the drivers were forcing them to do the described glitch. 16 microsteps then a sudden big step. The problem is also present in the 1/16 and 1/8 configurations but goes away using 1/4 microstepping so I suspect that the sudden big jump is a 1/4 microstep.
I tried lower voltage power supplies but not luck. Googling here and there for what the problem could be with the DRV8825 I stumbled upon the page Cedric posted and later with the diodes solution. Lacking any of the mentioned diodes, I opted for the fast decay modification. It was really difficult to solder such a small thing! I used resistor leads instead of a wire which are thinner and more comfortable to work with.
The modification was a success. Now the motors run smoother but they make more noise. Not a big deal since my CG-5 was able to pull a 10 mnts exposure with round stars having about 22 pounds of load on it
Haven't tried the diodes trick yet but now I feel tempted.
Cheers
Alex
7
DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: September 01, 2015, 23:32:02 »
Hi,
First, I'd like to thank Tom for this wonderful project.
I also had this problem when I completed my Arduino Astro EQ and solved it the same way. When tracking using 1/32 microstep mode, the motor rotates about 16 microsteps then it seems to stop or jump a full step. Looking here and there I found that it looks like the DRV8825 has a problem microstepping from 1/8 to 1/32 in its default mix decay mode. The mentioned fast decay modification seems to solve it but the motors get a little noisy (high pitch noise).
Another possible solution (which I haven't tried yet) can be found here: http://cabristor.blogspot.com/2015/02/drv8825-missing-steps.html . The solution still uses the drivers mix decay mode but the 1/32 microstepping is smooth and the motors run more silent. In one of the paragraphs it cites " in mixed decay mode, the driver cannot do any voltage lower than 12% of the supply voltage. So the small currents needed for the microstepping will not be possible ". This seems to be the culprit of the missing microsteps when using the 8825 with motors rated with a lower voltage than the supply. At least is true for 1.8° steppers.
Like I said before, I haven't try this fix yet. I'd like to know if its practical or better than the fast decay setup or if there's a more simple solution to the missing microsteps problem.
Regards
Alex
First, I'd like to thank Tom for this wonderful project.
I also had this problem when I completed my Arduino Astro EQ and solved it the same way. When tracking using 1/32 microstep mode, the motor rotates about 16 microsteps then it seems to stop or jump a full step. Looking here and there I found that it looks like the DRV8825 has a problem microstepping from 1/8 to 1/32 in its default mix decay mode. The mentioned fast decay modification seems to solve it but the motors get a little noisy (high pitch noise).
Another possible solution (which I haven't tried yet) can be found here: http://cabristor.blogspot.com/2015/02/drv8825-missing-steps.html . The solution still uses the drivers mix decay mode but the 1/32 microstepping is smooth and the motors run more silent. In one of the paragraphs it cites " in mixed decay mode, the driver cannot do any voltage lower than 12% of the supply voltage. So the small currents needed for the microstepping will not be possible ". This seems to be the culprit of the missing microsteps when using the 8825 with motors rated with a lower voltage than the supply. At least is true for 1.8° steppers.
Like I said before, I haven't try this fix yet. I'd like to know if its practical or better than the fast decay setup or if there's a more simple solution to the missing microsteps problem.
Regards
Alex
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