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DIY AstroEQ / Re: Astoeq tracking pause every seconds.
« on: September 25, 2017, 17:51:44 »
Many thanks to everyone in this thread for super useful info! Sharing my (newbie) success story below.
Pulled Orion SVP mount (EQ-5 equivalent) from collecting dust, re-greased it, fine-tuned it, and bought the cheapest NEMA17 motors I could find on ebay - 4.2V / 1.2A, "reversed-shaft" to use for the mount. These "reversed shaft" motors despite being super cheap (~ $12), turned out as an DIY advantage for me at the end, because I could use standard "off the shelf" pololu motor bracket, which would cover more usable area against the mount when placed in reverse to the motor's shaft. Got brackets attached to 6mm aluminum plates via tapped M5 holes, and aluminum plates to the mount via tapped M6 hole.
Got the 8825 driver current output calibrated measuring 0.6V = 1.2A, and while everything was running fine in high speed / slew mode, I got the clock ticking effect (micro-stepping half way, and then jumping to a full step) while tracking. Tried fast decay mode, by shorting 2 neighboring pins per earlier post, and while it made things much much smoother on expense of the extra noise, it did NOT fix the skipping effect entirely in my case. Remains of a jerky skipping effect could still be seen when looked super-closely. I attached a thin long straw to the motor's shaft with some blue tuck and obsessively looked at the far end of the straw while tracking. Next, connected 8 diodes per motor, as described in the linked blog post, and things got way better if not perfect! Not sure if I can still see a little (barely noticeable) thug per step when looking at the straw's end, but perhaps it is also the looping / grinding sound of the motor per step that makes me see what is not there. Movement does appear extremely smooth now in comparison, but I did notice that even with diodes, lowering current (below 0.6V = 1.2A) makes this subtle remaining thug a little more noticeable, but at 0.6V or cranked at 0.7V it is almost if not completely gone (only the slightest hint of a thug near the end of the step). Anyone with similar experience?
As I am using full current to drive motors, they are very loud while micro-stepping and sound like an old school fax modem or noisy/broken sound card. Perhaps due to cheap motor quality or is this to be expected with any motor?
Had cloudy weather since, so keeping fingers crossed it will work smooth while tracking / guiding in real use. Considering that I was opting for cheapest and shortest route to motorize the mount, I am pretty happy where I got to, so again, thanks everyone for contributing and of course Tom for making this project available / taking care of everything else.
Lastly, perhaps it would not be a bad idea to factor these issues on the motor recommendation page. When I first looked it was in lines of "the lower the better" in terms of voltage, which is not entirely true without having 8 big diodes in place, per this thread. That said, I did need a PCB fabricated to mount RJ11 to Motor connectors near the motors, so including 8 vertically placed diodes in the final design will not be a biggie. =)
Pulled Orion SVP mount (EQ-5 equivalent) from collecting dust, re-greased it, fine-tuned it, and bought the cheapest NEMA17 motors I could find on ebay - 4.2V / 1.2A, "reversed-shaft" to use for the mount. These "reversed shaft" motors despite being super cheap (~ $12), turned out as an DIY advantage for me at the end, because I could use standard "off the shelf" pololu motor bracket, which would cover more usable area against the mount when placed in reverse to the motor's shaft. Got brackets attached to 6mm aluminum plates via tapped M5 holes, and aluminum plates to the mount via tapped M6 hole.
Got the 8825 driver current output calibrated measuring 0.6V = 1.2A, and while everything was running fine in high speed / slew mode, I got the clock ticking effect (micro-stepping half way, and then jumping to a full step) while tracking. Tried fast decay mode, by shorting 2 neighboring pins per earlier post, and while it made things much much smoother on expense of the extra noise, it did NOT fix the skipping effect entirely in my case. Remains of a jerky skipping effect could still be seen when looked super-closely. I attached a thin long straw to the motor's shaft with some blue tuck and obsessively looked at the far end of the straw while tracking. Next, connected 8 diodes per motor, as described in the linked blog post, and things got way better if not perfect! Not sure if I can still see a little (barely noticeable) thug per step when looking at the straw's end, but perhaps it is also the looping / grinding sound of the motor per step that makes me see what is not there. Movement does appear extremely smooth now in comparison, but I did notice that even with diodes, lowering current (below 0.6V = 1.2A) makes this subtle remaining thug a little more noticeable, but at 0.6V or cranked at 0.7V it is almost if not completely gone (only the slightest hint of a thug near the end of the step). Anyone with similar experience?
As I am using full current to drive motors, they are very loud while micro-stepping and sound like an old school fax modem or noisy/broken sound card. Perhaps due to cheap motor quality or is this to be expected with any motor?
Had cloudy weather since, so keeping fingers crossed it will work smooth while tracking / guiding in real use. Considering that I was opting for cheapest and shortest route to motorize the mount, I am pretty happy where I got to, so again, thanks everyone for contributing and of course Tom for making this project available / taking care of everything else.
Lastly, perhaps it would not be a bad idea to factor these issues on the motor recommendation page. When I first looked it was in lines of "the lower the better" in terms of voltage, which is not entirely true without having 8 big diodes in place, per this thread. That said, I did need a PCB fabricated to mount RJ11 to Motor connectors near the motors, so including 8 vertically placed diodes in the final design will not be a biggie. =)
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