Quote:
Originally Posted by Rod
Hi Greg
I agree a stepper motor will be more accurate and consistent. You can also add nice features like automatic rewind.
I've made a couple of platforms. Friends have helped with the stepper motors and coding. However, I found the biggest source of tracking error was poor platform alignment and construction errors in the platform itself. The other issue I had was I got too fussy sometimes trying to get the perfect speed using a narrow field cross hair eyepiece. I found for visual use some speed error was not that noticeable when using moderate magnification.
With one of my platforms I spent ages adjusting speed. A friend then went over the platform. He ensured bearings were properly located and moving smoothly, removed any play in the motor connection etc. The improvement was dramatic.
You are probably a much better builder than I am. But I suggest you check these other potential sources of error (platform polar alignment and construction) before concluding motor speed is the issue.
Hope that helps. BTW please post some pictures. I for one would love to see what you have done.
Rod.
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Hey Rod,
Apologies i missed this post.
Regarding my mods i got rid of the battery and and wires in a PWM form Jay car, photo attached, between the motor and a 12v power supply. unfortunately this was a wasted of time as it didn't give me the extra sensitivity/precision i needed. If the motor was moving slightly too fast turning the nob tiny bits at a time would do nothing the first few times then all of a sudden it would make a big change and slow motor right down! last night was a very frustrating night.
I will be removing the PWM today and making something to connect to the tiny built in potentiometer of the motor drive. I hear a peg works well but i couldn't get one that gripped on tight enough.
What type of mount do you have? I have a VNS and definitely not sure on the accuracy of my build. Having said that, i'm extremely confident that everything is where i want it to be based on my calculations, but were my calculations right?
the main confusion I had was where was the pivoting point for the south segment to 90 degrees with the base and pivoting the segments in the other direction (don't know how to explain)
So I'm wondering if i should invest in the stepper motor of just remake a platform or both!
Stepper motors seems to be the quickest options as im pretty pressed for time with work and a newborn. And then if its still not quite right it kinda confirms the problem is the mount.
For stepper motor i'm looking at getting a high torque motor with a planetary gearbox so I can run it as a direct drive so I don't need to modify the platform. Although as mentioned the more i read the more I'm confused. lol