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Hi, checking in, asking some advices


Pedro Miguel Barbosa Moutinho Nunes dos Reis
 

Hi
First of all, thank you for the project, it seems really nice!
I would like to try this project on my eq3-2.
Currently, I have laying around some mega2650, some ramps 1.4, and these drivers:
https://www.banggood.com/Super-Silent-TMC2208-V1_2-Stepper-Motor-Driver-Module-+-Stepstick-Smoother-+-Heatsink-For-3D-Printer-Parts-p-1383270.html?rmmds=myorder&cur_warehouse=CN
Some wantmotors, 42BYGHM810, http://www.wantmotor.com/product/42BYGHM_EN.html
All of this from previous projects, surplus... 3d printers, etc
Is this setup possible? 
I'm willing to buy more parts if needed, please advise.

Thanks, 
Pedro


Khalid Baheyeldin
 

On Wed, Nov 25, 2020 at 08:00 PM, Pedro Miguel Barbosa Moutinho Nunes dos Reis wrote:
I would like to try this project on my eq3-2.
Currently, I have laying around some mega2650, some ramps 1.4, and these drivers (TMC2208):
That setup will work, but will may be slow when slewing.
Also, the TMC2208 has limitations (e.g. 1/16 microstepping because UART mode is not supported in OnStep).

Some wantmotors, 42BYGHM810, http://www.wantmotor.com/product/42BYGHM_EN.html
These have way too much current for such a small mount.
But they should work if you adjust the drivers to less current.

All of this from previous projects, surplus... 3d printers, etc
Is this setup possible? 
Yes, there will be some limitations, but since you already have the parts, then go ahead and
build your controller that way.
Then, test things out, and based on the results, decide whether they are adequate or you need
something different.


Pedro Miguel Barbosa Moutinho Nunes dos Reis
 

Thank you for the quick answer! Will try with this setup then waiting for the pulleys and belts :)
Regarding the drivers, on the description it says:

"The latest version of the TMC2208 V1.2 takes the UART out and uses the UART function directly, eliminating the need for more wiring."

Does this change anything?
Do these drivers also need to be powerup from the motor before connecting the USB for programming?

Also, regarding the motors, why is necessary to adjust the current? 

Thanks!


Khalid Baheyeldin
 

On Wed, Nov 25, 2020 at 08:40 PM, Pedro Miguel Barbosa Moutinho Nunes dos Reis wrote:
Does this change anything?
Depends on the gear reduction you will use.
Get the spreadsheet from the Construction page on the Wiki, read the entire page, then fill in the info you know.
Then let us know the values

RA: 400, 32, 3, 130 = steps per degree?
DE: 400, 32, 3, 65 = steps per degree?

We will discuss the values when you know what the last number for each axis is (worm wheel teeth).

Do these drivers also need to be powerup from the motor before connecting the USB for programming?
The drivers are not programmed at all. They are plugged into the RAMPS board, and jumpers underneath them.

Also, regarding the motors, why is necessary to adjust the current? 
There is a page on the Wiki on Stepper Driver Adjustment. Read it.


Pedro Miguel Barbosa Moutinho Nunes dos Reis
 

On Thu, Nov 26, 2020 at 02:15 AM, Khalid Baheyeldin wrote:
We will discuss the values when you know what the last number for each axis is (worm wheel teeth).
OK... need some help here. What I know, for the EQ3-2, is:
                                            RA.        DEC
Worm Gear Ratio 130:1 65:1

Also, I bought 15 teeth pulleys for the motor and 40 teeth pulleys for the mount.
The belts have 61 and 63 teeth.

How do I calculate the gear reduction values?
and, what are the stepper steps?
If is available a wiki with this just point me there ;)

thanks



Khalid Baheyeldin
 

The lines in the spreadsheet are:

Axis 1:
GR1 = 40/15 = 2.66667
GR2 = 130

Axis 2:
GR1 = same if using the same pulleys
GR2 = 65

So your spreadsheet lines will look like this for TMC2208, which are limited to 16 microsteps.

400, 16, 2.66667, 130 = 6162.970
400, 16, 2.66667, 65 = 3081.485

400 = steps per rotation for a 0.9 degree motor

Ignore steps per worm rotation for now, use 0 for that.

Slewing speed, set it to 2.0 for now.

The overall steps per degree are below the recommended 12,8000 if you want to do imaging.
If you only want to use for visual, then the above may work.

Again, since you have the parts, just try them out. There is nothing to lose, and you can
swap components later if you want to improve things.


Pedro Miguel Barbosa Moutinho Nunes dos Reis
 

Thanks for the explanation on how to fill the spreasheet.

On Thu, Nov 26, 2020 at 03:08 AM, Khalid Baheyeldin wrote:
Again, since you have the parts, just try them out. There is nothing to lose, and you can
swap components later if you want to improve things.
Yes, I'll do it. Just waiting for the belts and pulleys,,, 
I think I have another pair of drivers, don't remember which... I'll look for them.
Thanks