Arduino focuser (myFocuserPro)

[bojan]

Originally Posted by Sunfish

... Is there focuser control under Onstep that could manage a stepper motor for focus?

Because OnStep uses Arduino stepper drivers (STEP/DIR) for 4-wire steppers, and this motor has 5 wires (two coils with joined middle contacts) so you have to modify it first, by opening the blue plastic cover and add middle wire for another coil (after cutting the connection between coils)).

Then you can use only 4 wires (1/2 coil, Red-Blue and Black-Orange wires for 5V, the whole coils for 12V) to connect the motor to driver.

See details here and here.

[ChrisV (Chris)]

Works a treat. I've converted a few of these and other 5-wire stepper motors like this then run them on drv8825s tmc21xx drivers

[Sunfish (Ray)]

Thanks Bojan,
Interesting details.

R.

[QUOTE=bojan;1580106]Because OnStep uses Arduino stepper drivers (STEP/DIR) for 4-wire steppers, and this motor has 5 wires (two coils with joined middle contacts) so you have to modify it first, by opening the blue plastic cover and add middle wire for another coil (after cutting the connection between coils)).

[bojan]

*.stl attached (2 versions + update).

[Leo.G (Leo)]

Interesting project overall!


What is the quality of the 3D printed gears in this project?
Not so much as in what is the quality and reliability of your work but in printed gears overall?
If I ever get to welding up the frame I have a milling machine here and a new cross slide table for it and I'd likely be more inclined to machine alloy gears but 3D printed would be so much easier (were I to get a 3D printer that is). I have a few telescopes I want to do electronic focusers for.


You make mention of an encoder, what type have you used for this project?
I recently purchased 6 very nice quality units from AliExpress quite cheap (compared to RS components) for another project my son is playing with and I'd like to incorporate one with a focus motor for repeatability. I know there's the 2 types, mine would be the cheaper type, incremental. I'd like some Absolute encoders to play with, I should check AliExpress come to think of it.
Though a remote focus unit I purchased used on here has the incremental encoder and it works OK except when I'm trying to use my phone to control the thing.
The only mobile phone screen I could actually consider useful would have to be 55" minimum, my eyes are far from good. Then it wouldn't be quite so mobile I guess.

[bojan]

Leo,

Printed gears are quite adequate for this particular purpose (and many other).. and I am perfectly happy with their performance as part of this focuser (where there are no heavy loads - remember, this is plastics.. and printing is not as good as molding ).
Of course, when in doubt, the best approach is to try and see for yourself ;-)

As to encoder as additional input to focuser controller, I used similar to this one from ebay. It is incremental and I use it very occasionally (mostly I focus via USB).. More often, when I need to focus my C11 between presence of FR and native FL, I simply disengage the gears (by rotation motor bracket) and focus manually (as designed by Celestron).

[Leo.G (Leo)]

Thanks Bojan!
I would guess they are suitable because under general use there's not high torques required. Though that too would depend on whether viewing or imaging as far as load goes.
I would imagine it's also easy to print a spare when doing them (or sometime after) just in case and it's not going to cost a fortune.