Which cheap stepper-motor based focusers?

[michaelmorris]

My current imaging rig includes a 66mm apo and an 80mm apo.  Both have Skywatcher 'Autofocuser'  focus motors - this is serving me fine at the moment. However, I am hopefully soon to upgrade form a DSLR to a CCD  and I can see a day that approaching when I'm going to look to invoke computer-controlled automated focussing routines.  From all the reading I've done this is really only practicable when using stepper motors rather than the  DC motors in the SW Autofocusers I currently have.

With two scopes, replacing both motors with offerings from the likes of Lakeside or Seletek is going to cost around £750 to £800.  That's WAY above my budget.

1. Are there (much) cheaper alternatives?
2. Many people have extolled the virtues of Arduino-based systems.  With virtually no programming experience and no time to learn anything but the most rudimentary programming skills, how difficult is it to set up an Arduino-based focuser system?  Also, how expensive is it to buy all the necessary kit to build one?

Thanks

 

 

 

[Dr_Ju_ju]

Hi Michael,

How do you intend to drive the motor? as this will define the requirements... Have a look at the attached which details a control system and makes some reccomendations for steppers.

I use a mixture of NEMA 14\17 motors some with reduction gears, and using direct spindle coupling, some belt driven..

myFocuserPro2.pdf

[michaelmorris]

7 minutes ago, Dr_Ju_ju said:

How do you intend to drive the motor?

ASCOM drivers.

[Dr_Ju_ju]

I meant motor electonics and control, not software control, that comes later... Have read of the PDF

[Davey-T]

There's a very long thread on build your own focuser, pretty easy, must be as I built one 

Will find it

Dave 

https://stargazerslounge.com/topic/218975-arduino-ascom-focuser-mark2/?page=1

https://sourceforge.net/projects/arduinoascomfocuser/files/Mark2/Software/V2.4.0/

[ejp1684]

Add my vote to Davey-T's link. I've built one and it works very well. The author of the project is also very helpful if you have difficulties.

Eric.

[Mike Hawtin]

Michael, I have been using one of these for over a year with no problems.

http://www.teleskop-express.de/shop/product_info.php/info/p6773_USB-Focus-v3-Set--Controller--temperature-sensor--strong-motor-for---1-5-kg-payload.html

Mike

[Jonk]

I second "my focuser pro 2". Find it on sourceforge.

I tried with a cheap byj type motor and all worked fine on the bench until connected to the focuser then it wouldn't move the weight.

I now have an nema17 with 27:1 gearbox and these are only about £30. Bracket is made and just waiting for some long 3mm screws to arrive so i can put it all together and test.

Programming an arduino is easy if you're loading someone else's code, but can be confusing if you dont have the right libraries installed, so read up on this first.

All in all, an arduino nano and driver board is all you need, a bit of wiring, an enclosure plus a 12v power supply and usb cable.

It's all ascom compliant so should work with most ascom focus programs or with the standalone windows software .

[michaelmorris]

Thanks Folks

It looks as the Arduino route would seem to be the only affordable option open to me.  It would come with the advantage that I could start off building a system to run my existing focus motors, https://sourceforge.net/projects/mydcfocuserrelativedcfocuser/  then change over to stepper motors at a later date.

[ChrisLX200]

I've built several of Rob Brown's autofocus kits, they're reliable and simple to build - at least the electronics are simple. You do need some practical DIY ability to fit one to your scope but it's not difficult unless you have 5 thumbs on each hand   Personally I would dive straight in and purchase the necessary geared stepper (the most expensive part) rather than mess with a relative DC motor drive but that's just MHO. Once you have autofocus capability you'll wonder how you ever put up with anything else.

ChrisH

[michaelmorris]

14 hours ago, ChrisLX200 said:

Personally I would dive straight in and purchase the necessary geared stepper (the most expensive part) rather than mess with a relative DC motor drive but that's just MHO. Once you have autofocus capability you'll wonder how you ever put up with anything else.

ChrisH

Hi Chris

What I didn't mention was that my largest scope is an SCT with a Meade zero shift focuser on the back.  This is basically a Crayford focuser with a built-in DC motor.  Replacing this would be pricey.  Building a DC focuser Arduino system should hopefully allow me to start off using the same controller for all three focusers (I wouldn't need to use two adjust focusers at the same time!).  Next I would add a stepper motor board and replace the Skywatcher DC motors with stepper motors.  Finally, once I have saved up the pennies I could replace the Meade focuser with a separate Crayford focuser and stepper motor.