DIY USB Motor Control for Focuser

[safaritn]

Hi all amateur astronomers,

I've got a SkyWatcher Newtonian 200/1000 Telescope on which the focuser is motorized with the following kit :

I want to build a motor controller system with the "AccuFocus" Inside circuit system or use another circuit card to render the focus to be USB controlled.

There is any suggestions ? Thanks in advance.

[Starlight 1]

That look the same as SW auto Focus may the Hitecastro  DC focus  may work with it.

[pete_l]

The first thing I would suggest is to replace the coiled cable with a straight one. I know that those telephone cables are popular with DC motor focusers, but they really are evil and should never have been designed in.

[safaritn]

Thank you for replying :-)

Yes, exactly, the same system that is manufactured by SkyWatcher :

But, although to buy the following motor controller,

 

I want to Diy the same system with accessible electronic components. I have the that it is possible to use the hand controller in the first image in the manner that I change the 2 buttons with electric impulsions transmitted by USB cable.

 

[Dr_Ju_ju]

Have a search for TechyDave's focuser on this site, there is also Mr Brown's @ https://sourceforge.net/projects/arduinoascomfocuserpro2diy  both will be able to drive the motor....

[Starlight 1]

OK this unit is not DIY , but some times cost less in the long run, I am one that like making things,  So good luck and hope it all go well.

Les

[brown_rb]

For a DC motor focuser, try

https://sourceforge.net/projects/mydcfocuserrelativedcfocuser/?source=navbar

At least the motor will work with this controller and software

[SteveBz]

Hi,

  I have this and I have completely automated it with an Arduino controller. 

Here the original board and my first attempt to bypass the power supply:

This was my first successful attempt to replace it with a PWM board:

 

Here is the final setup (Arduino not shown):

The hub also controls the camera exposure, heaters and cooling fans.  Because you can no longer use the manual focus, there is an electronic manual over-ride (that's the toggle switch and the PWM knob on the bottom of the OTA hub.)

The focus has been shimmed to make it easier to use and the couplings have been replaced with better timer pulleys from eBay.

Here is the controlling Arduino, there is a DHT22 on its left to measure temperature for calibrating darks:

It's connected to my laptop with a USB cable and my focusing software is written in Python.

I still use the Bahtinov focus method, I haven't yet upgraded to those sort of "Half flux radius" type algorithms yet, although it's in the plan to do so.

Any questions please ask.

Regards,

Steve

[safaritn]

Thank you SteveBz for your excellent project  I hope for you to success your Half flux radius algorithms in the future.

In fact, that I beleave is to change the minimum connectors and to make easy a circuit to motor controlling.

I have the idea to change the 2 buttons of the manual focus motor controller with 2 electric wires that will be connected in the places of buttons and linked, in the other side, with a type A USB connector. So, the electric impulse provited by typing the button is changed to electric impulse generated by a click on an application button on PC.

Finaly, the attached picture illustrates clearly what I plan to do.

Sincerely,

Hedi

 

[SteveBz]

2 hours ago, safaritn said:

In fact, that I beleave is to change the minimum connectors and to make easy a circuit to motor controlling.

You can indeed change the wiring to the motor.  The connectors are 4P4C, but there are only 2 connections.  I use a standard 2-pin jack at one end and the 4P4C at the other.

The wiring to the USB does not work the way you think.  I too thought it might but it doesn't.  You need to use an optocoupler to switch the connectors.  In fact the motors will accept a 12v supply, which makes it easier than the 9v battery it comes with.  It will work with anything from 6-9v.  It's better to use a pulse-width modulator (PWM) which can operate through an optocoupler or not.

There are many devices that work in a similar way that can be adapted to focusing, a dimmer light-switch, a dew-heater controller, an arduino and PWM from eBay (less than £2.00).

Sadly USB does not connect straight to the switch.

Good luck.

Regards

Steve.

[wimvb]

I did just what you aim to do. Used the SW focus motor and connected it through Arduino to INDI running on a Raspberry Pi. The Arduino sketch I used is based on the MoonLite protocol. No need to hack the controller that comes with the focus motor

 

[SteveBz]

8 minutes ago, wimvb said:

I did just what you aim to do. Used the SW focus motor and connected it through Arduino to INDI running on a Raspberry Pi. The Arduino sketch I used is based on the MoonLite protocol. No need to hack the controller that comes with the focus motor

 

Oh look, you have a ditherbox.  What is that and how does it work?  I'm thinking of implementing software dither, but how did you do yours?

[wimvb]

My home made ditherbox contains a small microcontroller that gets input from the snap port on my (eq3) mount and uses this information to:

A. remotely release the shutter in my Pentax DSLR

B. send a guide pulse to the ST4 input on the mount between exposures to move the target mount about 15 pixels in an outward spiraling pattern.

The reason for this DIY project was that my aging DSLR no longer connects to any computer. Probably a broken usb port. So I can't use camera control software, but use the snap port on the EQ3 hand controller as an intervalometer.

Here's more information: https://github.com/wberlo/AutoDither

 

[safaritn]

Waw ! The are many idea to effectively change the manual focus motor controller with different manners. And, what will to be the finely circuit illustration with these different components (Arduino, Moto Shield, etc.) ? Can I use the USB port to create an ASCOM driver for this project ?

[wimvb]

For mine, I used an arduino uno with the Velleman motorshield. An arduino nano with a smaller motor driver would make it more compact. The skywatcher focus motor uses a 9 V battery, but I think it can handle 12 V as well (I read somewhere that it's a 12 V motor). You can even have speed control through pulse width modulation. The gear has backlash but works with the indi focus module in ekos/kstars without a problem.

[safaritn]

Thank you Dear wimvb.

I don't use INDI library, instead I use ASCOM drivers for all my drivers, like filter wheel, Camera Canon EOS 1100D, ZWO ASI120MM and EQMOD for HEQ5 mount controlling.

[JamesF]

I use a number of these focuser motors, especially for imaging where I don't want to cause vibration by touching the focuser when adjusting it.  I've thought of making them controllable over USB (or indirectly via a USB to serial adaptor, which might be possible to do quite simply by using the serial port control lines to control the motor) before now, but I've decided that if I'm going to end up throwing out most of the components then I might as well start again with something like an Arduino and a stepper motor that allows me to move the focuser by exact amounts and to a specific position.

Of course if you're going to leave things under the control of something as stupid as a computer then you might also want a mechanism for preventing the motor from trying to run the focuser beyond the limits of its travel.

James

[safaritn]

Hi wimvb,

I'm very pleased of your project in this topic and it's very amazing circuit. If I would use this circuit prototype, can I c create an ASCOM driver for this motor controller ? All the components are available for me and it's very easy to implement it.

Your sincerely,

Hedi

[wimvb]

2 hours ago, safaritn said:

Hi wimvb,

I'm very pleased of your project in this topic and it's very amazing circuit. If I would use this circuit prototype, can I c create an ASCOM driver for this motor controller ? All the components are available for me and it's very easy to implement it.

Your sincerely,

Hedi

I've never tried writing a driver. The arduino code I use is adapted from code for a stepper. There is a reference in the header of the arduino sketch (.ino file).

The moonlite protocol that is used is very straight forward: the driver sends a text command to the focus controller, which interprets it and drives the (stepper) motor. The controller can also send data back to the driver. The arduino just replaces or emulates the Moonlite focus controller hardware. I think that it also would work with the ASCOM driver, since the hardware is the same for both INDI and ASCOM. Never tried it, though.

[safaritn]

Thank you very much wimvb ,

I will command the Velleman motor controller shield for Arduino which is MODULE MOTOR SHIELD PONT H L293D. For the other electronic components, I already have them in my possession.

I will return to you if I have any problem, if you accept of course 

Is there any modification in this motor shield or I can use it intact ?

Hedi

[wimvb]

I just use it as it came out of the box.

Good luck with your build.

[safaritn]

Many thanks for your support and encouragement.

After two or three days, I'll received this component and I'll worked hard to get to my project. I'll noticed you for events.

Hedi

[safaritn]

Good morning wimvb,

Is it possible that you communicate me a photo of your Arduino card with the different components linked ?

Thank you in advance.

Hedi

[wimvb]

I'll send you a personal message this evening.

[safaritn]

Thank you very much Dear wimvb