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cjdawson

Arduino focuser for Meade LX-90?

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Hi all.  Over the last few months, I've seen a few posts go up about building an electric focusser.   currently, I've got an electric focusser the Meade #1205.   however, it's a simple DC motor and doesn't use a stepper motor.   So that means that I can't use it with SGPro.

I've had a look around the web and havent really found anything suitable for my scope.  The Pegasus Cube looks interesting, and they have done some tests connecting it to an LX-90 classic.  The design looks good, however, I don't really fancy spending £250 on what is essentially some cheapish parts and some bent metal.

 

For the control, I figured that I could use

 

At first glance it looks idea.

 

i'm thinking about using the 5V or 12V version of the 28BYJ-48  as I already have one of each. Would be great if I can power everything from my USB hub.

looking at this video the it looks like it's possible to power everything over USB, no need for extra power.    As I'm looking to control my SCT focus knob, there's no need to worry about having enough torque, or holding power, the camera gear isn't connected to the focuser.

https://www.instructables.com/id/Arduino-Nano-and-Visuino-Control-Stepper-Motor-Wit/

 

The meade #1205 focusser had a kit that connected everything neatly.   One of the parts, which I'm going to re-use is a toothed collar that fits around the focus knob.

There is a metal gear on the focus motor that connects to this, and meshes.     Would be great if I can find a gear wheel that will work with this.

What I like most about the BYJ design is that the shaft can be mounted facing toward the scope, so that the moving parts are not seen as easily.  

 

I think the hardest parts of this project will be to build the bracket to mount the motor onto the telescope.

I'd also like to be able to enclose the stepper, and the other electronics in a small box, so that only a usb cable needs to be added.

Another thing that I'm considering is whether to try to design in some kind of mechanism to allow the motor to be easily dis-engaged allowing access to manual focusing.

 

First things first though.  I'm going to break out the breadboard and see if I can get this working on a test bench.  Then it'll be time to think about wiring everything up properly.

 

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Sorry for the repeated link, Julian beat me to it. :BangHead:

Well it endorses Rob Browns site, doesn't it :)

Steve

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Yep. that's the kind of thing that I'm thinking to drive the stepper.  And yes, I will be looking to add a temperature probe too.  Don't know how it helps, but it'll be there for a reason, so more the merrier :D

 

Been thinking about the disengagement feature that I want.  What I'm thinking is that the bracket will be in two parts.   First will be bolted around the focus knob.  This will hold the focusser on the scope.

The second part will be connected to the first using thumb screws/wingnuts. The first plate will have countersunk screws pushed through from the reverse side, these will be welded/screwed/glued in place so they don't spin.    The second plate will have slots, which will allow the motor to move.  The thumbscrews will be used to hold the two plates together with the gears either together or apart.   Should be fairly simple any effective.   Quickly undo the screw and hey presto manual focussing possible.  Do it up again and electric focusing engaged.

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There’s a thread on cloudy nights google pnp  focuser https://www.cloudynights.com/topic/594658-pnp-focus-the-simplest-ever-arduino-focus-controller/  I looked at doing it but bought a deep sky dad autofocus unit instead £120 ish https://deepskydad.com/autofocuser compact and works a treat I know sometimes it’s nice to make something and see it working , I took the easy option 

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+1 for Roberts offering - only I use direct connection no belts for better control IMHO. You can then use any software or system that has Moonlite focuser support - Indi,Ascom,etc

The only negative,IMO, is I prefer Accel Stepper Library which gives neater code , is far more flexible and has more inbuilt functions but is a relatively simple mod to Roberts excellent code.

You can go a bit further if you want and use Wemos D1 Mini Pro instead of Nano and the like - this will give you one less wires if you decide to use 12v stepper.  Or just use Roberts Wireless version.

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1 hour ago, bottletopburly said:

There’s a thread on cloudy nights google pnp  focuser https://www.cloudynights.com/topic/594658-pnp-focus-the-simplest-ever-arduino-focus-controller/  I looked at doing it but bought a deep sky dad autofocus unit instead £120 ish https://deepskydad.com/autofocuser compact and works a treat I know sometimes it’s nice to make something and see it working , I took the easy option 

Had a look at that and its code - Looks very like Robert Browns Arduino code for the Nano(The set up excluding box/adapter is the same Nano plus DRV8825 controller) - hope its not a case of plagiarism  for profit.?

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39 minutes ago, stash_old said:

Had a look at that and its code - Looks very like Robert Browns Arduino code for the Nano(The set up excluding box/adapter is the same Nano plus DRV8825 controller) - hope its not a case of plagiarism  for profit.?

 which one the CN one or the DSD one 

Edited by bottletopburly

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1 hour ago, stash_old said:

Had a look at that and its code - Looks very like Robert Browns Arduino code for the Nano(The set up excluding box/adapter is the same Nano plus DRV8825 controller) - hope its not a case of plagiarism  for profit.?

Hi All,

DSD here. It is true that I based my first protoype on some parts of Robert's code and it was initially only for my personal usage and for a few of colleaguse free of charge + it is open sourced under MIT license on Github (that is what you checked out, DRV8825 version).  I learned a lot from it.

Because of potential heating issues with constant current in DRV8825 I tried to roll on my own. Equiped with understanding of Arduino framework and stepper motor basics to offer people budget version of autofocuser, I switched to stepper driver with digital current contorl. So the autofocuser I am selling is actually based on MP6500 Pololu stepper driver, which is not even a part of  HW in Roberts project. But It is true that code is somewhat similar, because I did not write it from scratch.  So I don't deny it does look like plagiarism if you quickly browser through the code, but the finished version is actually a result of hours and hours of tweaking firmware, writing ASCOM driver (writtten from scratch), testing with SGPro under sky, designing many variations of 3d printed housings and adapters... all in good faith to try and offer people a budget, stable product for their hobby. It is not a "copy paste for money" but an honest attempt to contribute to astronomy community.

The profit from this is not big, it is not something I live from. But it does cover my expenses (material, shipping, time and website hosting) + enables me to buy piece of gear every now and then. But your post is kind of a wake up call -  this is a potentially problematic legal issue and I am already developing the Autofocuser 2 which will be written from scratch and based on ESP32 + MP6500 .... so I might stop the production of Nano based version because of this risk....

The ironic thing is, if I did not share my experience and code on GitHub, nobody would even care that I learned from the Roberts project... but I guess that is beside the point :) 

Best regards,

Pavle

Edited by sunka

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1 hour ago, sunka said:

Hi All,

DSD here. It is true that I based my first protoype on some parts of Robert's code and it was initially only for my personal usage and for a few of colleaguse free of charge + it is open sourced under MIT license on Github (that is what you checked out, DRV8825 version).  I learned a lot from it.

Because of potential heating issues with constant current in DRV8825 I tried to roll on my own. Equiped with understanding of Arduino framework and stepper motor basics to offer people budget version of autofocuser, I switched to stepper driver with digital current contorl. So the autofocuser I am selling is actually based on MP6500 Pololu stepper driver, which is not even a part of  HW in Roberts project. But It is true that code is somewhat similar, because I did not write it from scratch.  So I don't deny it does look like plagiarism if you quickly browser through the code, but the finished version is actually a result of hours and hours of tweaking firmware, writing ASCOM driver (writtten from scratch), testing with SGPro under sky, designing many variations of 3d printed housings and adapters... all in good faith to try and offer people a budget, stable product for their hobby. It is not a "copy paste for money" but an honest attempt to contribute to astronomy community.

The profit from this is not big, it is not something I live from. But it does cover my expenses (material, shipping, time and website hosting) + enables me to buy piece of gear every now and then. But your post is kind of a wake up call -  this is a potentially problematic legal issue and I am already developing the Autofocuser 2 which will be written from scratch and based on ESP32 + MP6500 .... so I might stop the production of Nano based version because of this risk....

The ironic thing is, if I did not share my experience and code on GitHub, nobody would even care that I learned from the Roberts project... but I guess that is beside the point :) 

Best regards,

Pavle

Then at least say so in your code !  - sorry you are wrong IMHO - its not "somewhat similar" the action codes "SP etc" are a copy of Robert's Arduino code no matter how you disguise it !

I applaud you for coming clean but you could probably sell the items such as adapters/box's ,useful as they are , as there are without infringing Copyright

You also removed the references to Roberts Code on your original web site - that looks like you are trying to hide something IMO.

Sorry  IMHO its  stealing !

Nothing wrong with learning from someone else's code  and creating your own but as I say its not in the nature of what is meant by "Open Source".

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Either way, I don’t want o get involved in that debate.    I’m trying to build a stepper based focusser here for m6 own use.

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3 hours ago, stash_old said:

Then at least say so in your code !  - sorry you are wrong IMHO - its not "somewhat similar" the action codes "SP etc" are a copy of Robert's Arduino code no matter how you disguise it !

I applaud you for coming clean but you could probably sell the items such as adapters/box's ,useful as they are , as there are without infringing Copyright

You also removed the references to Roberts Code on your original web site - that looks like you are trying to hide something IMO.

Sorry  IMHO its  stealing !

Nothing wrong with learning from someone else's code  and creating your own but as I say its not in the nature of what is meant by "Open Source".

Firstly to the OP - sorry for hijacking this thread. This is my last post in the thread, stash_old we can continue via private messages or new topic if you have any more comments/questions. Back to the copyright infringement.

I have added credit to Robert on the top of the firmware code at the moment and I have also contacted the Robert about this directly, asking his permission (waiting for response). It just seemed to me that the actual firmware is simple enough and customized to my hardware so I felt no need for reference. Lesson learned.

But as you especially pointed out serial protocol:

1. starting commands with ":" and ending them with "#" is standard procedure, its not Roberts invention (i've used that before for telescope controller firmware, it originates with Meade I think https://www.meade.com/support/LX200CommandSet.pdf)

2. commands with 2 letters are standard procedure...

3. The actual set of commands is required by the ASCOM interface protocol and not something Robert came up with, see ASCOM docs for reference: https://ascom-standards.org/Help/Platform/html/T_ASCOM_DeviceInterface_IFocuserV3.htm

4. In regard to specific serial protocol commands you are mentioning - if you'll check further you'll see that in prinicple this is a Moonlite compatible protocol that is implemented by most DIY focusers - so as such can't be a matter of Robert's copyright. For example you can check, the other "Open source" link in this thread (PnP focus). It uses same commands.

I hope this clarifies the matter at hand.

Best regards,
Pavle

 

Edited by sunka

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3 hours ago, cjdawson said:

Either way, I don’t want o get involved in that debate.    I’m trying to build a stepper based focusser here for m6 own use.

OK no problem - sorry for the hijack !

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After doing some more looking I've decided that I would prefer to go with the Arduino ASCOM Focuser Pro2 DIY from brownrb.   Overall looks like the more rounded of the projects overall.

My arduino's arrived, got 3 of them.   And I've just ordered the PCB's.  The rest of the kit I'll get over time.  I'll be looking to build three of these focusers.  Why three, one for my LX-90, one for my ST-80 and another, because I can.    Not sure what I'll do with the third one yet.  I'm sure that I'll some up with something useful.

 

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Making progress on my focusser.

Got the Ardunio, stepper driver in place.  Wired up the Red, Green and Blue LED's, the two manual focussing push buttons.   Added loads of headers, ready for the rest of the parts.

 

Decided to modify my original plan of using it USB and I'm going to try to get the bluetooth module working.   Just waiting now for the rest of the parts to arrive.

IMG_2398.thumb.JPG.26ebd3f23c97ab61c46c06fada5cd14d.JPG

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Posted (edited)

just in case anyone thinks that I've abandoned this probject. Actually, it's making progress.

 

I've got it working, via bluetooth.   I'm running a NEMA 14 motor with 400 steps per rev.   There's a belt pully with a 4:1 ration, so 4 motor turns is one focuser turn.  The big wheel on the pully, I had custom made with a 22mm Bore, this will fit over the LX-90 focus knob with a snug fit.

 

Still to do to complete this project...

Mount the circuits in a Hammod project box.

Build a mount for the motor to attach to the scope.   So start this, I have a NMEA 14 L Bracket attached to the motor, and a piece of 2mm Alu, 40mm width and 1 meter length.   The plan is to make an L Bracket that will slip over the focus knob and attach in place of the existing electric motor bracket.    This will then attach to the motor mount.   still need to figure out how to tidy up the motor wires.  Will probably end up mounting a small box to the bracket for the GX16 socket to be mounted, and provide a space to put any spare motor wires.

Edited by cjdawson
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Spurred on by getting the circuit working, my attention has now switch to the mounting

 

Here's my focus controller in all it's glory.  There's no access to the USB port, as I'll be connecting via bluetooth.  On the left side of the box is a 2.1mm DC power socket, and a GX16-7 which is to connect both the motor and the temperature probe.    I did make up a 5 meter cable, but the temp probe didn't like it.  I built up a shorter 1.5 meter cable and everything is working great.

IMG_2443.thumb.jpeg.d6d6f7df310fb9c98583d21385e4236a.jpeg

 

My attention has now shifted from the controller box, so the telescope side.   The plan is to mount the motor so that the base is away from the user, and the pully is in line.  Here's the large gear wheel seated on the focus knob.

IMG_2444.thumb.jpeg.a4e34253ac063873516c99e72c78f072.jpeg

 

And the only points I have to mount to the scope is around the focusser itself

IMG_2445.thumb.jpeg.f8af4a84f985d413be5c5c3e38b11d2f.jpeg

 

My plan is to drill a 22mm hole in a piece of aluminium then drill smaller holes to make a bracket that will fit snug over the focus knob, this will then be held to the scope by the existing three screws.

The piece of alu, will be bent to form an L-Bracket, to which the motor mount can attach.  This should bring everything in line and make for a neat mounting.

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Just taken delivery of a complete set of belts of my 4:1 ratio pully.  At first offering up, looks like I’ll be using a 120mm belt, possibly a 130mm.  Either way.  Just need to make up the bracket so that I can mount the motor near the focusser.  Still not 100% sure how the bracket will look.

This project is getting closer :)

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