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New guy considering an LXD55 OnStep mod

Greg Baggs
 

Hello All, I'm literally starting at square one and have some small amount of experience with electronics and arduino. I have a mechanical engineering background and I've been a serious amateur astronomer for over 10 yrs but have been away from observing for several years. I'm considering modifying my old LXD55 mount to OnStep as my old 497 Autostar controller is kaput.

I don't expect to be spoonfed I'm just looking to get an idea how much will be involved in this project. I would like to use my original DC gearmotors and encoders if possible but I've only seen stepper motors being used in some of the example projects. I am also thinking of using the OnStep app and Stellarium on an android tablet and also possibly a standalone simple controller box just for easy tracking and slewing. Does anyone know if using the original DC RA/DEC motors will be possible or if I will have to replace them with steppers? I'm just trying to avoid mechanical modifications as much as possible and stick to the electronics only. Any other beginner pointers on how to start would be appreciated. 

Cheers, Greg

Alexander Varakin
 

I modified my LXD55 to use OnStep and it is working much better than the original system - it has lower noise, goes to target directly (LXD does it in a roundabout way) and with bluetooth adapter, I can control it with Arduino and SkySafari.
Unfortunately, you can not use original motors, it has to be steppers.
You need to implement GT2 timing belt pulleys with about 2-3 reduction rate and build some fairly simple brackets for connecting the motors. I used 3mm AL plates for the brackets.
It is one of the simpler OnStep builds. 
I used MKS Gen L 1.0 controller and DRV8825 drivers and the mount runs 9.25" SCT for visual.
Make sure you get decent larger Nema 17 motors.

Greg Baggs
 

Thanks for the info Alexander. Should drive my 8in SCT just fine. 


On Sat, Jun 27, 2020 at 9:17 PM Alexander Varakin <avarakin@...> wrote:
I modified my LXD55 to use OnStep and it is working much better than the original system - it has lower noise, goes to target directly (LXD does it in a roundabout way) and with bluetooth adapter, I can control it with Arduino and SkySafari.
Unfortunately, you can not use original motors, it has to be steppers.
You need to implement GT2 timing belt pulleys with about 2-3 reduction rate and build some fairly simple brackets for connecting the motors. I used 3mm AL plates for the brackets.
It is one of the simpler OnStep builds. 
I used MKS Gen L 1.0 controller and DRV8825 drivers and the mount runs 9.25" SCT for visual.
Make sure you get decent larger Nema 17 motors.

simpsonj@...
 

Have you posted any photos of your LXD55 conversion?  I have an LXD75 (very similar) that might be a good candidate for an on-step setup.  Thanks in advance.

Greg Baggs
 

I haven't even started a conversion yet - that was my first post. I was mainly looking to see if I could use the original dc ra and dec motors but it seems OnStep is designed for stepper motors only. I may still go ahead with the mod but I am only getting my head around it at this point. The first project in the wiki is by a guy named alex who modded a skywatcher EQ mount should give you some ideas. Cheers


On Sun, Jun 28, 2020 at 4:30 PM simpsonj via groups.io <simpsonj=verizon.net@groups.io> wrote:
Have you posted any photos of your LXD55 conversion?  I have an LXD75 (very similar) that might be a good candidate for an on-step setup.  Thanks in advance.

George Cushing
 

Working on a conversion for s Vixen GP, basically the same thing. Budget $100-135. The more you DIY the less it costs. As always, time vs. money. 

Though I posted these, but I don't see them.



These were made of 1/8" by 2" by 2" angle and 1/4" by 1" bar. Motors are NEMA 17. Waiting on 48 tooth pulleys for the final belt length is determined.

Greg Baggs
 

Looks good George and motors/brackets are smaller than I imagined. Not much bigger than the original motors really. Your mount does look very similar to the LXD55 for sure. Thanks for the pics looks easier than I was expecting. Greg


On Sun, Jun 28, 2020 at 9:38 PM George Cushing <pinyachta@...> wrote:
Working on a conversion for s Vixen GP, basically the same thing. Budget $100-135. The more you DIY the less it costs. As always, time vs. money. 

Though I posted these, but I don't see them.



These were made of 1/8" by 2" by 2" angle and 1/4" by 1" bar. Motors are NEMA 17. Waiting on 48 tooth pulleys for the final belt length is determined.

Dave Schwartz
 

Yup... pretty much the quintessential way of doing an EQ-5-like mount. Very neatly done.

On 2020-06-28 8:08 p.m., George Cushing wrote:
Working on a conversion for s Vixen GP, basically the same thing. Budget $100-135. The more you DIY the less it costs. As always, time vs. money.

Joe
 

3D printing is also a good option. John S. from this group kindly printer and redesigned some stepper mounts for my Vixen GP. I’ll be posting for the showcase page with specs this week..

Rafael Barberá Córdoba
 
Edited

These were made of 1/8" by 2" by 2" angle and 1/4" by 1" 
Those aluminium brackets looks really good. I've 3D printed mines and it ended been too fragile. On the RA one I can see how the tension from he screw has started to separate the plastic layers.

George Cushing
 

You can buy similar Chinese brackets in steel for a few bucks, but they are heavy and I'm cheap. The engineering of the motor positioning is probably the most difficult part of any conversion, but the path for the Vixen GP and it's copies is pretty well worn.

Forgot to mention that the sale of your Meade motors and their housings will finance most of this project. I sold the last of my working LX-55/75 Autostar items a couple years ago and I still get requests for parts. I sell them on conversion to OnStep. I'd think a working set of LXD55/75 motors would go for $100 on Cloudy Nights.
.
The motors are from Hetai Electronics They are most similar to their 42BYGHM805 model. Hetai BYGHM series
I picked up ten on eBay for $8 a piece last year.

Drew 🔭📷🚴‍♂️
 

On Mon, Jun 29, 2020 at 08:35 AM, George Cushing wrote:
You can buy similar Chinese brackets in steel for a few bucks, but they are heavy and I'm cheap.I
Honestly George you CB! I get them for less than $2 each. From a design standpoint they are the solution when using 3D printed interfaces. Here is one version I am currently working on. I will post my designs and files in the "Files" section as I get them finalized.

Dan Sawyer
 

What S/W do you use for layout? I have fabricated aluminum plates to mount my motors. They run smooth, however there is some vibration and occasional harmonic. I suspect plastic would be far quieter. Thanks Dan

On 6/29/20 7:06 AM, Drew 🔭📷🚴‍♂️ wrote:
On Mon, Jun 29, 2020 at 08:35 AM, George Cushing wrote:
You can buy similar Chinese brackets in steel for a few bucks, but they are heavy and I'm cheap.I
Honestly George you CB! I get them for less than $2 each. From a design standpoint they are the solution when using 3D printed interfaces. Here is one version I am currently working on. I will post my designs and files in the "Files" section as I get them finalized.

Rafael Barberá Córdoba
 

Yes I'm using a similar approach Steel Chinese brackets and 3D print adapters. But, the plastic is not the best material to bear the traction that the nuts are applying :) 

Khalid Baheyeldin
 

Regular PLA is too soft for this.
There are other materials that can do the job.
For example ABS, or one of the newer composite filaments.

Drew 🔭📷🚴‍♂️
 

I am using FreeCad for the most part. The proper bracket design and material is essential for success. I am using ASA currently. Other materials do not have the strength or resistance to the elements that this requires. Composites (carbon fiber + plastic) require their own design approach. You cannot just simply print any design in composite. Many of the existing designs will delaminate over time.

There are 3D printable vibration reducing spacers. There are commercial versions of these also if I am not mistaken. Using vibration spacers and/or a design like mine with a plastic element can eliminate or reduce that annoying harmonic.

Drew 🔭📷🚴‍♂️
 
Edited

I should add that I have printed and experimented with all of the 3D printable LXD55/75 bracket designs I could find. The one I have shown is the most promising design so far.