Remote controlled etalon angle adjuster ...

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Remote controlled etalon angle adjuster ...

Post by rsfoto »

... Project in Progress ... which will be available to any interested soalr imager here. I will also need some help ...

Hi,

Some avid readers of Solar Chat know that I developed a fancy remote controlled fine adjustment for my double stacked Original Coronado SM 60 etalons. I finished the original first working example on December 16th 2012 (9 years ago :o ). In those days 3D plastic filament printing was starting to appear and 3D printers had a cost of About US $ 2,000.00 (https://en.wikipedia.org/wiki/3D_printing#2000s) and so I made them out of Aluminum using a milling shop in Mexico City.

Eta-Mot_et1.jpg
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Eta-Mot_et2.jpg
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Nowadays 3D printing is nearly in everything technical minded home and huge amounts of plastic is melted and modelled into thousands and thousand of differente parts be them just pretty, crazy and somtimes useful.

Inspired by the post here viewtopic.php?f=9&t=33970 I thought, why not develop an easy adapter for a stepper motor for remote angle adjustment for etalons. At the moment only possible from my part for the open Coronado etalons. Unfortunately the Lunt etalons are closed on the outside and so no access to both rings. Look at the next image of what I mean ...

Double-Stack-Filter-50F-Vertical.jpg
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Now I started with some ideas already and now after getting the stepper motor with 20 steps per revolution and a pitch of 0.5mm which means a single step is moving just 0.025 mm I can continue with my design of the upper and lower part. I bought this stepper here in Amazon Mexico.

Eta-Mot_08.jpg
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This is for Coronado SM 60 etalons. The change for SM90 or SM 40 should be easy as the golden wheel is the same on all just need to know two diameters and adapt them.

Below some images of the rings, the first prototype parts. Any questions are welcome. The 3D files for printing will be available FOC but donations are welcome in order to cover up a bit the cost for the stepper motor I had to but (approx. US $ 20.00). I know this stepper motor arrangement is possibly not available everywhere but I am willing to adapt the design to other stepper motors.

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Eta-Mot_07.jpg
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The drive of the stepper motor is an easy solution using an Arduino with a piggy back breakout board as well as some A4988 drivers. A friend and I already have a written program for a focuser using an Arduino and it is ASCOM capable which at the end is not necessary in this case. We can easily step down the program a little in order to make it more user friendly. It is just a question of having the ability to drive the motor forward or backward. Perhaps some keen programmer integrates this into an SSM ¿? :shock: :o :shock: :o

As written somewhere before. Any questions or ideas are welcome

regards Rainer


regards Rainer

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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

I had fun all day and here is the first prototype with bith pieces for a Meade / Coronado SM 60 etalon.

I know some people will say the lead screw in length is overkill and I fully agree as my plan is to cut it off, but after disassembling the whole Enchilada it is not going to be easy ... as on both ends the lead screw has a bearing in form of a single ball with a diameter less then 1 mm. On the other side as it is only a prototype there is still room for searching for a shorter lead screw which of course would mean to redesign bot parts but that helps me practice and understand better FreeCAD ...

Eta-Mot_09.jpg
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Eta-Mot_10.jpg
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Eta-Mot_13.jpg
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The angle change per step with this lead screw and 18°/step motor is 0.0129°. Need to compare this with my set up and so I can judge if it is OK or if there is a reduction gearbox necessary. ;)

As far as I can judge there is zero play in the rider on the lead screw.


regards Rainer

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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

Very good Rainer!


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Re: Remote controlled etalon angle adjuster ...

Post by Bob Yoesle »

Awesome!

Thanks Rainer :bow


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Re: Remote controlled etalon angle adjuster ...

Post by christian viladrich »

Excellent ! Thanks for sharing.


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi Mark, Bob and Christian,

Thanks. I have been looking for other type of stepper motors but hard to find a different one. 80 mm of lead screw from which we need not more then maximum 3mm :lol:

Also a lot of the stepper motors at the Smiley company do not have any specifications ...

Work in progress ... :seesaw


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

Yesterday I finished another Prototype being a little sturdier ...

BTW it looks like a friend found a way to remotely adjust the LUNT filters, have not seen it, but so far it looks like he just added the Coronado rings ... Waiting for him to send me some images ...

Work in Progress ... :seesaw

Eta-Mot_14.jpg
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Eta-Mot_15.jpg
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Eta-Mot_16.jpg
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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

Interesting to see, it is developing well Rainer!


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

First test and sorry for the bad quality of the focus


https://rainerehlert.com/00_SCHForum/20 ... ter_v1.mp4


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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

That works well!


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

marktownley wrote: Tue Dec 21, 2021 6:39 am That works well!
Hi Mark,

Thanks. The only nitbit is that that motor gets very warm. You can not even touch it with your fingers and I do not know why.

It is specified to be a 12V motor with 800mA per phase. We adjusted correctly the A4988 driver as per the instruction and formula.

Interestingwise the seller specifies a Motor surface temperature of 80°C. :?

The second test will be done with the famous Stepper motor 28BYJ48. This Unipolar motors can also be driven as Bipolar motors by just cutting away the common and splitting the copper on the motor PCB. :mrgreen:

Motor_Etalon.JPG
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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

Maybe the surface of the motor is designed to work as a heat sink? The fact is being specified at 80c so is normal I guess...


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

marktownley wrote: Wed Dec 22, 2021 6:58 am Maybe the surface of the motor is designed to work as a heat sink? The fact is being specified at 80c so is normal I guess...
Hi Mark,

Strange because I have worked with other type of Stepper motors and none gets as hot as this one ¿? Maybe I need to implement in the program the ability to just shut down current when motor is not working ... Will talk to my friend who is writing the program and the GUI

Any volunteer with programming skills willing to write a little simple program for this project using an Arduino ?

Thanks


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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

Not me i'm afraid Rainer, not worked with Arduino before.


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

Second version is ready and now I need a simple program for the control. At the moment I am controlling it with a focuser control program.

This type of motor makes 2048 steps for a full turn at the output. I used a M3x0.5 screw which means 0.5 mm / 2048 steps is a resolution of 0.000244 or 0.244 micron :o and this would correspond to an angle change of 0.079' arc minutes.

This motors warms up to about 50°C

The first version with the long lead screw has a weight of 70g and this scond version has a weight of 50g

Below some images and a video. The video was set to 200% in order not to make it too long. For 2048 steps it takes about 21" = 0.5 mm movement

https://vimeo.com/659767646

Eta-28BYJ_17.jpg
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RZ_Focus.JPG
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regards Rainer

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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

Looking for more solutions reading the internet I found out that one can modify Servomotors used in RC models and make them rotate 360 degrees continously in both directions.

So I bought some of them and made the 3rd version which is the cheapest but the worst solution as one never knows where the motor really is and even this tiny servomotor SG90 has a torque of 2.5 kg/cm and as I am driving it axially right through the center with a lever of 1.4mm the force is " brutal " :mrgreen: but that would be no problem as I mentioned before one never knows where the motor really is unless on is sitting just beside it and watch the angle of the rings.

I tried to stop the rotation with the fingers on the screw, impossible and making the calculation there is a force of about 17.85 kg on the screw teeth if my calculation is correct.

One just needs four 1.2V batteries or a 5V wall power, one servo tester and a micro servo for modfying or buy already a continuous capable Servomotor (half of the tinkering fun)

Below some images and a video of it working (again sorry for the unsharpness but as it loks like I am not able to take a sharp video :lol: )

Eta-SG90-360_20.jpg
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Eta-SG90-360_21.jpg
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I doubled the speed of the video as it was 1 minute long and now it is just 30 seconds.


https://vimeo.com/660732361


OK, I guess this is my adventure in doing some etalon adjusters and now I need to find a solution for a still to find new problem or task.

¿ Maybe a Cloud Blower ?


Happy New Year 2022 and hopefully a better one then the past poopy 2021 :bow2 and hopefully some day of the next year the Palm tree just disappears miraculously :cool: or " Divine " intervention ...

regards Rainer
Last edited by rsfoto on Sat Feb 19, 2022 7:57 pm, edited 1 time in total.


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Re: Remote controlled etalon angle adjuster ...

Post by marktownley »

It looks a tidy package Rainer!


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

marktownley wrote: Wed Dec 29, 2021 8:07 pm It looks a tidy package Rainer!
Hi Mark,

If you mean the 3rd version yes but as I said I do not see a bright future for that solution ... unless I can somehow slow down the movement of the servo rotation.

A possibility for that is to integrate a LED which signalizes the lowest position and so the upper movable ring does not crash into the lower fixed ring ...

This would mean a micro switch fed by the power line to the servo ... and an actuator which activates the LED ...


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Re: Remote controlled etalon angle adjuster ...

Post by rsfoto »

Hi,

Made a cost calculation for the 2nd version and for about US $ 29.00 (Arduino UNO, Motor + ULN2003 diver break out board and 3D print) one could have a nice adjuster, software cost not included but there are many examples for programs which can be used and modified. I assume everybody here has a friend who knows hosw to prgram Arduino and GUI.

In the case of my software I need a CNC shield and that one costs about US $ 15.00 and the software with or without modification would be free :mrgreen:

Arduino US $ 25.00 - 30.00
Motor US $ 2.00 (packages of 5 motors and 5 ULN2003 break out boards cost US $ 10.00)
3D print about US $ 2.00 (that would be my printing cost)

This solution is for Meade / Coronado filters as fot the lunt filters we need a set of rings and I do not know if Meade / Coronado still them as spare part as I got them 9 years ago.

If I put that in relation to the ceapest cost of an Meade / Coronado etalon scope or just filters

https://optcorp.com/collections/solar-t ... ter-w-bf15 = US $ 1599.00

we are talking about an investment of ~ 2% and according to the highest price maybe a

https://optcorp.com/collections/sun-sol ... scope-30mm = US $ 7999.00

it is an investment of ~ 0.5%

Now this is the DIY and now imagine if a company makes hundreds of it the price could be the same, the whole execution more professional and better looking. If I buy one motor or one hundred of each I get them much cheaper.

Is it not interesting that a Solar Ha telescope cost that much and not a single company has made a simple etalon adjuster instead of the stupid golden wheel driven by a finger ...

Happy New Year 2022


regards Rainer

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