Automating a 2.1 metre Pulsar Dome. Phase One - Dome Rotation

[sloz1664 1,082]

Ever since I purchased my Pulsar 2.1 Metre Dome I've been itching to automate it, to extend my imaging time and increase my sleeping hours. 
The first hurdle was how to mount a suitable drive system to rotate the mount. As anyone who posesses an older 2.1 metre Pulsar dome knows, it is not conjusive to being automated as there is no suitable means of support for driving the dome.

I have decided  to use the Levesdome project route. http://www.dppobservatory.net/DomeAutomation/DomeDriver.php . I have built all the electrics and it works ok.

I am going to drive my dome using a toothed belt mounted onto a wooden shelf attached to the inside of  dome. It will be driven by a heavy duty windscreen wiper motor, with positioning sequenced with a Mouser Encoder. The "wooden Shelf"  or will be segments spanning the 16 flats of the dome, forming a complete circle and fastened from the outside by stainless steel screws. The circumference in which the toothed belt will be bonded, will be machined with a router attached "fixed" to the wall inner rim and  trimmed to size by slowly rotating the dome. After bonding the timing belt in position the Motor will be mounted to the wall inner rim, with the drive gear sprung loaded onto the belt. Hope that makes sense.

The drive belt mount segments were roughly cut to a master segment. They, in turn, will be individually fitted to the dome and it's manufacturing irregularities.

The segments were secured to the dome with 5mm x 40mm long AB point security torx stainless steel screws. Two per segment.

Photo showing the outer shell of the Dome with the torx screws in position.

Photo showing the router mounted in position prior to machining.

 

Now the "shelf / Drive Belt Mount" is positioned, secured and machined. I have now ordered the Timing Belt form Beltingonline. A type T10 toothed belt. 20mm wide & 6.250 metres long.

 

Steve

Edited July 30, 2017 by sloz1664

[JeremyS 1,992]

Interesting project, Steve. I've got one of those domes and have wondered how easy it would be to automate, considering there are no commercially available solutions.

Let us know how you get on.

Jeremy

[skybadger 235]

Interesting approach. Won't the wood rot from accumulated condensation running down the dome onto the flat surface where the wood is mounted ?

I don't understand the need for the wood, others have bonded the belting direct to the inside surface. The trick is to make the motor move to take up the in and out variation. The whole dome can move back and forth an inch or so and will be in a different place in each rotation. 

The approach I have taken for this, since I have what seems to be a copy of a pulsar dome, is to squeeze the motor between the inside lip and outside edge, on an expanding spring to keep the pressure up. The problem is more ensuring motor grip than motor power. You might find that you need another motor at 180 degrees to prevent skew driving increasing the overall friction. Good luck.

Mike

[sloz1664 1,082]

Hi Mike,

Your questions and many other factors have been going through my mind over the last year during my thoughts on how to automate the Dome. To answer your specific questions:-

The wood is to be painted stopping any water ingress and I have no immediate condensation as i have a dehumidifier installed in the dome. The dome is a 16 sided hexadecagon, hence the need for the wooden shelf  to ensure the belt is accurate to the motor and yes there is some Dome movement, although the addition of the wooden segments seems to have strengthened the structure. The compression spring will hopefully compensate. If not, I will be adding  a fixed idler wheel on the opposite wall. Yes Mike, luck needed 

Steve

[steppenwolf 6,004]

I shall be watching this project with great interest as, before my upgrade of a couple of years ago, I too had this style of Pulsar observatory and had on paper a different solution, although I think your solution has much merit as it keeps the motor in a 'fixed' position. I was going to use Subaru Impreza cam belts for my toothed belt but in my design, the belt would have been attached to the wall and the motor was going to be fitted to the dome on a sprung mounting. In either design, you do have to make allowance for the dome moving laterally, which it will do.

The LesveDome system is excellent and I used it for a year or so on my new style Pulsar dome but upgraded to Pulsar's newest system when it was introduced 18 months or so ago. You will find the LesveDome system to be very capable and flexible with a real bonus thrown in - buying a second K8055N controller will give you access to 8 software controlled ports to further automate your observatory.

I wish you luck with the automation project.

[sloz1664 1,082]

1 hour ago, steppenwolf said:

I shall be watching this project with great interest as, before my upgrade of a couple of years ago, I too had this style of Pulsar observatory and had on paper a different solution, although I think your solution has much merit as it keeps the motor in a 'fixed' position. I was going to use Subaru Impreza cam belts for my toothed belt but in my design, the belt would have been attached to the wall and the motor was going to be fitted to the dome on a sprung mounting. In either design, you do have to make allowance for the dome moving laterally, which it will do.

The LesveDome system is excellent and I used it for a year or so on my new style Pulsar dome but upgraded to Pulsar's newest system when it was introduced 18 months or so ago. You will find the LesveDome system to be very capable and flexible with a real bonus thrown in - buying a second K8055N controller will give you access to 8 software controlled ports to further automate your observatory.

I wish you luck with the automation project.

Thank you Steve. I have the Levesdome circuitry set-up on a test board which works fine. I also have the second board which will be integrated when I have the Dome automation working.

 

Steve

[sloz1664 1,082]

I have now received my Timing Belt from Beltingonline. So today,I will attempt to fit the Timing belt and mount the motor.

 

Timing Belt secured to the Drive Belt Mount using Evostick Impact Adhesive (Dome Shutter fully open to extract the fumes).

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Motor mounted onto the Inner Wall and aligned with the Timing Belt.

 

Well the Rain Gods were smiling on me so I had time to tension the Motor onto the Belt and connected the Motor to a 12 volt battery. The resulting action can be found here.........

 

Dome Rotation.mp4

 

Who's a very happy bunny then..........

Next step.......Integrating it with the Levesdome & SGPro.....

 

Steve

 

 

[steppenwolf 6,004]

Excellent - that is working very well indeed - the drive ring looks very circular and smooth, nicely done! As you already have the electronics working on the bench, the hook-up to the motor-drive should be pretty straightforward. Is that the encoder on top of the drive cog?

[sloz1664 1,082]

Thank you Steve. Yes it's worked out very well indeed & yes that's a "damaged"  Bourne encoder on top of the drive cog. I inadvertently damaged it by giving it too many amps. It needed restricting....doh 

Luckily I have a spare 

 

Steve

[Anne S 155]

I also have an old style Pulsar dome, unfortunately I don't have the knowledge or skills to automate it!

Anne

[skybadger 235]

Anne, could you provide a picture of the internal s of the dome please - so I can compare with mine? 

Sloz, that's a fab drive. Well done. How do you couple the sprocket to the motor ? I have several of those motors which have a male mating thread on the output shaft which means  a threaded shaft extension could undo itself occasionally ...

Mike

Edited August 7, 2017 by skybadger
Sp.

[Anne S 155]

1 hour ago, skybadger said:

Anne, could you provide a picture of the internal s of the dome please - so I can compare with mine?

PM sent.

[sloz1664 1,082]

49 minutes ago, skybadger said:

Anne, could you provide a picture of the internal s of the dome please - so I can compare with mine? 

Sloz, that's a fab drive. Well done. How do you couple the sprocket to the motor ? I have several of those motors which have a male mating thread on the output shaft which means  a threaded shaft extension could undo itself occasionally ...

Mike

Hi Mike

My motor drive shaft has a tapered spline at the base of the thread. I machined my drive gear with the same taper to mate with the motor drive shaft. Using a hand press I then "pressed" the drive gear onto the motor drive shaft . This then keyed the gear to the motor. I then locked it all together with the threaded shaft extension.

Steve

[skybadger 235]

It looks like mine is a copy of a pulsar then, based on Anne's pictures rather than an original. (Ta muchly!). I'll upload some pics into my gallery https://stargazerslounge.com/gallery/album/4361-skybadger-dome/tonight to show what I mean. Basically I have internal ribs that project into the dome which means I can't drive off the inner surface which is why I've had to make a drive unit to fit inside the internal lip.

Cheers

Mike

[Gina 14,895]

I'm amazed how accurately you made the drive ring - the sprung motor unit barely moves.  Using a router was a brilliant idea.  Love it

[sloz1664 1,082]

Thanks Gina, It's still working as well as it did from day one. The phase two stage - Automating the shutter has been more of a head scratcher. Hoping to start this next spring. Watch this space

Steve

[Gina 14,895]

Ah yes.  A while ago I made a 3D printed micro-dome for an astro camera plus SLR camera lens for widefield imaging, the rotation was relatively easy but the shutter was a different matter.  At that point I put the project on the back burner and got on with other things.  I might resurrect the project one day - it's the mad sort of thing I like

Glad to hear it's still working well.  That's the sign of a job well engineered.  Congratulations 

Edited December 14, 2018 by Gina

[Nightwatchman 0]

Thanks Steve for sharing your automation build. Nicely engineered, congratulations. I bought a Pulsar 2.2m dome recently (age uncertain- round dome - sliding shutter) and just about to start automating it.. Did you obtain the (40 tooth?) cog from beltingonline as well?  Any particular windscreen motor you would recommend? Would appreciate any tips you would like to share of the build. Graham

[Anne S 155]

49 minutes ago, Nightwatchman said:

Thanks Steve for sharing your automation build. Nicely engineered, congratulations. I bought a Pulsar 2.2m dome recently (age uncertain- round dome - sliding shutter) and just about to start automating it.. Did you obtain the (40 tooth?) cog from beltingonline as well?  Any particular windscreen motor you would recommend? Would appreciate any tips you would like to share of the build. Graham

I'd be interested in how you do it. I keep hoping someone will develop a very simple (and cheap) way of motorising the dome. I only want it to track so I don't have to keep going out to turn it when I'm imaging. I don't know that I'd trust our weather to image all night!

[Nightwatchman 0]

OK, I'll post updates as I go along. Hoping to start by mid March. Photo: Just temporarily assembled after purchasing to see how it all goes together.

 

Edited February 12 by Nightwatchman
image added

[Anne S 155]

That looks like the newer Pulsar. It's got the extra section under the sliding section of the dome. It also  has the inside of the dome overlapping the walls on the inside. Mine is like sloz1664's dome.

[sloz1664 1,082]

12 hours ago, Anne S said:

That looks like the newer Pulsar. It's got the extra section under the sliding section of the dome. It also  has the inside of the dome overlapping the walls on the inside. Mine is like sloz1664's dome.

I agree with Anne, yours is the newer 2.2 Pulsar Dome and Anne & mine are the older 2.1 Pulsar Domes. When you assemble your  dome, if can take some photos of the wall and dome configuration I could possibly help on how to modify it.

Steve

[skybadger 235]

21 hours ago, Anne S said:

I'd be interested in how you do it. I keep hoping someone will develop a very simple (and cheap) way of motorising the dome. I only want it to track so I don't have to keep going out to turn it when I'm imaging. I don't know that I'd trust our weather to image all night!

I thought we'd done as a community that via the belting and pulley solution.. 

What more do you need? There are ascom drivers for those solutions in open source.

[Anne S 155]

I've no technical background at all and no knowledge of the what the parts are and where to source the .It would need to be a kit of some sorts. I also don't want to wreck my dome in trying. 

I need someone to make and fit one for me!

[skybadger 235]

And what would your price point be ?

You can buy pulsar after-market dome drives to do this. £750?

How easily does your dome revolve ? Can you measure it ?

I can t think of a kit that is cheap enough in brand new parts. Even using scrap parts, you still need new motor control parts , brackets, housing and software. 

What about a print-yourself kit?