Old style Pulsar 2.2m Dome rotation automation

[tony210]

Hi -I thought I would share my rather "Heath Robinson" take on the old style Pulsar Dome rotation -I had been using a wind screen wiper motor with a gear engaging with a timing belt on the dome wall and a motor controller . This I had given a few second nudges by a timer board but it was never right and I had to go out at all hours to move the dome when imaging. I have had  a few months of various prototype failures as I decided to use an aluminium track pick up system for power as the buggy battery I previously used ran out of power very quickly. This of course created a whole world of pain as my electrode pickups have to be orthogonal and  held to the track with some force otherwise the whole thing kept stopping. In the end I had two sets of pick ups which seems to prevent much in the way of poor contact and some high capacity "tank " capacitors across the pickups that smooths things a bit too. I feed the strips with the power output from a 12v motor controller that itself is controlled by LesveDome system via a Velleman board . The controller links to ASCOM and POTH via a USB and then slaves to the telescope and mostly keeps the observatory aperture in line with my 12 inch RCT but I may still have to tinker with the geometry settings in LesveDome a little. However you can sync the dome with the telescope and realign the dome slave position which works well if things seem a bit out on the night. The encoder rotates with the roof and has its own 5v battery supply ( blue LED reduces 9v battery nicely to 5v) It is not attached to the motor drive system which is great because its gear needs only a bit of force to ensure traction with the timing belt attached to the stationary dome wall. One thing of note the Bourns encoder must have three outputs A B and ground -found this out eventually after much stress and confusion from a forum - thought it was broken.They do break if you don't treat them gently and I did destroy one so be careful with them . Anyway finally it works! I only really wanted it to track fairly well for a couple of hours while I stay in the warm which I have achieved ! The Lesvedome system works well - thanks to Pierre. I have manual control on the mounted box as well but still have one lead that trails with the encoder output. I have toyed with the idea of transmitting the output to lose this but frankly it works OK and I am not sure I will bother - seemed a little tricky in any case. Circuits for Lesvedome are not too bad once you have enough diodes! I blew a few so use the best ones otherwise smoke and a burning smell and all fails. The result looks a bit tatty but I will work on that I promise- brief video included-Tony

20180225_110718.mp4

Edited February 25, 2018 by tony210

[JeremyS]

Very nice Tony. I which I had the skills to do that with my Pulsar dome!

[tony210]

2 minutes ago, JeremyS said:

Very nice Tony. I which I had the skills to do that with my Pulsar dome!

Hi -not that difficult once you start - if you ever consider it I can let you know the short cuts that caused me so many false starts - best wishes Tony

[sloz1664]

Hi Tony,

I did something similar with my Pulsar 2.1M dome. I also used a windscreen wiper motor to drive the dome, via the Velleman project and  didn't want to use batteries. I built an extended support onto the dome to mount the drive belt so I could use a mains 12v dc 10 amp power supply.

Dome Rotation.mp4

Steve

 

[tony210]

Hi Steve - yes saw your mod - very nice - I had already opted for a mounted motor mounted on the dome roof so just changed that but I like your wooden supports for your belt. Happy to have got mine automated at last and can sit inside and just watch the subs coming in on my computer and not keep going out to shift the dome!- Tony

Edited February 25, 2018 by tony210

[sloz1664]

13 minutes ago, tony210 said:

Hi Steve - yes saw your mod - very nice - I had already opted for a mounted motor mounted on the dome roof so just changed that but I like your wooden supports for your belt. Happy to have got mine automated at last and can sit inside and just watch the subs coming in on my computer and not keep going out to shift the dome!- Tony

Totally agree with that Tony. In fact my dome is automatically inching it's way round now whilst I'm obtaining some nice subs of the Soul Nebula

Steve

[tony210]

Great Steve - I would be doing the same but the little galaxy I am imaging vanishes with that enormous moon! I'll just have to wait...Tony

[Nightwatchman]

Hi Tony,

Thanks for posting your dome automation MP4 which gives me much encouragement.  I'm just about to start on a 2.2m Pulsar automation and would greatly appreciate any hints and tips you could offer. Many thanks, Graham

[Nigella Bryant]

Hi all, I've an older pulsar dome. Can someone get in touch with me with all the items needed. I'm not particularly interested in automation just being able to rotate and nudge the dome electrically. I  bought a wiper motor but that burnt out so not sure what I did I'd just connected it to a 12v transformer and hadn't worked out how this was going to run , ie track wise. I quite familiar with electrics, but not electronics, etc, so was just thinking of a forward backward switch. Any help would be great. 

Ella

Edited April 7, 2019 by Nigella Bryant

[tony210]

Hi Nigella - a windscreen motor is the right way to go with a 12v dc power supply -with the older style dome  a 12v battery and motor attached via a shelf on the roof is the simplest way to go . The motor engages with a belt attached to the wall of the dome via a gear that can all be obtained from motionco an on line retailer -can pm you pictures of my setup if you want . I have gone on to use the Vellerman board and Lesvedome software to slave the dome rotation to the scope which is a great help.

Best wishes - Tony

[sloz1664]

Hi Nigella, Can you post some photos of the inside of the dome, in particular views of the top of the inner wall where it meets the dome.

Steve

[Nigella Bryant]

1 hour ago, sloz1664 said:

Hi Nigella, Can you post some photos of the inside of the dome, in particular views of the top of the inner wall where it meets the dome.

Steve

Hi, will take some pics of inside dome tomorrow,  thanks

Nigella 

[pmlogg]

Nigella

Your dome looks similar to mine - a first generation Pulsar one.  Another alternative to dome mounting the motor etc. is to emulate what Michael O'Connell did with his.

If you haven't seen it already check this link:  https://www.irishastronomy.org/kunena?view=topic&catid=22&id=95329#96208. He used off-the-shelf equipment sourced from Exploradome in the U.S. but the motors they supply are very expensive (but are also supposed to be very good).  However the Exploradome track is not very expensive - and some have done DIY versions; same goes for the 'acorn' gear.  So, a DIY combination using bought track and acorn gear with locally purchased motors would come in a lot cheaper.  If you don't want to automate you could stop at that, just have a toggle switch to sent clockwise or counter clockwise. 

My motor system (an original Pulsar 'Rigel' one, for a  2.2m dome) is not as quick as just moving the dome by hand, but it is semi-automated so it will nudge itself around during an imaging session.  That was primarily what I wanted to achieve but the aim I continue to work towards is slaving the dome to the mount.  Seeing what others have done is getting me closer to that. 

Motorising or automating the shutter is even more taxing due to the two-part shutter but Michael O'Connell's system includes that too.  Again a DIY version of that would be a lot less costly than buying from Exploradome.  For it to be worthwhile to me it would need to be automated to shut in bad weather and that means weather sensors etc. plus confidence in its reliability.  Michael has told me that despite incorporating all those features he still doesn't trust it to react quickly enough. 

[tteedd]

Hi Steve

Where did you get the rack and pinion?

Ted

[sloz1664]

Hi Ted,

I purchased the pulley and belt from:- https://www.hpcgears.com/n/products/1.pulleys_belts/pulleys_belts.php

You could also try:- https://www.beltingonline.com/index.php?main_page=index&cPath=213&gclid=CjwKCAjw5fzrBRASEiwAD2OSV0B9sUJZY2HMfTLUrBucMSQb7aHcK8ODQMNPoxKaluk_VZBvHZZu0hoCXBMQAvD_BwE

Steve

[tteedd]

Thanks Steve

I have (as you see) a v old second hand 2.7m dome.

It has a skirt from the dome inside the structure and there is a large amount of play between dome and wall.

I have some 12V dc golf trolley motors and gearboxes which should provide plenty of motive force. I did try a lash up (a couple of years ago) with rubber wheels directly on to the fibreglass. This just ripped up the rubber and I concluded that I needed some form of rack. I have been Thinking of sliding gate gear but something similar to your system may do the job.

Due to the afore mentioned play, I think I may need to provide some guidance and was thinking of two motors equally spaced (120 deg) with a dolly that I can later use for measuring movement in the third position.

Perhaps there is someone out there who has already done something similar on a dome like mine?

 

[sloz1664]

I wouldn't advise using two motors as one would be fighting against the other which may cause issues. I would have one motor, which would be sprung loaded against the belt and two fixed idler pulleys set at 120 degrees to stop the dome from flexing.

Steve