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DIY - Dome Automation

ribuck

By ribuck
in DIY Astronomer

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ribuck

ribuck

Posted
Posted

Hi All,

I've decided i would like to automate my Diy dome and would really appreciate some pointers in the right directions.

Motors

I'm not sure what i'm looking for motor wise, but i'm assuming from my old electonic days that for form of stepper motor will be needed for precision control.

My dome weighs about 25kg, but i'm going to upgrade it's runner system so it wont take much effort to turn. Does anyone have any recommendation on size of motors / Amp loads / Torque etc

Controllers

So far i've been looking at stepper motor drivers, and i'm looking for something to that can be controlled from a laptop through either a serial port or a usb port. again not quite sure where to start but i have found some fairly cheap controllers, but i guess it all depends on the motor rating people recommend.

An example of the controllers i've been looking at : Motor controller

software

I'm assuming that i'll probably write something like this myself if there isn't already something available. Should be ok doing that as i'm not too bad a programming in Visual Basic.

Rich :)

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ncjunk

ncjunk

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The most important thing for you will be the size and type of motor you use, you then just size the switching circuitry to cope with the spec of the motor (that bit is easy). I am interested to see what the spec of the motor would need to be to shift 25kg someone must have done something similar.

Neil C

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mattifor

mattifor

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I have been looking on a yahoo group site in the hope that someone had done some thing similar but as yet no luck.

The the price from Pulsar

was £1195.00 for rotation drive system

and £1695.00 for shutter drive system

I am sure I can do it for less, I might be proved wrong

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ribuck

ribuck

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To be honest i dont know how they have the nerve to charge that, as controller circuits aren't all that expensive, anywhere between £15 - £100 depnding on what you want, and i imagine you could pick up motors fairly cheeply.

The hard part is firslty finding the motor you need then matching it up with a controller. Choosing a motor type is my first stumbling block, but i'm going to call my local electronics shop tomorrow to see what they say.

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mattifor

mattifor

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Please let me Know what the recomendation is.

I have ordered one of those control boards to use on a seperate project, to complete my robofocuser, I have tried getting the official unit but its $300 plus shipping and import duties.

this control board has all the right connections for the Robofocuser servo unit.

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steppenwolf

steppenwolf

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I have the 7 foot Pulsar dome and have plans in place to motorise it from a rotation point of view - at it is in my garden, I don't see any need for an aperture control as I have to go out to the dome to take off dust covers etc. so I may just as well open the aperture myself. My dome can be turned by (literally) pushing with my little finger so the motor I have chosen does not have to be that powerful and I can buy it for £30.00 to £40.00. For control, I am not going for PC, I simply want to avoid nudging it around every 10 to 15 minutes so that I can set up come inside to my study and concentrate on mount control and imaging via my network.

Now I am into fast cars and one of mine is a Subaru Impreza STi and having recently changed the cam belt (which is huge as the engine is a 'boxer engine') I have the ideal mechanism - attach several cam-belts to the inside edge of the dome roof and drive them with a matching cam pulley in a sprung enclosure to keep constant pressure on the cam-belt/pulley meshing.

The motor? 18v battery powered electric drill in the sprung enclosure. Electronic control? 555 timer controlled circuit to activate the motor every minute of so with a short pulse to just nudge the dome section round enough to keep both imaging 'scope and autoguider 'scope peeping through the aperture.

What could possibly go wrong!!?? :)

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ribuck

ribuck

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I'm trying to achive the same goal, for the purposes of imaging, as i too have to pause imaging and rotate the dome. I want to try and be a litttle more sophisticaed and tie in the dome's rotation with the position of the scope, this will really help with 3-star alignments / polar alignments with PAM.

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ncjunk

ncjunk

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Steve,

A List of things that could go wrong :)

The belt might slip off

The belt could loosen and keep slipping

Speed control adjustment may be entertaining on initial set up with a 555 timer.

What if you accidently have the drill motor set to Hammer :)

I am sure it will be fine!

I was just umming and ahhhhing over Stepper or "normal" Motor if you get the pulses right on your motor it should work fine. I am a control freak though and love playing with software and circuits.....on my roof it will be a garage door opener when I do it.

I think a stepper would be over kill. I suppose you could gear a motor to go slowly enough (as we used to for those homemade astrophotography mounts before the days of cheap goto) in theory much easier.

Neil C

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albedo0.39

albedo0.39

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I've spent a lifetime (well allright.. 25+ years) in motors, drives, controls, software and automation so might be able to help.

If I were you, I'd pick up a 2nd hand geared 240v 3ph Fractional HP AC motor (check out e-bay) and a simple 1ph in - 3ph out AC inverter. These can be controlled from a pot, digital key pad or an RS232 port. They are not expensive (I might even have some in the garage somewhere)

More ££ drives can sit on a network and be linked up to your PC in realtime. If you wish to have the dome move automatically, then you need some intelligence in the software to let your drive system know when an object is close to zenith (i.e. slow speed) or the horizon (fast speed).

I suspect, this signal could come from the mount somewhere, but how you get it... Hmmm...alternatively you could program the drive it so that it varies in speed based on an angle sensor as one of the inputs to the master reference controller.

Plenty of options. It's a nice project. Perhaps we could talk off-line ?

Rgds

Steve

PS - don't forget, all the modern drives chop up the mains a bit which introduces EMC both airborne and mains-borne. You will need an EMC filter (a few pounds from RS components) and perhaps drop the lot into a little steel cabinet

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ribuck

ribuck

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Hi steve,

Thanks for the reply. You sound just like the perosn i need to get this project off the ground and proto typed. It would be great to chat offline sometime.

My plan is to retrofit is to upgrade my diy obs rail system to a new one this week to get smooth running and then start to look at the look at the rotation control.

If we could touch base during the week, and use your expertise to understand what sort of kit i should be ordering in terms of controllers and mototrs that would be great.

I'll send you a message offline with my number, if you could give me a call sometime at your convenience it would be greatly apreciated.

Rich.

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ribuck

ribuck

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Steve,

This is what i'm currently looking at to start the project. I'm not sure if the Arudmoto shield supports stepper motors but i'm sure there are lots that do, i also included an alternative that i quicky found late lastnight. In terms of Motor spec i was looking at the Nema 17 motor.

The problem i have is that i dont know how to quantify something that takes only gentle finger pressure to turn into torque (Nm).

Stepper Motors

Motion Control Products Ltd, For Stepper Motors, Servo Drives and all motion products

Usb Computer Interface

Arduino Duemilanove (Updated 328 Version) from Cool Components

Motor Driver

ArduMoto - Motor Driver Shield from Cool Components

Stepper Motor Controller & Driver: Virtual Village - UK

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ribuck

ribuck

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Dome Automation Project Kick-Off

Hi all, just a quick update on this project, and i'm happy to say that it's making a good start and we've got the help of some clever people with a great deal of experience and expertise.

The People (Most Important part)

Steve (Albedo0.39)

We have some great help on board satrting with Steve (Albedo0.39) who has kindly offered to help with the motor side of things. Steve is currently looking at the motor torque calculations required to drive a dome based on weight, diameter, points of contact etc. To give you an idea of steve's experience, he's been involved with massive large scale projects like the roof at wembly, and fly by wire controls found in most airliners and 20+ years in the automation control industry. Steve is aslo going to make motor recommendations based on his calculations.

Chris Rowlands

Chris rowlands is the programmer of the Ascom driver for the Celestron Range of telescopes, which all works with Synstar mounts such as the Heq5 Pro, EQ6 pro etc. Chris has pointed me in the direction of some very useful information.

Myself & Other forum members

I will be looking after the physical prototyping and the main programming aspects of the project along with the great advice and suggestions of other forum users.

Hardware

Hardware <-> PC Interface Ordered (Arduino Interface) + associated electonics (Resistors, Diades, Caps etc) along with a 4x20 char lcd display to assist with testing during the proto typing stage.

Ref Materials

Arduino Programming Ref Book Ordered

Testing

For the purposes of testing a prototype, all testing will be initally done with a Heq5 Pro mount (Synstar). If the prototype proves successful then I will look at driving other mounts.

Initial testing will be done with a small motor to test simulated movements based on the output from the scope.

What's Next ?

Well watch this space folks. Hopefully all the equiptment will arrive by early next week, a possibly have some better idea's of the type of motor we need for testing.

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mattifor

mattifor

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I hope that you succeed, I have a vixen spynx mount in my observatory, hopefully it can be adapted to work with this mount.

very usefull helpers, I am afrade most of mine is trial and error, which can result in more expence.

best of luck please let me know your result and cost involved.

mattifor

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ribuck

ribuck

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Hi Mattfor,

I'm going to create a blog/Diary on my website this weekend which will make it easier for me to post photo's / updates etc. I just think it will be easier to follow if it's contiguous Vs items been split between posts.

I want to keep the discussion on here, with links to the Blog / Diary update which will be easier to read and follow.

Rich.

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