Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

DIY - Dome Automation

ribuck

By ribuck
in DIY Astronomer

Recommended Posts

ribuck

ribuck

Posted
  • Author
Posted

Michael,

Using something that somebody else has already done is always going to be the easier option. I can't comment on lesvedome as i haven't got any experience of the Lesvedome system.

I guess my stubborn side wasn't going to pay $40 for a license for a bit of sotware which was just using Eqascom which is free. Guess it's just a principle thing for me.

The Lesvedome system has been around for a while, so if you're looking for a more established system, give thier's a try.

Rich.

Link to comment
Share on other sites
  • Replies 162
  • Created
  • Last Reply
astroshot

astroshot

Posted
Posted

I've been looking at it alright but the electronics details involved with the sensors, motors etc has me confused. Just a complete lack of knowledge on my part. Personally, I'd be quite happy to part with $40 and buy my way out of ignorance on the software-side. The electronics & motors though are a different kettle of fish :-(

Michael.

Link to comment
Share on other sites
ribuck

ribuck

Posted
  • Author
Posted

Michael, there is a tried and tested system, it's called Maxdome II and costs several thousand pounds.

If you want to design your own system, work backwards :-

1) How would the motor physically move the dome or shutter. Maybe using a motor with a cog on the spindle, and maybe use cheap car cam belts to attach to the dome for the cog to move.

2) Decide on the motors, how powerful do you need ? What motors can you get cheaply.

3) Once you've decided on the motors, what motor driver/controller circuit do you need for them, in terms of power & Amp draw / think about cost of power supply unit. Cheapest from ebay from china.

4) What power supply do i need to drive the motors in terms of voltage and amps

5) What main contoller circuit willl you use ? Arduino or LesveDome or other

These are the main key components you need to think about ?

Link to comment
Share on other sites
GeoC

GeoC

Posted
Posted

I have taken the first step and have bought a Sharp proximity sensor http://www.active-robots.co.uk/media/pdf/gp2y0a02yk.pdf

This has 3 leads: power, ground and output signal. The output voltage will vary as the distance to the object is changed.

I have the sensor attached to the end of the telescope, pointing out of the dome aperture. A Picaxe microcontroller monitors the output voltage and starts bleeping if it rises above a certain value.

Initial tests are very encouraging, and the bleeps start sounding a few minutes before the dome starts to obscure the telescope. I then move the dome by hand.

Now comes the hard part - getting the microcontroller to activate a motor to rotate the dome.

Question: People have mentioned Car wiper motors. I imagine these have some complicated gearing to convert the rotation to a to and fro movement. Is it easy to remove the gearing to get a motor that turns in one direction only?

Link to comment
Share on other sites
ribuck

ribuck

Posted
  • Author
Posted

The Gearing should be fairly easy to remove, i guess is just depends on the motor rpm after you remove anyt gearing.

To control the motor, you will need to buy a motor controller, you can't just connect it directly to a power supply. Bear this in mind as when a motor starts up, it can have a peak draw of several hundred amps and without a controller it would literally blow up anything attached to it.

you can then control the direction of the motor through the motor controller.

Rich.

Link to comment
Share on other sites
GeoC

GeoC

Posted
Posted

Thanks Rich. What about running the motor via a relay?

How do they switch them on when they are in a car?

I know the starting current can be very high. If a relay won't do it I will buy a motor controller.

Is there a good make I should know about?

Link to comment
Share on other sites
  • 3 weeks later...
ribuck

ribuck

Posted
  • Author
Posted

Hi George, i had thought about this using car cam belt kits which aren't expensive at all, it's just a case of figuring out how i can attach the cambelt to the my plywood ring ?

I can use screws as this will hinder the gear head turning the belt.

Link to comment
Share on other sites
George

George

Posted
Posted

You could countersink the screws into the belt or maybe even epoxy glue them to the plywood or maybe some long staples would do the trick, if you spaced them every couple of inches they would be strong enough to stop the belt from slipping.

If they were placed in the groove I doubt they would hinder the toothed pulley wheel.

Link to comment
Share on other sites
tinvek

tinvek

Posted
Posted

a few things to watch out for, firstly make sure you have access to a pully off the engine the belt is designed for, you'd be amazed how many teath shape / pitch variations there are so you may aswell make it simple. secondly check how the pully is secured, quite alot these days rely on friction on a tapered spigot which isn't the easiest thing to replicate. thirdly try and find the longest belt you can allowing for the first and second points, if you're planning to put a belt all round the dome then the joints are always going to be the trickiest bit so the fewer the better.

i've been out of the motor trade for a while now but the one that springs to mind is the peugeot / citroen 1.7 / 1.9 diesel as it's fairly long, is hard waring (citroen actually went for a while with no recomended replacement distance )and the fuel pump pully is held to a flange by 3 bolts which may make mounting it on a shaft easier.

only problem is the size of the pully may give you too high gearing, there is a car witha nice small cambelt drive gear held on the crank by 4 bolts but i can't for the life of me remember which one, if i had to guess i'd say it was in the VW /audi family.

re wiper motors, the gearing is usually dead simple, just a worm drive to a round gear with an offset arm coming off that gives a crank action to drive the wipers (think of the links to a steam trains wheels only with the wheel driving the link) one advantage of course is that you could end up with 2 or 3 different speeds available, the bad news is the shaft is very narrow.

Link to comment
Share on other sites
GeoC

GeoC

Posted
Posted
Having problems moving my dome with rubber wheels, as i can't get enough traction to turn it.

Does anyone have any idea for chain / belt or any other ways to turn a dome with a motor. desperate in need of help here.

Where is your rubber wheel making contact with the dome?

I am intending to try placing the wheel against the fixed vertical fibreglass circle that runs around the dome support. The motor will be attached to the dome.

I am also thinking about two wheels that pinch the fibreglass.

Also considering a long rubber tube around the fibreglas, split down the length, to provide more traction.

Link to comment
Share on other sites
ribuck

ribuck

Posted
  • Author
Posted

I have to agree with Bizbuider on this one, as it seems a strange to have the motor attached to a moving part, as this will cuase all kind of cable issues.

Remember you will have an encoder to contend with as well, and that means another cable.

Rich.

Link to comment
Share on other sites
ribuck

ribuck

Posted
  • Author
Posted

p.s. you might get away with the rubber wheel pressed agains the dome ring, i just can't get enough traction as my diy dome ring isn't the smoothest in operation, hence needing a chain solution.

My chain is getting delivered on Tuesday.

Rich.

Link to comment
Share on other sites
GeoC

GeoC

Posted
Posted

These pics will show what I intend:

1_1a46.jpg

A shelf is attached to the inside of the dome that will support the battery and motor. Infra red control so no trailing cables.

1a3e7.jpg

A thin fibreglass circle runs around the base.

2d2f.jpg

Rubber drive wheel presses against outside surface of fibreglass.

2a5fb.jpg

If there isn't enough traction then perhaps a second idler wheel on the other side to grip tighter. Or perhaps a timing belt all the way around the circumference...

Link to comment
Share on other sites
ribuck

ribuck

Posted
  • Author
Posted

Thanks for that. Dont think that sort of configuration would work for me, as the belt has to be attached to the dome so couldn't pass through the pully.

I've ordered some chain and a cog to drive the chain which was supposed to arrive today but it may be delayed due to the heavy snow.

Richard.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.