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DIY - Dome Automation

ribuck

By ribuck
in DIY Astronomer

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ribuck

ribuck

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Well I tried the use of a mouse wheel as a rotary encoder as a test, it worked but it wasn't very accurate. Looked at more heavy duty rotary encoders, but again they have limited life cycles of approx 20k revolutions.

I think it's going to have to be a a 5v photoMicro sensor of some sort, just need to find a uk supplier online. looked at prices of these in the US and they were onlu a few dollars.

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skybadger

skybadger

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why are you gearing it to match RA speed ? Its there as a dome driver wheel and does about 2 minutes to a complete dome rev of an 8 foot diameter dome using a 80 mm drive wheel .

the current is between 1/2 and 2 amps at 12V and controlled using a Robot electronics PWM DC motor controller via the I2C interface.

The dome only needs to move in 5 degree increments or so when tracking the scope.

Note that some wiper motors have a built in encoder which puts a digital output every rev, giving a position indicator but no direction information.

regards

Mike

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ribuck

ribuck

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I've finished building the first test version of my dome rotation controller. I'm now just waiting for my replacement power supply to arrive and i'll be ready to start testing in the real world.

I still have some coding bugs to work out, but they should be done this weekend.

Anyway, here's the first roughly made controller box, when i'm happy with the final design i'm going to get a proper circuit board made up, so i dont have tons of wires, and i'll get some proper housing made up, so it doesn't look like a home diy test :D:D

IMAG0027.jpg-for-web-NORMAL.jpg

IMAG0028.jpg-for-web-NORMAL.jpg

IMAG0029.jpg-for-web-NORMAL.jpg

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ribuck

ribuck

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Hi Niel,

Yeah this is just a temporary build. When i do things i like to do them properly.

Once my power supply turns up i'll test it for a while to make sure everything works, the i'll do a final stage box with a proper pcb for reliability and i'll compact the design so a smaller box can be used.

Rich.

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GeoC

GeoC

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Hello people. I have just installed a Pulsar 2.7m dome and have rapidly discovered that you need to nudge the dome every 30 minutes or even less. I have been thinking of automating the process and then discovered this thread.

My first idea was to arrange a system whereby the motor was attached to the inside of the dome, and the motor drove a rubber wheel that made contact with the outer, shiny surface of the white fibreglass at the top of the wall or track. (I have the dome and track system).

There would be another wheel, undriven, gripping the inside rougher surface. Springs could be used to make the two wheels pinch together.

Has any one tried such a system, or can anyone see a problem with it?

I still haven't decided how to control the speed other than to think of some sort of proximity detector to sense when the scope was getting a bit close to the side of the shutter opening. Perhaps Hall effect magnet detection?

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ribuck

ribuck

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Hi guys progress has been delayed slightly as i'm waiting for a faulty power supply to be replaced off a chinese ebay supplier.

For speed of rotation i haven't looking into that as my motor is geared to 6 rpm so should give a nice steady rotation speed.

The motor itself has a brake, so i intend to just activate the motor then stop it when it reaches the same position as the Azimuth readout from EQASCOM.

To get the motor positoinal feedback i'm planning on using a Microphoto sensor which are about £2 or $2 from most electronics distributors. This will just sense a turning wheel with and it's direction to give feedback to my controller box which drives the motor.

I think the power supply is going to take another 1-2 weeks to be replaced so i'm afraid no progress until then. i'll put some details up about the encoder wheel later this weekend.

If anyone else has any comments on the question on the issue of controller the dome rotation speed i would love to hear.

Rich.

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  • 1 month later...
ribuck

ribuck

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Finally Finished......

Hi all, after 2 crazy months at work I finally got some spare time to finish my dome rotation project.

in a nutshell, my box reads A/Z data from the mount at set intervals and then adjusts the dome accordingly. The system uses a combination of Eqascom and my own software to interface between the mount and the controller box.

I've uploaded a video on youtube demostrating the system on a bench running with the Eqascom software to simulate being connected to a mount

YouTube - AstroSky Dome Runner

A big shout out to everyone who has helped, especially to Chris over on the EQMOD yahoo forum.

If anyone is interested in building their own, let me know and i'll happily share the knowledge i've learnt from my experience as a way of giving a little something back the astronomy community and the good people of this forum.

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ribuck

ribuck

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Hi Ivor,

I think for a pulsar dome, probably the easiest way to to use some form of gear and belt system. You could buy cheap car cambelts from ebay which go for as little as 99p and the cambelt gear cog with are normally only a few quid or you can buy them as kits.

You could try attaching a few cambelts along the inner edge of your dome using a hot glue gun, thus no damage to you dome, no drilling etc, then attach the cam gear cog to the motor spindle.

to mount the motor i would be inclined to just build a cheap rough wood timber frame, from the floor to the height you need the motor, again this stop the need for any drilling into your precious dome.

I'm going to be installed my setup this week. My diy dome that i built is a slightly different design to your dome, so i'm going to try using a rubber wheel to turn the dome first, but if I have any issues with that i'll probably just use the cam belt option myself.

to give you a rouch idea on pricing, i've probably spend about £170 in total, but i think that could be brought down a little, but i guess it just depends on pricing of items at the time.

Worse case scenario, if you budgeted £200 you could easily build it, and you would be left with change for a celebration feast and beer on completetion of the project.

Rich.

Rich.

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mattifor

mattifor

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Hi Rich.

All my projects are on hold at present, just keeping an eye on this project though.

Had some bad news that my wife is going to have urgent surgery, so it will be a while before I can devote time to the automation project.

Life is a bitch at times.

Ivor

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ribuck

ribuck

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Hi Chris,

Thanks for the message. It was just my browser acting up, so the video wouldn't play properly.

Thanks for all your help on the project, i couldn't have done it without your help.

Over the next few weeks, work pending, i'll be putting together some step by step instructions on my web site on how to build the unit, including the basic component, step by step wiring diagrams.

Will be nice to give something back to the Astronomy community after 2 years of asking lots of questions.

Rich.

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Keithp

Keithp

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As I'm contemplating my dome build early in the new year I was pondering controlled power systems to move the dome in sync with the mount. So what about this for an idea.

Once the motor to drive the dome round is sorted and hooked up to what ever power supply how about having 3 photo electric cells mounted inside the dome at the base of the opening say about 6 inches apart. Sort of like * * * Then have a laser mounted on the telescope mount that moves with the mount as it turns. If the laser falls on the centre cell the motor is off if the laser moves off the centre and hits the photo cell either side then the drive motor for the dome is activated and moves the dome back in the appropriate direction until it hits the centre one again and switches the motor off. Maybe a little testing to adjust the spacing of the cells so that the appeture is kept with in the field of vew of the telescope would be needed.

Using this method would only then require power to the laser and would utilize the scope mount to in effect position the dome.

Any comments? Please say if you think it's a crazy idea. I just thought we've already invested dosh in the scope mount why not utilize it for other things?

Regards

Keithp

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ribuck

ribuck

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Hi keithp,

The biggest single problem i can see with your idea is that when a mount moves it doesn't move in a flat plane (i.e. it doesn't turn on a single flat Axis), it's a combination of Right Asencion and Declanation and this is how the Azimuth value is calculated. So with this in mind, you couldn't just use a few evenly spaced photoelectric sensors, you would have to cover the entire inside of the dome with them.

This would also apply to a fork mount with a wedge.

About the only way that i could see it work would be with a fork mount, without a wedge, which means you can't do astro imaging, so you're limited to visual viewing only.

Regards,

Rich.

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astroshot

astroshot

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Hi Rich,

Just joined this forum when I came across the work by yourselves and others here.

Very inteesting.

I have a 2.7m Pulsar Obhservatory that I would love to automate.

Unfortunately, my knowledge of electronics and motroes is zilch. ;-(

I'll be keeping a close eye on this thread.

Thanks,

Michael

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astroshot

astroshot

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Hi Rich,

Just joined this forum when I came across the work by yourselves and others here.

Very inteesting.

I have a 2.7m Pulsar Obhservatory that I would love to automate.

Unfortunately, my knowledge of electronics and motroes is zilch. ;-(

I'll be keeping a close eye on this thread.

Thanks,

Michael O'Connell

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ribuck

ribuck

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Hi Michael,

I'll be posting a step by step guide as soon as i can, but it might be a few weeks with it being the busy holiday season.

I'm planning to write my guide to make it a simple and clear as possible so that anybody can follow it, even without any prior knowledge of motors or electronics.

The actual real hard part is the programming of Arduino interface, but i'll be supplying my code to anyone who wants it, if they are planning to build the same interface.

Rich.

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