DIY - Dome Automation

[ribuck]

Let me know how you get on. My plan is similar, i'm using duplex chain, which is effectively 2 chains connected together.

I will use the bottom to screw the chain in place then a cog will turn against the top chain.

Rich.

[Keithp]

Just had a quick look in on this thread and one thing struck me as very useful, those belts and pullies setup look like a neat starter for an automated roll off roof. That's got me thinking along the cheaper option of a shed for the new year.

Regards

Keithp

[innivodave]

Hi Rich,

nice work on the dome controller. I'm currently building an arduino based controller, which is how I found this thread.

Is there reason that you didn't create an ascom driver for the controller? (or have I misunderstood your setup?) I'd have thought all the pointing calculations would have been done for you then.

I'd be interested to hear more detail about how the bits of software interface with each other. You mention that you use your own software, but what exactly does that do?

I've been going down the route of writing an ascom driver in the hope that it will allow me to use any ascom compliant software, and do all the pointing calculations for me, but just wanted to check if I'm missing something.

My build seems to be going ok so far, the ardiuno is receiving and displaying the commands sent from the ascom dome control using the driver I'm developing, so I think I'm on the right tracks.

Thanks

Dave

[ribuck]

Hi Dave,

I wanted tomake a stand alone system at first, mainly for a bit of a challenge. I got it working standalone, then decided it was a bit pointless in that anyone in a dome will have a laptop for imaging.

So i scrapped the standalone route and decided to tie it in with Eqascom.

My driver was written in VB.NET basically becuase i didn't have any experience of Ascom. I should have really looked into Ascom programming but i didn't for some reason.

My driver simply performs the communication between the Arduino and the Eqascom software, or the Ascom Simulator. The driver polls the Eqascom ever 10 seconds and to check the position of the scope, thne relays this to the Arduino unit, which then determins which direction to turn the motor and for how long.

Unfortunately work has got in the way again, and i've not has much time to fiddle with installing the motor into the dome.

Becuase my diy dome runner track isn't perfect it's rotation takes a little extra force, which using a rubber wheel and friction couldn't provide.

I've just had a duplex chain and sprocket delivered this week so i should finally be able to finish the project.

Rich.

[innivodave]

if you did want to go down the ascom route, there are VB example drivers included with the ascom platform if you select it on installation. I'm a web developer, so writing drivers is pretty alien to me, but it's fun learning, and the examples help a lot. I'm basing my driver on the C# driver shell that's included as it's closer to the languages I'm used to (javascript, actionscript, etc).

I'm interested to see how you get on with the chain drive, I had been thinking along the same lines as GeoC with the belt glued to the dome and a cog to turn it, but I'm still undecided really. How are you going to use the chain to drive the dome?

Dave

[ribuck]

Hi Dave, i'm using duplex chain. the top part of the chain will be screwed to the dome and the bottom part of the chain will be driven by a cog to turn the dome. hopefully fitting it tomorrow or sat .

[innivodave]

ah I see, sounds like that should work nicely. Hope it all goes to plan

[ribuck]

Dave,

I actually pinched the idea from a lot of people using lesve dome. I had thought about using rubber belt systems, but they are prone to crack with colder temps, stretching and wear, so i just thought chain would be a much more solid approach.

The other thing with using belts, is that i'm not keen on using to to attach something to a dome, as again glue is prone to giveway at low tempratures

I'll hopefully get some pictures up this weekend.

Rich.

[innivodave]

Hi Rich,

good point about the cold weather affecting the materials used. Hadn't really thought about that too much, and if this winter's anything to go by, the dome could see some pretty low temps. I'll definitely be giving the chain idea some thought. Will keep my eyes peeled for your pics.

Thanks

Dave

[ribuck]

Good think about the duplex chain is that it allows you to screw it to anything to get a solid grip. i'm fitting mine in the morning.

Rich.

[innivodave]

Good stuff, will look forward to seeing it.

BTW, I just had a look at MaxDome II, I can't believe how much they charge for that board, and they don't even give you an enclosure! Crazy price when most of the functionality can be achieved with an arduino and a few components.

Dave

[ribuck]

Hi Dave,

Here the pics of my chain config i promised. The chain worked a treat. The only thing that let me down was my plastic running track.

Unfortunately, the cold weather looks like it had cracked my plastic runner ring and when one of the wheels running on the ring hit this it got snagged up and due to the high torque of the motor/chain config it ended up shattering the plastic guide ring .

Yet another set back. i've been trying to find someone to make me a proper steel ring for a while, looks like i'm going to have to put some extra effort in finding someone to make it for me now

Going back to what i said the other day, i would avoid glueing anything in place due to the cold affecting it, my Diy plastic track is testament to what the cold can do (R.I.P Plastic track lol)

Hope the photo's help.

Here's the motor and chain.

Close up of chain Fixed with screws.

[Bizibilder]

Looks good!

Is the motor fixed or have you put it on a "swinging arm"? By this I mean a hinged mount which is held in mesh with a decent sized spring arrangement. This will ensure full meshing of the gears even if the whole thing is even a little "out" - I bet 5mm is enough to disengage the drive!! Also it means that with a suitable "device" you would have a "quick release" of the cog from the chain to allow you to swing the dome manually to a new position when setting up? and then re-engage the drive.

just a thought while you still have your tools out!!

Hope this helps.

[ribuck]

Hi Biz,

I am planning on a spring mounted solution, i just wanted to test the motor turning the dome today.

Unfortunately with the plastic running track shattering today, i'm pretty stuck for a while until i can find someone to make me a metal running track.

Rich.

[GeoC]

The duplex chain looks like a good idea!

Unfortunately there isnt a good place in a Pulsar dome to attach a chain. It might be possible to make a large wooden ring that attaches to the dome. This could also be used to draught proof the dome which would help to cure the condensation problem.

[ribuck]

Hi GeoC,

the problem is bending the wood into a ring. the ring i'm referring to is not not flat plywood it's need's to be a hoop of sorts for my castors to run on.

I don't have any drafts as such, but I do allow for airflow though my dome, as my understanding is that Airflow does the opposite of what your suggesting and actually helps prevent moisture / condensation build up due to humidity.

circulating the air helps keep a more balanced temprature as it lets the heat escape during the day

Rich.

[mattifor]

The duplex chain looks like a good idea!

Unfortunately there isnt a good place in a Pulsar dome to attach a chain. It might be possible to make a large wooden ring that attaches to the dome. This could also be used to draught proof the dome which would help to cure the condensation problem.

I KNow the problem with Pulsar dome.

I have partly reduced but not removed all together the condensation problem by making a 28Ft long sock polythene tube filled fibre, this I lay arround the gap when Obs not in use. It has almost removed the problem but does need weights on to stop the wind blowing it out of the gap.

I have been trying to motorise my dome but like you have not found a way to fix something for the motor to drive without severly damaging the fiberglass construction

[ribuck]

For Fixing the motor, why not create a freestanding framework which is bolted to the floor of the observatory. The motor could then be attached to the framework without damaging the dome.

I think i saw somone else doing this for a pulsar on the Lesvedome site.

Rich.

[pmlogg]

I've read this thread with great interest as I'm considering the best way to motorise and provide automatic slewing of a Pulsar 2.7m dome to match the movement of my mount. So far I haven't seen anything directly applicable because of differences in the design of the Pulsar dome from other similar products.

Just motorising the Pulsar dome is made more complex because a smooth dome ring is not presented for mounting a chain or timing belt or for a pneumatic tyre or solid wheel to run on. Pulsar's own system mounts the motors on the inside of the dome acting on the top edge of the observatory walls with a solar charged 12V battery power source. So providing mains 12V as an alternative to the provided battery is very difficult and components for automation of the motors would have to be dome mounted too, connecting wirelessly to a controlling computer.

AWR Technology www.awrtech.co.uk/autodome.htm has an interesting section on the subject. They seem to suggest quite powerful motors.

Robot Electronics www.robot-electronics.co.uk/acatalog/Drive_Systems.html, referred to in an earlier posting, seems to have components that might be useful to replicate the Pulsar's Rigel power system. The motors incorporate encoders but are much less powerful that those suggested by AWR.

My immediate questions are what torque is actually needed for slewing the dome and, if anyone has sucessully motorised a Pulsar dome without using a Rigel motor system, how did you do it?

Thanks

[ribuck]

is itpossibleto look up themotor that comes with in the pulsar kit to find it's torque rating ?

Most people tind to find they can get away with windscreen wiper motors, perhaps look up the spec of an verage windscreen wiper motor and at least you will have some idea what to aim for.

Dont forget, it's not just the torque of the motor, you need to consider the motor speed and how many amps it draws under full load and make sure your power system is capable of delivering this.

Rich.

[Euan]

Hi Rich,

Have you looked at LesveDome?

Link: DomeDriver

I have a K8055 and LesveDome license going spare if you want to try it

I don't need it any more since CCD Commander was updated to include custom scripts for dome closure

[ribuck]

Hi Euan,

That's a very kind offer. I actually have my dome automation working already with an Arduino box that i built, but it's not perfect as there is some kind of bug in my programming that cuases the dome to ocassionally go a bit mad and just decide to slew back to the home position.

Would be interesting to try the other board and the lesve dome software and if i can get it all working then i'll buy the stuff off you.

Rich.

[Euan]

No bother I will PM you

Better someone getting some use out it

[pmlogg]

I have been reading this thread with interest.

Has anyone managed to successfully motorise (or even automate) a Pulsar 2.2m or 2.7m dome without use of Pulsar's own motor drive? If so could you please post details?

[ribuck]

Yes There's a guy in the LesveDome yahoo group that had retrofitted his 2.7m Pulsar with home custom kit.

Most DIY dome systems all use the same basic priniples, the only thing that really differs is the software that runs it and the I/O board to control it all.

When doping a DIY dome project you need to kind fo work in reverse when planning the design.

1) Firstly decide on how you plan to actually turn the dome (e.g. how will the motor actually turn the dome ? Some people use chain /cog, some use friction method with rubber wheels (less reliable in my mind), some use pvc cladding with holes drilled and a plastic cog of sorts.

2) Choose your motor, something low rpm and enough power, something like a wheel chair motor or windscreen wiper motor. I paid around £25 for a very powerful ParvaLux motor from Ebay. The guy who did the pulsar dome on LesveDome also used a ParvaLux.

3) Now choose suitable power supply for your motor

4) Choose a power / motor control circuit, to match your motor power draw and your power supply.

5) Choose some form of positional encoder, you can make your own or buy pre-made encoder circuits, this must be chosen based on what I/O board you want to use.

6) Choose you I/O board. For the LesveDome you will need a vellerman.

7) Project box, lcd, buttons. You will need to buy suitable ancillary devices like lcd screen to match your equiptment.

Here's a rough overview........ (I forgot to add in the Encoder in the image)