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Author Topic: Dome Motorisation  (Read 1864 times)

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Offline petevasey

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Re: Dome Motorisation
« Reply #45 on: 21:46:44, 17 March, 2017 »
This guy gave me an idea with his toothed belt drive.  For a few ┬ús (I already have suitable Aluminium bits for a frame) I can manage 4:1 or slightly better reduction within the diameter of my proposed acorn wheel which I would bolt direct to the larger belt wheel so wouldn't need a particularly strong main shaft.  A bit Heath Robinson although I would make bronze bushes for the main shaft.  Or even go posh with small ball races, but hardly necessary for such a low tech application.  Might be the best solution in the long run.  Even with my 112 RPM motor I'd get down to around 25 RPM loaded.  So should manage 5 rpm or less with PWM and probably plenty of torque.

https://youtu.be/hoxBkrD4xCo

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline petevasey

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Re: Dome Motorisation
« Reply #46 on: 16:43:26, 29 March, 2017 »
Hi, Chris, hope you're still following this thread.

I've been quite busy over the last week or so  ;)   The PWM drive unit works well, still waiting for the interval timer, but that's not required for the main testing. 

I've never lubricated the plain bearing nylon support wheels on my dome, but thought it might reduce the turning load.  And it did indeed by around 40%. So I'm pretty confident my drive unit will do the business.    The toothed belt speed reduction is 72/14 teeth i.e. 5.14:1.  The driven wheels are held on their shaft by stepping the shaft with a nut on top, so although the shaft rotates in its bushes, it's not actually doing any driving.  What looks like a bush between the driven wheel and the frame is actually a spacer with a very small clearance.  Just there in case the lower shaft collar slips.  The brass bushes for the main shaft are pressed into the frame.  But if they slacken and start to turn in future I'll use grub screws to fix them.

Slightly confusing in the photo, but the acorn wheel and large toothed wheel are bolted together - one of the two bolt heads is directly in front of the shaft nut. The motor mounting plate has a slotted hole for the bolt nearest the main wheel, for belt tensioning, and the hinge holes under the clamping plate are enlarged to enable final adjustments for level and height.

Still experimenting with hole size and spacing in scrap bits of wood to match the acorn wheel.  Once I'm happy with that it's onto the dome itself.  Probably make a jig for the dome drilling - an awful lot of holes to keep correctly positioned.  But I'll only do a few at first to test the system.  Also need a tensioning system to press the wheel against the dome rim.  But I've got a cunning plan for that (see those tapped holes behind the main shaft.)

Almost there!

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Online chris.bailey

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Re: Dome Motorisation
« Reply #47 on: 17:29:22, 29 March, 2017 »
Looks very good to me Pete. Does that motor 'feel' as thought its generating enough torque to turn the dome. Hard to judge I know but with one of the little Nema 17 steppers with a similar sort of timing cog on it is hard to stop the turn.

Chris
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Offline petevasey

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Re: Dome Motorisation
« Reply #48 on: 17:46:25, 29 March, 2017 »
Looks very good to me Pete. Does that motor 'feel' as thought its generating enough torque to turn the dome. Hard to judge I know but with one of the little Nema 17 steppers with a similar sort of timing cog on it is hard to stop the turn.

Chris

Hi, Chris, yes, even at a final RPM of around 6 there's more than 10 KG pull on the acorn wheel.  Very promising  ;)

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline petevasey

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Re: Dome Motorisation
« Reply #49 on: 19:08:30, 02 April, 2017 »
I'm still waiting for a couple of parts to finish off, although the wiring (wired remote control box etc.) is all complete.  But this link just came up on a different site.  Although the source is in America, pity I hadn't seen it a few weeks ago - one of the slower motors would have done the job directly, particularly with the encoder.

https://www.servocity.com/motors-actuators/gear-motors/heavy-duty-gear-motors

Maybe if I eventually go the Arduino route, I would think about one of them (45 RPM) still using my reduction belt drive but maybe with an Exploradome acorn gear and strip.

Or to directly replace my wiper motor if it turns out to be struggling to go slowly enough, maybe this one from ebay, half the no load speed and plenty power:

http://tinyurl.com/n3sokdx

Worth keeping on record.

Cheers,

Peter
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

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Re: Dome Motorisation
« Reply #50 on: 22:24:10, 02 April, 2017 »
The motor with built in quad encoder is a nice find but a high torque stepper is easier to code.

Chris
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Offline petevasey

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Re: Dome Motorisation.
« Reply #51 on: 13:23:36, 10 April, 2017 »
UPDATE

It works!   :thumbup:  Not quite finished, I still need to add tensioning, and drill lots more holes.  So far 33 out of around 260, but enough to do a workable test.  It looks as though the acorn wheel will run slowly at around 3 RPM under load and 10+ RPM at full speed, again under load.  So a 3 second 'nudge' every 10 minutes or so for unattended long exposures, and a full rotation of the dome at speed in about 2 1/2 minutes.  Still waiting for the interval timer.

But I discovered some worrying rot in a section of the rim.  Until I come to drill that part I won't know whether some of it will need replacing - a tricky job because the external panels are screwed to it.  Hopefully I will prevail, but I fear a new dome will be needed in the not so far future.  I just might be able to fit a Pulsar 9' dome on my existing base, but that will need some tricky carpentry!

Later - on looking at dimensions a Pulsar dome will not be practical.  So probably a full dome and base assembly.  At least I'll be able to modify my drive unit with a rubber wheel instead of the acorn and fit a pressure wheel behind the inner rim, so that work will not have been wasted.

Once all is finished I'll post some more photos.

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

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Re: Dome Motorisation
« Reply #52 on: 08:11:05, 11 April, 2017 »
Great stuff Peter. Lets hope the rot is not too extensive as your tests sound as though it is a workable solution.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
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Offline petevasey

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Re: Dome Motorisation
« Reply #53 on: 15:55:43, 18 April, 2017 »
Well, although the rot was nasty, a liberal application of wood hardener stabilised things and all is working ok.  For now anyway!  I'm still waiting for the electronic timer unit to arrive from the Far East, but everything else is now installed and connected, and 264 (!) holes have been drilled in the dome inner ring using a jig following a line scribed on the dome rim using a sharpened bolt screwed into one of the acorn wheel holes.  Took a few hours but worth the effort!

I made a hand controller so I can get in the best place for initial positioning of the dome at the start of a session.  The main switch from a 12 volt battery is self illuminating.

The toggle switch on the hand controller is to switch between timer pulsed and manual control, the rocker switch for forward and reverse, and the potentiometer is of course to control the speed.  Both the rocker switch and potentiometer came with the drive unit.  The item covered with black film is a burglar alarm sensor!  The loose wires are eagerly awaiting the arrival of the timer unit - I hope it arrives soon before we get right into the light summer nights.  I used the drive manually last night - worked beautifully  ;)

Pics below, and a (5.75MB) video here. http://www.madpc.co.uk/~peterv/astroplover/equipnbits/bitspics/DomeDrive.mp4

The creaking noise is just that - the wooden dome flexing a bit as it rotates. Nowhere near as bad as it sounds in the video.  The motor runs faster in reverse than forward - just a feature of the motor, probably slight misalignment of the brushes, but nothing I can do about it, and not a problem.  Towards the left of the top photo you can see where a small piece of the outer lamination of the plywood has split off between a couple of holes due to the action of the acorn wheel.  This has happened in several places, but once it has happened there is no further damage, and it doesn't affect the working of the wheel.  A lick of paint will tidy it up!

Cheers,

Peter.

GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

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Re: Dome Motorisation
« Reply #54 on: 18:06:00, 18 April, 2017 »
That looks to be working really well Peter. It will be interesting to see how well the pulse timer add-on works or if you will want to then go on with full automation, its not as big a step as it seems...you have done the hard bit.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
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Offline petevasey

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Re: Dome Motorisation
« Reply #55 on: 21:29:04, 18 April, 2017 »
Thanks, Chris.

And very many thanks for all your help and encouragement.

Yes, full automation would be an interesting challenge.  I may at some time upgrade to a stepper motor system - finer speed control and maybe a wider speed range.  But slaving it to the telescope might overtax my ageing brain  :crazy:  Time will tell....

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline petevasey

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Re: Dome Motorisation
« Reply #56 on: 15:20:04, 19 April, 2017 »
The timer unit has arrived  :D

And does exactly what I'd hoped - set for a long interval followed by a short activation of the motor.  The sequence repeats endlessly and can be manually reset to the start of the sequence either by the built in reset button or by switching the power off and on again - remembers the settings all the time.  Easily set up once I re translated the rather confusing instructions.   Just a reminder (it's early in this thread), it's this type (the original seller is no longer listing it):  http://tinyurl.com/lxhohgg

and this is the variable speed unit:
http://www.ebay.co.uk/itm/10-50V-40A-PWM-DC-Motor-Speed-Controller-CW-CCW-Reversible-Pulse-Driver-TE535-/262521215361  Cheaper to buy from China, but I wanted it more quickly!

Cheers,

Peter.

 
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

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Re: Dome Motorisation
« Reply #57 on: 15:53:36, 23 April, 2017 »
Great news that it works Peter. So you are all up and running now?

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
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Offline petevasey

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Re: Dome Motorisation
« Reply #58 on: 00:03:42, 24 April, 2017 »
Hi, Chris,

Hopefully! I was away over the weekend, and it looks like I missed a couple of clear nights.  But when there's another one....

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

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Re: Dome Motorisation
« Reply #59 on: 17:39:16, 25 April, 2017 »
Ok - Last night was a beauty (finished off my NGC4151) and the drive worked flawlessly  :yes:   But I need to work more on the speeds and intervals.  At the lowest speeds it's very sensitive to slight changes in the speed setting.  So maybe a longer interval (I was using 3 seconds every 5 minutes) at a faster speed will be easier to manage.   Nevertheless I was able to go 1 1/2 hours without attention.  Hopefully will manage 2 or 3 hours eventually.  Of course I can experiment during the day - no need to use precious imaging time!

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

 

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