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Author Topic: Dome Motorisation  (Read 3280 times)

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Offline ngwillym

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Re: Dome Motorisation
« Reply #30 on: 16:53:52, 14 March, 2017 »
Chris, Peter, thanks for the dome instructions - amazingly I still have an original copy of mine!. As  suspected, that's for the newer version of the dome, where the wheels are attached to the base - mine are attached to the dome so the only way seems to be to put motor and power supply (battery I assume)also attached to the dome - possibly taking the place of one of the wheels. Hadn't considered that until now - was always looking to mount the motor and drive mechanism on the base wall

In which case, I just need to find out the type of motor and wheels to use.
Thanks for all your help.
Neil
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Online chris.bailey

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Re: Dome Motorisation
« Reply #31 on: 17:22:39, 14 March, 2017 »
Neil

All of my drive gear is mounted in the recess on the non opening side of the dome. Hopefully the attached shows how I have done it. I retained the mounting bracket of the original Rigel dome stepper system but replaced everything else. I use an 11 aH UPS battery to drive the motor, easily lasts the night for the occasional nudge . I do have a solar panel for charging it but find a trickle charger more effective in winter months.

Chris
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Offline ngwillym

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Re: Dome Motorisation
« Reply #32 on: 20:18:44, 14 March, 2017 »
Thanks Chris, that helps a lot.
Neil G
50.8920° N, 1.4530° W
Scopes: Celestron C11 Fastar, Opticstar 127mm Apo, Celestron SLT 102, Celestron Travelscope 70
Mounts: Skywatcher EQ8, Skywatcher EQ5+Synscan, Celestron SLT 102
Cameras: QHY5L-IIM, DFK21AU, AVS DSO-1, Watec 120n, Sony A100/A580
Eyepieces: Quark Chromosphere, Parks Gold, Lumicon GEG

Offline ngwillym

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Re: Dome Motorisation
« Reply #33 on: 21:08:08, 14 March, 2017 »
Chris,

however, being a complete electrical/electronic numpty - i have no idea how this stuff gets wired together - I'm assuming its not as simple as connecting the motor to a battery with an on/off switch or a toggle switch for forward/backward?

any and all help gratefully received.
Neil
Neil G
50.8920° N, 1.4530° W
Scopes: Celestron C11 Fastar, Opticstar 127mm Apo, Celestron SLT 102, Celestron Travelscope 70
Mounts: Skywatcher EQ8, Skywatcher EQ5+Synscan, Celestron SLT 102
Cameras: QHY5L-IIM, DFK21AU, AVS DSO-1, Watec 120n, Sony A100/A580
Eyepieces: Quark Chromosphere, Parks Gold, Lumicon GEG

Online chris.bailey

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Re: Dome Motorisation
« Reply #34 on: 21:11:22, 14 March, 2017 »
Neil

It could be but its just as easy to push it!

I started off with the Rigel system installed that is basically an adjustable timer that nudges the dome over a variable amount of time. Thats about as simple as you want it. It prolongs the period over which the dome slit stays over the scope but its not perfect. To go all the way where the dome syncs with the scope pointing is a lot more complex as outlined in this thread.

Chris
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Offline petevasey

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Re: Dome Motorisation
« Reply #35 on: 00:54:34, 15 March, 2017 »
Hi, guys,

This thread is getting quite extensive isn't it!  Chris, I thought you were using a wiper motor.  But that's not really important.  Neil, all I'm hoping to do initially is a system which will automatically nudge from time to time like the Rigel system.  But a LOT cheaper and suitable for my particular dome design.  Earlier in this thread I suggested drilling the wooden rim for an acorn drive.  And indeed have the parts to make one.  But I fear Chris is correct that the timber would wear relatively quickly.  Attached is a scale cross section of what I might do.  It shows that layout would probably work.

I've had a go with a socket cap screw (8mm as in the photo).  Turned to shape (approx. 12 mm diameter x 9 mm long), inserted in a hole (I enlarged an existing one) and pushed by hand it does move the dome.  Until actually on a wheel I don't know if the bolts would try to jump out.  But I'm pretty sure it would work.  For a while.  I would need to get a smooth finish on the bolt heads to minimise wear and probably also oil the wood.  I suspect the Explora-dome system is made from a hard slippery plastic, maybe nylon or polypropylene.   For my home made system I'll have to drill around 280 holes accurately spaced!  Hmmm.

I'd get a lot of satisfaction from making my own acorn system, but it would be a pity if I had to start over after a few months.  Watch this space  ;)

Cheers,

Peter
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Offline petevasey

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Re: Dome Motorisation
« Reply #36 on: 10:26:03, 15 March, 2017 »
Just spotted this on ebay:

http://www.ebay.co.uk/itm/10-50V-40A-PWM-DC-Motor-Speed-Controller-CW-CCW-Reversible-Pulse-Driver-TE535-/262521215361

Looks promising, already has an external potentiometer speed control and a reversing on-off switch.  Even cheaper versions at the foot of the advert.  I'd probably mark settings of the pot. for fast, medium and slow, with the little relay unit I linked earlier to pulse every 10 or 15 minutes in slow speed to give near sidereal.  Just bypass that unit for manual control.  But I'm not quite sure what they mean by "Output voltage: Load linear, Speed principle: Current regulation".  I assumed PWM would be applying full voltage (and therefore maximum torque) every pulse.  I've queried the seller.  What do you think, Chris?

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 #37 on: 10:46:28, 15 March, 2017 »
Peter

I saw those and yes that should work with the timer unit you linked to earlier. You could ultimately replaced the switch with the output from an Arduino though you wold need to check the logic voltage, probably safer to put a relay in between to separate the two, but thats looking ahead.

I 'think' the load linear current attenuation bit refers to the way the pulse width modulates current rather than voltage as motors don't like chopping the voltage. Not 100% sure though.

Chris

ps the motor I have had a Suzuki label on it so I assumed it was a wiper motor (can't think of anything else vehicle related), it is bigger than the ones currently shown on eBay so maybe its not
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Offline petevasey

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Re: Dome Motorisation
« Reply #38 on: 11:04:57, 15 March, 2017 »
Thanks, Chris,

With the motor on its way, I've already ordered the little timer unit, and stuff from Hong Kong etc. seems to take a few weeks, so might as well order one of the motor controllers.  At around £6 or£7 it's only a couple of pints of beer!  Then once I know what the motor system is capable of I can decide which route to go to actually drive the dome.  I suspect I'm going to go for the home made acorn system for now.  If it wears unacceptably quickly, then dig deep for either the professional acorn or a toothed belt.  But then we're talking £100s instead of £10s.

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 #39 on: 11:09:38, 15 March, 2017 »
Peter

If you don't mind I am going to split this thread away to a new one. I'm sure others will be interested at some point in the future and "Sorry about the weather" doesn't make for easy searching.

Chris
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Offline petevasey

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Re: Dome Motorisation
« Reply #40 on: 11:56:10, 15 March, 2017 »
Peter

If you don't mind I am going to split this thread away to a new one. I'm sure others will be interested at some point in the future and "Sorry about the weather" doesn't make for easy searching.

Chris
Absolutely, Chris.  And yes, could be very useful for others.  If all comes to bear good fruit, maybe make it a 'sticky'.

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 #41 on: 23:06:34, 15 March, 2017 »
Hi again, Chris,

I've got a problem!  All of the windscreen wiper motors I looked at which specified a speed stated values around 60 RPM.  But muggins goes and buys a non specified one.  It arrived today, very nicely made, quiet and smooth, BUT the no load speed is around 112 RPM!  I think I'll be hard pressed to get it down to even 10 RPM never mind 2 or 3 with enough power to drive the dome  :(

I should have the PWM drive unit in a few days and will give it a try, but I'm not optimistic.  In the meantime I spotted this one.  http://tinyurl.com/hwh8ser  Also available at 6 RPM, which if it is the same motor will of course have twice the torque although maybe a bit slow.  With the home made acorn wheel (or a 3" toothed belt wheel)  the 6 RPM unit will take at least 5 minutes for a full rotation.  Probably not too bad really.  2 or 3 minutes for the 13 RPM version.   I've asked the vendor for torque figures.  Fingers crossed!

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 #42 on: 17:48:26, 17 March, 2017 »
Hi, All,

This is a photo from an ebay advert showing the wiring into a Vauxhall Astra wiper motor, advertised as 65 RPM.  Does anybody know what the various connections are for?  I imagine the ones onto the back of the gearbox are to do with the park position.  But why three into the motor itself?  Maybe two speed which implies field coils and possible difficulty in reversing without opening up the motor and altering connections internally, even if that is possible.

In hope,

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 #43 on: 19:39:24, 17 March, 2017 »
Peter

They have two brushes so one is high speed and the other low speed and yes the contacts on the gearbox will be the park position sensor switch and the reverse position sensor. Most modern wiper reverse before the park. Park puts the wipers lower down.
Should be no issue in wiring to the high or low speed, may even be a way of wiring to both to get more torque. Brown looks to be +ve so I would try allying a battery between it and one of the other two and see what happens. I have had a few things go bang during "experiments" but the biggest was from a biggish capacitor I wired the wring way around. That led to a bit of ceiling re-painting!

Chris
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Offline petevasey

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Re: Dome Motorisation
« Reply #44 on: 20:13:19, 17 March, 2017 »
Many thanks, Chris,

At the moment I'm waiting to see what the speed controller can achieve with my existing motor, but looking for alternatives.  And for the seller to confirm the 65 RPM for the Astra motor.  Fingers crossed.  If I get one, I'll put a test meter on the motor wires before going boom  ;)  I never blew up a capacitor, but overcharged some NiCads once.  Resulting in burn marks in several places in the kitchen!  Fortunately I wasn't in the room at the time  :snore:

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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