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scorpius

RA DIY Motors

15 posts in this topic

I posted that I was getting an RA motor for the EQ1 that came with my Mak90.   At the same time I toyed with the ideal of making my own and doing a search I found what appeared to be some suitable geared motors.  one of them was 12Volt DC motor with built in gearbox that revolved at 0.6 RPM see:  http://tinyurl.com/jezzajl  I have 2 of them and they appear to have good torque and tests so far is that they will run quite happily on 6v at even a much slower speed.  I have yet to do further tests, but there are 2 methods one is purely lowering the voltage by using variable power supply or by using the PWM power control units which are also very cheap.

The advantage of using PWM is that the voltage remains at 12v and the pulses are widened or narrowed to increase or reduce the motor speed.  I use these on my model railway locos and can have a loco screaming around at 100mph or simply very slowly crawling.  My only concern about using PWM is that with Photography on timed shots the pulse could be an issue with the resultant exposure.  For general viewing it would really have no effect on the image presented.  So far I have not found a reduction gearbox slower that 0.6 RPM The units are selling around $12 ea and the Speed controllers start at around $5 

For EQ1/2 Tripods the control shafts are 6mm in diameter and the motors are 1/4" output shaft  Spiral metal couplers are available 6mm to 6.36mm which is 0.01mm oversize.  http://tinyurl.com/z8cyfp8

When the temperature drops below 40C I go back to my shed and do some more tests.  The motors will fit in a similar sized  box as the Sky Watcher RA motor unit

 

Dave

 

 

 s-l200.jpg

 

s-l1600 (1).jpg

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Looking good. With a my bench power supply set to 6 Volts regulated DC. the output dropped to 1 revolution every 3 minutes.  The SW RA device by the way runs off a 9Volt battery and claimed to last up to 40 hours.  A simple variable  LM338 voltage regulator (7 amp) device  and a pair of   3.7V  3amp  #18650 batteries would last a week !! (maybe) built into a small zippy box.  

I also have a number of 10 turn potentiometers with a small 1/2" calibrated dial for accurate calibration and resetting. 

PS the Skywatcher RA module appears to rotate at  1 Rev per 6 minutes (app) 

The gearbox motor will rotate as low as 3V DC.  But think PWM is probably better to gain more tourque.   Tests continue/

Dave

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Jeesuz Dave, what a sneaky little mod you've done. Very impressive, I hope it works out. Keep us posted on the testing, be handy for others to see. 

Ray

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A wee update to things. having celebrated 2 Christmas's and 2 New Years (Julian and Gregorian with Val), during the period Planets and moon have been in all the wrong places, then the weather broke and been very cloudy with rain, jeepers anyone would think we had moved to a Summer in Sydney or Melbourne. Rain in January and temps below 30C virtually unheard of in Perth.  

Howsomeever did some more tests using a PWM source of control of the motor/gearbox and still had it running at 1RPM per 8 minutes, far less than I need at 1rpm/6 mins I was unable to stop the motor, so the torque is there.   Still waiting for some couplers etc and then will make up a power pack and mounting  bracket. 

Received a Bahtinov Focusing grid today 31/01/17 very well made and will fit the SW 90/1250 scope nicely.  Also downloaded a sheaf of info on using the device and this may be the answer to my failing eyes, I have also picked up a 10 inch monitor with HDMI/AV/Comp inputs which I can use with the 500D Canon in Live mode. I will make up an "easel" on which to mount my control and monitor device.  With my small Notebook (Asus) on a fold down table. This  unit will also be very useful for when I eventually drag out the EQ6Pro/10"   So Lots of things to do, but it will make life so much easier.

Couple of Pics, the Focuser and a ready to run external screen that are available on EBay.  Quite pricey compared with buying a basic 10" monitor plus it is only a 7"  display. You're paying for the Frame and mounting etc. Probby OK for young eyes :)

Looks like the skies will clear at the end of the week. 

Dave 

 

 

 p.jpgCV.jpg

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Hi Dave,

the Bahtinov mask will definately make life easier, you can also download software for the mask which helps heaps as well. It is called Bahtinov Grabber and is free, it may be a bit hard to find but try googling it and it should come up. The author has passed away and his wife didn't want to worry about upkeep of his site, but it can still be found through wayback machine. If you can't find it just shoot me a pm with your email and I'll send the setup file to you. After that spiel I just got the web address for you to try out .lol

https://web.archive.org/web/20160220123031/http://www.njnoordhoek.com/?cat=10

 

Shane

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Thanks Shane - Yep I found a copy 32/64 bit version and downloaded it earlier,  apparently is now abandon ware.  The link works, some of the contents have 404 error, which is to be expected.

Have grabbed some alternate versions to what I have. :)

Just replaced the 12volt 10Amp  SLA battery in my "Scope power Box".  Supplies power to EQ6Pro, focuser and fans etc with sockets for 12V/5V DC and a 10amp 13.6V AC PSU for charging or running of an invertor Also has socket for 12V Solar panel input. 

Dave

 

IMG_4055.jpg

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Epic rig coming together there mate. The mask will help you, its quite easy to tell (good eyes or not) when things are in focus. I use one of these, just downloaded the same grabber software as well, but as you know, the weather here in Perth is terrible at the moment so I haven't had a chance to test it yet. This hobby never ceases to amaze me at how much there is to learn (I feel I am constantly climbing upwards). 

Ray

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You never stop learning Ray.  When I left school to Join the Navy aged 16, the headmaster said to my father "Well, that is the end of his his education!"  My father replied "Mr Birtles, there you are very wrong, today his education starts, you have only given him the tools to learn".   My father was a Fen Drainage Engineer and was classed as an "Essential Worker" and excused call-up in WWII because of his Engineering skills.

Have never forgotten that day and yes, it is an upward climb, hobbies, pastimes etc, the more you learn about them,  the more enjoyable they become.  

A motto of one of the schools I attended was: "If its worth doing, its worth doing well"  I think that says it all. 

BTW. I think there is a conjuction of Venus, Mars and the Moon this evening  in WA.  Break in the rain and clouds also, seems we have broken a bunch of records for January for foul weather.

https://www.joe.ie/news/make-sure-look-sky-tonight-see-mars-venus-moon-rare-sight/575671

Dave 

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I agree. I'm always learning and studying something Dave. As you know just finished a degree last year, chasing a second this year. And yeah the weather is shocking for this time of year, I can't believe it. Its like the middle of a Perth winter. Not happy, supposed to be 40 degrees each day. Its almost sub tropical, which is a worry. 

Ray

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With cloudy skies at night and sunny days (for the moment) made up the controller mentioned above, and fitted it to the EQ1.  Together with the reversable PWM speed controller, as this is on the DEC control it will only need to be used to touch up any minor error in tracking and has a reversable switch.   On my control panel I will have this mounted plus a press button to activate such for minor movement. this will also work as an RA driver as I can run it at around 1 rpm per 6 mins.  The aluminium bracket I made conveniently uses the rear scope mounting screw which is long enough to hold the controller and the scope :) 

The joy of this? its 1/4 the cost of a SW RA motor drive commercially available.   (I have some spring type shaft joiners coming. But the fixed one should be OK the alignment is pretty spot on.)

Any one interested in source of parts can PM or Email me :)  Luckily I found a bag of screws for the gear box in my junk box I think they are 2.5mm Jif

 

Dave

 

IMG_4072.jpg   IMG_4066.jpg

 

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Tks Shane.    Will tidy up the wiring and give the job a lick of  black paint.  I will make a power unit control box and include the PWM unit plus interface of the 500D to the 10" monitor I now have for "live" focusing. 

The whole set up will be really easy and convenient to use remotely with the laptop. 

Weather in the West is shocking  today coldest Jan on record apparently and we have a week of rain from Tropical Lows coming down from the NW.  (Global Warming ?)!

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3 hours ago, scorpius said:

Weather in the West is shocking  today coldest Jan on record apparently and we have a week of rain from Tropical Lows coming down from the NW.  (Global Warming ?)!

At least the bad weather is during the full moon Dave. But yeah, shocking weather for February. Can't believe it. If that tropical storm up North heads down our way I'll be hopping in the car and chasing it for an hour or two, should be some good photo ops. 

Mount mod is looking good. Well done. 

Ray

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OK Ray - Even too cold to paint that mod,  struggled to reach 19C here today Bah - Still we need the rain to fill the dams, understand the Avon is flowing again. Bells could be an interesting shoot. (with a cam not a canoe!!!)

See current flow  https://www.youtube.com/watch?v=cjvUmF-6XXA

 

 

Dave

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1 hour ago, scorpius said:

OK Ray - Even too cold to paint that mod,  struggled to reach 19C here today Bah - Still we need the rain to fill the dams, understand the Avon is flowing again. Bells could be an interesting shoot. (with a cam not a canoe!!!)

See current flow  https://www.youtube.com/watch?v=cjvUmF-6XXA

 

 

Dave

42C here today, 10:30pm and still 30C.

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