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Tcerbulis15

Skywatcher EQ 3-2 Motor set integration with EQDrive

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Hello,

I am currently setting up my EQDrive unitrack with my EQ 3-2 mount and upon opening the EQDrive config, I press read and stare into the abyss as I realize that I know nothing about the motor parameters and gear ratios. 

I'd be greatly thankful if somebody could put me on the right track.

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Hi, and welcome to SGL.

The EQ3-2   RA worm gear ratio is 130:1 and the DEC is 65:1.

The other parameters will depend on which stepper motors you are using & what gear sets  or pulleys & belts you intend to use to connect them to the worm shafts.

 

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11 minutes ago, Tcerbulis15 said:

I have the stock EQ 3-2 motor drive upgrade kit. 

I assume that you have either the "Dual Axis Motors" or these "Enhanced Dual Axis Motors"   sold under Skywatcher or several other brands;

https://www.firstlightoptics.com/sky-watcher-mount-accessories/enhanced-dual-axis-dc-motor-drive-for-eq3-2.html

These are OK for converting a manual EQ3-2 into a tracking mount but I would NOT recommend them as the basis of a GoTo system.

It can be done and It has been done,  but these motors are not capable of being driven fast enough to produce a satisfactory  GoTo system. It would be very sluggish at best  & I believe you would be disappointed with the result.

I believe that EQDrive sell motor kits to go with their controller. I haven't used them myself but assume they would be fit for purpose, although maybe expensive.

I built a diy GoTo system for my EQ3-2 based on the open source OnStep project using a pair of NEMA 17 stepper motors and belt drives. Since you already have the EQDrive controller you would not need the OnStep software or controller, but there is enough information in the Wiki  to enable you to select motors & drives for yourself if you wish, which would be a lower cost solution.    onstep@groups.io | Wiki

There is another similar project, AstroEQ, which may be of interest.   Tutorials & FAQ’s

Food for thought?

 

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Hi,

Thank you very much! I have tried setting up AstroEQ but the one I had ordered was a bit out-dated and one of the stepper motor drivers blew up. XD

I will definetly look into the options I have for the stepper motors!

Cheers!

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Hello,

I have finally settled on using NEMA 17 motors. I did some research in my free time, but did not come to a clear understanding on the pulley/belt system that would fit my needs the best. 

What belt/pulley system do you have on your EQ3-2 mount? 

Cheers!

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I used type T2.5 Timing Belts & Pulleys from;   https://www.beltingonline.com/timing-pulleys-bars-272/t2-5-pulleys-279/?zenid=8fkphh3cp60497d3o16aq3vkv3

On the motors;  15 tooth pulleys, bored to 5mm (check your motor shaft dia), each with 2 off M3 grubscrew holes.

On the worms;   30 tooth pulleys, standard 6mm bore, each with 2 off M3 grubscrew holes.

This obviously gives a ratio of 2:1 which works fine. If I was starting again I would use 40 & 16 teeth for a ratio of 2.5:1 giving more precision for a few pennies extra.

I used these motor mounting brackets;  https://www.ebay.co.uk/itm/3D-Printer-Parts-42mm-L-Bracket-Mount-for-Nema17-Stepper-Motor-Alloy-Steel

One of these brackets mounts the Dec motor as is. I had to make  a second angle bracket to fit the RA Motor+bracket to the mount.

I suggest you mount the motors before ordering the pulleys & belts so that you can check pulley clearances & accurately measure the distances between the relevant shafts & calculate the required belt lengths. There is no room for error with these tiny belts.

Here is a belt-length calculator;  https://bepltd.com/pages/how-to-calculate-belt-length

These are the belts I used,  6mm wide;  https://www.beltingonline.com/t2-5-synchroflex-timing-belts-2903?zenid=8fkphh3cp60497d3o16aq3vkv3

Hope this helps.

Out of interest, how many steps/rev are your motors and what microstepping options does your EQDrive controller allow?

 

 

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Hello!

Truly, thank you for the information and help!

On the datasheet it says that the EQDrive unitrack supports gear ratios 1:1 to 1:2000 and slew speeds up to 10 degrees per second.

I have not yet purchased the motors, but I am planning on buying 400 step motors for more precision.

Clear nights, cheers!

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If you use 400 step motors and a 2.5:1 belt drive ratio,  32 microsteps would give a (theoretical) precision of  0.3 arcsec on RA, which is about the same as the factory Synscan Goto's achieve.

3 or 4 deg/sec is a good slewing speed.

10 deg/sec would be more like a missile launcher than a scope mount, but if the motors have enough torque, why not. 😀

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