Motorising the EQ3-2

[Avocette 129]

I've just about got used to operating my EQ3-2 by its flexible manual control knobs but I'm increasingly aware of the wobble I introduce each time I adjust them them. So I would seem to be a natural candidate for a set of SW motors. However I don't want to spend £90+ for some 6 volt motors which have a reputation for blowing up hand controls and eating up batteries. I have read the AstroEQ (excellent piece of work by Tom Carpenter!) thread in this DIY section which offers a very attractive pathway towards full control and go-to tracking of the mount. I am therefore particularly interested in avoiding the SW motor drives and making use of some stepper motors with home constructed brackets as a first stage modification. But is there any way I could do this and control the motors in a semi-manual way without needing always to use a laptop running EQMOD etc? In other words, for instance, could a version of AstroEQ be interfaced with a manual control box (especially IR linked) driving stepper motors and offering simple object tracking?

I started this as a new topic because I have some difficulty navigating within the AstroEQ 20+ page thread and don't want to distract.

[Squagnut 35]

If I have it clear that you'd like to be able to control the RA and Dec stepper motors without needing AstroEQ/EQMOD to be plugged in then ... in short, yes.

If you make another setup which plugs into the motors (i.e after unplugging the AstroEQ box from them), you could easily get a microcontroller + stepper control board to run the steppers at whatever speed you like, governed by e.g. potentiometers (but, by "IR linked", did you mean you'd like to control this with an IR remote? If so, that too can be done). That should do simple tracking. This sort of thing is exactly what Arduinos are good at. It wouldn't be a version of AstroEQ, of course, it would be just a way to control stepper motors.

To run steppers for any significant time can also be very power-hungry, especially those chunky 12v motors, because they're on all the time - they consume ~the same energy staying still as they do moving. You'll need a car battery or power tank or something similar.

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Hi and thanks for your encouragement! Since posting the first question I have come across AstroTux's thread on a similar topic. So now all I have to do is start to get to grips with Arduinos and the like. I am a (retired) electronic engineer and had plenty of laboratory experience of digital technology in broadcasting. We usually did our digital processing in hardware for speed so my use of software is more Windows/Office 2007 than C or similar. And driving stepper motors is a step ('scuse pun) into the unknown.

[Squagnut 35]

Terrible pun! Well, you asked if it's possible! All I can say is that four years ago, I'd have been completely unable to do the things I can do now. I still have my first stepper motor, and I can still make it go! My knowledge of C++ is still pretty scant, but luckily there's a lot of public domain Arduino code online, waiting to be used and adapted. There probably are other ways to run steppers, but this is probably the most accessible way. Some minor geekery is hard to avoid!

I'll look up some helpful websites. There's a massive amount of useful info out there. The arduino site is a good start: http://arduino.cc/

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Thanks for your help!

[m000c400 67]

 In other words, for instance, could a version of AstroEQ be interfaced with a manual control box (especially IR linked) driving stepper motors and offering simple object tracking?

I started this as a new topic because I have some difficulty navigating within the AstroEQ 20+ page thread and don't want to distract.

As other have said this is very do-able these days, and with all the Arduino and Arduino-like prototyping stuff around (both hardware and software) you can pretty much do it by assembling off the shelf components; both in hardware and software, and just do the "glue" your self. My own "project" is pretty much as you describe, starting with a vanilla EQ2-3, but I've implemented a full GOTO system; once you start this isn't much more difficult.   

But, your IR control is an interesting idea that I hadn't though of.  A quick look shows that there are quite a few TV like IR remotes plus receivers around for "pocket money". So this bit would be easy to do too.  In fact based on this I think I'll add this feature to mine over the next few weeks.  A pocket size remote seems a lot more practical in the dark muddy back garden that my current solution... a good idea!!

Mike 

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Hi Mike,

A lot of DIYers seem to start with the EQ5, and obviously the larger/heavier the mount the more stable in use, but I already find the EQ3-2 heavy and clumsy enough to handle so I'm keen to stay with it as a sort of grab and go. Did you start from the SW motor set or make the more radical move to your own stepper motors? I'd like to be sure that I get the most suitable ones for the EQ3-2 with 150p payload.

Thanks, Ed

[Squagnut 35]

Yeah, the fun thing with Arduinos, etc., is that you get options. I'd start simple, just controlling steppers by a couple of potentiometers on analogue pins to get the basic principles, but this sort of thing can go as far as you let it.

A useful resource is EasyDriver inventor Brian Schmalz's example code page - Click.

[m000c400 67]

Hi Mike,

A lot of DIYers seem to start with the EQ5, and obviously the larger/heavier the mount the more stable in use, but I already find the EQ3-2 heavy and clumsy enough to handle so I'm keen to stay with it as a sort of grab and go. Did you start from the SW motor set or make the more radical move to your own stepper motors? I'd like to be sure that I get the most suitable ones for the EQ3-2 with 150p payload.

Thanks, Ed

Hi,

I went "radical" from the start.  I wanted to be able to leave the hand slow-motion controls in place so I could still jump out into the garden and set up in <10 seconds when the children say "Hey Jupiter is visible, can we look". But I also still had an eye to eventually wanting very fine control. To square these two, I bought the highest torque NMEA 17 motors I could find (ebay is teeming with them), and have them on "direct drive", with no gear box.  With the power off, you can still use the hand controls like normal, but because the available motor torque is so high with power on, I can microstep down far further than the usual x16 that people tend to use ( I can set upto x128 ) and get the same sort of resolution as a traditional geared design. So I have something that now covers everything from hand controls to sub arc-second GOTO all in a single package.. the best of all worlds  . 

Like the others have said, start simple.  My first go was just the RA axis on a fixed sidereal speed. Nothing helps you make progress more than a few simple succsses, and nothing slows you down more than something complex that doesn't work

Based on you idea above I ordered my IR handset and receiver earlier. A whole £1.80, although I expect delivery  from China could be slow.....

[Avocette 129]

Hi again,

 I bought the highest torque NMEA 17 motors I could find .... and have them on "direct drive", with no gear box.  

Does this mean that you literally connected the motor with a simple coupler to the free end of the slow motion control driveshaft? I noticed that a number of the NEMA 17 motors on eBay come with MXL belt drive pulleys and belt drives seem to be quite popular with (EQ6) mount modifiers. 

Based on you idea above I ordered my IR handset and receiver earlier. A whole £1.80, although I expect delivery  from China could be slow.....

I saw these incredibly cheap products offered with free delivery from Hong Kong and China and wondered how slow the boat may be? I read elsewhere that FLO suggest that orders for Sky-Watcher spare parts can take five months to be delivered! 

[m000c400 67]

Hi again,

Does this mean that you literally connected the motor with a simple coupler to the free end of the slow motion control driveshaft? I noticed that a number of the NEMA 17 motors on eBay come with MXL belt drive pulleys and belt drives seem to be quite popular with (EQ6) mount modifiers. 

I saw these incredibly cheap products offered with free delivery from Hong Kong and China and wondered how slow the boat may be? I read elsewhere that FLO suggest that orders for Sky-Watcher spare parts can take five months to be delivered! 

Yes, that's it for the RA axis.  The motor for the DEC axis is tucked round the corner so needs a MXL belt drive.  This has a very modest 30:18 ratio on it solely because that was the sweet spot of pulley sizes and belts that were in stock at the time I ordered.  You can see it all here, which reminds me to tidy up those last few wires...

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Many thanks, a picture is worth a thousand.....!

[clertem 1]

Hi  m000c400,

Great work !

I am working on a similar project as yours and would be interested to know what type of NEMA 17 ones you chose (these are sold in a variety of torque / steps) ?

I can see on your photo above that the RA stepper is directly connected to the mount shaft, and I am surprised that the idle torque of the motor is enough to immobilize the mount. Is it the same for the other axis (we can't see the other side). I have tried with a couple of CNC pulleys and belt for the DECL axis but unfortunately the weight of the scope+camera was too high and the belt was skipping on the pulleys all the time...

Another thing I am interested in is how you actually fixed the motors to the mount. I've been working a lot on possible design for this and came up with little successful results... The one I have for the moment is kind of supported by the counterweight shaft using a circular bracket. 

Originally the motors I got (from the bin of our engineering building at Uni) were too fast and I had to go with a worm/gear combo of about 40:1 ratio. Tests were OK on the RA axis, but the way I've got it mounted is not great and the motor vibrates, thus worm moving slowly out of its gear. I am surprised that you have achieved a working RA tracking simply on a direct connection like this !

I just have to solve that mechanical part, because for the rest, it's pretty allright. I'm driving them by an arduino (with dual stepper driver shield).

I've posted where I am so far here : 

I've also created a 3D model of the SkyWatcher EQ3 Mount piece 

http://www.123dapp.com/project/Skywatcher%20EQ3%20Mount/3366365

Thanks for helping,

Regards

Mathieu

[GigiG 14]

Hi all. Here is my solution (sorry, it's in italian but with image gallery and video in the bottom of page) for an EQ3 with DIY motors and controller (PicGoto). The motors are intenally geared (42:1) 12V unipolar cheap chinese steppers, directly connected to the worm gear. Hope can help.

Gigi