Are stepper motors the same???

[Dickie Doughnut]

Hi -  For a few years i have been using an old eq5 mount with the Skywatcher GOTO upgrade bolted on. Recently I acquired an old eq6 mount, and i am looking to upgrade it as cheaply as possible (skint). Thus, I was wondering whether the stepper motors in the SW eq5 upgrade kit would be happy in the eq6? I appreciate I'll need different mounting options for the motors, and possibly gearing etc, but that's easily achievable with a bit of metalwork. There are a couple of stickers on the motors from the kit ie "eq5gt-f90-6 dw1611150423" and "eq5gt-f00-7ra dw161128 0223" which suggests they might be dedicated to eq5, but I remain ever hopeful. If these are not suitable is there a full motor specification for turning an eq6 using the existing gearing - with the objective of sourcing some secondhand from anything that uses steppers. Many thanks. 

[malc-c]

It would not be possible to take the control board and steppers from an EQ5 and use them in the EQ6.  Aside from the physical differences, the firmware (the code inside the microcontrolers) has all the gear ratios etc for the mount they control, and as the two mounts use different worm  and gear ratios it would never slew to the correct place if  you did manage to replace the steppers with the correct ones (the microstepping of the motors used is also different, so you would need the correct spec motors as well).  And before you download the firmware updater application and try uploading the EQ6 firmware to the EQ5 board, it won't work, and the application will report the file is not correct for the board being updated.  You would need to reprogram the controllers directly with an edited version of the code.  One major factor is that the EQ5 synscan boards of that age use a single controller, where as the EQ6 uses two (one for each axis), with each one requiring a copy of the code burnt into them.

There are open source alternatives to the synscan units, based around Arduinos... that may be an alternative.  But using the existing controller won't work.  Oh and good luck sourcing the steppers.  The boards used in HEQ5 and EQ6 boost the 12v to around 30v to run the steppers due to the increased payloads.  Lets say for argument sake the motors physically fitted, the internal coils would not handle the increased current draw the larger mount would need, so they would run hot or possibly burn out.

Unfortunately  being skint and having an interest in telescopes is not a great combination.  A replacement EQ6 control board is circa £160.  You could ask FLO (sponsors of the forum) if replacement steppers are available, and how much they would cost, but I doubt you would get much change out of £100 for the set.  The only good news is that the synscan handset you use with the EQ5 will work with the EQ6 as the the controllers in the handset interrogate the mount to ID which mount its being used on.

I did have a few EQ6 boards that I repaired a few months ago. but these went quite quickly.  I normally offer a repair on an exchange basis, but a lot of kind SGL members who had already gone out and bought new boards kindly sent their old damaged boards to me for repair, so I had a few surplus.  If I get any more faulty ones that can be repaired I'll let you know, but don't hold your breath :-) 

[Dickie Doughnut]

Malc-c - thanks very much for such a comprehensive reply. OK, in summary I'd better start saving, but at least I now know not to flog the dead horse that is the eq5 upgrade kit - except I might get a few quid for it secondhand. Whilst I'm saving my pennies I might look further into modifying off the shelf kit as I already have a box of bits and pieces like arduino, driver chips and a few steppers/gears etc from non-astro related projects. If I go down the eqmod route I think it would give me some bandwidth to specify gear ratios etc. 

Once again, many thanks for your help.

[malc-c]

Why re-invent the wheel - Can't vouch for it, but here is a typical example of an open source Arduino based, standalone (use an app on your phone) goto system 

And another system, but this links to a PC

Wait, there's more 

 

Details here

Just google "arduino telsecope control"

[Dickie Doughnut]

Thanks very much for the extra info, Malc-c. Looks like it's entirely possible to do it on the cheap. Firstly, some reading to be done 😀

[malc-c]

If you want something simple that offers a wifi based controller that supports the Skywatcher protocol making a direct alternative to the synscan board have a look at the Open Synscan project  which will allow you to use any application compliant with Synscan protocol to manage the telescope mount over WIFI network connection

[orly_andico]

OnStep is probably the most mature Arduino-based GoTo controller solution out there.

 

The old non-GoTo EQ6 had unipolar tin can steppers with built-in spur gearboxes, if I recall correctly. The GoTo EQ6 has hybrid steppers and uses an external gear reduction. The use of the hybrid steppers allows for faster slew rates.

 

Interestingly, the old tin cans can be made to slew a bit faster with the new stepper motor controllers like the TMC220x (which are dirt cheap now because of the proliferation of 3D printers).  So with an OnStep implementation and the right stepper motor controller boards, you can use the existing EQ6 motors. GoTo slew rate will be under 100X ... i.e. agonisingly slow. These old tin cans could manage 32X with old-style unipolar stepping, and with the new stepper boards they can probably do 100X. That still means a horizon-to-horizon slew would take 7 minutes. But... no need for mechanical adaptations.

[orly_andico]

I forgot to mention.. the "MKS Gen-L" 3D printer motherboard can be used as-is as an OnStep GoTo controller, just upload the correct OnStep firmware into it. This is because the MKS Gen-L is essentially an Arduino Mega 1280 (or 2560.. I forget which) and four stepper motor controllers (X, Y, Z, and extruder) all on a single (very cheap) motherboard.

 

Again, 3D printers being vastly more popular than telescope mounts, means anything 3D-printer related is dirt cheap.