4 replies to this topic

[BKBrown]

I have a terrific T-Rex Apex mount that I have been using with slow motion cable controls for nearly 15 years, and I now want to go a different route for fine control. Avalon in Italy offers a set of stepper motors with hardware for converting to powered drive, but with the catch that they must (apparently) be used with their proprietary StarGo Control System (another $1400 I don't want to spend) for go-to functionality. All I want is a simple dual axis motors to hand control setup that will allow me to mash buttons instead of turning knobs while trying to keep the cables out of the way. As I grow older I have increasing difficulty in use my rig effectively, and I don't really want to have to sell it. So my desired endgame is to have motors on both axis' run by a hand controller that will allow me to retain the simplicity of push-to functionality and use of my Nexus box, while allowing me to make fine corrections when I have my target in the EP field. Does anyone have thoughts on this? Has anyone done anything similar? I'm no Luddite, but my electronics skills in this department are limited. I can, however, follow directions pretty well  Thanks!

 

Clear Skies,

Brian 

[Spinwiz]

I'm not expert on telescope controls but that $1400 for the controller seems like a lot, especially if the motors are added on.

 

Stepper motors are good choices but I'm really thinking if you go this far you might as well make a complete axis drives.   that might mean spending a bit more on mechanical hardware.

 

As for stepper motors depending upon the size the electronics can be fairly cheap for the drive amps.   However those amps need to be driven and in a large number of cases they are driven by what are called step and direction signals.   The direction signal can be as easy as a switch or done completely under computer control.   The step signal is a pulse train that switches the motor coils, through the driver amps, at a fixed rate.   There are simple approaches to creating step signals, probably a 555 timer being both cheap and dated or as sophisticated as a microprocessor controlled system.

 

I would avoid approaches that mash buttons to speed up or slow down a drive in a low end solution..   Instead make use of photometers to minutely adjust the rate of the step pulses.   A "high end" solution, something driven with a microprocessor, can be button driven.

 

Designing a good, well working, drive is a lot of work.   You will want a mechanical system that puts the motor in it optimal run range.   There is a massive amount of info on the net from people that do DIY home CNC systems that may be worth a review.   A good number of these CNC systems use steppers with a wide arrays of electronics implemented, so plenty of mental stimulation.

[BKBrown]

I'm not expert on telescope controls but that $1400 for the controller seems like a lot, especially if the motors are added on.

 

Stepper motors are good choices but I'm really thinking if you go this far you might as well make a complete axis drives.   that might mean spending a bit more on mechanical hardware.

 

As for stepper motors depending upon the size the electronics can be fairly cheap for the drive amps.   However those amps need to be driven and in a large number of cases they are driven by what are called step and direction signals.   The direction signal can be as easy as a switch or done completely under computer control.   The step signal is a pulse train that switches the motor coils, through the driver amps, at a fixed rate.   There are simple approaches to creating step signals, probably a 555 timer being both cheap and dated or as sophisticated as a microprocessor controlled system.

 

I would avoid approaches that mash buttons to speed up or slow down a drive in a low end solution..   Instead make use of photometers to minutely adjust the rate of the step pulses.   A "high end" solution, something driven with a microprocessor, can be button driven.

 

Designing a good, well working, drive is a lot of work.   You will want a mechanical system that puts the motor in it optimal run range.   There is a massive amount of info on the net from people that do DIY home CNC systems that may be worth a review.   A good number of these CNC systems use steppers with a wide arrays of electronics implemented, so plenty of mental stimulation.

Thanks Spinwiz! Yeah, the $1400 is for the fancy control box; motors and hardware are an additional $300. That is more than twice what I am hoping to spend. While I understand what you are saying above, I am looking for something uncomplicated and less prone to failure. So if it can be done with reasonably little fuss and a modicum of tinkering, I am all in. On a more realistic note, I am not an electronics guru or programmer of any kind, so anything really complex is beyond the scope of my abilities.

 

"A man's got to know his limitations" - Inspector Harry Callahan, Magnum Force (1973)

 

Clear Skies,

Brian 

[Binofrac]

For a long time in my head I've had a rough design to do a similar thing to my Skywatcher EQ5. I have a few spare RC servos from my model helicopter days and am thinking about using them for the purpose. They have a drive torque of 5kg which is a lot more than required and are quite cheap new. They would need modifying so that they are capable of continuous turns. I like the idea of using a third servo in a hand held box with a crank to use as a generator. There would be a switch from this to allow the output to be directed to either mount servo as required (I use my EQ5 as an AZ not EQ). This would then hopefully give some proportional control rather than just a button. moving the crank fast, slow, forward or reverse would give the control necessary without the problem of batteries failing in cold weather, or remembering to charge them.

 

This method is well known for diy battery free electric focusers and so seems a promising way to replace the slow notion cables. See this post- https://www.cloudyni...y-free-focuser/

 

Since learning about microcontrollers I thought I could perhaps use the generator to charge a battery and then add a simple tracking functionality. This should be good enough for visual. It seems a cool idea and has stayed with me so I might not need another lifetime to get round to it.

[Spinwiz]

Thanks Spinwiz! Yeah, the $1400 is for the fancy control box; motors and hardware are an additional $300. That is more than twice what I am hoping to spend. While I understand what you are saying above, I am looking for something uncomplicated and less prone to failure. So if it can be done with reasonably little fuss and a modicum of tinkering, I am all in. On a more realistic note, I am not an electronics guru or programmer of any kind, so anything really complex is beyond the scope of my abilities.

 

"A man's got to know his limitations" - Inspector Harry Callahan, Magnum Force (1973)

 

Clear Skies,

Brian 

There are some really simple ways to drive stepper motors but unfortunately I still work for a living so haven't explored any other online solutions.   I can't design any at the moment either so I'd suggest looking on line for step and direction generators for steppers.

 

Your other option is to go with a DC motor and gear box.   That still requires a bit of engineering to figure out an optimal mechanical gear box but the electronics can be simple with DC motor controllers.