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Topics - RAF_Blackace

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AstroEQ Support / Need help with Declination axis Stepper Motor.
« on: August 27, 2018, 20:55:10 »
Hi.

I am changing my DC motors on my equatorial platform to steppers but am having trouble finding one for the declination axis that conforms to the requirements.

This motor raises and lowers around 50kg through a lead screw and has an effective worm gear ratio of 1:3600

It requires around 2N/m torque to drive it reliably (1.4 N/m normally). I can use anything from 1:5 to about 1:20 gearbox for this stepper motor to get the required torque.

But the only motors that fit this are Nema 17 motors at 1.68 amps per winding.

I was wondering, since this motor seldom runs, and it should need no holding power since the platform would not move if the motor was switched off. Is there anyway I could use the DRV8825 to drive it? I know the driver would get hot, but it can supply more then the 1.2 amps if it only needs to do so infrequently.

I have no intention of slewing the drive, it's an equatorial platform after all so it's not possible to do that. All the declination motor would be required to do is to adjust the Dec axis during auto guiding. So it would probably run no longer than 10 seconds every few minutes or so.

What do you think?

Or does anyone know of a NEMA geared stepper with a gearbox anything between 1:5 and 1:20 that gives 2N/m at the gearbox output and draws around 1.2 amps a winding?

thanks for the help.


2
General Discussion / A strange design.
« on: July 21, 2018, 03:32:57 »
Hello all.

I built myself an equatorial platform for by Dob and it tracks surprisingly well. But not well enough for deep sky astrophotography. But I see no reason why I can't make it good enough to do that.

Some background. I built it from a design I found on the internet. Currently it uses a simple astromaster drive motor at 9.5 revs per hour. This tracks well but as it is a DC drive it does need adjusting as the load shifts.

I am now considering replacing this drive with a stepper motor, also I am making a declination drive adjuster that should give me +-2 degrees declination adjustment.

The ultimate aim is to use auto tracking using PHD2 guiding with guide camera.

So far from being a go-to mount, or having the capability of moving to anywhere, I simply want a solution that tracks using a guide camera.

My Equatorial platform gives me a maximum 1 and a half hours of RA tracking, currently it is incapable of Dec tracking but I'm designing a solution for it.

My question is.

Is ASTROEQ a possible design interface between the tracking camera and the drives (both of which will be stepper motors but would obviously be limited in their possible movements).

I'm at the early stages of the design and looking for help, so any would be greatly appreciated.

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