So, as I like to shoot semi-high resolution panoramas and partial panoramas, I've been looking for a way to automate at least part of the process.
My first attempt, bolting my NN3 to the stepper motor shaft ended with a slightly less straight shaft. Thankfully, after reading the description of the new rotators for the NN5, I realized that a similar idea should work for a stepper drive. So, with a 1.5" ID thrust washer, a 1.5" OD x 1" long piece of aluminum, I made a coupler for my stepper motor, and a place for the NN5 arm to ride.
Initial tests are promising, I can get apparently back to almost the same pixel coming from the same direction and the same previous location. Coming just from the previous direction I'm seeing errors of about 6-10 pixels(85mm lens, Nikon D70) or about 0.02-0.6 degree error.
Absolute step size, which should average out to 1.8 degrees for this motor, varies by about 0.3 degrees. So I'm probably not going to be able to stitch using a template, but at least the shooting will be automated, and provided the automated control-point generator isn't too horrible, the work should be easy.
The next iteration will be to add a plate for the NN5 lower arm to ride on so it's not directly on the thrust bearing. Then a way to make it portable. Then maybe a worm drive, and then maybe a tilt axis worm drive... many months in the future.
looks interesting.... would you not get even greater accuracy to gear it down,
after all rotation speed is not vital, in fact slowing things down might give less over run.
You could then use a smaller stepping motor, as you would need less power.
The plan is to gear it down, eventually, however that requires more precision machining the parts to make sure there is no play in the gear train, so I went with the easy way for now. Currently the system will stop in the same place every time for each step on the motor, the problem is that each step is not the same width so it couldn't be used to match things up for different shots, and I'm not sure if there's enough repeatability there to do a mapping of step numbers to absolute positions.
I agree that the footprint is a little large for VR type work, I could envision a smaller motor with an in-line gear train to get the footprint down to the NN5 rotator size, but quite a bit taller. Luckily, I don't do VR type panos. In the pictures you might notice the cable off the camera, it's already set up for remote shutter release(and shutter speed control) which I've been using for HDR panos.
Right now the major issue is the support hardware is several pieces, once I get that condensed down I hope to go shoot some actual panoramas with it and get them posted.
I am not sure that you need any greater precision in the gear train as it only rotates in one direction so any slack will be taken up.
It will also even up any uneven steps as they would be averaged. though a more accurate step motor as used in an inkjet, would perhaps be better. you can prevent any back movement with a coil spring clutch around the shaft.
I've got some final tweaks to make to the code that runs the stepper, need to finish the USB interface and then I hope to take it out in the field sometime in the next couple weeks when I have time off work. We'll see how that goes.