Premise first, details second.
I’m a physics student at Purdue University. I’m working on research that involves a moving stage that can be controlled manually with turn-able knobs. The problem is that this is inconvenient because it’s inside a device that uses X-rays, and adjustments require turning off the device to open it up. I’m trying to make this process controllable from the outside without turning these knobs by hand by simply attaching motors to these knobs.
These adjustments need to be incredibly precise, though. I need a motor that may be capable of anywhere between 0.1-2 degrees of angular resolution so that if I need to really slightly shift the stage, I can. However, when considering servos, they also need to be continuous in case the adjustments I need to make are larger than 1 full rotation. SparkFun lists some good continuous high-torque motors, but parts like SM-S4303R don’t list a minimum speed without slippage. They only list a max speed in their datasheets from what I can find. Ideally, I would also like the motor to be controllable with an Arduino with a max 5V output. However, I would be happy with suggestions for motors that don’t meet this requirement. I also don’t need the motor to include an encoder. The exact position is unimportant to me. I just want to accurately adjust the motor’s relative position (i.e., I may want to rotate by 1 degree CW, but I don’t really care that I’m at 170 degrees and going for 171 degrees. The change by 1 degree is the important part).
I’m posting this in Miscellaneous because I’m not sure where else to post it. The organization of this forum is hard for me to understand and navigate. I haven’t found another post that has asked something similar, though. If there are such posts, I couldn’t find them with searches, or they were too technical for me to understand with my simple physicist brain.
The knob part is simple, just get a micro controller with a high resolution ADC and some nice potentiometers (or optical encoders)
I would recommend taking a look at this https://www.sparkfun.com/products/10846 (0.8 degree angular resolution) paired with this https://www.sparkfun.com/products/16836 - the driver board has robust micro-stepping (partial step) modes you could use to achieve the resolution you’re after
You could also use the same setup without micro stepping (if it proves glitchy/cumbersome/inaccurate somehow) and some gearing instead to accomplish similar
I think this is a good starting point when it comes to a motor to use. I’ve worked with servos before, but not stepper motors and didn’t know enough about them to realize that they were readily available solution. Thank you for your suggestion!
As a follow-up question, I’m not sure what was meant with the microcontroller, but I have an Arduino at my disposal that I will use, and I don’t believe that’s necessary.
Regarding mounting, first, I need to be able to attach the motor to the knob that I had mentioned. Here’s a picture:
My intention was to attach the two with a shaft coupler (or at the very least a mechanical part that I 3D print myself). If you think that’s inadequate, I would appreciate an alternative recommendation.
Second, this equipment is also sitting on top of an optical board. I will be looking for a plastic equivalent to an aluminum extrusion to make the frame that will hold the motors (plastic so as to not be reflective in the presence of x-rays). The motor controlling the Y knob needs to move with the Y knob when adjustments are made in the X direction, and by keeping the connection to the frame loose, the motor should slide with the stage.
The question is, does anything come to mind for how to connect this motor to the extrusion? If not, then I’ll simply 3D print a mounting mechanism.
I consider this enough input to work with, but if you or anyone else has further suggestions, I’d love to hear them.
