Need help choosing Steppers for a medium sized project

i have been remodeling an ancient DJ light that spun on 2 axis, to something completely new.

i have been remodeling this light piece by piece, and it's time for me to tackle the most difficult part. changing the 2 AC motors with built in gearboxes for some decent continuous rotation stepper motors.

steppers/servos are miles outside of my comfort zone, and i know nothing so i have no idea at all where i can find what i need.
first thing to note: ALL AC power has been removed from the fixture, and a DC power supply has not been picked out yet, so voltage does not matter at all.

there is 2 motors.
A motor that spins aN approximately 15lb steel/glass disk full of lights
and a motor that tilts the entire frame holding the disk continuous 360 barrel rolls (approx 25lb of weight)

The 2 pink boxes in this linked images are where the motors will sit


unfortunately i do not have all the measurements on hand, and will not be back home for a few days, but i wanted to get this ball rolling,
what i can remember is the shafts are approx 1/4" D shafts,
and the mounting spaces are about 6" squared each, (mounting holes i can drill to suit my needs)(i can build a bigger mount if i need to use a motor physically bigger than the factory AC motors)
the entire fixture is about 2 wide, with the disk being about 1'6"
(i thought i had measurements written down, but i'll get them as soon as i get home)

the steppers need to be continuous rotation, spin motor doesn't need to be reset/zeroed, but tilt does (i have a fair few ideas on how to make that simple)

my big problem is the spin motor, as the wires for it need to pass through a slip ring that already has 3-5 wires going through it, i'm having troubles finding slip rings that have both heavier wires and many wires (for obvious reasons) so i need to try to avoid high amp draws so i can get away with thinner wires.
(i have found a slip ring that's 12 wires @ 5 amp, and one that's 6 wires @ 30 amp)

Linked image of wire paths

(quick note: the frame and shafts are hollow and could easily carry a lot of high gauge wires, slip ring is my only restriction)
(just noticed my diagram doesn't show where the slip ring sits, the shaft actually extends 2" past the frame on the right side, and the slip ring sits on the protrusion)

I live in canada so i'd prefer to avoid ordering from overseas if possible, as duties will drain my pockets dry,

i need any and all advice on what would work and where to get it.
i have an arduino, but no servo/stepper controllers.
currently all pins but one digital output are free on the arduino.

Why not simply use DC motors. I assume it only rotates in one direction, if you want reverse you need to add a H-Bridge either discrete or integrated. Increasing the voltage reduces the current. Since you are not there currently why not get the Arduino cookbook and read it. Also on line there are many videos etc showing the Arduino and how to do what you want. This additional information will go a long way in getting your problem solved. Once you get past this you then need to select your sensors and actuators. At that point you start on the hardware design and write your software.

Sorry, should've been clearer.
The way I'm designing this I'd like to be able to control it like a spotlight. Hence, steppers.

The disk has already been completely rebuilt, and now contains 14 indexed LEDs I have full control of,
By mixing controlled lighting effects with precise movements, I can make a DJ light that will be beyond breathtaking

pictures please.

Simple Image Posting Guide

...R

Edited original post. fixed image links, added an image of the light before the rebuild started.

Also: i found my measurements, for some reason they were all pictures.

height of the disk:

Diameter of the disk:

The part that connects the disk to the motor shaft:

Where the frame connects to the tilt motor:

Where the spin motor sits:

Where the tilt motor sits:

the two original motors:

A close up of one motor:

A photo of everything dismantled:

To estimate the required motor torque and power, you need to determine the moments of inertia of the two objects to be rotated, and decide on how quickly you want to reorient either, so that you can determine the required angular acceleration and velocity.

Start with the inner rotor, because its motor will increase the moment of inertia that the outer motor has to handle.

I was thinking about 30rpm max, I don't really know what ideal acceleration would be

By mixing controlled lighting effects with precise movements

What sort of "precise movements" do you have in mind, and how do those movements fit in with "30 RPM"?

What sort of "precise movements" do you have in mind, and how do those movements fit in with "30 RPM"?

think spotlight. there are 14 beams of light coming out of this fixture, each of which i can control individually. say if i turned off all but one, the fixture would essentially work like a spotlight, i'd be able to move it to exact positions,
it will be live controlled from a computer, and i'd be able to tell it to tilt 90 degrees vertical, then spin continuously, or slowly tilt back and forth while alternating spin direction.
(this style of DJ light is called a "UFO light")

some speed is definitely wanted, but it doesn't need to violently snap to positions,

I wonder if this is a project that just needs a little money spent on experiments. My suggestion is to buy a cheap Nema 17 sized stepper motor that has low resistance coils and a current-draw of about 1.5 amps (not more than 1.7 amps) and a DRV8825 stepper motor driver.

Learn how to write a program to control the motor and then experiment to see if it can provide the performance you require.

...R
Stepper Motor Basics
Simple Stepper Code

also look up the AccelStepper library

some speed is definitely wanted, but it doesn't need to violently snap to positions,

Unfortunately, to size the motor, the motor driver and the motor power supply, you need to replace those words with actual numbers.

For example, suppose you want to change the angle of a spotlight by 90 degrees in 2 seconds. That would be an average angular velocity of 45 degrees per second (0.79 rad/s), but the motor has to accelerate for some time to reach maximum angular velocity, then decelerate at the end.

The motor you choose must be able to deliver the required torque, which is the angular acceleration times the moment of inertia of the object being driven.

Obviously, if you choose a motor that has too little torque, it won't be able to accomplish the task. You either need to do your homework, or plan on buying motors in stages until you get ones "big enough".

Also consider that your spinning disk will act as a flywheel and add to the force required to tilt it.

I'm a great fan of not re-inventing the wheel... I say grab a cheap GRBL board with stepper drivers already on it... Probably best to go with stepper motors with stepdown gearboxes too since it doesn't seem you need much top speed but high holding torques.
GRBL is easy to test values of velocity/acceleration to test the numbers

well, i spent way too much money, but i should have everything needed now.

i bought some rather basic nema 17s, i somewhat doubt they'll work, but they sound the best for a starting point.

will update after I have a chance to test how it all goes

(am thankful for all the suggestions and thoughts, wouldn't have had any idea where to start without them)

Schradieck:
well, i spent way too much money, but i should have everything needed now.

i bought some rather basic nema 17s,

Being mindful of your wallet I only suggested buying one motor at this stage :slight_smile: :slight_smile:

...R