Advice on choosing a servo motor and timing belt for projection mapping project

I need help sourcing parts for a similar project as shown in the video. I tried contacting the author, but it seems his public email is no longer active. Maybe some of you have attempted something similar. The author mentions these parts: NEMA 23 Stepper Motor, Adafruit motor shield, timing belt, heat sinks. In the comments, he says: 'Ideally you would have another system checking the position independently, for which some servo motors provide possibilities.' Which servo motors was he referring to, or which ones today, after 8 years, would perform this task better? Also, where can I buy a timing belt for stepper motors once I decide on the most suitable motor model? Thanks in advance for any help or suggestions!

video link

There are many on line suppliers of stepper motor timing belts and pulleys. A search for "stepper timing belts pulleys" will find them. McMaster-Carr is one of the gold standards.

If you choose a stepper motor with sufficient torque for the project and a suitable driver for the stepper motor (the "Adafruit motor shield" is probably not one of them), the motor won't skip steps. Pololu has a good selection.

Starting from a "home" position using a limit switch as a zero reference should suffice to keep track of position at all times.

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At 4:00 into the video the builder is rotating the stepper pulley by hand, indicating you don't need a strong stepper to rotate the projection cube. I'd bet Pololu's cheapest 1A NEMA 23 stepper would be more than sufficient. That cube isn't going to be much of a load so an optical or mechanical endstop/limit switch would be enough to register a home position.

The trickier sourcing would be for the huge pulley under the cube. Since the loads are light, I'd 3d print a large plastic pulley.

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Could you recommend a specific Nema 23 stepper motor model for my project, along with a suitable driver shield (preferably from Pololu)? I'm looking for one with an appropriate holding torque (please specify) and step angle. I'm placing an order for Europe and would like to avoid mistakes in the selection. Thanks!

This does not look to be a demanding application, so I'd pick the simplest NEMA23 on the Pololu's list:

and almost any driver from Pololu - Stepper Motor Drivers

I'd first try a generic driver from my junkbox, but if I was going to try a new one from Pololu, I'd get one of these: Pololu - MP6500 Stepper Motor Driver Carrier, Potentiometer Current Control because of the 1.5A no-heatsink rating and the wide range of supply voltages.

Look first for a readily availabble continuous timing belt with the GT2 tooth profile commonly used in 3d-printing, and design and source pulleys around that.

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Be sure to include the spring loaded idler pulley shown in your pictures. Tension on the timing belt is very necessary.

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Would this Motor Shield Rev3 be a suitable replacement for the Pololu MP6500 Stepper Motor Driver?

I think my biggest challenge will be finding the right timing belt pulley (number of teeth, diameter), the belt length, and the spring-loaded idler pulley mentioned by @Paul_KD7HB.

The pulley is NOT toothed. It has flat sides and runs on the flat side of the toothed belt. Just as in the video.

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The modern chopper-type MOSFET stepper drivers are at least 10x more efficient than the L298 transistor drivers. And they have a lot of extra features, like adjustable current, wide supply voltage range, microstepping, current sensing, etc.

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It is also called a spring-loaded belt tensioner?

Yes, same thing, different name!

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And 4 times cheaper :slightly_smiling_face:

Will I need a heat sink for this project?

If you have some component that is heating up too much without, yes.
Do you have something you are aware of?
When prototyping, it's always good to keep on eye on temperatures.
But many components are built to work at higher temperatures than human skin, so something that "feels hot" is not necessarily too hot.

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No. That is not a stepper motor driver, rather it is for small brushed DC motors.

Best to do position control on the turntable, not the motor. I would use a BLDC motor and driver.

@JCA34F, which specific motor did you mean?

Selecting a motor requires detailed knowledge of your apparatus' physical characteristics, rotating mass, maximum rotation speed, etc.
At 77 Years old, my working knowledge of mechanical physics is fading fast, but there or many gifted "heads" here (@jremington among them) who I'm sure can help if detailed info is supplied.
Good luck.

@DaveX I contacted Pololu support, and they told me that I might consider one of their Tic stepper motor controllers instead of the #2966 stepper motor driver you mentioned:

They have built-in support for homing/limit switches, have many
configurable settings (including an automatic homing feature and
acceleration/deceleration limiting), and support multiple interfaces
such as USB, TTL serial, I2C, analog voltage, and RC.

Which one of these models would you choose?

What does it mean that I shouldn’t need to order a separate limit switch to set a "home" reference position since it says it has an automatic homing feature? If I do need to buy a limit switch separately, which of these switches would be suitable for that purpose:

Thanks!

With no documentation, it seems to mean the controller configuration and specify some number of steps short of a complete 360 degree rotation can be set as a home position. However your project requires many, many turns of the stepper, so that feature is of no use to you.
The selection of a home indicating switch will be part of the turntable you are creating. You can use any type of a cam to trigger the switch. So a standard micro switch with a leaf to operate the switch would be my choice. The cam part of the table will depress the leaf and switch the switch.

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