Hello. I'd like to use arduino for a lab project I'm doing. The goal is to be able to initially rotate a small cylinder back and forth (a stepper motor would be fine), but after a short time of doing these rotations I'd like to be able to freely rotate the same cylinder manually. I've heard that brushless motors, when detached from power, are able to do this. I've also heard that stepper motors are brushless as well. However on this forum I've seen that people warned against manually turning stepper motors, since it could cause problems. Anyone recommend a basic stepper motor or brushless motor I could use for this purpose? Or at least confirm that this kind of motor would be good for the project.
I am not picturing what you want to do. Rotate? On which axis? Are you building a rocker, circular shaker or vortex spinner? How will your cylinder be attached? How fast does it need to spin?
A brushless motor is easy to manually reposition if no power is applied. The problem with servos is that the are geared and manual movement can strip the plastic gears inside. Stepper motors may or may not be geared.
Ah, perhaps because I didn’t give full context it wasn’t so clear, my mistake. The full project involves putting a flag into a water tunnel, the flag will then need to rotate in order to disturb the fluid flow, and then once it’s sufficiently disturbed, we need the flag to freely rotate as a result of the new fluid flow. We were thinking of using an acrylic cylinder for the flag shaft. I’m still not 100% sure how we will attach it yet.
Turning any gear train backward is asking for trouble, but steppers and other brushless motors can be turned manually without concern unless one does so fast as to generate a voltage high enough to damage the control electronics.
Pretty close to freely when the enable pin is properly set. The coil winder I built years ago would disable the stepper controller when the set number of turns were completed so the operator could solder the end of the wire to the bobbin terminal. Easily turned to whatever position they wanted.
Paul
Yes you are correct.
Didn't see the back and forth.
Still, one way might be sufficient anyhow.
Unless one includes all possibilities, one may never know the full list.
I assume by a "flag" you mean some sort of vane. You will need to define how the vane will be positioned. If it needs to take up a specific orientation then you would need a stepper or a drive mechanism that includes feedback, as presumably there will be some resistance from the fluid flow. The amount of resistance and the accuracy of positioning needed would determine the power you need from the motor. And more power would imply less freedom of movement.
Maybe you need a clutch between the drive mech and the shaft controlling the vane?
Yes, I would say not "maybe" but definitely. Surely if this is some kind of scientific experiment, the flag must be completely free to move in the current - presumably to illustrate turbulence, or something.
There is no motor that behaves just like a shaft on a pair of bearings when unpowered. Not only must the friction be minimal, so must the inertia.
So, I would support @johnerrington's suggestion: this probably needs a servo motor with positional feedback, and a clutch to allow the flag to move completely freely.
