I have a pan mount for a webcam that needs to be smoothly and quietly rotated. The load is small (the camera weighs 3 oz) and is supported by the axle so I do not need a lot of torque.
I was considering a small stepper like this one:
But from what I've read, steppers are inefficient and consuming power all the time. Since the camera will spend more time standing still and only move occasionally, it might make more sense to use a dc motor with an encoder. However, I have no idea how to code an arduino to move a dc motor with encoder to specific positions.
Steppers step. Stepping =/= smooth.
It's up to you to figure out if the step resolution is small enough to be indistinguishable.
As for constantly needing power, not always. Sometimes the internal resistance of gearing is enough to keep a stepper spindle still, definitely if there's no load trying to turn it. It takes a good amount of force to turn an unpowered stepper, but that is dependent on distance from the axis. I imagine your cam is just sitting parallel to the axis and isn't putting any perpendicular force that would try to spin it.
thank you for your replies. yes the cam is attached to a shaft that is supported by a bearing. The shaft will be attached to the motor spindle with an appropriate coupler. I guess I don't know 'when a stepper is consuming power'. From what I've read, it sounds like the controller board is powering the windings all the time. I guess my code could power off the motor when it is done moving and power it on again when it's time to move it. In terms of noise, I got a cheap stepper and tried it - at very slow rpm (1 rev per 10 sec) I can't hear it.
skypickle:
I don't know 'when a stepper is consuming power'. From what I've read, it sounds like the controller board is powering the windings all the time. I guess my code could power off the motor when it is done moving and power it on again when it's time to move it.
You can do that. Most stepper drivers have an enable pin for that purpose.
However if you disable the power to the motor there is no guarantee that when you re-power the motor it will be at the same place. Even if no external force has moved things the motor might move one step forward or back to the nearest node.
i suppose the same problem occurs with a d/c motor with an encoder. I guess I could put an encoder on the stepper as well to know where it is at all times? or is that just silly?
Do you need to know the position? What will be the input? User control?
If so, limit switches to prevent over-rotation might be enough. Let the user pan left or right to their hearts content. They will stop when the camera is pointed in the direction they want. And your limit switches will prevent them from rotating past any physical limits.