I recently got an Arduino UNO and started immediately with hacking the shutter of my Canon 5D: I put some buttons, LEDs, LCD monitor, bells and whistles... all works fine and I'm having lots of fun with it. For the next step I would like to rotate the camera in synch with the shutter during the time-lapses. I am a reasonably experienced programmer so the software doesn't worry me, but the hardware is an issue.
After browsing a lot I came to the following conclusions, but before I start buying stuff I would like to ask the community if I'm on the right track.
The camera is heavy so, even if I balance it well on a pivot, I will need some torque. I saw this motor on Amazon for example: "Stepper motor - 200 steps/rev, 12V 350mA". Any better suggestions?
Do I need to buy a motor shield or can I just use the "SN754410 H-Bridge 1A"? From other posts I seem to understand that it should do.
A stepper will use energy the whole time though (if I understand correctly), and time-lapses can be hours long. Is it better if I use a servo instead? I am still quite unsure about the choice of motor.
If you use a stepper motor you should use a specialized stepper motor driver rather than a h-bridge. See Stepper Motor Basics. It also includes a simple system to estimate the torque requirement.
A stepper motor is convenient because it can be positioned accurately and predictably but, as you say, it is very inefficient.
A simple DC motor with a worm-gear drive will have lots of torque and will hold position without power - but you would probably need to use a rotary encoder (either on the motor or the turntable) to keep track of position.
A servo may be suitable if your range of movement is within the range of the servo. Most servos move through about 180 deg (maybe a bit less). Most sail-winch servos move through 3 full rotations (some can do 6). However you may need to experiment to see if the servo can position the turntable with the accuracy you require.
You will get better advice if you provide the specifications for the movement you want to achieve.
I assume you are taking "still" photos rather than movie shots.
Thank you Robin2, much appreciated.
Just to clarify: yes I am taking still photos, for example a 10-seconds exposure every minute (I love night-time photography). I would like the camera to move between exposures.
180 degrees rotation should be plenty for my needs, so it looks like a servo is what I need; and if I understood correctly I should only need an H-bridge and an external power supply.
I'll push my luck here: any suggestion on which motor I should buy?
It's a bit hard for me to estimate the torque required (I haven't built the pivot yet), but I'd rather buy something bigger which then can be useful for other projects...
If the only other criteria is money, let's say under 40Euros. Sorry I'm a bit generic at this stage!
so it looks like a servo is what I need; and if I understood correctly I should only need an H-bridge and an external power supply.
I assume you mean a hobby servo of the sort used to control model aircraft. If so they have all their electronics included and you just need to take a signal from the Arduino. Look at the servo-sweep example that comes with the Arduino IDE.
Give the servo its own power supply with a common GND with the Arduino.
I have some really nice brushless servos that will do the job . Text me if you're interested 2706708783 , these are upper end hobby grade for airplane use but I may have some cheaper ones If you choose that route .
You might make a cam support based on the below lazy Susan platform with a hobby servo centered underneath the platform to rotate the cam (and not support any cam weight). Hobby servos I've checked have about .5 deg max rotation resolution.