Slowly Rotating Device For a Camera Pan Timelapse

[EzraF]

Hello all!

I just discovered PF as I have been searching about a project I have been pondering for a day. The idea is to have a device that I can set my 3lb camera and have the device rotate left-to-right && || right-to-left over the duration of 2 hours for use in a sunset/cloud timelapse.

This is my first electrical/mechanical project ever, so go easy on me ;)

I am no mathematician but I was able to figure that if I wanted the camera to pan ~30degrees in the span of 2 hours, the camera would have to rotate at a rate of .000833333RPM

I found https://www.ebay.com/itm/3Vdc-0-5rpm-Small-Low-Speed-DC-Turbo-Motor-With-Metal-Gearbox-370-Motor-/321342148487, the slowest one I could find during my quick search. Couple questions about this motor. How do I find a gear that can mount to the spinning part of the motor? What is the spinning part even called? If I find an applicable gear how do I find out how big the gears should be to achieve .0008RPM movement on a .5RPM motor? Should I use gears or form some sort of belt driven design, and finally is that enough torque to move a 3lb camera?

Are there slower motors i can use?

I know that is a lot of info and questions, I have more but will wait for feedback before diving deeper.

You guys don't have to hold my hand through this, I just feel like I don''t know the terminology to use in Google and wanted to talk to a human about this :)

 

[JBA]

Have you carefully considered what type of results you will get from a photography standpoint; because, there are only two methods of getting good pictures of sunsets or cloud movement and they are compressed time lapse still shots and low speed video, and both prefer a fixed camera position because a fixed Earth horizon reference is generally preferred to to a fixed sun or cloud reference with the moving Earth based horizon that you will get with a rotating camera movement.

 

[EzraF]

Have you carefully considered what type of results you will get from a photography standpoint;

Thank you for the thoughts.

This project is more so for experimenting with motors rather than the quality of the video at the end

 

[FactChecker]

You can figure out the ratio of the motor RPM to the desired RPM and that should give you the ratio of the gear radii or teeth. A motor that turns that slowly probably has gears that give it enough torque to maintain that RPM while moving the camera.

 

[AZFIREBALL]

If your figures are right you will need a 600 to 1 reduction drive.
BTW- clock hands run at 1 rev./min., 1 rev./hr. and 1 rev./12 hrs.
Does that give you any ideas?

 

[EzraF]

Shortly after posting I called my very mechanically mindful grandpa for his thoughts, he mentioned how telescopes have motors to track stars in the sky, and they move at about the same speed while being able to rotate a decent amount of weight.

You can figure out the ratio of the motor RPM to the desired RPM and that should give you the ratio of the gear radii or teeth. A motor that turns that slowly probably has gears that give it enough torque to maintain that RPM while moving the camera.

Yes that helps a lot, gives me insight on the terminology for sure, thank you!

If your figures are right you will need a 600 to 1 reduction drive.
BTW- clock hands run at 1 rev./min., 1 rev./hr. and 1 rev./12 hrs.
Does that give you any ideas?

The clock comment was extremely helpful, clock motors is where I continued this journey.

While keeping in mind what my grandpa said I decided to look at the internals of Quartz clocks and watched this great video. I decided on clocks before telescopes because of how cheap and available they are. Better to break a Quartz clock that a $50-$100 telescope drive IMO.

So moving forward I think I have decided on buying this High Torque Continuous Sweep Quartz Clock Motor. Going to wait a few days to continue searching, but as of now I believe that is the best first step.

These motors say they can rotate a hand up to 7" long. I'm wondering if that is enough torque? I'm thinking that balancing as much of the weight of the camera directly over the shaft of the motor would help the motor move the load, as normally these clock motors have a majority of the weight residing on one side of the shaft. I also should keep in mind that any offset weight when putting my camera on the shaft could result in warping the speed of the rotation. Separately, It would be nice to be able to have the camera angled up slightly, also changing the center of mass slightly. If the motor has enough torque to easily move the camera, I should have a little wiggle room when it comes to the center of mass.

 

[AZFIREBALL]

Mount the camera on a WalMart Lazy Susan (Rotating tray) using two sided tape. Place the clock motor above the camera some how, connect a shaft from the clock motor to the top of the camera, all centered over the rotational center of the tray. As the shaft turns it will turn the tray and camera without any effort at all.

 

[FactChecker]

The motor probably has enough torque because of the gears involved. But the gears and clock hand mounts may not be strong enough. They are probably only built to turn very light clock hands.

 

[CWatters]

Perhaps look at stackable planetary gearboxes. Use a light spring or rubber band to stop camera moving due to backlash in the gearbox. Think about vibration from the motor?

 

[JBA]

Using the suggested clock hour hand drive would only require a 2:1 ratio gear or belt & pulley speed reducer to achieve the 30° per 2 hrs you are looking for; and, would reduce the required motor torque by 50%.

 

[gmax137]

I have a friend who does this kind of thing with stepper motors and arduino controls. One advantage is, he can move the camera, wait a few seconds for the vibrations to stop, then release the shutter. Move, short wait, snap, wait interval, move... The arduino controls are integrated into the camera control to tell it when to release the shutter.

Assuming you were going to make multiple exposures, not a continuously open shot, right?

 

[EzraF]

Thank you everyone for the thoughts! I went ahead and bought a continuous sweep high torque 12 hour clock motor. Meaning I would have to find a way to reduce it 2:1. Will have to see if the reduced speed is worth the reduced torque. Motor should be here any day now.

I have a friend who does this kind of thing with stepper motors and arduino controls.
Assuming you were going to make multiple exposures, not a continuously open shot, right?

I haven't messed with arduinos at all but they look very interesting. Learning how to use those would probably make my life a little easier.

As for multiple exposures vs continuous open shot, I will most likely do multiple exposures to avoid the 30 minute limit on my DSLR's video function.

 

[JBA]

Ezra,
As per my #10 post. A 2 to 1 speed reducer will reduce, not increase the torque load on your motor for a given table load.