Instructables

Very slow rotation (1rotation/hr) electric motor?

I am  looking to build an electronically controlled time lapse pan device for my camera. I want to be able to rotate the camera for a specifically timed time lapse (e.g 90 degrees every 20 minutes of shooting). My problem is finding an electric motor that is slow enough RPM to create this slow of a motion... Right now I would need a motor capable of going down to about 1 rotation in 6 hours... at the very least 1 rotation/hr. 

So, do those motors even exist? Right now I am thinking the best solution would be to have a stepper motor, connected to a gearbox (right now that would be the inside of a kitchen timer, somehow), that would allow a very slow rotation of 1 axis. However, as this is a mobile build, power constraints are really an issue. I would like to be able to shoot for 6 hours max continually, and I dont know if that could be done without a very low power motor....

If I did the stepper motor connected to a gearbox, do you think that would affect the linearity of the time lapses? E.g would the stepping motion of the motor create a choppy vid? 

I have looked into the kitchen timer timelapse but have yet to find a timer that can hold up my relatively light Panasonic FZ-100 without locking up...

\Work it out.

How many steps will the motor take per rev ? In single step mode, probably 200. Add a belt reduction to increase the torque, say 2:1, and now one rev is 400 steps. HALF step the motor, and you have EIGHT hundred steps per rev, you really aren't going to see that.
astroboy907 (author)  steveastrouk1 year ago
Ok, I see that 800 steps/rev is going to get me into the resolution beyond the human eye. But if you take more than a few pictures a step (take 4 pics/step), will the outcome be a bit choppy?

I saw on adafruit a stepper that had a 512 step resolution. Might just need to get that and put it in a 2:1 reducer gearbox...

I am also thinking about being able to pan/tilt the camera. Would be much more complicated, but so much cooler... too bad I only have 3 weeks to build it :\ I'm freaking out a bit here...
Why should it be ?
astroboy907 (author)  steveastrouk1 year ago
Well, lets say you take a step, then take 8 photos, then another step and 8 photos.

8 photos at 24fps = 1/3 of a second. So you would have 1/3 of a second of the same placed images. Then after that it would change. If you have more steps you could take more photos without creating a visual disturbance.

Or am I totally wrong about this?
Work out how much it moves for a given step.

If the pictures are the same, why take repeats ? Just process multiple copies into the output movie.
astroboy907 (author)  steveastrouk1 year ago
Easy solution if I can find gears to fit onto a 5mm shaft- get a worm gear and cut down on power requirements because everything would lock if power is removed...
astroboy907 (author)  astroboy9071 year ago
Servos seem to be used a lot in this type of pan/tilt device... I cant decide if they would be a better option because steppers are accurate and provide really nice, repeatable results...
Steppers also stop when you tell 'em, servos can jitter slightly, and waste power. Steppers consume power all the time though.
artworker11 months ago
Use a clock as the motor and the spindle for the minute arm as the axle. You can also use other arms too and also different gears that work inside.
Wouldn't this slow down (and potentially stop) if you loaded it with more than just a clock handle?
i dont know if this will help, but you know those timers that plug into a wall socket and you push the pins down on the wheel to make your appliances go off and on? they turn once every 24 hours but you maybe able to pull out some of the gears to make it go faster.
oldmicah1 year ago
Is there a reason you need a stepper motor(precision incremental turning) ? Stepper motors only have so many positions (~200 steps for the ones I've worked with), so I'd guess you are going to have to either use gears to slow it down or belt driven wheels.

And as long as you are having to slow it down, I would guess that a small normal motor would give you plenty of torque for what you need. Just use good bearings so your wheels spin freely. This would simplify your control and power requirements greatly.

Best of luck!
astroboy907 (author)  oldmicah1 year ago
I guess just to have a reliable way of measuring the speed and eventual total rotation of the axis of the camera, e.g Ive taken 1100 steps, and that creates one rotation. I suppose just a plain linear motor would be fine, but it would be more mathematical and time based...

I am planning to slow it down either through a gearbox or the internals of a kitchen timer (seems to have a pretty good down ratio)...