Control tripod-head with servo's - where to start?
murc
Posts: 3
Hi,
Using a couple of parallax products I'd like to manufacture a setup that would allow me to program my tripod to perfom certain movements. The actual mechanical stuff is something for the (near) future, I'm just looking for leads on how to control the servo's that will drive the tripod.
Parallax Servo Controller – USB (#28823) Rev B
16-Channel Servo Control with a USB Interface
Would this be the unit to use in such a project? At most I want to control and animate 3 servo's.
Please let me outline the requirements:
- rotation over 3 axes in both directions
- the possibility to configure the ease-in and ease-out of the motion
- the possibillity to set extremely slow rates (like 45 degrees in 1 hr, probably using gears)
Not so required but also very nice:
- standalone, preprogrammed, maybe with a reset switch that restarts the motion
I did see that there is already a nice piece of software for controlling and animating, would that cover my requirements?
Eventually I want to use this to make time-lapse-shots with movements in them
Thanks for taking time to read this, hope you can help me out =]
Kind regards,
Marc
ps. I'm a video/computer guy, don't know a lot about electronics other than the basics (learn fast though
)
Using a couple of parallax products I'd like to manufacture a setup that would allow me to program my tripod to perfom certain movements. The actual mechanical stuff is something for the (near) future, I'm just looking for leads on how to control the servo's that will drive the tripod.
Parallax Servo Controller – USB (#28823) Rev B
16-Channel Servo Control with a USB Interface
Would this be the unit to use in such a project? At most I want to control and animate 3 servo's.
Please let me outline the requirements:
- rotation over 3 axes in both directions
- the possibility to configure the ease-in and ease-out of the motion
- the possibillity to set extremely slow rates (like 45 degrees in 1 hr, probably using gears)
Not so required but also very nice:
- standalone, preprogrammed, maybe with a reset switch that restarts the motion
I did see that there is already a nice piece of software for controlling and animating, would that cover my requirements?
Eventually I want to use this to make time-lapse-shots with movements in them
Thanks for taking time to read this, hope you can help me out =]
Kind regards,
Marc
ps. I'm a video/computer guy, don't know a lot about electronics other than the basics (learn fast though
)
Comments
I love the PSC myself, but I will add that if you are looking for reaaaaalllllyyyyy slow pan/tilt times, the resolution of the ramping in the controller may not be smooth enough for you (it's 2us resolution). You might want to get the servos first and see just how small a change you can feed the servo mechanism over time without jerky camera movements.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST
I was just browsing that site before I clicked here to see if there were any replies =]
Any hints on prefab software I could use for controlling/animating?
Wouldn't a high gearratio in combination with a high rpm servo solve that issue? Although I guess with the above mentioned kit I would have to resort with the gears that are integrated in the kit..
Thanks for replying so quickly!
Marc
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
YOWZA!
Your slow speed requirement may make the R/C servos unfeasable. You might want to look into geared stepper motors instead, at least on the horizontal axis. Actually there is no reason why you can't use both, and get the specific benefits of each type for each individual axis.
I'd think that with a little pre-planning, thought and careful programming, three axes (regardless of the motor types) ought to be fairly easy with (say) a BS-2SX or any of the more advanced Stamp models without the use of a motor controller. If you plan expansion however, a motor controller may not be a bad idea.
Here are a few things to consider. The ramping requirement is going to take a bit of doing on the slower BS-2 (plain), and so too a pallette of different movement stratagies. The other advantage of the BS-2SX (or better) is the large 8 x 2K banked programming space which would allow you to segment a larger program than the smaller 2K (only) memory as found on the BS-2 (plain).
Regards,
Bruce Bates
Post Edited (Bruce Bates) : 11/8/2006 11:28:57 AM GMT
You may need to turn to steppers and worm-gears to achieve that speed/resolution.
In that case I'd recommnd that you don't use your tripod head as it is.
Not all cameras have the mounting-hole exactly centered on the bottom of the camera(you want it to be exactly under the middle of the film frame, so that if it was extended upwards it'd split the film in two equal sized pieces), but more importantly, it doesn't pivot up/down on an axis that goes through the film, either. (The pivot is underneath the camera after all)
There's also the weight to consider, particularly when tilting the camera up/down.
With a heavy lens, that can take a lot of force, and it's easy for motors to 'miss' on the positioning if they're getting close to their ratings.
Instead, you should put together some kind of gimballed frame(something like those used in gyroscopes) to replace the normal pan and tilt head.
And no, it's not very difficult to make. (A couple of U-shaped brackets, the bearings from a skateboard... )
This will not only reduce parallax-errors on short-range photography and ease the translation of direction/speed information into motor-instructions, but it will allow you to add weights to counterbalance the weight of the lens so that you get a much more stable platform and can use smaller motors.
You may also want to add code-wheels to read out the actual position of the camera now and then, to compansate for mechanical 'drift'.
I'd build one myself, except that I don't do this kind of photography.
(not at the moment anyhow)
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Don't visit my new website...
The camera will be a Sony Z1 HDV camcorder that weighs about 6 kg. No heavy lenses.
I have seen those gimballed frames on commercial websites that sell these systems for big $$. You are right about the placement of the pivot, however in my case this is less significant (also no short range usage).
Actually i like Zoot's reccomendation www.servocity.com/html/pan___tilt_systems.html.. Gonna mail them and see if they see a possibility for the very low rpm i would like.
Any suggestions on what software to use, where to find resources on that..?
Thanks again!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
YOWZA!
If you do that, you can take any chunk of metal and drill a hole into it to create a secure camera mount.
Use a counter weight to have it provide a balanced center of gravity.
With that in mind, build or modify a well balanced motor driven gimbal and worry last about fitting the camera to it.
Most tripods are designed for compactness, eliminating motion, and light weight use.
Stepper motors may jitter at certain speeds. Not a good thing for pan motion. High speed motor, geared down and with a large fly wheel are very smooth.
In some cases, hanging the camera from the ceiling is a wonderful way to get both motion and good camera angle. You can zoom and pan simultaneously.
Similarly, a wall mount might be useful.
At times, a heavy support will be useful to damped jitter. So building it with steel is not a bad idea.
You don't have to use servos, to use PWM control. There are a lot of multiple PWM boards with PC software that will allow you to control speed and position. You will have to create a PWM reciever that convert the signal to position or speed. A BasicStamp or an SX-28 can easily do that.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"If you want more fiber, eat the package.· Not enough?· Eat the manual."········