T&L Publications

Hi,
First post and thanks for having a great forum. I have some electrical background and some hobby background but I guess not enough in either to figure this out. I will first reference a video of what I want to make and then explain where I am at with it.
The video can be found here:
http://vimeo.com/9827192

It seems simple enough to build as I can manufacture all of the connecting parts for the motor. I can weld and fabricate and such, but I am having a hard time deciding the best way to approach this. I had thought maybe the easiest solution would be to use an RC controller and servo and then it would be wireless. I thought that might drive the price up as well. Then I thought maybe just use a servo tester and use it wired. I am still thinking that might be the best solution once I can settle in on which servo might be the best to use. I need a fairly slow servo to control focus and most I have found either are lightning fast or have the torque to rip the lens right off the camera.

Maybe I am missing the best solution as I don't know much about steppers, servos, and their controlling circuits. I do know I need the motor to not be jumpy as this would cause video focus to be erratic. It looks like this setup will be WAY out of most peoples price range and DIY'ers could benefit from a much cheaper solution.

Thanks in advance for helping me bridge the gap in my knowledge.
Chris

Is this a serious plea for help or a veiled act of self-promotion?

The price on this thing looks to be $2000+ (2490Euro) so it is not in my price range. I am a photographer and I have been an aircraft mechanic for 20+ years. The project doesn't seem that complicated but I do need some expertise that is not in my field. I want to move in to some video as that is a major selling point for photographers these days.
It is a serious plea to help make a low budget item. I would certainly not be a marketing genius trying to sell it to the very people who could do make it out of their spare parts.

Any ideas on the best motor and controller to get the job done?
Thanks, Chris.

So you are looking for a "one up" product for your own use?
That's only slightly easier than going into production, since you still must determine your exact requirements, evaluate what's available, and build prototypes until you have one that works.
Are you looking to add motorized focus to just one camera? Have you examined the existing systems/motors and see how it's currently being done?
Could you get by with a friction-drive, DC gearmotor and a variable voltage source, or do you need something more elaborate?
John

Will the friction drive DC motor allow very slow movement? I don't know much about the types of motors. Since it will be limited to basically one revolution I wasn't sure a motor was what I was looking for. That's why I started heading down the servo path since travel is limited to degrees or at the most 3 or 4 complete turns.

There is another company that is trying to come out with a system around $500 but it will be wired and for $1000 it will be controlled from an ipod. A quick search for Red rock remote follow focus will show the system. They have announced it but it has not hit the market yet for some reason. It looks like they are using a simple servo and controller on their wired system. Watching the video when it sets the rotation limits, it seems to move quickly back to a center point. I can purchase their ring gears for the lenses and that might be a better connection between the motor and lens. The drive belt offers some chance of slippage which might act as a over rotation safety.

From what I can see from the two systems I have found it would be great if I could set servo travel and control servo speed. Will one of the servo testers allow you to set travel?

I had started looking into using the Remote control car radio system as that would give me wireless, but the radio itself would be a bulky item that would not fit in with how I shoot video. A thumb wheel control knob could be mounted on the handle and provide a much smaller profile package. I think I can accomplish making a small L bracket to hold the servo, making it adjustable to control tension on the drive belt and to allow different lenses.

I stopped by the local hobby shop and talked to them. The guy I spoke too was very helpful and watched both videos and suggested a stepper and controller might be the best way.
Any newbie primers for stepper control circuits. I just need a simple control from a pot to be mimicked to a stepper motor.
Thanks, Chris.

A regular broadcast quality ENG or field production TV camera has motorised and servo-controlled zoom c/w remote connector. I'm surprised that you don't just adapt one of these zoom mechanism to the focus. you'll need to talk to a lens repair tech; see if he is capable.

Focus adapter gears are also available to adapt these lenses for studio dolly mounting, moving the zoom and focus controls to the dolly handles.

I've got a robotic camera out in the shop, posted a year of so back to see if anyone was interested.. its a new unit, but sitting here doing nothing.. has motor, rotation, forward backward, and a sony camera on it. along with all the electronics (if you can figure out what or how to use them).. will get a picture in the next day or so to see if this is anything like what your looking to do..

I came across this while browsing today. It's an option, K'nex Follow Focus.

ok.. finally found those pictures of this robotic contraption I have.. I downloaded 3 pic's of it to Photobucket.. now.. how do I get the links in here?

http://i653.photobucket.com/albums/uu25 ... G_0290.jpg

http://i653.photobucket.com/albums/uu25 ... G_0289.jpg

http://i653.photobucket.com/albums/uu25 ... G_0291.jpg

frhrwa, what are you going to do with that?