I really like building robots.
So I’m going to built another one. I am going to call this Project3.
While Otto was very expensive to build, and Lil’ Wayne used parts I had laying around, I want to take the challenge to build a super low cost budget system.
Project3 is an exercise in demonstrating that motion control does not have to break the bank, and DIY Prototyping does not have to involve machining expensive custom parts and 3D printing. You just have to learn where to source the parts you need. When I look at the list of Dragonframe compatible systems, it seems that getting a 4 axis setup going sits you in the $2,500+ ballpark.
Lets say you are an aspiring animator. You have been doing everything on a shoe string budget. You finally get a solid camera, finally get a copy of Dragonframe, and have spent lots of money on materials for building the puppets and sets. You really want to get into the motion control side of things, but just don’t have the money for a system from Ditogear or eMotimo. You don’t need a weather sealed system, you don’t need something that can handle the abuse of travel and field work, all you need is a system to sit in a studio to move your camera around.
My goal is to show that you don’t HAVE to spend thousands of dollars to have a studio system that can perform exceptionally well. I would hesitate to make any comparisons against systems like Kessler or Ditogear, those are different animals altogether and made to withstand the abuse of travel and field work. But as far as working in a controlled studio enviornment, there is no reason this system could not perform equally as well.
Goals with Project3
- Under $500 budget
- Must include Pan/Tilt/Slide/Focus control
- Dragonframe compatible.
- Must not require any expensive machining equipment. (basic hand tools, a miter saw, drill press, tap and die kit)
- Must perform its task as well as a multi thousand dollar system.
When I first set out to start the design process, I ran into a robotics system called Actobotics, and initially I was very excited. It looks like a very well laid out system. I downloaded all the parts into google sketchup and quickly put together a pan/tilt system and felt pretty good about it. The only problem I some of the parts cost more than I was willing to spend. I believe I can do it for cheaper. So I am moving away from using Actobotics as the core of the system, but will still use some of their parts.
Things are now back at the drawing board with a new design coming along. I will be sure to blog about the process of this and keep plenty of BTS material with my progress.
Part 1) FOCUS
One of the big challenges I ran into in the past was with “Lens Tug”
Lens tug happens when you shift directions on an automated focus pull. It applies torque against the lens, causing it to move ever so slightly. It is much less of an issue one wide angle than telephoto, and more prone when using non-native lenses. It is very obvious when using Macro. If you mount the lens motor to the lens, you remove the lens tug. Simple enough right?
Here is an older video where I was using a lens apparatus to shift a zoom lens. If you skip to the 45 second mark to the 1 min 21 second mark, I address this and demonstrate what I mean by lens tug.
The best way to eliminate this? Attach the damn focus directly to the lens. Then the linkage between the camera and lens no longer matters. Seen below, this 15mm rod mount connects direct to the lens.
So, here is my universal lens mounted focus motor.
OK, Ok, I know. It is kind of ugly. But guess what? It mounts to any lens, and it works extremely well! I have already tested it on half a dozen lenses and so far it works with all of them.
How about a parts list?
Stepper Motor $44.05
3 inch Hose Clamp $3.99
22mm Swivel Clamp $5.99
B Style Motor Mount $4.99
Motor Mount Swivel Mount $3.99
6mm Bore, 32 Pitch Pinion Gear $13.90 (You might need to shop around a bit. SDP-SI is great unless you order under $30 of stuff in which they charge you an extra $10 and shipping is ususally stupid expensive, $18 or so minimum. )
Total cost will be in the ballpark of $80 bucks. (+shipping)
You will also need
Four 6-32 x 1/2 inch Button head screws. (approx $1 at your local hardware store)
and a Tap, because the holes on the 3.99 mount are not the right size. I used a 6-32 tap.
You will also need a Tap handle.
Assembly is easy. the Swivel clamp wraps around the motor, then attaches to the swivel mount via the supplied screws. The swivel mount attaches to the motor bracket on the flat side where the holes line up. Run the tap through the feet of the motor mount then into the swivel mount. Tapping it this way will keep the threads lined up. Then once the swivel mount is tapped, run the 6-32 screws up into it to secure it, and the other screws in the other feet. You can adjust these in and out to make it fit on various contours of the lenses. Wrap the hose clamp around it, put the stepper in the Swivel Clamp and the gear on the shaft of the stepper.
Presto. Focus motor.
being a stepper, it can be controlled via Dragonframe, eMotimo, NMX, and quite a few other systems.
I have a page build for Project3 under Robots on the upper menu. I will start updating it as things move along as well as blogging about it.