For the past few months I have been building up a DSLR camera rig for making video. This week I am concentrating on controlling a motorised slider (a really nice affordable DIY kit from ratrig.com), a motorised pan/tilt head (Bescor MP-101) and a focusing servo for my main manual lens, a Samyang 35mm T1.5.
The pan tilt head is a simple device with two geared DC motors and a remote control for moving the camera up and down, and from left to right in a fixed position. The remote only allows movement of one axis at a time, and the speed control is a slide potentiometer with a narrow range. It moves a bit too robotically for my liking!
My immediate goal for this project was to have control over these motors with MIDI, so I could use Ableton Live to automate motion in both axes simultaneously in a precise and predictable fashion (hopefully). This is an important requirment for a miniature music video I'll be shooting in my studio the next few weeks. I also have a 3D mouse (3DConnexion SpaceMouse Wireless) that has 6 axes of control, which struck me as being the ideal controller. Thankfully, a program called OSCulator exists which converts data coming from the mouse directly to MIDI, so communication with Ableton Live is trivial.
For the bridge from computer to motion control, I used a Teensy LC Arduino. Having spent quite a lot time messing around with hacked USB-MIDI cables and ATMega328 chips, this thing is so easy to use. It has a native USB-MIDI mode so sending or recieving MIDI over USB is very quick to implement. Also, the Teensy is very small, so will comfortably fit into the enclosure in place of the original PCB. I'll be CNC milling a PCB to the same dimensions to securely fasten the DIN socket, Teensy, and deal with connections to the motors.
Some advantages and disadvantages to taking this approach:
- precise motion control of both axes of the pan tilt head, with independent variable speed.
- wider range of speeds by using 7.4V instead of 6V, and using PWM
- MIDI control allows movements to be stored as MIDI Continuous Controller data in Ableton Live or other DAW
- by automating the process, I'll be able to get exactly the frame I want, so will be able to concentrate more on what's in front of the camera than behind it.
- bypassing on-board battery / mains power in favour of using a high capacity Li-Ion battery pack or mains means the unit will no longer be stand-alone.
- the use of Pulse Width Modulation has inherent audible noise at lower speeds. While this won't be a problem as long as external mics are used, in some situations the sound could be an issue.
- by hacking the unit, its resale value could be greatly reduced, but I think it'll actually be far more useful this way!
More information and documentation of this hack and my motion control rig next week.