Submitted by shutterdrone on Tue, 07/13/2010 - 04:47
Posted in
The DollyShield provides an easy hardware setup for two axis motion control photography using simple DC motors. With an isolated camera connection, LCD, pushbuttons, and auxilliary inputs, it provides everything needed for controlling a simple 2-axis moco rig.
Once connected to an Arduino microcontroller, the MX2 Firmware provides a basic and easy-to-use interface for creating time-lapse videos with motion control on a budget. This document describes how to interact with and use the MX2 Engine.
Current Version
MX2 Dolly Engine v. 0.1 beta
(c) 2010 Dynamic Perception LLC
Feature Overview
- Three models of movement:
- Continuous, PWM-driven
- Shoot-Move-Shoot
- Pulsing
- Pulsing and Shoot-Move-Shoot open up very slow motion movement
- Movement model is automatically determined based on speed
- Speed Input in Absolute (ex: 0.5"/min) or Relative (ex: 50%)
- Manual Motor Control (real-time motion)
- Camera Intervalometer
- Automatic shutter trigger through remote cable
- Focus line control
- Non-blocking operation
- Two sets of auxillary digital inputs
- Limit switches
- Encoders for Servo operation
- Serial Communication
- etc.
General Operation
While the MX2 firmware provides full control over the Dollyshield through a simple user interface, the core act of shooting a timelapse film with motion using a DSLR is controlled through a simple timing loop. The motors are turned on when configured to be running, and the camera events fire at their set intervals.
All control over the camera shutter, focus, and motors is done in a non-blocking fashion, so any parameter may be changed at any time and will take effect immediately. In normal, PWM mode operation, each motor that has a speed greater than zero is turned on as soon as the shoot is turned on, and turned off when the shoot is turned off. However, once a motor is set to a speed lower than the configured minimum speed, one of the special motion modes kicks in for that motor. In Pulsing mode, the motor is moved at full PWM speed for brief periods of time, reducing problems with slow PWM affecting torque under heavy loads. This results in a slower travel speed than can be achieved with basic PWM on average. In Interleaved, or Shoot-Move-Shoot mode the motors are moved at full-speed for a set amount of time between camera exposures. Interleaved mode enables one to tie movement speed to camera interval speed, thereby greatly decreasing the available speeds and stretching out shots over hours and days. All values for the more advanced motion controls are automatically determined for you by the simple values that you input: motor speed (distance or percentage), and exposure interval.