Hardware

Project Chronos, a DIY motion control platform for timelapse.
 

After you've selected the motor type appropriate for your project, it's time to move to the next stage of building your first motion control rig: gear selection.  Unless you've bought a motor with an attached gearbox (and even if you have, in some cases), it's time to figure out exactly how you intend transfer power from the motor into your final motion.  Just like the process of selecting a motor, you'll need to first examine your requirements, and how they might change over time.  In this article, we'll walk through the basic process of selecting the proper gear train, and the different factors that should affect your decision.

The basic factors to consider are: building vs. buying, complexity, gear ratio, precision, and braking requirements.

The DollyShield is an adaptation of the Arduino Motor Shield v3 that provides directional PWM control of two DC motors, at up to 1A of current each.  In addition to the motor drivers, it also provides a stereo plug with dual opto-coupled outputs for direct camera control, a 2x16 LCD, five user input buttons, and four auxilliary inputs or outputs through two stereo jacks.  It is designed to provide an inexpensive and easy-to-use interface for two-axis motion control integrated with a camera.

One of the more daunting tasks for your first motion control project is to decide on which kind of motor you need.  The right choice in motor can save you money and effort in the long run, not to mention increase your chances of getting the shots you're looking for.  Before selecting your motor, you need to first examine what your requirements are, and how they might change over time.  In this article we'll walk you through the process of selecting a motor for a motion control rig and the different factors that should play into the decision.

The basic principles you'll need to consider in motor selection, outside of cost, are: timeframe (how long your shoots will run for), power requirements, and repeatability.

Introduction

While we spend a lot of our time focusing on stepper motors, we'd rather not leave out brushed DC motors!  It's hard to beat them for their simplicity and low cost.  When it comes to drivers for DC motors, there are a lot of options - from cheap $15 PWM drivers that can be found on eBay, to professional units that can cost up to several thousand dollars.  I've been using the Pololu JRK 21v3 driver with great success.  It offers rarely found in drivers several times its cost.  At approximately $50 USD it might seem a little pricey until you explore the options it gives you. In this article, we'll cover how to make an easy-to-use carrier board for the JRK 21v3 that will let you hook it right up into an OpenMoco system, and especially the dedicated hand-held engine model, while still retaining all of the features and flexibility of the driver.

We're making progress with hardware kits that will soon (maybe early Q2 2010?) be available for purchase. The idea is to use laser-cut acrylic panels and mostly off-the-shelf hardware (there will only be a couple of custom circuit boards, and one gear has to be custom-bored) to provide simple kits for the DIY motion control enthusiast to build their own systems without heavy investment in tooling and without having to focus on all of the fundamentals. In such a world, you could create new software, or just get out and shoot without first buying expensive CNC machines, or have to figure out yet one more way to come up with that right gear ratio.

The idea is that these kits would trade a little sweat equity from the end-user for cost, providing a system capable of just about anything you can imagine at a fraction of some of the pre-built systems' cost.