Since I had to do a study project, that was equally effecting my grade point average, as two evil programming tests would do, I decided to come up with something cool. A simple, neat and very low budget 3 axes motion control rig should to the trick.
While keeping mechanical things quick and dirty, the controller should be something, you want to reprogram and use for future projects.
I set out to find the most sturdy and low cost linear guide. A pretty suitable one, was offered by a German Company named Isel, which mainly consists of an aluminum profile with two steel rods pressed in at both sides. The Dolly is traveling along the rails, using four steel reels, mounted on ball bearings. They all have an eccentric bolt inside, to adjust the play of each reel individually. I think one meter of rail, including the dolly was about 50€. All I had to do, was attaching some simple stand to it, as well as a NEMA 17 stepper and two pulleys + belt. (T 2.5, 6mm). Et voliá, I had a simple but accurate motor slider.
Notice: This pan/tilt head is nothing I would recommend to rebuilt, because it was more like a construction made out of stuff I had laying around!
The next thing to figure out, was how to build a compact pan/tilt head. I started by using an axial bearing from Makeblock (this was originally intended to be a robotic arm rotational base), to form the base of my pan axis. I mounted it on top of an aluminium construction, holding a NEMA 14 Stepper with a cheap worm drive gear. The tilt axis consists of four pieces 6mm aluminium, a double ball bearing mount, and a NEMA 17 Stepper with a belt drive. This combination is able to handle DSLRS like the Canon EOD 600D. Especially the axial bearing in the pan axis is not offering 100% smooth motion, but with some After Effects stabilization, the results are quite cool.
The controller is based on an Arduino Mega 2560, with two boards (one shield) attached to it. The board underneath holds three stepper drivers, that can take up to 2.2A per phase (even if getting quite hot when coming close to 2A). Every connection was done using screw terminals and pin headers, to keep things flexible and tidy.
The shield on top contains two optocouplers for controlling two Cameras and distributes power and signal pins for the I/O components and the stepper drivers. By using a graphical LCD, a rotary-push-encoder and a button for interaction, there is much space for future improvements.
After hooking everything up and a bit of coding, I had a really compact and lightweight time-lapse MoCo system, which rans for quite a long time with a cheap 12V 7.2AH lead battery (I set the motor currents as low as possible).