I'm building a motorized camera dolly, to be used for timelapse photography - powered by a Raspberry Pi of course
The dolly is based on the Igus "DryLin W" rails, to which I attached a NEMA17 stepper motor and built a simple belt drive for the carriage. The stepper motor is connected to a Pololu A4988 driver which in turn is connected to the Pi's GPIO (the STEP and DIR pins for now). This way I can drive the motor by simply triggering a GPIO pin repeatedly.
I also built a simple camera trigger using a ULN2803 (which is overkill, I only need one of its drivers for the trigger... ). This could be used to trigger any camera that has a simple "switch" style remote connector, like Canon or Nikon DSLRs.
The Pi is running a node.js server, containing the software which controls the timelapse sequence (basically an interval timer + motor control). It has a small web frontend for mobile phones.
The Pi acts as a Wifi access point, so you can just connect to it with your mobile and control everything via the webapp.
Everything is battery powered of course, with a mobile battery pack for the Pi and eight AA cells for the motor (needs more than 9V).
This image shows what the whole rig looks like.
(from left to right: mobile battery pack, AA battery pack, Pi, case with motor controller, motor - everything held in place by velcro tape
And this is the first test footage, it's only a 10sec clip but it's a start
I'm planning to release the source of the software and schematics for the electronics once it is a bit more stable and has some needed features (like a "power saving" feature for the motor).
Right now I'm trying to add gphoto2 support, so the software could also change camera settings during the timelapse sequence. Might be useful to implement an "exposure ramp" feature or maybe even change the focus distance over time, we'll see...