Cats do what they want, which rarely coincides with what their owner wants them to do. In [Dumitru]‘s case, his girlfriend’s cat [Pufu] tended to make it outside into the cold more often than desired. Rather than settle with the normal bell which gets obnoxious even when the cat isn’t misbehaving, he decided to put together a custom Cat Finding collar. He used a PIC microcontroller as the brains, and temperature and light sensors to decide whether the cat had snuck into the cold, dark night. Once the cat has been marked as being outside, a buzzer and LED are set to go off at regular intervals until returned into the safety of the indoors.

[Dumitru]‘s website along with his YouTube videos are in Romanian, though the schematics and source code provided speak for themselves. He does a wonderful job walking through the entire design process, including time spend in the IDE as well as EAGLE designing the board. YouTube has managed to subtitle the majority of the details, but we imagine this post will be a real treat to any Romanian speaking hobbyists out there. Be sure to catch both videos after the break.

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[Brian Grabski] was asked by a friend to design and build a dolly that would move a camera during a time-lapse sequence. Above you can see the product of his toils, and the videos after the break show off the parts that went into the design and showcase effectiveness of the build.

The dolly is designed to ride on a pair of tubular rails. These can be bent to match any desired path and the dolly will have no problem following it thanks to two features. First, the triad of skateboard wheels on each of the three corners are mounted on a swivel bearing that allows them to rotate without binding. The other piece of the puzzle is a set of drawer slides that let the third support move perpendicular to the other two sets of rollers. A motor drives a geared wheel to move the dolly along the track with speed adjustments courtesy of the motor controller. There’s also a failsafe that will shut the system down when it runs out of track, protecting that fancy piece of hardware taking the pictures.

We’ve seen timelapse equipment that moves the camera in the past, but those hacks usually involve rotating the camera along and axis. This track-based setup is a well executed tool useful at all levels of photography. We can’t wait to see the arch-based dolly that is teased at the end of the demo video.

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Have a room in your house that really could benefit from some sunlight? Build a Suntrack to reflect light in as long as possible. The two axis motor set up is built from a couple of  satellite dish positioning motors with the control electronics removed. The whole thing is controlled with a PIC 18f2520.  Once calibrated, it will reflect the sun into your room, updating every twenty seconds. While this may not be the most efficient way of lighting a room, it is a cool way to do it if you absolutely must have sunlight. We can’t help but wonder if there would be a way of using a solar powered system to do this to save energy. Could this possibly be done using BEAM “head” circuit?

[via Hacked Gadgets]