[BahaTanju] sent in this oh so simple fish feeder. It’s a mechanical light timer with a simple dispensing bottle mounted to the rotating time wheel. As the timer rotates, food is dispensed and the aquarium light is activated. If you have bigger fish, you could adapt this to work on a solenoid and use a timer with multiple on/off settings.
This is the kind of engineering that gets us excited, and not just because we like machines modeled on living things. Science Daily reports that Associate professor [Kristi Morgansen] from The University of Washington has developed these robofish for underwater data collection. Her technology is notable for two major reasons: the small robots use fins for locomotion instead of propellers, which reduces drag and creates greater maneuverability. The second and more important reason is that the robofish can communicate with each other via sonar, largely obviating the need for the robofish to surface for more instructions. Both design concepts were inspired by the shape and behavior of real fish. Currently the robots are only programmed to swim with or away from each other, but these are still prototypes and the technology looks promising. For more tech specs on these “Fin Actuated Autonomous Underwater Vehicles” (see why Robofish is better?), you can have a look at Morgansen’s notes.
Chances are you’ve never wondered what your goldfish is trying to say, but if you have (or if you just want a project), check out this DIY hydrophone.
You will need a computer microphone, vegetable oil, plastic wrap, scissors, solder, and a small unused plastic bottle. Solder the mic capsule to an appropriate length of cable and test. The entire assembly can then be submerged in vegetable oil inside a plastic bottle. Yes, vegetable oil. Seal the bottle and you’re done.