It's been a while since I've browsed the Hack a Day pages. Moving, new job, new school for the kids, new house -- it all takes up a lot of time. But I took a look and found a project that made me laugh out loud. The user mrigsby has collected a flock of Dippy Birds and taught them how to tell time. He only has four, so they only tell the current hour, but the idea is entertaining nonetheless.
You've seen the Dippy Bird before. A glass tube in the vague shape of a bird is filled with a colored fluid. When the fluid warms to room temperature, it boils and rises into the head, causing the bird to dip down. The beak then dunks into a glass of water, causing the fluid to cool and fall back into the reservoir at the bottom, and the bird stands up again. We have one somewhere, and my kids always get a kick out of playing with it. (Thanks to Hack a Day, I now know that the fluid is dichloromethane, with a boiling point of about 100F.)
The clever mrigsby has removed the glass of water and placed a resistor directly under the Dippy Bird reservoir. When current passes through, the resistor warms, lighting a metaphorical fire under the bird's posterior and setting it into motion. This flock tells the current hour in binary language -- a Dippy Bird in motion counts as one, and a Dippy Bird at rest counts as zero.
I'd like to see Dippy Birds count off minutes, as well, and it would be great if the bird's position, rather than whether it is in motion, indicated the binary digit. How to achieve that level of control? The first thing I'd try would be a small Peltier device attached directly to the reservoir. You apply heat to make the bird dip and cold to make it stand up. That also removes any dependency on ambient temperature to provide the return function. You'd have to try it out to see if it gave you enough control to count seconds (probably not) or minutes (seems like it should work).
For Christmas many years ago, my sister gave me an LED binary digital clock. (Technically, it's BCD, not binary, and I quite ungraciously pointed that out to her after I plugged it in.) Now I'm thinking a Dippy Bird array clock would be a great return present. However, if I actually put that much work into building one, I'd probably keep it for myself.