## The Flock Clock

by: Mike Rigsby

The normal way to operate a drinking bird is to have him dip his head in water.  The water on his felt head evaporates, leaving the head cooler than the bird’s body.  The liquid flowing into the upper bulb (head) changes the center of gravity, causing the bird to tip forward.  Liquid flows back to the bottom bulb and the bird returns to his upright position.  As long as an adequate temperature difference (head cooler than body) remains, the cycle will repeat.

Instead of cooling the head, why not warm the body?  If you place an electrical resistor below the bird’s body and pass current through the resistor, the resistor will get warm.  The warmth will cause the bird to bob.

I used a 12 ohm, 3 watt resistor and applied 5 volts direct current.  This allows 5/12 amp to flow through the resistor for a total power applied of 2 1/12 watts (P=VI;  5 X 5/12).  The resistor gets hot enough to operate the bird, but not so hot that it melts plastic.

What can you do with this?  I built a clock (actually, I used Peltier cells for the heat, but they are \$15. each and they cool slowly, leaving a notable shut off lag).

Binary addition of the bobbing female birds (red) left to right yields the hour.  Binary addition of the bobbing male birds (blue) left to right (multiplied by five) yields the minute (to the nearest five minutes).

Complete instructions and an operating video can be found at: http://www.instructables.com/id/Flock-Clock/

This is a good higher level project that involves math (working in binary), electricity (wiring, relays, transistors, a processor), construction (acrylic, drilling, screws), software (programming the Arduino processor) and art (how you arrange the birds, how you make it look).

It takes about 70 seconds for the bird to start bobbing.  He/she will quit bobbing within 60 seconds after removing power from the resistor.  You can use batteries to power the resistor, but the current load will drain the batteries pretty fast.  If you can obtain an electrical on/off signal, you can make a bird bob on command (with a time delay).  The only limit is your imagination!

Mike Rigsby is a licensed (P.E.) electrical engineer. He writes books and creates projects for children. His latest book, Doable Renewables, Chicago Review Press, Oct. 2009 includes 16 Alternative Energy Projects for Young Scientists.  Chapter three is titled “Solar Drinking Bird.”

You can find the Drinking Bird at Educational Innovations.

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