While searching the web for artbot ideas, I came across Ralf Schreiber's "Solar Sound Modules".
Ralf Schreiber uses a solar powered 74HC14 hex inverter along with different resistors, capacitors and a piezospeaker to make objects that create sound. The sounds that are generated are simular to that made by insects, frogs and other creatures found in nature. As I experimented with his circuit, I wanted to make a more permanent fixture that would allow full adjustability of all the components. Not only does the 74HCT14 inverter have the ability to produce sound with a piezo, but can also drive leds if enough power is supplied to them.
Now I can experiment with different values of components till I get the disired effect, then go ahead and build my object. Ralf Schreiber calls these objects "Living Particles", a name fitting for circuits that constantly adjust themselves with the enviroment.
My Schematic for the Fixture
How it works:
The six inverters form three oscillators. The frequency of the oscillators are set by the values of variable resistors R2, R5, R8 and by the values of "C", externally selected capacitors. Interaction of the three oscillators is achivied by inserting resistance at the positive power lead with R1 and R11. As the three oscillators run, a voltage drop across this resistance changes the output frequency. A further load on this resistance is provided by adjusting R4, R7, R10. As the inverters change state, current draw between R4, R7, R10 will vary. When this circuit is powered by a solar cell, each inverter will share it's demand for the restricted power. This fixture was made to test circuits that will be using external power sources, but can be applied to solar powered circuits if power demands are respected. The 74HCT14 is designed to work with voltages to 5 volts, while a CD40106 can operate to 15 volts. Keep in mind the values of load resistors at higher voltages. I selected values that are safe for voltages below 5 volts.
PDF of the schematic
