78 Nicolas Collins
Experiment with different value capacitors and pots for the different stages. You
can substitute photocells or electrodes for the resistors/pots in any of these
circuits.
Note that even though the control input might be connected to + 9 volts we still
need to connect + 9 volts to pin 14 and ground (- voltage) to pin 7. These
voltages are used for two distinct purposes in our circuit: through pins 14 and 7
they provide power to the chip, needed to run its internal operations – this is the
“gas.” But + and – voltage also have arithmetic value, and are evaluated as part
of the (admittedly simple) mathematical calculations that the circuit performs in
order to oscillate. As with our previous circuit with the 74C14, sometimes this
chip will make sound without proper power connections, but it will be
“coasting”, and probably will not perform reliably (or go up hills.)