64 Nicolas Collins
Chapter 18: The World’s Simplest Oscillator
You will need:
- A plastic prototyping board (“breadboard”.)
- 1 CMOS Hex Schmitt Trigger Integrated Circuit (4584, 40106, or 74C14)
(see text below.) - Assorted resistors, capacitors, pots and photocells.
- Some small signal diodes, such as 1N914.
- Some solid hookup wire.
- A plug to match your amp.
- A 9 volt battery and connector.
- An amplifier – preferably battery powered.
- Hand tools.
In the contrarian spirit of hacking, the first circuit we build from scratch is based
on the misuse of an Integrated Circuit (IC) never intended for making sound. The
“Hex Schmitt Trigger” is a CMOS digital logic building block consisting of 6
identical “inverters.” An inverter takes a logical input, 1 or 0, and puts out its
opposite (so 1 becomes 0, 0 becomes 1.) This particular version of the inverter is
useful to us because it runs for a long time on a 9 volt battery, it is very cheap,
and it contains a circuit known as a “Schmitt Trigger”, whose fine points you
don't need to understand at this point but, trust me, transforms the chip from a
simple digital no-man (as opposed to a “yes man”) into a versatile sound
generator.
The Hex Schmitt Trigger may be labeled with the numbers 4584, 40106, or 74C14.
There may be prefixes, suffixes or additional number strings that you can ignore,
but chips with a different “innerfix” may not work: if labeled 74HC14 or 74AC14
they will not run on a 9 volt battery and so are less suitable for this project. Here
are the internal configuration and connections:
+ 9 voltsground
74C14