The Simplest Oscillator

A project log for Logic Noise Playground

Circuits and Snippets that go with

Mike SzczysMike Szczys 06/08/2015 at 23:180 Comments

Making sound with a single logic chip is really quite easy. Let's take a look at the most basic sound producing circuit we cover in our serise. The full details of this are covered in the first installment of Logic Noise, but here we're going to boil it down even further. You need:

Here is a connection illustration:

When connecting your computer speakers you will also need a connection to ground (the blue lines in the diagram).

The heart of the circuit is shown below. The circuit makes sound using a concept called Hysteresis. This is a type of delay found in some integrated circuits. The 40106 chip we're using has a time delay between producing a low signal and a high signal; this is an oscillator. This change from low to high is at a frequency that produces a note. The protentiometer can change this frequency, making the sound higher or lower.