Atari Punk Console
I came across this circuit on www.getlofi.com
It is apparently from “Engineer’s Mini-Notebook - 555 Circuits” by Forrest M. Mims, III (Siliconcepts, 1984) and appears to be a fun circuit to start with on this website.
The circuit uses an LM556 which is just a dual 555. The schematic can be found at Kaustic Machines.
There are a few other neat links too.
http://www.geocities.com/worthekik//atari.html
http://matrixsynth.blogspot.com/2006/09/atari-punk-console.html
Tons of cool 555 things can be found here and HERE!!!!
Explaination
Its not particularly interesting unless your turning knobs. For the most part, its a square wave oscillator driving a monostable oscillator which…by definition, creates a single (square) pulse. There are two controls. One for the frequency of the oscillator and one to control the length of the pulse.
I decomposed the schmatic from Kaustic Machines into the respective components in 555 form.
Schematic
The first stage is the astable oscillator. The frequency (RC constant) is determined by the capacitor and the resistor/pot.
The second stage puts out a square pulse with a length that is determined by the other cap/pot.
So long as you dont touch anything, its just putting out a squarewave.
A little experimenting demonstrated the following.
Fixed frequency, change pulse width
When you pick a frequency close to the width of the second stage, you get the neat octave dropping sound.
This is why
Fixed width, change frequency
When the width of the pulse is fixed, your not going to have full flexibility of the frequencies as the width of the pulse will limit the smallest period.
example
Mods
There are probibly lots of mods…but for the most part, its a square wave generator, so your pretty limited. (pun intended). The first stage simply drives the next, so changes in the waveform are not going to do much. Time/frequency is your key.
The second stage is a pulse…waveshaping perhaps? Technically, just about anything can drive that monostable oscillator. Perhaps a Cmos oscillator instead, then use the second half of the 555 as an ADSR instead?
Filters?
Optoresistors. Here is the same circuit with optoresistors and me waving me hands wildly.