Thursday, November 17, 2011

How to Use Cmos Logic In Lunetta Design

Okay, once you build some oscillators you are going to want methods of controlling or dictating when things go bleep and bloop. Enter CMOS logic. NOR/NAND/OR/AND/XOR may sound intimidating at first but are pretty similar in this regard. These are various Gating ics.  The High and Low state of a chip's outputs are at the mercy of the logic built in each type chip. Think of it as a set of conditions have to be met before a beep can well, beep.

Take the cd4070. It's a quad 2 input XOR chip. According to the data sheet, when both inputs are Low or High, the output is Low. When either input is High, the output will be high. By choosing your logic with the emphasis on variety, more interesting patterns emerge. Pick a few NAND and XOR gates (think of a gate as an open/closed, on/off ic) and you're ramping up the complexity in sound design without being overly complex to build. You don't need a ton of these in your lunetta to make cool sounds so add as much as your time permits.

One of the super cool things about some of these logic chips is the number of inputs. The 4012 for instance, is a Dual 4 input NAND gate, while the 4011 is a Quad 2 input NAND gate.  The 4000 is a Dual 3 input NOR gate plus inverter!  So, by mixing up the number of IN's as well as the type (NOR/NAND/XOR), the path to your sonic visions becomes a personal one.  Some sounds will be fairly gap free while at other times, there will be interesting pauses and patterns the longer it plays.

For me, it's about getting as close to the V'GER concept from Star Trek the Motion Picture as possible. 


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