Part 5: Adding Octaves

Next I decided to add two extra octaves to my keyboard. This can be done with either a frequency divider or a frequency multiplier: I chose to use a frequency divider. I used a JK flip flop IC to run a breadboard test, and got the results I was looking for:

Test with breadboard and JKflipflop

Divide by 2

Divide by 4

The design:

After running these tests, I was having a hard time finding this IC in the package I wanted (surface mount), so I switched to using a double package 4 bit binary counter. This chip does the same thing, but can only divide by two and four. And that's exactly what I need!

Here's a basic schematic of how it works:

Divide by two, four, eight, or sixteen!

The module design:

This is for 3 octaves total: the original frequency, one octave lower, and two octaves lower. This board will be fed from the keyboard and output to the summing circuit. For clarity, this shows one circuit, but there will actually be two circuits per chip; for a total of 6 chips and twelve 3-way switches. You will be able to switch between 3 octaves on each note using the 3 way slide switch.

Inputs will be coming from the keyboard PCB, and outputs will be going to the summing circuit. The original frequency trace is a simple bypass