Harmonic Divider

[synaesthesia]

One thing I wanted to build for quite a while is a divider that creates multiple divisions of a single input frequency that can be used at the same time. The famous melody generator generates divisions, but only one division is available at one time. I wanted multiple division simultaneously, like from an octave generator. (Has anybody built something similar already that uses a simple circuit?)

My first idea was to use a 4022 and a diode-OR gates to combine the outputs to regular square wave patterns, but that didn't sound too nice. So I settled for a simpler goal first: a divider that creates two output frequencies from one input frequency. Dividers are easy to build using a shift register that is wired as a Johnson-Counter. With half of a 4015 and one NAND gate you can create all divisions from 2 to 8, plus a division by 2.5.

[revtor]

Nice! yes that melody is quite a hook!

~Steve

[synaesthesia]

Update regarding the variations: it's not the RS-FlipFlop. It happens with an XOR as well. It is indeed the phase shift between f1 and f2. Each time the divider ratio is changed the shift registers start with different initial (current) values. That produces phase shifted outputs that stay in sync until the dividers change again.

Using the combination of divide by 4 and 6 as an example, there are indeed two possible phase shifts that would generate two different outputs through an XOR or NAND.

[synaesthesia]

This circuit multiplies an input frequency simultaneously by 1/16 to 8/16. It uses four XOR gates and a 4-bit counter for that. However, the uneven divisions are not precise enough for a chromatic scale.
Actually, this circuit might actually be more useful as a rhythm generator. The table in the lower right corner gives you the bit stream for each of the eight outputs at the connector above.

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