tirsdag den 27. januar 2015

Aristoteles Logic Synth Update #5: Sequencer

I couldn't hold myself back after finishing the AND-gate module for dear Aristoteles so I dug up the schematic I drew for the 10-step sequencer module and jumped right in. In the video below I'll demonstrate how it works and the possibilities are vast! Combined with the AND-gates it's very convenient for creating melodies and patterns.

The sequencer is based on the '4017 CMOS Decade Counter' which counts from 0 to 9; adding 1 every time a clock pulse is received on the CLK input. It has 10 outputs going high/low one at a time depending on the current count. Only one output at a time can be high; the one corresponding to the count.
There's a reset pin which decides when the counter will reset to 0 so it's possible to have it count to any number below 9. I've implemented a rotary switch for setting the count from 9 to 0. If the reset pin is set to ground, the count limit will be set to 9 (default).

If an audio range signal is sent to the clock pin and one listens to one of the outputs, you get harmonic intervals when reducing the count limit. This makes sense as it only takes half the time to count to 5 instead of 10.
The frequency ratio to the frequency we get when counting to 10 (which can be seen as our fundamental) can be calculated by dividing 10 with the desired count. So the relation between i.e. 10 and 5 (10/5) is 2. We multiply our fundamental with this number to calculate the interval, which in this case would be an octave.
The chart below shows the intervals we get when we're adding the value of the fundamental - which is what happens every time we add a step for the counter. Interesting stuff!

Multiple of
within octave
Common name Hz and chroma
1x 1/1 Fundamental 110 (A2)
2x 2/1 Octave 220 (A3)
3x 3/2 Perfect Fifth 330 (E4)
4x 4/2 Octave 440 (A4)
5x 5/4 Major Third 550 (C5)
6x 6/4 Perfect Fifth 660 (E5)
7x 7/4 Harmonic Seventh 770 (G5)
8x 8/4 Octave 880 (A5)
9x 9/8 Major Second 990 (B5)
10x 10/8 Major Third 1100 (C6)

As is the custom, I've attached the scheme for the circuit for this module. It's not that intricate, just LED's and output jacks on each output. I see that I forgot to add the transistor LED-drivers, but it's just as usual - look in the schematics for the other Aristoteles modules to see how they should be wired.
I've used a 12 position rotary switch for the reset switch, I couldn't find any 10-pos so 2 of the positions are grounded which just sets the count limit to 9 (all 10 steps). It can be tricky to find out which pins correspond to the switch positions but easy enough when using a multimeter for testing continuity between the output and the desired pin.

I will post all my stripboard layouts in a single package when I am finished with the last module :-)

 UPDATE 7/2-15:

My brother and I (as the duo SNU) had a really nice jam with the Aristoteles modules so far.  Here's a video of  our session when the sequencer was still on breadboard. I had my Clock Box (which also runs on 40106 and 4040 oscillators) control the power for the 4017 so a lot of modulations back and forth.

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