8 Step Sequencer

This is my take on the Arduino 8 Step Sequencer Keyboard by LMNC. Significant changes are:

  • Addition of a Zero gate jack
  • Addition of switches to disable steps
  • Addition of Reverse Time switch
  • Addition of switch to select sequence length and patterns
  • Ability to sequence only those steps whose buttons are held down
  • Correction of some problems in the circuit design

I don’t understand why Sam provided a switch to do Reset and Zero but only a jack for Reset; I added one for Zero.

I added a toggle switch for each step. If turned off then no gate is produced at that step, and the CV is set to 0.

The Reverse Time switch exchanges the role of the Forward and Backward jacks, so the sequence can be reversed under voltage control

There’s a rotary switch allowing you to choose any sequence length from 2 to 8. The last four positions let you choose different patterns: Inclusive (1-2-3-4-5-6-7-8-8-7-6-5-4-3-2-1-1-2-3…), Exclusive (1-2-3-4-5-6-7-8-7-6-5-4-3-2-1-2-3…), Double (1-1-2-2-3-3-4-4-5-5…, with a small break between gates), and Random.

If you press one button at a time you can use the sequencer like a keyboard, playing notes of the sequence in any order; but if you hold down two or more buttons simultaneously and send in a clock signal, it will sequence only the steps you’re holding down. In this case the sequence length selected with the rotary switch (if any) is ignored, but if the rotary switch is pointing to an alternate pattern, it will be applied. So if you hold down buttons 1, 3, and 5 with the switch in the Exclusive position you’ll get 1-3-5-3-1-3-5-3-1…

I made a few circuit changes, getting rid of some redundant parts, adding some input protections, and putting the input pulldown resistors after the diodes where they belong.

Schematic:

and similar for other seven stages

Stripboard (following LMNC, most of the circuitry is wired point to point on the front panel, but the Arduino Nano, power components, and protection diodes are on a stripboard):

lmnc_8step_strip.png

Schematics, KiCad design files, Gerbers, documentation