[sdiy] eqys-q sequencer

[fmg]

Hi all

eqys-q is a 16 steps sequencer with independent control of each
output step-lenght, based around 4017s. It's just a proto, I
tested some parts individually and am going to put all together
in a single pcb this weekend (I hope). A preliminary schematic is
in geocities if someone wishes look at it. I don't recommend to
build anything yet cause (me, myself) don't know if it will work 8-|

Como funciona ?
Clockless, an output hi from 4017 charges a C through a R (1M pot).
A comparator senses this charge and once Vc reach Vref, its output
clocks the 4017 starting again the process with the next step. All
4017's outputs have identical circuit. All comparators share Vref
that can be varied within a limited range to get a "master" speed
control.
Each 4017 conform a block of 8 "usable" outputs (Q0 and Q9 are used
for cascading). While nothing limit the posibility to keep adding
blocks, I used two (16 steps) because considered it practical
(economically speaking).
A 12 points rotary selector controls the sequence lenght (5 to 16),
a simple switch the mode: single sequence or continuos loop.
There are 3 controls: Launch, Freeze and Reset, they do *approximatly*
what these words mean...
Trigger Out is a sharp positive pulse that appears each time a
step advance.

Notes:
The "pushbutton logic" is pretty simple, I used conductive rubber
contacts and big buttons saved from a broken toy. For metal contacts
debounce circuitry might be required.
At really high speed 4017 goes hot. I think 470...1K current limit
resistors at the 4017's outputs could solve this.
Glide might not work (P35 and C24 have random values), also R59
should not be there (my Xfig version doesn't check for voltage drops :-)

Finally:
Despite its simplicity the schematic (or the sequencer itself)
could have lots of errors/misses, and most of these, obvious/hidden.

http://www.geocities.com/eqys/var_tmp/eqys_q.pdf

I designed this with the idea to program and play Solos with it. If
it works as expected I'm planning to put a switch to select some
independent effect for each step, as pitch bend, vibrato or one-step
only glissando.

Regards

Fabio