[sdiy] eqys-q sequencer

[harrybissell]

Hi Fabio

cool idea. Maybe your trouble with the 4017 getting hot is from the
capacitors
discharging through the diode.  Essentially... there is no series resistance
except the
CMOS output impedance.

Why not bring all the discharge diodes to a single (large) transistor that
would
be turned on by the comparator going high... it could better handle the
current.
The CMOS output that is trying to go high (the next stage) would be
protected by the
pot and series resistor.


H^) harry

fmg wrote:

> 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