[sdiy] CV to rotary encoder?

[Theo]

Hi Eduardo
Sadly there is a problem with the  X-volt per position method you suggest.
Pulse type encoders can only increase or decrease sequential, you can't
"jump" them to a given position.
In itself not a problem but you also don't know the start "position" of the
encoder,
therefore it's not known how many pulses up or down your X volt position is.
IMO "nulling" the encoder (e.g.. pulse it all the way down to zero first) is
not a solution,
every time you touch the knob by hand, do a program change or alter the
value via midi, the system is messed up.

Absolute encoders don't have this problem, but like potmeters they always
output their actual position.
So the only way to change their value is by turning knob mechanically.

I use absolute encoders for the Step One sequencer (256 steps per
rotation!).
These give much better feel and control than the usual 24 step/rotation (or
so) encoders.
However to allow midi control I now need to store both;
- a offset between the encoder "value" and the parameter value
- the actual parameter value.
When you turn the knob the offset is changed,
and the parameter value is calculated from the offset value.

There are 5 DAC channels sitting idle in the current Step One design.
Maybe I should use them for CV inputs, in this case a volt/position setup
would be the easiest.
(aaaargh, not again a other thing to implement)  ;)

Cheers,
Theo



----- Original Message -----
From: elmacaco <elmacaco at nyc.rr.com>
To: Grant Richter <grichter at asapnet.net>; Paul Perry
<pfperry at melbpc.org.au>; <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, April 29, 2003 8:43 PM
Subject: Re: [sdiy] CV to rotary encoder?


> I would think you would want something that would not necessarily go
through
> the modes sequentially  (voltage control up  or down).  I am thinking of a
> setup like X volt per position.
>
> Say a voltage input range of 5 volts (or whatever) divided up by the
number
> of settings so you could do some bit swapping sequencing that jumps around
> to the different levels.  Not sure how useful that would be, but you could
> do the sequential up and down with a rising or falling voltage.
>
>
> ----- Original Message -----
> From: "Grant Richter" <grichter at asapnet.net>
> To: "Paul Perry" <pfperry at melbpc.org.au>; <synth-diy at dropmix.xs4all.nl>
> Sent: Tuesday, April 29, 2003 2:08 PM
> Subject: Re: [sdiy] CV to rotary encoder?
>
>
> > OK, I am not absolutely certain about how current this information is,
> this
> > is off the top of my head. I had to build an encoder simulator to test
> > theatrical rigging controllers which used incremental encoders.
> >
> > There are two types of encoders, absolute and incremental. An absolute
> > encoder outputs direct binary relating to it's position.
> >
> > An incremental encoder uses two square wave signals with a 90 degree
phase
> > separation (quadrature). The direction of travel is indicated by which
> phase
> > leads the other. I seem to recall one is a reference phase and the other
> can
> > reverse direction just by inverting the signal.
> >
> > This requires a 4 state machine which can be built from a 555, 4024 and
> > 4052. You just tie input pins to high or low to form the correct
signals.
> > For reference X out phase 1 (X0, X1 +)(X2, X3 gnd) Yout phase 2 (Y1, Y2
> > +)(Y0, Y3 gnd) invert phase 2 to switch direction.
> >
> > Hope this helps.
> >
> > > From: Paul Perry <pfperry at melbpc.org.au>
> > > Date: Tue, 29 Apr 2003 14:26:16 +1000
> > > To: synth-diy at dropmix.xs4all.nl
> > > Subject: [sdiy] CV to rotary encoder?
> > >
> > > A lot of gear now has a rotary encoder..
> > > there is probably an easy way to make a CV to rotary encoder
> > > converter, so when the CV increases by yea much, the encoder
> > > goes foward one unit and so on.
> > > Or just keeps going up while CV is above a threshold, back
> > > when below it.
> > >
> > > paul perry melbourne australia
> > >
> > >
> >
>
>
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