[sdiy] controlling switches with CV

[Dave Magnuson]

And if you want to get really low tech, find a LM3914 10-segment bar graph
driver IC, and put it in "dot mode".    Crappy 10 channel window comparator.
Your voltage "steps" won't be incredibly accurate, but it may work for you?
You would just set your VREF to a level where you could ignore 2 bits.

It would reduce your parts count by one IC vs dual quad op amps.   Depends
on the accuracy you need

Dave Magnuson

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of David
G Dixon
Sent: Thursday, April 20, 2017 3:56 PM
To: 'Elaine Klopke'; 'Kylee Kennedy'
Cc: '*SYNTH DIY'
Subject: Re: [sdiy] controlling switches with CV

With an AD converter, you can convert a CV into a string of binary numbers.
With that, you can control your CMOS switch.  Done.

An AD converter can be a chip, or you can use a string of comparators and a
priority encoder.  A priority encoder accepts 8 inputs, and spits out a
corresponding 3-bit binary code.  It makes a nice interface between either a
string of comparators or a rotary switch.  I use the CD4532, but there are
many others.  It costs 50 cents.

For analog switches, I use the Vishay DG chips.  For an 8-channel
multiplexer, the DG408 is a good choice.  The nice thing about this series
of chips is that they handle large bipolar voltages, up to 44V.  There
aren't that many chips around that still do that.  Also, they are available
through-hole.

So, with a pot or fader, two quad opamps, 8 or 9 resistors, a 4532 and a
DG408, you could have a voltage-controlled 8-way analog switch.  Total cost
about $7.


> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of 
> Elaine Klopke
> Sent: Thursday, April 20, 2017 1:31 AM
> To: Kylee Kennedy
> Cc: *SYNTH DIY
> Subject: Re: [sdiy] controlling switches with CV
> 
> 
> > look up CD4066 IC datasheet it's a bunch of FETs in an IC. 
> I'm still learning to use it myself in a design I'm working on but 
> just wanted to throw it out there as another option.
> 
> Oh! I thought you were talking about using CMOS chips for the ADC... 
> I'm already using CD4066s for the actual switches.
> THOSE are what I'm trying to control via CV. I have a scheme to 
> control them via MIDI for a paraphonic sort of deal, but I'm looking 
> at options to be able to close the switches via a pitch CV so the 
> module is more flexible.
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> Synth-diy mailing list
> Synth-diy at synth-diy.org
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