[sdiy] controlling switches with CV

[David G Dixon]

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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