[sdiy] Substitute for pin matrixes? Probability list update 2.

Mon Jan 25 01:52:05 CET 2010

Here's a thing from telecom design - you don't need a full N x N matrix. 

You can usually reduce switching paths to a N input mux/multiway, an N output mux/multiway, and some smaller number of signal paths and switchers between the inputs and outputs. 

You'll never connect every input to every output. So whatever hardware you choose, a full N X N matrix is redundant. 

It's fine for a patch panel, because the panel also functions as the interface. 

But if you're using digital switches, relays, or some other system, you can remove some of the redundancy behind the scenes, as long as you leave enough signal paths to be fairly sure you'll never run out of them. 

Likewise for summing nodes, if you're using them. 

Richard

On 25 Jan 2010, at 00:00, cheater cheater wrote:

> actually no, I think it's a 1 to 8 or 8 to 1 mux. My bad. So you take
> 8 of those and have an 8x8 matrix. Does anyone smarter with that stuff
> want to clarify how a 4051 REALLY works? :)
> 
> D.
> 
> On Sun, Jan 24, 2010 at 23:41, Kyle Stephens <lightburnx at yahoo.com> wrote:
>> D,
>> 
>> No, you got it. It was my bad thinking only in a one-for-one sense, though the idea could be applied to some interesting modulation routing - say 4 sound sources, 4 modulators, hopping between each other. Call it a stepped scanner.
>> 
>> 
>> _Kyle
>> 
>> --- On Sun, 1/24/10, cheater cheater <cheater00 at gmail.com> wrote:
>> 
>>> From: cheater cheater <cheater00 at gmail.com>
>>> Subject: Re: [sdiy] Substitute for pin matrixes? Probability list update 2.
>>> To: "Kyle Stephens" <lightburnx at yahoo.com>
>>> Cc: synth-diy at dropmix.xs4all.nl
>>> Date: Sunday, January 24, 2010, 1:48 PM
>>> Kyle,
>>> a 4051 is an 8 channel multiplexer which means it can can
>>> only make 4
>>> connections (with 8 ends) - correct me if I'm wrong?
>>> 
>>> Thanks
>>> D.
>>> 
>>> On Sun, Jan 24, 2010 at 21:54, Kyle Stephens <lightburnx at yahoo.com>
>>> wrote:
>>>> Here's a solution with only two pots for an 8x8
>>> matrix:
>>>> 
>>>> An X pot, and a Y pot, both wired as voltage dividers,
>>> each running into an 8-bit ADC. Each bit address intersects
>>> with an AND gate (quad AND, need 4 - and one input is for
>>> the X-axis, the other the Y-axis), the output of which turns
>>> on 1/8 of a 4051 (2x of those for 16 connections), with one
>>> switch 'pole' connected to a point on one axis, and the
>>> other pole to its respective spot on the other axis. If you
>>> need some visual indicator, a decoder and numerical LED
>>> array will get you there (more simply, if taking more space,
>>> two rows of LEDs tapped off of each address lines works
>>> too).
>>>> 
>>>> If you need more than 8x8 connections, you can just
>>> cascade an ADC with a binary weighted out and op amps,
>>> needing much, much less than 8 bits per 'bank' (vis-a-vis a
>>> VCDO), depending on how many connections we're talking here.
>>> (might want a coarse/fine pot setup at that point).
>>>> 
>>>> (8x8)^2 = 4096 possibilities (that's a Hans
>>> Zimmer-class synth!).
>>>> More reasonably, say (2x8)^2 = 256.
>>>> 
>>>> At its simplest as said, it's just two pots - if
>>> available real estate is an issue, this takes care of that.
>>>> 
>>>> You could even make the patching voltage controlled,
>>> putting CVs into the ADCs, ooh...just a thought.
>>>> 
>>>> The off-the-top-of-my-head-estimated bill for this
>>> would be, with surplus parts and let's say $0.50/most
>>> ICs...
>>>> 
>>>> 2x pot = $3
>>>> 2x ADC = $7
>>>> 4x AND = $2
>>>> 2x 4051 = $1
>>>> 2x decoder = $2 (optional)
>>>> 2x LED array = $6 (optional)
>>>> 
>>>> $15-23. Cheap?
>>>> 
>>>> 
>>>> _Kyle
>>>> 
>>>> --- On Sun, 1/24/10, karl dalen <dalenkarl at yahoo.se>
>>> wrote:
>>>> 
>>>>> From: karl dalen <dalenkarl at yahoo.se>
>>>>> Subject: Re: [sdiy] Substitute for pin matrixes?
>>> Probability list update 2.
>>>>> To: synth-diy at dropmix.xs4all.nl
>>>>> Date: Sunday, January 24, 2010, 9:20 AM
>>>>> Turning stones for something
>>>>> cheaper(dead cheap)then a Gillimetti matrix:
>>>>> 
>>>>> 1: Aligator clips on wire mesh as array.
>>>>> 2: Sub miniature SPDT arrays.
>>>>> 3: Toy railway/mechano sub sub bananas arrays.
>>>>> 4: 2.5mm tele arrays.
>>>>> 5: 3.5mm tele arrays.
>>>>> 6: 4mm bananas arrays.
>>>>> 7: Upside down IDC array resistor or wire as
>>> cross
>>>>> connects.
>>>>> 8. Turned IC holders arrays.
>>>>> 9:  Pin lists arrays.
>>>>> 10: Miniature push button arrays.
>>>>> 11: Veroboard layers as arrays, with bridge
>>> shorting
>>>>> between.
>>>>> 12: MT8816 and others, 4066, serial latches, MCU
>>> etc.
>>>>> 13: Latching Hall sensor arrays, controlling
>>> muxes.
>>>>> 14: Relay arrays, klicketi klack sound on its
>>> own.
>>>>> 15: Buchla paper solder punch card holders
>>> pluggable
>>>>> something.
>>>>> 16: A gigantic array of pots.
>>>>> 17: Fuse holder array.
>>>>> 18: Automatic fuse array.
>>>>> 19: Rims of plastic Lab plates arranged in
>>> arrays.
>>>>> 20: Standing sub miniature USB connectors, can
>>> carry 4
>>>>> signals each.
>>>>> 19: Replace the analog shit with digital DSP shit
>>> for plain
>>>>> convenience?
>>>>> 20: LDR Matrix with card with holes blocking a
>>> light
>>>>> source.
>>>>> 21: Spark gap and other high voltage switches,
>>> watch out
>>>>> for your safety.
>>>>> 
>>>>> At the moment im out of ideas so i just post a
>>> updated
>>>>> probability
>>>>> list as a reference for folks to know what has
>>> been
>>>>> discussed so far!
>>>>> Not saying you shouldn't evolve over it again,
>>> perhaps you
>>>>> find
>>>>> something this time you didn't find the first?
>>>>> 
>>>>> KD
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>> __________________________________________________________
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>>>>> 
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>>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
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>>> 
>> 
>> 
>> 
>> 
> 
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