Programmable switches?

Hello all,

For fun (obviously not profit :) I am designing (and will soon start building) an analog computer. Currently, the design has 78 inputs and 52 outputs. This includes connections to a DAQ card in a PC.

While I am prepared to bring these connections to a plug board and wire it up with banana cables (to think that some people actually complain about UNIX's shell interface :) I'd rather devise a way to enable the PC to supply the required connections.

But how? I loathe the idea of wiring up a bucket full of transistors. I'd rather use relays at that point -- at least I'd get a satisfying click-clack when setting up the analog machine.

Analog Devices sells digitally programmable arrays of DPST switches.

4-per array. So I'd need 1014 of them, at about $1.60 a piece. Ouch. (I'm thinking DPST here so that ground can be routed to the analog computer inputs instead of leaving them open, otherwise I could has an 8 switch array of SPSTs...)

Is there some other type of cheap analog switching solution that I'm not aware of? Something like this has to exist for the AV guys, no?

As a last resort, if the price is unbearable, I could have only a fraction of the analog connections under PC control, but this isn't nearly as sexy.

Ideas? I really want to make the best hybrid I can, but this is new waters for me -- I've never used an analog computer before (which is basically why I'm building one).

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Many thanks,

Don Lancaster
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Don Lancaster

[snip re plug board vs programmable connections]


I don't know what AD part you are thinking of, so don't know its specs. If +/- 7.5 V is a wide enough range you could use CD4051 parts. ["precision low-voltage CMOS analog multiplexer/switch, eight-channel single-ended mux"]. Attach the commons of 8 of them to one output, and attach each of IO0...7 to a different input line. Repeat for each output. 8 x 53 = 424; about $157 if you pay $0.37 each at

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I wrote 53 instead of 52 because you want to be able to ground inputs. You would also need 53 each 74LS138's and 74LS164's.


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James Waldby

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