> Having done some research it seems to me that a PIC based system is 
> probably the best way to go, but I was wondering whats the best way to 
> interface the 90 wires to the PIC? All the example projects I can find 
> so far interface to a much smaller number of wires.

Any micrcontroller with an (internal or external) USB interface will do. 
For a one-off use an usb-to-serial converter, max232, and a PIC with a UART.

For reading N inputs: use a chain of shift registers (like 74HC165), or 
I/O expanders (like MCP23016 or MPC23S016). Or (analog or digital) 
multiplexers.

If isolation is a requirement use optocouplers. I think the secondary 
side of the opto's could be arranged as a matrix, so with maybe an extra 
diode per opto you could read 100 signals with 20 I/O pins.

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Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu

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