----- Original Message ----- 
  From: Andrew Wood 
  To: piclist@mit.edu 
  Sent: Friday, May 21, 2010 7:41 AM
  Subject: [PIC] Using PIC to sample 90 wires


  Hi

  Im new to PIC and electronics in general, having come from a software 
  background. Im looking to design something which can sample 90 wires for 
  the presence or absence of a DC voltage (50v, but can be taken down to 
  say 5v with a voltage divider if needed). It then needs to store a bit 
  in memory for each wire indicating if the wire was live or not and then 
  interface to a computer over USB so the computer can read the bits.

  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.

  Thanks
  Andrew
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I'd use 12 74HC245s to select the lines to be tested.
You enable 1 of the 12 a byte at a time.
You could even use a 74HC154 to select the 12 receivers.

Tom
  *
  |  __O    Thomas C. Sefranek  wa1rhp@comcast.net
  |_-\<,_   Amateur Radio Operator: WA1RHP
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