The one question I still have is whether or not any of these
bilateral analog switches can be driven from 12 volts VDD and made to
respond to TTL-level switching signals?
There are lots of good ways to shift level from 3 or 5-volt
logic to higher voltages such as open-collector logic chips that can
take the higher voltage being sinked, op-amps, comparators which are
just op-amps with buffered outputs, etc.
If I need to put a level shifter on the board, that's not a
problem because my original idea for this project was to use old TTL
logic chips. Seven IC's later, the board was almost out of space and
my project still didn't do what I was aiming for. The PIC, on the
other hand, will do all that the 7 counter and logic chips did plus a
lot more.
A level shifter would add one more socket to the board, but
still leave a wide-open expanse of perf board for enhancements.
So, if there is a cheap and abundant analog mux or switch that
can run at 12 or 15 volts and be set to switch on 0--5 volt levels,
then that takes care of everything and I can run it directly from the
PIC's outputs.
Thanks for all the good ideas several of you have contributed.
Martin McCormick WB5AGZ Stillwater, OK
OSU Information Technology Division Network Operations Group
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Author: Martin McCormick
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Fat City Network Services -- 858-538-5051 http://www.fatcity.com
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