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"Ron Aaron" <ron.aa…@worldnet.att.net> wrote:

> Hello,

> I want to control a dust-collector with a PIC, so that at each power tool I
> hit a push-button which:
>    1) turns on the dust collector
>    2) pulses a solenoid on an automatic blast-gate
>    3) checks to make sure the gate opened.

> I have no problems programming the PIC, but the interfacing questions are
> another issue (!).

> I have six stations, each of which will have a switch.  My PIC has 12 I/O
> lines, so I want to multiplex the triggers together.

> My basic idea was to do something like:
>    1>——–X———–|———-|—————-
>    2>———|———-X———-|—————
>    3>———X———-X———|————–
>    4>———|———–|———-X————
>    5>———X———-|———-X————
>    6>———|———–X———X————
>    7>———X———-X———X————
>                          |           |          |
>            A       B       C

> Where ‘X’ means a connection.  Then pressing switch number ’5′ would make
> the ‘A’ and ‘C’ lines go high, for instance.

> This seems simple, but my question runs along the lines of:
>    1) How do I make sure the non-triggered (A,B,C) lines stay low?
>    2) Is there a cheap and simple IC to do this part of things? (for output,
> I’ll be using a 4028 to unscramble the BCD into separate output lines)
>    3) How do I guarantee the triggered lines go high (i.e., might there be a
> problem of one going "higher" than the other)?

> I’ll be using a PIC16C84 to do the main logic.

> Thank you for your input (no pun intended!),
> Ron
> —
> The opinions expressed in this message are my own personal views
> and do not reflect the official views of Microsoft Corporation

Try diodes and load each input with a 1 k resistor pull the diodes
up (use germaniun sig diodes 0.3 volt drop 1n914 e.g. y using diodes
simple input closed contacts and direct signals to your matrix with diodes
    good luck
 elliott

bi…@voicenet.com<elliott>