Are you talking about physically touching the port pin with your finger?
If so, you might want to take precautions when a 4000 volt static
discharge from your finger jumps to the pin.
Rick

PicDude wrote:

> Thinking of using the case on a PIC-based project as a simple
> touch switch.  Can anyone comment on if this idea will work...
>
> I've seen a circuit similar to this using 2 port pins with
> the top of the resistor going to the other port pin (instead
> of +5V).  However, I'm thinking I can do this with just one
> port pin as follows...
>
>               ^ +5V
> --------      |
>        |      R
>    P   |      |
>    I   |----------C---.
>    C   |              |
>        |             ---
> --------              -
>
> To see if the switch is being touched, the pin would be at
> LOW logic level.  Then I would switch it to HIGH, flip the
> pin to an input, then read-back the level.  If HIGH, then
> no finger is present, else if LOW, then a finger is present.
>
> The key to this is using as few components as possible, so I
> may replace C with PCB pads, if I can calculate C to be small
> enough.
>
> Cheers,
> -Neil.
>

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