Rob wrote:
>PROJECT:
>   Infared line detection circuit
>
>DESCRIPTION:
>   Ability to correctly identify a significant variance in contrast by
>sampling at least 6-8 phototransistors while emitting infared light.
>
>PROBLEM:
>   Is there some way (using a flip-flop, or otherwise) to only use 2-3
>pins to sample all 8 inputs?  I'm currently using a 16F84A to do this,
>run some servos, an LCD, etc (yes, a "robot").  The line detection
>routines I've seen on the net use a 1-1 sensor to pin configuration...
>There just HAS to be a better way... :)

You could use a shift register to pull in 8 lines quickly. That will use
only 3 lines I think. (load, clock, data) It also has the advantage of
being expandable to more inputs without using any more I/O pins.
This is the way to go if digital inputs are what you need. If you want
to sample analog voltages then you need a MUX (CD4051) but that
will need 3 lines to select 1 of 8 inputs and one line for the selected
input itself. Hope this gives you some ideas.

>OTHER USES:
>   Obstacle detection.  I've heard of a similar circuit altered slightly
>to provide obstacle detection up to 1m or so.  Modification was
>something along the lines of sending a modulated pulse and "listening"
>for that specific pulse, and computing the delay.  Has anybody heard of
>this?  Any ideas, code, resources, etc. for either of these would be
>greatly appreciated...
>
>P.S. I'm not necessarily looking for the solution, just a pointer in
>the right direction on the best way of doing either or both of these.
>Thanks.
>
>While I'm at it, where is the best place to pic up some ultrasonic
>stuff for obstacle detection (might as well do both, this is a learning
>experience, right?)

Check piclist.com - there should be something in there about this...

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