IR detector - signal or not...

hi everyone,
am diving in , writing first arduino script, after doing small handful of examples/tutorials on site.

my circuit this:

except i'm using pin 9 instead of 12.   (picture borrowed older post, circa 2009.  credit user: jerryanet)

the ir detector side side , facing in same direction, rather facing each other.  when object put in front of them, can detect small difference on pin9 ir reflected detector.  unubstructed reads typically 20 or 21, , reflected jumps 23 or 24.

the floating value @ either level driving me crazy, becuase makes harder determine if change determined object present (reflection) or not. i'm guessing ambient light partial culprit in this!

what can settle down detection, or increase difference between 2 states, can more certain?

thanks in advance!

peter

so assume on machine has pin 9 1 of analogue inputs.
the simplest thing can make 10k resistor 100k one. give bit more range / difference. can try angling emitter , detector both @ point @ distance interested in.

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