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The sensor isn’t super sensitive, with the recommended resistors it sits around 1020 in ambient lighting, when you put something close to it it will only change 2-10 digits usually. if light is shining on the sensor it will drop down dramatically (500-900) range. This makes it easy to see if something breaks the light going to the sensor. For our project we had it enclosed in a tube & to sense if there is a ball there or not. So we put an LED across from the sensor so if the ball broke the light it would be obvious to the sensor.
I bought these for embedding in a “pinewood derby” race track to detect when the cars pass over the finish line, and it seems to be working well for this after a few tweaks..
I was very worried when prototyping by the fact that the object has to be REALLY close (about half an inch) to reliably “trip”. I had to play around quite a bit with how much of a “drop” to treat as a real detection, and how much of a delay, as if I made the drop too big, and moved slowly, it wouldn’t register.
Also, this using an infrared detector, it gets a bit flaky in light/shadows. Many times my prototype would “trip” if a shadow inadvertently fell across it, or if a light was shined on it. I ended up having to build a “hood” to try to block as much as possible.
It is working well now that it is mounted in the track under the shelf, will update after the official raceday where we run hundreds of heats.
Thank you Sparkfun.