[TriEmbed] Why Did This Stop Working?

[Shane Trent]

Brian,


Just change back to the 100k. The larger resistor provides a weaker pull-up and makes it easier for your IR signal to turn on the photo-transistor and pull down the output signal. The higher value of the 100k will make your sensor more sensitive to external light sources. But it sounds like your light shield on the  detector is keeping out any extra light. Just be careful in the future if you start getting false triggers due to new light sources or moving the track to a new location. 




Another option would be using a smaller value resistor on your LED but you must stay under the LED current limit. I recommend the 100k pull- up since you already know it works. 




Shane








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