IR Beam Based Object Crossing Detector

Projects General Guidance
21

Restrict the view of the LDR to block out or reduce effects from ambient light.

Did you try using the photodiode to ground a pin moded INPUT_PULLUP? How close did you have to hold the IR led and was it lit?

Search for: techwalla How to Use a Photodiode

It has step by step with pictures.

22

I just didn't like the fact that the ambient light in the room drove large variations in how this worked.

You have to use modulated IR for that.

Take a look at this if you want to avoid making much circuitry.