Quoted from Roamin:Instead of blindly changing the IR diodes on the opto , why not look at it on your phone with the camera ? Most cameras on mobile phones will capture the light emitted by IR diodes. If the front facing camera doesn't work , the selfie camera most likely will because it almost never has an IR filter in the lens.
This is an awesome tip!! I never knew this and it worked perfect on my iPhone. I tested it by pointing my tv remote at the phone while pressing a button. It did not work on the regular camera but it did work on the front facing camera. I could see the light flash when pressing the remote button.