[Mark McLeod]

Have you read the FAQ at Kevin's site?

Extremely sloppy will nail you.
Ther IR sensors are highly sensitive and they must be sealed against light from any direction except front and to one side.

-Make sure no light of any kind can reach the back of the sensors
-Don't test in a small crowded room.
-Keep the beacon at least a few feet away from the sensors
-Use a larger black tube.
-Try pointing your tubes more apart from each other like a "V" shape to see if that cuts down on what they're seeing.
-Try enclosing the tubes more, so they are looking out of a tube, like a shotgun barrel. Start by enclosing them almost entirely then trim tube material away until you get the field of view you want.