garage door optical sensor

I have a garage door opener that allegedly senses pressure, in case of an object in its path, and reverses. I say "allegedly" because the other day it tried to self-destruct when it wouldn't reverse for a wheelbarrow in the way. Ten hours later, it is back in functional condition, and the door looks pretty good. The opener has neither an obvious brand name, nor any obvious way to adjust the pressure sensor.

Being a cheapskate, I'd rather add an optical circuit, so that if a beam across the path of the door is broken by an object, the door won't activate at all. The electronics of this is simple, but I haven't ever implemented an optical circuit like this, so I'd like any experienced advice as to what is the best choice of optics. Should it be infrared, or visible, and if visible, is one color better than another? How much LED do I need (intensity), and any other gotchas which might affect a design like this?

Thanks in advance for any suggestions.

Are you thinking of having a light beam along the bottom edge of the door itself that goes up and down as the door moves?

If you are thinking of having a fixed beam, not along the bottom of the door, I doubt one beam would be sufficient. The door could come down on the roof of a car, on a wheelbarrow or something quite small. One beam may well not detect such obstructions.

Is the garage door of the up-and-over canopy, sectional or roller type?

If there is any chance of a child playing with the door, don't risk injury, get the mechanism replaced or repaired.

How old is the thing?

Most garage doors have both the beam circuit and the pressure sense built in. There is usually as terminal strip on the opener for the door beam connections and pots to adjust the opening and closing pressure.

Motor current detection. Leo..