HO-LEE SCHMIDT those things are expensive. Maybe I'll go with a ball on the end of a 1/2" PVC hanging from a pivot. When the door is open it closes a switch. When the ball swings back (maybe) a foot a microswitch will complete the circuit and light a stop light telling my wife to stop. That'd be easier than going with lasers and reflectors and sensors. BTW: A phototransistor would need to be mounted in a tube with two 1/4" ID washers so that ONLY the reflected light from the reflector would trigger it. Switches are just easier. Maybe add a car horn for if she over-stages. Something that will really get her attention. Then to stop the horn she'll HAVE to pull forward slightly. Until the horn shuts off. Of course, hanging a ball and tube in the middle of the garage may prove bothersome when moving heavy pieces of wood around. Maybe I'll still go the laser and reflector route. A simple comparator should provide sufficient adjustment to adjust out any ambient light.

I put a phototransistor on a digital counter one time. Every time the lighting would flash it could count 30, 40 even over 50 flashes in a single strike. But that was way back in the early days of my electronics experiments. Even put one in the refrigerator so I'd know how many times the door was opened.

 

I'm old school and still don't depend on backup cameras. The backup assist in our Explorer drives me nuts. Every time I back up I need to turn off it's warnings. All of it's "alignment" indicators are useless when you only have a few inches of clearance.

The blind spot function on the mirrors is also distracting.

The one in my new Equinox is worthless in the sun light, the screen can't be seen.

 

Again, provided she hits them. She can put the back end anywhere up to 3 feet. 1 foot to the left and she's gone more than 2 feet to the right.

Ok then, instead of bricks a row of gravel-filled sacks.