looking for the right IR emitter, receiver, and help with OR(ing)

I'm pretty sure a sensor could be set up to detect a ball falling just a couple of inches.

It is definitely an inexpensive sensor.

I would prefer to wait on publishing the circuit until the person I designed it for has had a chance to publish her research paper. Not a question of rights and it is a completely different application, its just a courtesy. I will discuss it with her.

Yes, I was thinking it could be detected, if I could replace 80 sensors with 2 chips that would save me a lot of money. So, since it would be less expensive I could at least build the circuit and test it to see if it works. If it doesn't then I wont lose much money , and I could probably find a way to use it later with another project. I don't mean to sound pushy if I do I'm sorry, but do you happen to know when she has to turn the paper in? I do understand and it is fine for me to wait on her to turn it in though. This table is actually tuned down because my original design was to make a grid of IR sensors for each side to make a grid so the machine knew exactly where the ball was then where it landed make an animation at that location, but I couldn't afford it so I settled with just being able to sense the ball altogether. That is why I started out thinking the IR sensors were best. I will continue to work on that IR method while I wait because in the future when I do have the money( I'm talking 10-15 years) to build the table the original way I will be able to just build it and not worry if it will work or not. Thank you for telling me about your circuit though it will be nice to see if it will be able to see if it will work which I'm pretty sure it will.

If you had one of these shock sensors under each corner of the table, you could use time-of-arrival of the shock wave to determine X-Y ratios and pinpoint where the ball hit.

You might be able to do everything with 4 microphones instead. They could detect both the ball hitting the bat and the table, giving you position of when and where the bat hit the ball and when and where it hit the table. This also gives you velocity and direction of the ball. If you want a better idea of what height the ball hit the bat you would need at least one more microphone. Of course, you would also need to  figure out how to prevent or ignore other sounds.

That is  a good idea. Thank you. Not only would that save me time but money as well. I think my best bet would would be the sock sensor. I don't think I would be able to do the microphone idea because it can get pretty loud when playing unless I can find the frequency range that comes when a ball hits the table. I will be waiting to see about that shock sensor though so because as of right now that is the easiest and cheapest way I can think of. Thank you again for the help.

The shock sensor solution gives you some information about how fast the ball is travelling - just by the time between ball strikes on the table. It wouldn't be super accurate, because you don't know exactly where the bat is, but still pretty useful for simulating the action. And if you know where the ball hits on both sides and the rough speed, you actually know roughly where the ball gets hit from.

That would be for later on down the road when I can afford the parts for that advanced project. The version I am making just needs to know if the ball hits the table and which side it hit. so I could just have a shock sensor on each side and that could detect if the ball hits that side or not. As for the advanced project, my goal was to have big tvs act as a monitor for each side so 2 tvs total and I could have them show the animations to where the ball would hit. That is why I can not afford it right now, and so I am just settling with making this version.