We've been experimenting with some Velleman PEM10D sensors. (So, something like this.)
The main reason chose, was they have a 10m length (we need a good 6m or so).
I have found that, the response is a bit slow for our needs.
So for example: if you drop a basketball through the beam from a height of two feet, it is travelling slow enough it will register. However if you drop a basketball through from 6 feet height, it is too fast, it will not trigger the device.
I surmise, we need the device to be (let's say) a good ten times faster.
Now, the spec of the device suggests .. "Response time: 5 - 100ms" I don't really know what that means - is that the minimum time of cutting the beam which will register? If so, what does the 10x spread mean? Perhaps someone here will know.
Secondly, in general is this a well-known problem, are there "much faster" photoelectric beam sensors? Or no, or ...?
Thirdly, indeed could the whole thing be a fubar on our end ... say, poor programming on the Arduino, wrong ... power supply or something, or some other mess-up by us?
So, to be perfectly clear, the thing cutting the beam in our setup is a fast-moving ball-like object, which can be moving quite fast .. some 10 or even 20 m/s.
Finally I apologise if this is not in fact the optimum forum. Thx