I have thought about a commercial PIR sensor l.

I had intended to imply Ultrasonic, they can be had fairly cheap for experimental purposes.
Ebay 360857671987 etc.
Max.

 

8.65" soccer ball. Five detectors/laser-emitter pairs spaced 4" apart vertically (16" of 19.5") across a 39" opening. At 46MPH the minimum blockage time of two of the 5 OR'd beams would be ~9mS. Pulsing the lasers at say 2kHZ or more, and feed the OR'd detector outputs to a missing pulse detector, and then to a monostable.

Just typing out loud.

Ken

 

8.65" soccer ball. Five detectors/laser-emitter pairs spaced 4" apart vertically (16" of 19.5") across a 39" opening. At 46MPH the minimum blockage time of two of the 5 OR'd beams would be ~9mS. Pulsing the lasers at say 2kHZ or more, and feed the OR'd detector outputs to a missing pulse detector, and then to a monostable.

Just typing out loud.

Ken

I agree with the laser concept, but I would put the lasers horizontal. With a C5 ball, you could do with only two, but for a C3 ball, you would need three. Or, as I said in my earlier post, one laser, one receiver, and three mirrors.

 

Sorry, my bad. My main reason for not wanting to use the industrial safety curtains is cost. The unit you sent a link to is reasonable but if I want to build a few of these; I currently intend to build at least 2, I need to be able to source the same components and the new ones are very expensive. I find the idea of ultrasonic sensors interesting since waterproof and reliable units are available but I had not thought about trying to have 2 work together.

Another thought that I had, keeping in mind that i am trying to keep this as simple as possible and reliable under the likely usage, is to have some sort of pressure plate sensors perhaps hanging from the inside top of the goal box in a series of strips (sort of like the clingy things in a automated car wash) that would be flexible enough to allow a ball to pass through them and through the goal box. I have not really found any pressure pad "strips" that would work as the ones i have found have a focused sensing area which would likely not work.

You're right, the surplus purchase is only for a one time project.

As far as the mechanical method. Some string trimmer type line suspended on sensitive micro-switches or near/thru hall effect triggers might work.

The stiffness of material used could be adjusted for ignoring winds up to the level of ability to play.

Seems the modulated ir tx/rx is the best.
Putting each end in a tube is a poor man's lens.

 

I agree with the laser concept, but I would put the lasers horizontal. ....

Yes, I was placing the laser/detectors horizontally, but spaced 4" vertically. I was using a 4" chord of the ball to always break two beams. Not really necessary, except to preclude those pesky butterflies from scoring goals.

Ken

 

Thinking in a different direction, how about a knock sensor that detects when a ball hits the inside of the goal? Nested boxes would prevent detecting external hits. In fact, in this case, the goal could simply be a target and a frame (simulating the posts). A piezo sensor would detect impact and it could be processed by a μprocessor. Take a look at this link for ideas.
http://arduino.cc/en/Tutorial/Knock#.UwaXrHi9LTo

 

Thinking in a different direction, how about a knock sensor that detects when a ball hits the inside of the goal? Nested boxes would prevent detecting external hits. In fact, in this case, the goal could simply be a target and a frame (simulating the posts). A piezo sensor would detect impact and it could be processed by a μprocessor. Take a look at this link for ideas.
http://arduino.cc/en/Tutorial/Knock#.UwaXrHi9LTo

Yes, I have given some thought to knock detectors and the like. I do need the goal box to be open and allow balls to go through it and into an area behind the goal where they can be collected after a drill. The problem with any type of a knock or similar detector is that it would need to allow a ball to pass the detection area; keep in mind as balls are passed (one by one) into the goal they need to continue through the box otherwise they will clog up the goal box and either prevent other balls from making it to the detection area or polluting the detection area.

 

Thank you everyone for some great thoughts, ideas, suggestions, and especially the links to possible solutions. Much appreciated.

Now, if I could only find someone local to me (Tampa, FL) to actually help me experiment with some of the different methods and then build a prototype of the preferred method, I would be set.

Again, I am happy to pay someone to help me so if you know of anyone in my area, PLEASE let me or them know to contact me. Thanks again.

 

What are you going to do with the detected ball passage?
For fun reading put beam break in find box, this page upper right.