ball detector

[willoughby]

i am currently investigating the use of LEDs or LASERs to detect if a ball crosses the goal posts in a game of rugby, (a version of american football for real men) but i have come up with a few problems of divergence and detecting the beam once broken. any ideas you intelligent lot? thanks for any help :lol:

 

[zachtheterrible]

One problem youre going to have is you'll have to have multiple phototransistors or photoresistors, whatever you use, spaced just a little bit less than the diameter of the ball, so that the ball cannot slip through without being detected.

Perhaps you could post the circuit you're using, and tell us exactly what the problem is. Is it inermitent, does it not work at all . . .? you get the idea.

 

[checkmate]

Infrared is commonly used in beam breaker security systems as well as motion sensors. The basic idea is similar in that you detect a break in the beam.

Edited : Just noticed it was for a rugby goal post. At that distance, probably lasers would have to be used. But that would mean a lot of laser diodes. Wouldn't it be easier to just easier to implement a photo-finish system just like track events?

 

[stevez]

You might borrow some ideas from the material handling industry where they use "light curtains" as a barrier or shield around dangerous equipment. If the barrier is broken an alarm sounds or the machinery stops. The "light curtain", as I recall, was an array of LEDs and sensors - LEDs on one side, sensors on the other.

One problem - differentiating between a bird, windblown trash and a ball might be a challenge unless you use some video recording for verification.

 

[pike]

yeh I would also have to say that high speed cameras is the way. Optics would be too hard unless the ball was colored a specifc color, but then you would have to integrate computers and software to detect this certain colour of the ball. A goal keeper for example would set off the goal alarm several times in a match.

You need some thing that can differentiate between a person, bird, goalkeeper, streaker and a ball. Optics wouldn't work that well otherwise...

 

[atferrari]

No goalkeeper, AFAIK

Never seen one for that game :?:

Seriously now, I think that time of the day with the sun incidence changing along time could be a real concern.

My question, not even knowing the rules of rugby: is there any case that a doubt exists about if the ball passed IN BETWEEN the goal posts? It's an honest question :!: :?:

Agustín Tomás

 

[zachtheterrible]

Yeah, didnt think about that, the goalie crossing the beam is going to cause HUGE problems and complicate things like crazy!

 

[willoughby]

update

thanks for the help. i was thinking of an array of semiconductor lasers. and for atferrari trouble might arise from a drop goal where the referee might be out of place to see the ball go over. as for birds, and other things triping the circuit, the circuit will discriminate between the average speed and size of the ball to that of spurious other objects. a bit like the system used on shooting ranges to detect the impact of the bullet. once again thank you all for your help. :lol:

 

[willoughby]

confusion

in rugby the posts are in the shape of a H, think of american football the ball must go over the post, ie the top half of the H. but unlike american football the ball can be kicked from anywhere on the pitch and at any time. :lol:

 

[tansis]

I would go with high speed cameras like the hawkeye system used in tennis

 

[pike]

That would be called a field goal: kicked from within the field.