Hi,
Assume the following:
You have a 5-6 m long virtual tunnel of 50 cm in diameter! You want to detect anything that wonders through / across your "tunnel"!
How would you do it?
I've toyed with the idea of playing around with cheap lenses and narrow angle PIR detectors!
I happen to be of the school that says - "re-inventing the wheel is pointless!"
If anyone can point me in the direction of a cheap ready made solution / suitable sensor it would make my day ( or even month!)
Thanks!

 

hi M1,
Welcome to AAC.
I would fit two PIR sensors about 50cms apart inside the top of the tunnel.
Connect the two PIR outputs using an AND gate, so both PIR's have to detect, before an alarm is raised.

E
https://www.ebay.co.uk/itm/263030279451?hash=item3d3dd38d1b:g:4JcAAOSwAs9g5uBn

 

How accurately do you need to detect anything in this virtual tunnel?
In other words, what is the dimensional tolerance on the tunnel?

 

How accurately do you need to detect anything in this virtual tunnel?
In other words, what is the dimensional tolerance on the tunnel?

Tolerances are fairly loose! 50% deviation at end of 5-6m "tunnel" would be acceptable! It would still do the job!

 

hi M1,
Welcome to AAC.
I would fit two PIR sensors about 50cms apart inside the top of the tunnel.
Connect the two PIR outputs using an AND gate, so both PIR's have to detect, before an alarm is raised.

E
https://www.ebay.co.uk/itm/263030279451?hash=item3d3dd38d1b:g:4JcAAOSwAs9g5uBn

Thanks for that! Took me a few seconds to understand that you were talking about the intersection of two cones! It will still take some experimentation to get the tolerances right! Will follow that path if I have too but was really after something of the shelf!!!

 

Two sets of an LED emitter and photo-transistor detector at each end of the "tunnel" may also work.