IR barrier

[HERMES_PT]

Hi:
I need a circuit, IR barrier, that really works!
Usually made with an pair os leds (one receiver, one transmitter).
This will work as an counter: each time barrier is broken by an object (coin, for example), will count.
Thanks.
Regards

 

[HERMES_PT]

20/05/2006
I made a circuit with TX IR Led and RX IR led, but when a object interrupts the barrier nothing happened

 

[Nigel Goodwin]

20/05/2006
I made a circuit with TX IR Led and RX IR led, but when a object interrupts the barrier nothing happened

You need to amplify the output of the RX diode, a LOT!!!.

I would also suggest modulating the transmitter and checking for the modulation at the receiver. It would be a LOT easier to use an IR receiver IC, which does all this for you, and a simple 555 at the transmitter.

 

[HERMES_PT]

Hi:
Thanks for your reply.
Yes, i used an circuit with a 555 and a 4N25, but only for simplification questions i have to use leds.
But i solved the problem: the guy in the electonic store give me 6 TX leds and only 2 RX leds, and not 4 of each one as i required.
But now all my 9 IR barriers works well: i will use to measure the size of the 8 euro coins, in my coin validator project.
Regards from Portugal.
Hermes.