Break Beam Sensor problem

Discussion in 'The Projects Forum' started by jpope85, Oct 8, 2010.

  1. jpope85

    Thread Starter New Member

    Oct 8, 2010
    2
    0
    I'm building a circuit to detect when a laserpointer's beam has been broken. Im using a photocell, 741op amp, and a relay in the circuit. I have a small buzzer on a NC contact of the relay, so when the beam is broke, it buzzes. Now it works fine right when i turn it on, and i can break the beam and the buzzer sounds. But if i leave the laser on the photocell for a minute or so, when i break the beam, the buzzer starts up, and keeps going despite the beam being back on the photocell. Any input would be awesome. thanks
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Wild guess: Try attenuating laser beam slightly & see if it makes a difference.
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Can you post a schematic?

    It looks like something "hangs up".

    Bertus
     
  4. jpope85

    Thread Starter New Member

    Oct 8, 2010
    2
    0
    heh, well, turns out that the voltage to the relay coil was dropping out a tiny bit .1 volts or so after it had been on for a few min. ran a little more power to it and it works fine :D thanks for the help though guys
     
Loading...