Break Beam Sensor problem

Thread Starter

jpope85

Joined Oct 8, 2010
2
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
 

Thread Starter

jpope85

Joined Oct 8, 2010
2
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
 
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