yeah i am taking the output voltage of the buzzer, the thing i don't want the buzzer to go off when it detects the smoke, only to give input the PIC
the problem is i can't test the sensor inside the laboratory because of the smoke detectors in the lab. so i checked tht outside the laboratory with a digital voltmeter so i am not sure if its a square wave or not, but the voltage was not constant,
plus the buzzer have three wires, one is black, the second one is red and the third one is white, so i believe the black is for ground, red for positive and the white is for the signal, where should i measure the voltage across ground and positive supply or the signal ???