DC 9-15V HYD-4218 Active Piezo Electronic Alarm Buzzer (90dB, 5Pcs)

what can you get from a broken smoke alarm the answer is most likely a piezo transducer in this installment of electronics on the floor or run through a few things you can do with a piezo transducer it's useful for various audio and sensor applications the piezo transducer is the thing in the smoke alarm that makes the noise it's not an oscillator or buzzed up by itself it needs some driving circuitry most have two connections but this particular one has three we know how loud one of these transducers can sound if we've ever heard a smoke alarm going off but they also do the reverse they're fantastic for detecting minut vibrations and you can use them as earphones as we will demonstrate later on I've just connected my transducer to a three and a half millimeter socket the outer connection is connected to earth and there are two other connections they are shorted together and they go to