INEKO 5Pcs 3-24V Small Enclosed Piezo Electronic Buzzer Alarm 95DB w/Wires

Poor piezo circuit and steel plate piezo instead of copper plate piezo. I bought it due to inductor. It is working up 24v if you want to use up to 30v use a 1k 1/2w carbon resistance. For better performance use IN4007 diode across with emmiter and collector. Diode by pass the high voltage of inductor and give safety for transister.

Good