A electronic buzzer is simple. But useful well worth and the price is lower than 1$. By use just a 9-volts battery only. So without worrying about electrical leakage or electric shock from 220V to buzzer. Unless also has LED will glow. Show that the circuit the normal operation as well.
The working of circuit.
From circuit in figure 1 will see that we use both transistors, which are matched pair transistors(CS 9012, CS9013) ,works together with a few resistors, capacitors. In as the oscillator circuit build sound signal frequency.
Figure 1 the simple electronic buzzer by two-transistor
By has both resistors- R=1.2K and C=0.047uF to set the output frequency. Which can change slightly a value of both components, so the output sound changed. However, from the experiments, this value, will be best frequency.
The components list
CS9012___ 50V 800mA PNP Transistor____= 1 pcs.
CS9013___ 50V 800mA NPP Transistor____= 1pcs.
*** for transistor please read note:
C-0.047uF 50V___Ceramic Capacitors_____ = 1 pcs.
C-33uF or 47uF 16V or 10uF 25V___Electrolytic Capacitor_= 1 pcs.
R-50K or 56K__1/4w 5% resistors______________= 1 pcs.
R-120 ohms or 100 ohms__1/4w 5% resistors__________= 1 pcs.
R-1.2K or 1K____1/4w 5% resistors__________= 1 pcs
LED-any color as you want______________= 1 pcs.
Piezo speaker,9-volt battery,PCB, and others.