piezo-buzzer
Recently, I have ordered smt-0440-t-r buzzer from Mouser.
Circuit is as shown in figure.
Microcontroller pin transmits square wave of 4kHz as mentioned in the datasheet. However, the sound isn't audible. When I am at a distance of 1-2cm from the buzzer, I am hearing very low intensity sound. Any fixes?
They're passive, you have to create the signal yourself. "Without circuit" is the most obvious way to tell, but there are also the frequency response curves. If the device would have an internal oscillator the frequency would be fixed, and the graph be unnecessary.
Connecting the piezo directly to an I/O pin is the best way to get a loud sound, but piezo elements are highly capacitive, and microcontrollers don't like capacitive loads. A series resistor will protect the I/O pin, but also reduce the loudness. The best thing is to use a transistor to drive the buzzer.
For the loudest sound, look in the datasheet at the frequency response curve, and pick the frequency where it peaks the highest.
You can add a small regulator such as an LM78L05 to supply all but the lamps and the buzzer. One part plus a couple small capacitors. You could use a 9V or 12V supply at the input for lots of noise and brightness (but make sure you stay within acceptable limits for current and voltage on the LEDs and piezo transducer). I suggest a small regulated wall plug adapter.
Presumably there's something else (not shown) to reset the SCRs because otherwise they will stay on until the power is cycled.
You may have damaged the 74L373 with 9V, that's well above its absolute maximum supply voltage of 7V.
Edit: See below. \$\mu\$A78xx is LM78M05 or LM78L05 or LM7805 (TO-220 will run cooler)
Best Answer
How is your hearing and what is your age? If you are 45 years old then your normal hearing loss at 4kHz is -23dB so you will barely hear it. Hearing aids like mine (I am 73 soon) will fix the loss.