12-15V short beep sound simple circuit?

Question

I need to implement the short beep sound at PSU being switched On/(Off - if easy). Are there any simple circuits for this problem? The piezo buzzers are preferable of their size and PCB mountable option. But is there any way to run them without controllers? Thanks!

Answer 1

Building on soosai steven's answer, if you use a DPDT relay, you only need one capacitor:

^{simulate this circuit – Schematic created using CircuitLab}

When the relay pulls in, the capacitor charges through the buzzer. When the relay drops out, the capacitor discharges through the buzzer again. The diode prevents the capacitor from partially discharging through the relay (and any other loads) before the relay drops out.

Answer 2

What you are asking can be done easily.. What you need are two 1000uF capacitors, a piezo buzzer, a 1 Amp diode and a single pole relay with normally closed contact.

During power up buzzer sounds momentarily until the first capacitor fully charged. During power down the second capacitor discharge through the buzzer again sounds the buzzer momentarily.

The first cap may need a high ohm resistor in parallel to discharge it to prepare it for next power up buzz.

Answer 3

If you use a piezo buzzer/beeper with an integral oscillator/driver, this is easy and will beep on power-up.

Beep on power-down is more difficult, so if you don't need it...

Here's the LTspice circuit list just in case you want to play with the circuit:

Version 4
SHEET 1 880 680
WIRE -320 64 -528 64
WIRE -272 64 -320 64
WIRE 48 64 -272 64
WIRE 128 64 48 64
WIRE 176 64 128 64
WIRE 224 64 176 64
WIRE 48 80 48 64
WIRE -320 112 -320 64
WIRE 176 112 176 64
WIRE -272 176 -272 64
WIRE -240 176 -272 176
WIRE 48 176 48 144
WIRE 48 176 -16 176
WIRE -320 240 -320 192
WIRE -272 240 -320 240
WIRE -240 240 -272 240
WIRE 176 240 176 192
WIRE 176 240 -16 240
WIRE -320 304 -320 240
WIRE -272 304 -272 240
WIRE -240 304 -272 304
WIRE 224 304 -16 304
WIRE -528 320 -528 64
WIRE 176 336 176 240
WIRE 128 368 128 64
WIRE 128 368 -16 368
WIRE -528 448 -528 400
WIRE -320 448 -320 368
WIRE -320 448 -528 448
WIRE 48 448 48 176
WIRE 48 448 -320 448
WIRE 176 448 176 400
WIRE 176 448 48 448
WIRE -528 512 -528 448
FLAG -528 512 0
FLAG 224 64 MCU_Vcc
FLAG 224 304 PIEZO_Vcc
SYMBOL Misc\\NE555 -128 272 M0
SYMATTR InstName U1
SYMBOL res -304 96 M0
WINDOW 0 44 46 Left 2
SYMATTR InstName Rt
SYMATTR Value 240k
SYMBOL cap -304 304 M0
WINDOW 0 46 33 Left 2
WINDOW 3 28 61 Left 2
SYMATTR InstName Ct
SYMATTR Value 1µ
SYMBOL cap 192 336 M0
WINDOW 0 -37 30 Left 2
WINDOW 3 -34 60 Left 2
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL res 160 208 M180
WINDOW 0 47 73 Left 2
WINDOW 3 35 45 Left 2
SYMATTR InstName R1
SYMATTR Value 100k
SYMBOL cap 64 80 M0
WINDOW 0 -37 30 Left 2
WINDOW 3 -41 60 Left 2
SYMATTR InstName C1
SYMATTR Value 100n
SYMBOL voltage -528 304 R0
WINDOW 0 16 103 Left 2
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 9 .1 10ms)
TEXT -512 304 Left 2 ;9V
TEXT -504 480 Left 2 ;tout = 1.1RtCt