Adding headphone jack to piezo buzzer

[lmrubin]

Sorry - this is probably a basic question for people who know what they're doing...
I built a metal detector (pcb with components) which works. It has a piezo buzzer only. I'd like to be able to add a headphone jack which only works when headphones are plugged in - so if there are no headphones plugged in, the buzzer still works. The PCB has 2 pads for the buzzer. I have a stereo 3.5mm jack. Can this be done without getting overly complicated? Any tips or assistance is greatly appreciated.

 

[Harald Kapp]

Assuming the buzzer is connected from a tone generator's output to ground (0 V):
You need a headphone jack with integrated switch. See the example here, figure 2:
pin 1 = ground (0 V)
pin 2 = signal output from tone generator
pin 0 = signal to buzzer

Show us a schematic diagram of your circuit so we can verify this will work.
Also note that there's a possible catch or two:

1. The tone generator may not have sufficient power to drive the headphones.
2. The buzzer may be of the active type which doesn't require a tone generator at all but beeps when connected to power.

In both cases headphones will not work.