How to detect when an gas alarm piezo (self drive - 3 wires) buzzer is active?

Hello guys,

I purchased a new smoke sensor for my workshop, I really want to hook it up to my “smart home” monitoring system I made, my ideea was to connect a wire to the positive side of the buzzer, and make an volt divider if the voltage was to high (the smoke detector runs on 9v battery) …BUT
my multimeter is not reporting any voltage when the piezo buzzer is active, after searching online about piezzo drives, I found out that there is not just +5v or +9v and ground, it’s a very high frequency …

Can I somehow use an ESP8266 to sense when the buzzer is active ? Without using a microphone.

The onboard led seems to flash once every few minutes, when smoke is detected it flashes every second, I think this could be another method, to connect the positive side of the led to one of the ESP digital pins, but the voltage of the led I think will not be enough to trigger an logic HIGH on the ESP, should I use the Analog input on the ESP, and monitor how often is in the high position ?
As I type this message I had a few ideeas, I think I will setup the ESP to send the pulse count every 10 seconds to my controller, than on the controller side to check the pulses count every minute and in case the pulse count is repeatedly higher than x it will send me a notification.

If I send the values to my controller it will be very easy to detect also when the battery is depleted, I don’t know how fast it will flash when the battery is low, but if I will plot the pulse count values on a graph it should be easy to interpret when the battery is low, and when the buzzer is ON (assuming that the led will not flash at the same interval when the battery is low with the interval used when smoke is detected)

What do you guys think ? is there another method to find out when the piezo buzzer is active ?

Hi, I would try a diode and a capacitor so when the alarm turn on it will charge the cap. You can read then the voltage across the cap. The diode will isolate the circuit from the piezo circuit. The cap will change the frequency pulses to an analog signal.