IMO:

The inductor is just an inductor; no other function. With three leads, it could be part of a flyback autotransformer voltage-boosted driver for the piezo element.

The piezo is just a beeper element, nothing else. As a motion detector, it is not a good one; it produces zero output in two of the three motion axes.

There are too many parts on the bottom of the board for just a piezo driver. If you are sure there is no other motion sensor or electronic assembly elsewhere in the device, then the IC probably is the sensor. I'd look around for a mercury switch tilt detector.

ak

It seems to me that the internal is not "just a beeper". Consider the TS statement: "I check that the blue and yellow cables to the piezo speaker, while the red and black cables come from the battery. The switch that is activated with the lock is located on the black cable. " So is it likely to have TWO noise-makers???
The problem I see is that getting more sound requires more power. Boosting efficiency could possibly benefit, but that would require understanding the present circuit, which we do not actually see.

 

It seems to me that the internal is not "just a beeper". Consider the TS statement: "I check that the blue and yellow cables to the piezo speaker, while the red and black cables come from the battery. The switch that is activated with the lock is located on the black cable. " So is it likely to have TWO noise-makers???
The problem I see is that getting more sound requires more power. Boosting efficiency could possibly benefit, but that would require understanding the present circuit, which we do not actually see.

Hi. Yes, it has two piezo speakers, one below the inductor and other connected to the main locker body. The second speaker is larger.

 

Hi. Yes, it has two piezo speakers, one below the inductor and other connected to the main locker body. The second speaker is larger.

Welllllll, that's news.

 

Welllllll, that's news.

Yes. You can kinda see it in the inductor pic behind the white box that contains the circuit.

 

Yes. You can kinda see it in the inductor pic behind the white box that contains the circuit.

In post #1 the TS states that:"It has a speaker." I guessed that it was connected to the other set of two wires. That buried piezo device I would not call a speaker.

 

In post #1 the TS states that:"It has a speaker." I guessed that it was connected to the other set of two wires. That buried piezo device I would not call a speaker.

Hi. Well it has two piezo pieces, the small below the inductor and the other still glue to the lock body connected with the blue and green cables to the pcb.

Best, Edwin.

 

Hi. Well it has two piezo pieces, the small below the inductor and the other still glue to the lock body connected with the blue and green cables to the pcb.

Best, Edwin.

Hello. Attached is the pic of the larger piezo speaker that is attached to the lock body with glue.

Best, Edwin.

 

How to make a piezoelectric transducer produce louder sound:

1. Increase the applied voltage

The inductance might be used as autotransformer to increase output voltage for the pieso speaker. The transistor nearby mounting hole seems to connected as output stage to drive speaker via this autotransformer.

 

I provided the solution in post #21: " The problem I see is that getting more sound requires more power. Boosting efficiency could possibly benefit" The problem is that a boost would require understanding the present circuit, which we do not actually see. The additional problem is that a greater power output will require a greater power source capability, which is limited to the present battery pack.