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what is this electronic part called? Answered

Hello, I got a cheap alarm from the dollar tree store, is one of those for windows and doors that one part goes on the door or window and other part to the frame, when you open door/window the alarm goes off.

I found a electronic part inside that I want to use in a project but I don't know what is called, when I unsoldered it, it looked like a capacitor but at the bottom has 4 straight terminals, each terminal was connected to the coil. I pilled the coating and the inside looks like a coil, by now you can tell I don't know much of electronics and english is not my first language, but I am trying to learn. I just want to know the name of it so I can buy some more for my projects.

I put some pictures of what it looks like.

In the side picture you can see the terminals but I bent them trying to unsolder them.

in the picture where you can see it from the bottom the red arrow points at the 1 of the straight terminals and the blue arrow points at glue that is located at the bottom of the terminal.

and in the third picture you see it from the side but I removed the plastic that was covering it and you can see that each of the terminals are connected to the coil.

Thank you for your help


From the description of where it was in the circuit, it is probably a mini-audio transformer. Most likely it was needed to raise the voltage up high enough to sound the piezo speaker. For confirmation, use your multimeter (if you have one) set to continuity and check to see if the "board" terminals are connected to the "speaker" terminals. The meter will sound if there is continuity/connection between the 2 probes. If it is a transformer, they will not be connected. If they do end up being connected, then it is probably a choke (coil) used to help keep the frequency of the circuit close to the resonant frequency of the piezo "speaker".

If you don't have a multimeter (you should if you are playing with electronics), you can use a low voltage battery powered light. Use a 1-1/2 volt light if you can and use the smallest battery that will make the light work, maybe a button cell. You don't want to fry the wires. Also, be quick with this method. As soon as you see the light come on, remove the power from the test points to also prevent it from frying the wires.


I think is a mini audio transformer, because when I connect my mp3 player to it it has a good volume but when I connect it to the other side direct to the piezo it has less volume about 30% less.

It looks like an inductor.  It may be the case that not all four of those wires are connected.  An inductor has just two terminals, essentially two ends of a coil of wire. The wiki article has more details.

Well, All four terminals were connected, 2 were connected to the circuit board ( I desoldered them ), and the other 2 were connected to the piezo electronic speaker (still connected to them).