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TonyDuell · 15th Oct 2019, 6:17 pm

My guess is that this is one of those piezo buzzer 'disks'. Some types have 3 connections, a common wire to the metal disk (and thus one side of the piezo-stuff), a large 'drive' electrode on the other side and a smaller electrode on the same size as the large one that can be used for feedback in an oscillator circuit. I seem to recall you can make an beeper with one of these 3-terminal piezo sounder, a transistors and a small number of resistors and capacitors.

If you want to use one as a speaker then use the wire to the disk and the wire to the drive electrode. Either ignore the feedback electrode or connect it to the drive electrode.

15th Oct 2019, 6:17 pm	#3
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Piezo element My guess is that this is one of those piezo buzzer 'disks'. Some types have 3 connections, a common wire to the metal disk (and thus one side of the piezo-stuff), a large 'drive' electrode on the other side and a smaller electrode on the same size as the large one that can be used for feedback in an oscillator circuit. I seem to recall you can make an beeper with one of these 3-terminal piezo sounder, a transistors and a small number of resistors and capacitors. If you want to use one as a speaker then use the wire to the disk and the wire to the drive electrode. Either ignore the feedback electrode or connect it to the drive electrode.