Wichit Sirichote, email@example.com
I made this tester for checking the line out signal from the CD player. The circuit has only two components, i.e. 1) piezo speaker from the washing machine and 2) RCA jack. Building also is very simple.
The signal from line out CD player is mV level. It can drive the piezo speaker without the need of amplifier. The sound level is quite small, but we can hear it.
Wiring from the piezo to the RCA jack has only two wires, RED and BLACK. Technically it will work for both polarities wiring.
We see that the piezo material is a thin layer with metallic electrodes for both sides. The AC signal in audio range makes the piezo material moving thus producing the longitudinal mechanical wave.
Using the sound detection is a very simple and very effective method.
30 April 2017