This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be easily implemented today, and the microphone is made of electret or ceramic.
This circuit was obtained in an English publication of 1975. It is a regulator circuit for...
In this circuit the relay triggers on when light falls onto the sensor, a common LDR. Power supply...
January 2017 - Mouser Electronics already has the new Ultra Low Drop controllers from Toshiba...