Found in an old Popular Electronics this circuit can also be adapted to be used as a shield. In this version the control can trigger loads from the light that falls on an LDR.
Found in documentation from the 1980s, this amplifier uses an integrated circuit from the time....
This is a one-channel application for the Texas Instruments TMP390 sensor obtained directly from...
This moisture-activated relay was obtained from an American documentation from the 1980s,...