The configuration shown was found in an old Poptronics but can be easily assembled using a common calculator photocell. The relay is according to the supply voltage.
This circuit can control two loads and is also equipped with a light sensor for its trip. The...
This linear oscillator was found in a 1968 publication. The operational amplifier is from that...
This circuit triggers the relay when the temperature exceeds the value set on the trimpot. The...