This circuit was found in a 1992 publication. What it does is to light an external lamp when it gets dark. The trigger point adjustment is made in a potentiometer or trimpot and the sensor is a common LDR.
This circuit is from the 1990 Motorola Linear Databook. The circuit can be implemented with other...
This circuit for very low frequencies was found in an American documentation from the 90's....
The two circuits we suggest are from the book Optoeletronics - Theory and Practice by Texas...