This circuit emits a warning sound when night falls. The circuit is from a Hands On Electronics from the 90s. The Sensor is a common LDR and R6 adjusts the trigger point.
This circuit is from an English publication from 1976 but can be easily assembled with BC548...
This configuration, found in many publications, is from an American book from 1981. The power...
The purpose of this circuit is to ensure that an auxiliary 12 V battery continues to supply power...