We found this circuit in the September 1971 issue of Radio Electronics magazine. The sensor is an LDR and R1 adjusts the sensitivity. A relay with the appropriate voltage can be used instead of a buzzer.
When this circuit is activated the LED flashes for a moment indicating that the function has been...
This is the basic configuration for using a moving bar indicator or bargraph using the LM3914...
This circuit was found in old documentation. Transistors can be general purpose JFET types and the...