This simple Bargraph photometer with 4 LEDs was found in a 1997 documentation. The scale is adjusted in a trimpot and the sensor can be any common LDR. Power can be supplied by cells or battery.
I found this circuit in an article in a 2003 publication. The circuit is an example of how to...
This circuit drives a buzzer or electric buzzer but can be used to trigger a relay or other load....
May 2017 - Mouser Electronics is already in stock with the new BCP1395 transistors from Nexperia....