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.
Written in an article in Radio Electronics magazine in April 1987, this circuit triggers an alarm...
This circuit was found in the April 1993 Electronics Now magazine. With it, it is possible to...
This circuit was obtained in a1969 magazine. The magazine no longer exists, but the circuit can be...