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.
This oscillator produces a signal with a central frequency in 1 MHz. This frequency can be...
This circuit was found in an Electronics Now of the 80s applying to NiCad batteries of the time....
This configuration, which does not have a very high Q, uses a 741 operational amplifier, but other...