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 regulator type series for charging batteries from solar panels was found in a technical...
We can use high value electrolytic capacitors in alternating current circuits with the...
We found this circuit in an old French documentation from the 70s, but it can be assembled using...