The configuration shown was found in an old Poptronics but can be easily assembled using a common calculator photocell. The relay is according to the supply voltage.
This integrated contains a Class B circuit originally developed to provide 6 W in a car radio...
The Texas Instruments TPS80 LDO (Low Dropout) series (www.ti.com) can provide output voltages from...
This circuit is from an English magazine Radio and Electronics Constructor of November 1978. The...