This circuit is from a 1968 Electronics World. It acts directly on a high voltage alternating current relay. The sensor can be a common LDR.
I found this circuit in an article in a 2003 publication. The circuit is an example of how to...
This 9 V amplifier has a gain of 20 and provides a power of a few hundred milliwatts. The circuit is...
Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an...