This circuit was published in an article in Radio Electronics magazine in October 1988. It uses components that are still common today, except for the sensor, which is a special type from that time.
Here we show how two 4017s can be cascaded to count above 10. The circuits are driven by a square...
The circuit in the figure represents a typical application of a phototransistor exciting a relay...
This circuit, in fact, what it does is a reactivation of the batteries through a brief pulsating...