This fast Schmitt trigger operates at frequencies from 10 Hz to 100 Hz, with very short rise time. The circuit is from an American documentation from 1968.
This circuit that we found in a 1990 documentation uses an LED as a sensor. The operational...
This 1988 circuit makes a back-and-forth of LEDs whose speed is controlled by P1. All components used...
This simple circuit can drive a reed-relay when light falls onto the photo-transistor. The...