Found in a 90s American documentation, this circuit can be used as a shield, just change the coupler for one that uses a phototransistor.
In this circuit of an American documentation of the 90s, when the light is cut, we have the...
The circuit shown was found in a 1995 documentation. This circuit is powered by a voltage of 6 to...
This simple regulated power supply was found in a 1977 documentation. The zener diode determines the...