This circuit was found in a 90's Electronic Design. The circuit can be adapted to use modern components. The power supply is made with 5 V which allows its use as a shield sensor.
This circuit maintains on a flashing LED at a frequency determined by the capacitor. The...
After starting, this circuit turns off the relay in a time that depends on the 4020 pulse-count. This...
This sophisticated circuit is from a 1975 documentation. The components are from the time and the...