This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times of several days or even weeks can be achieved depending on the value of C1.
This circuit is from an old American documentation. The circuit generates 20 to 200 ms steps for...
This circuit, found in American documentation, works as a voltage doubler, enabling the supply of a...
This circuit was taken from a Popular Electronics from January 1967. Transistors are from the...