Using the LM3909 this circuit was found in the January 1992 issue of Radio Electronics magazine. Resistor R1 should be chosen according to the table given next to the diagram.
The circuit shown in the figure below is suggested by ON Semiconductor (www.onsemi.com), based on...
In the figure we have a simple timer with two voltage comparators of the four of an LM339. The...
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...