Found in a PE Hobbyst Handbook of 1991, this circuit was originally proposed to time photographic baths in developing rooms but can be used for other purposes. The circuit beeps at 30-second intervals.
This circuit is more sensitive than the previous one, in the sense that we can use weaker and more...
This 3-transistor timer was found in the January 1994 issue of Electronics Now magazine. The...
This circuit appears in other articles in this section, but it is very interesting. It is a...