This circuit was found in a Popular Electronics from the 90s. The counter circuit is not common today. The circuit can be programmed for hourly intervals, according to the values of R4 and C2.
This circuit was obtained in a 1970 EEE and applies to almost any operational amplifier. The...
The circuit shown in the figure is suggested by National Semiconductor and makes use of an...
This circuit can function as a light alarm by changing the sound when light falls on the sensor....