This circuit was suggested by National Semiconductor in one of its manuals. The LM108 integrated circuit, uncommon nowadays, can be replaced by an equivalent. The power supply must be symmetrical.
Using a capacitor as a sensor, this circuit was found in the 1989 Radio Electronics Experimenter magazine....
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
This circuit is found in an American documentation from the 80's. The circuit measures the power of...