Using a 4046 PLL, which is not very common nowadays, this circuit was found in the October 1994 issue of Electronics Now magazine. The power is provided by the transistor and is small in this case.
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...