Found in a Popular Electronics from the 90s, this circuit can be adapted to use modern operational amplifiers. The output voltage is the square root of the input voltage.
Ordinary batteries cannot be recharged, but they can go through a process of "rejuvenation" that...
We found this basic circuit of a relaxation oscillator with unijunction transistor in a 1976...
This circuit, from a 2006 documentation, automatically controls the activation of a water pump, and...