This battery charger circuit was found in the August 1970 issue of Radio Electronics magazine. The circuit uses 4 transistors. Q1 must be provided with a good heat sink.
In the figure we have the way to use a stepper motor as an encoder. Operational amplifiers can be of...
Placed inside the refrigerator, this circuit triggers an oscillator when the part is opened...
We found this circuit in an old documentation from the 70s, but it can be assembled with more...