Using a sensor from the time, this circuit was found in the 1992 Radio Electronics Handbook magazine. The circuit uses a pair of integrated two-digit A/D converters.
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...