This circuit was found in the February 1999 issue of Electronics Now magazine. The circuit consists of a timer that triggers a visual and audible starting device.
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...