A controller can be automatic, such as the devices used to control sump pumps and refrigerators. A controller can also be operated manually. Most motor circuits consist of a combination of starting ...

I was planning to use the opto-coupler speed sensor as part of a motor speed ... work with simple single-supply op-amps – whose inputs and outputs work well near the 0V rail, but not necessarily near ...

This is very much a “lowest common denominator” circuit, and although you might build one on a breadboard for a very quick and dirty test of something, you would never want to field a device built ...