Differential Controller Concepts

solar heating system

All differential controllers have one thing in common. They respond to differences in physical conditions such as temperature, humidity and pressure. They can be used to automate solar hot water heating systems. You could switch on a pump every time solar heat becomes available but why? This is the job of a differential controller.  controller schematic




Notice how the output of the OpAmp goes high when collector thermistor C gets hotter than storage thermistor S