This Linear Technology circuit charges a battery from the energy produced by a wind generator that can be a 12 V dynamo driven by a propeller. FET admits equivalent.
This is one of the many hysteresis comparator circuits the reader may find in this section and on this...
This circuit is from the manual of the used operational amplifier itself. The same setting can be...
This circuit produces a loud sound in the speaker when water level reaches the sensor. The power...