Using an operational amplifier, this circuit from a 90s Popular Electronics, is characterized by its high sensitivity. R5 can be added to control the gain.
In the figure we have the way to obtain an adjustable 1 to 10 mAconstant current source. The...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...
This alarm uses several sensors that directly trigger a sensitive relay. A larger relay can be...