This simple water detector circuit uses alternative voltage in order to prevent the corrosion of the electrodes. It is easy to build and uses N1 as a trigger Schmitt gate which generate the AC. If ...

You tried to optimize the circuit for a full battery, without realizing that you’re cutting the useful duty from the other end of the battery voltage range. > At 2mA the Vf would be higher, that ...

AC voltage threshold detector. Note that the cathodes of D1 & D2 are unfiltered—this is necessary for rapid sensing of power loss—a filter capacitor would tend to hold up the voltage thus interfering ...

Designed to illuminate the work area when tracing ac circuits in dark areas or behind equipment, the SenseLite is a battery-powered flashlight with a noncontact ac voltage detection circuit and a ...

In the video embedded below, he shows off a homemade voltage detector circuit that he constructed using a trio of BC547 NPN transistors. The circuit is pretty simple though very useful all the same.