This electronic defense was found in the 1990 special issue of Radio Electronics Experimenter magazine. A few hundred volts is generated.
This flip-flop controlled by an LDR-type photocell was found in Radio Electroinics magazine from...
This very simple detector uses a hall sensor with a pendulum with a magnet, causing an LED to...
Here is a very useful circuit that can be expanded, including the use of more integrated circuits...