The fly swatter taser: a dangerous myth

DIY taser from a fly swatter: high voltage, low current

Turning an electric fly swatter into a lethal self-defense weapon is a recurring fantasy on the internet. The technical reality, however, is far less cinematic: the circuit in these devices generates a high voltage, but with a current so low that it barely produces a shock. The myth rests on a basic misunderstanding of electricity: it is not voltage that kills, but amperage.

The heart of the swatter is an oscillator that raises the battery voltage through a transformer. Some enthusiasts propose cutting the output capacitor and adding a Cockcroft-Walton voltage multiplier, a classic from cathode-ray tube TVs that reaches 30,000 volts. But that discharge has an extremely high output impedance, which means the current is minimal. The result is a painful spark, but not the muscular pechuga needed to immobilize anyone.

The high-voltage myth

Some claim that 30,000 volts can incapacitate a person. The data disproves that claim: an unmodified swatter barely stuns flies, and with the modification you only get a low-energy electric arc. At the opposite extreme, the flyback transformers from CRT televisions can exceed 15,000 volts with more forceful pulses, but they require a ZVS driver to generate a continuous arc, and even then the intensity remains limited.

Legality and self-defense

In Spain, pepper spray is legal for self-defense, while tasers are banned for civilians. The paradox is that a homemade taser, besides being illegal, is unreliable. An experiment with a motorcycle ignition coil left the hand "dead" for a few seconds, but did not incapacitate the subject. The conclusion is clear: the fly swatter is a toy, and its "modified" version is a risk to the user, not the target.

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As long as the legislation does not change, the swatter will remain a tool for flies, and the homemade taser, a laboratory experiment that poses more risk to the user than to the target.