Saturday, June 28, 2014

DIY Taser Gun Circuit

A Taser also known as Stun Gun is one non-lethal electric shock producing unit used to paralyze a person for a time being without causing any severe damage or injury. It is a very useful device, especially to immobilize an attacker.

The use of stun gun is restricted in most of the countries. However, in the United States of America, some state allows use of stun gun.

A stun gun is available in variety of styles like lipstick stun guns, cellphone stun guns, stun batons, police force stun guns, pink ribbon stun guns and disguised stun guns.

How it works?

A Taser functions like two-stage voltage converter. In the first stage, the high frequency switching transformer increases the battery voltage to several kV to charge the capacitor. After the capacitor is charged, it powers the second transformer by increasing the voltage to 10 – 50kV (approx.) with the repetition rate of 5-40 Hz (approx.).

Taser Type
There are basic types of Taser: Multiplier, Thyristor and spark gap. Multiplier Taser is made of one transformer having voltage of higher output and it runs on DC voltage. This type of Taser also has high-voltage capacitors and diodes and it is for the capacitors that multiplier Taser makes loud sound. The Thyristor type is the most efficient one. Here the voltage of the capacitor is not high (250 – 500 V approx.) and it functions with the aid two main components: resistive divider (neon lamp) and diac. The spark gap guns on the other hand is the most cheapest and ineffective stun gun. As the name implies, it has spark gap to function and the voltage of the battery is charged with transistor converter.

How I made my Taser

Of the three types of Tasers, I chose to go ahead with the Thyristor because of its effectiveness. I used MOSFET (Metal–Oxide–Semiconductor Field-Effect Transistor) to build the voltage converter. The main reason to use MOSFET is purely from the point of efficiency. In a push-pull converter which is generally used in stun guns, the level reaches around 20% whereas in MOSFET the converter gives efficiency as much as 75% with the working frequency of 80-120 kHz. I then used a gate thyristor for the second switch along with four neon glow lamps with the ignition voltage of 95V and the pulse repetition rate of 30 – 50 Hz. For inverter transformer, I preferred to use EE core based transformer keeping the middle column cross-section of 20 – 25 mm2. The air gap of 0.5mm thickness is place in the mid column. The primary polarity is set to 2x12 turns of the diameter of the wire (0.4mm) while the secondary polarity is set to 700 turns of wire (0.1mm). The secondary polarity is wounded in multiple isolated layers. The reason to isolate the layers is to avoid breaking the wire enamel under high voltage. There are two electrodes in a Taser gun. They look like a dart and are connected to the main unit with a conductive wire.

One can power a stun gun with either six 1.5 V cells or seven 1.2 V cells. The best option is to have two cells or Li-pol or Li-ion connecting the series. It should be note that stun gun draws current of around 1.5 V for which the ordinary batteries would not work in the same.

Written and Submitted By: Dhrubajyoti Biswas 

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