Stun Gun Help

I have a question about the stun gun schematic by Mark Stoker found on this site. To my knowledge dc voltage can not be stepped up by a transformer. I know the 555 timer produces a TTL logic square wave at a certain frequency set by the resistors and capacitors. This is still not an AC signal so how does the transformer step up this voltage. Also what is the purpose of the transistor. One last question what is the typical impedance of the human body. I know the skin has a large resistance. Thanks

harperj said:

To my knowledge dc voltage can not be stepped up by a transformer. I know the 555 timer produces a TTL logic square wave at a certain frequency set by the resistors and capacitors. This is still not an AC signal so how does the transformer step up this voltage.

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You are quite right that a transformer cannot transfer a DC voltage. However, you are totally wrong when you suggest that a square wave is not an AC signal - a square wave, like any other changing wave, is an AC signal. In fact, a square wave is the most efficient AC signal for these purposes.

You are quite right that a transformer cannot transfer a DC voltage. However, you are totally wrong when you suggest that a square wave is not an AC signal - a square wave, like any other changing wave, is an AC signal. In fact, a square wave is the most efficient AC signal for these purposes.

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Sorry Nigel, but the output from a 555 timer is not a true ac signal. The square wave is a 0v to 5V square wave. This is not a true AC signal. An AC signal has both positive and negative voltage. This wave would be considered a fluctuating dc square wave. I guess you could look at it this way and say it is a 5Vpp square wave with a 2.5Vdc offset. However, does this fluctuation still get amplified by the transformer's secondary?

harperj said:

Sorry Nigel, but the output from a 555 timer is not a true ac signal. The square wave is a 0v to 5V square wave. This is not a true AC signal. An AC signal has both positive and negative voltage. This wave would be considered a fluctuating dc square wave. I guess you could look at it this way and say it is a 5Vpp square wave with a 2.5Vdc offset. However, does this fluctuation still get amplified by the transformer's secondary?

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It makes no difference, AC is AC, neither is more 'true' than the other.

If you particularly want it symmetrical about a zero point, you can simply feed it through a suitably rated capacitor.