Why technically should a stun gun not kill?

Discussion in 'General Electronics Chat' started by cjdelphi, Sep 8, 2011.

  1. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
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    Because it's the Amps that kill you, I think we all got that sorted, glad we all agree on that, but a stun gun?

    Produce 1000v +AC

    What exactly in any given circuit after it's been converted from 9v to 1000v pulsed, what limits the current in the circuit to make it safe enough to abuse the public with when the police get bored? is there a Resistor come after the step up transformer? or does the transformer itself limit the current? or is there a resistor from the 9vac? 1000v 0.00000000000000001 amps sounds more like a transformer producing static electric..

    So is the current controlled somehow? I swear the video's i've seen of 'home made tasers' (no i'm not making one), I just can't imagine a real police issue taser simply having 5 components, I don't see anything to limit the current in home made ones, what goes?
     
  2. #12

    Expert

    Nov 30, 2010
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    All of the impedances come into play. For instance, a 9 volt battery would be well stressed to throw 1 amp. That calculates to 9 milliamps at 1000 volts. Then throw in inefficiency and other impedances.
     
    Last edited: Sep 8, 2011
  3. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
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    I think I get what you're saying to me if i understood it properly, the max possible current simply can't be that high if producing 1000vac due to the max current, but let's say the 9v battery was a 2 Lithium CR123a's which could deliver around 8amps stressed?..

    Replacing just the battery with a lithium would automatically make any stun gun become a deadly weapon?..

    or take the existing circuit and store it in a high voltage capacitor? this too should also make the circuit very deadly too right?
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    don't think so. It's the high Z output that limits the stun current
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
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    As long as the current from stun gun do not travel directly through your hart it will not kill you. Did you know that surgeons use electrical current to cut body tissue and stop bleeding during many types of surgery.
    However what I have said is somewhat simplified. You should NOT BY ANY means experiment with this in any form.
     
  6. TBayBoy

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    May 25, 2011
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    I think that the most significant failing if the system it that from an electrical engineering perspective the math is harmless, or as Douglas Adams put it "Mostly Harmless"; however, from a medical engineering standpoint the math can be very harmful.

    I remember many years ago, when defibrillators and oxymeters were being rolled out through the EMS system here, there were stiff requirements for training as the medical legal laws defined applying energy to the body as a medical act.

    Someone pointed out the police tazers and it was a loop hole no one seemed interested in researching.

    I guess the moral here is it depends from what perspective you look at the math.

    As John Wayne said "Go ahead and bet your life on it".
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
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    You need the mA (what is 4mA to kill? I don't remember) to go through your heart. If you have a handheld taser, the probes are like 2" apart. Assuming the current will take the shortest path through your body (however that's technically incorrect; it will take the path of least resistance which I suppose could be through your heart, but I doubt it), it would be difficult to imagine the current going in 3" into your body, 4" across your heart, and then 3" coming back out, just to get to the other proble, when it could take the easier path, 2" through your skin/muscle to get to the other probe. I guess the type that shoots the 2 probes out would be a little riskier, but still you would need to shoot/stab one probe into the front of the torso and one into the back; or one directly into each side in order to get the current path through your heart. not likely. Thats the way I look at it anyways. I think that's the reason for the placement of the electodes with a defibrillator, see below, to get the current going through the heart.
    [​IMG]
     
  8. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
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    ahhh ok so it's really about the path not the current that's being limited to make it safe, so if 1 probe failed to make contact? but the other probe did?
     
  9. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    If you google "killed by stun gun" you will find various cases of people who have been killed by these devices.
    According to THIS document, even if the probability is very low, the devices can cause ventricular fibrillation.
    I read on a manufacturer site that output energy is monitored and limited electronically and that the battery that powers it can only provide energy for a few minutes.

    I remember a case where a guy died because guards applied taser shocks repeatedly, I guess more than one guard/taser too.I think it was at an airport....
     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I'm not going to say that's bottom line the absolute correct answer, but that's my answer and I'm pretty sure I'm right.
    I don't follow.... If only one probe made contact then there would be no current path and no shock.
     
  11. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
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    i once accidently touched 1 of the 300vac terminals from a small 12v to whatever inverter circuit to drive a small 7watt cfl, i def felt a little tingle when i once brush passed the metal contact, i figured it must have gone to ground through me... The other ac out terminal was seperated in case of just that...
     
  12. TBayBoy

    Member

    May 25, 2011
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    I think this is the incident your thinking of.

    http://www.cbc.ca/news/canada/british-columbia/story/2007/11/14/bc-taservideo.html

    The side issue is a person agitated or restrained can build up acid in the heart and become more susceptible to cardiac arrhythmia. So the tazer is even more dangerous in these cases.
     
  13. saturation

    Member

    Dec 21, 2008
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    One should keep in mind all non-lethal weapons can potentially kill its intended target. Any low current charge assumes the assailant is normal and in generally good health, but if they have heart disease, it could push them 'over' the edge. Sticky foam is fine so long as you don't shoot them in the face and asphyxiate them; the heat gun can potentially overdose folks who have metal implants from prosthetics to body piercings or even Fe content in tattoos; it could cause them to boil over or explode; it can also focus energy on individuals with the intent of cooking them, either accidentally by setting it wrong or on purpose.

    http://en.wikipedia.org/wiki/Active_Denial_System#Controversy
     
  14. Adjuster

    Well-Known Member

    Dec 26, 2010
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    When current flows, there generally has to be a circuit. In some cases current may flow into an apparently isolated conductor which can be regarded as having capacitance to its environment, or which may act as an antenna radiating electromagnetic (radio) waves. If you touch only one terminal of some power supply and nevertheless feel something, it is certain that there is some path linking you to some other potential in the supply, even if this link is only capacitive.

    In the case of your cfl inverter, perhaps the internal capacitance between the high-voltage winding of the output transformer and other parts might pass enough to current give a tingle - or there might even have been some internal breakdown occurring, particularly if the tube was not connected so that the voltage was higher than normal. Finally, the output winding might be deliberately grounded in some way - opinions differ on what is safest here, but some equipment practices discourage floating elements.

    Your body of course always has a small capacitance to the universe, but it also has a bigger capacitance of the order of hundreds of pF to Earth - a bit less up a dry wooden ladder, rather more if lying on a plastic floor. Added to that there may be significant resistive contact if any part of you is in contact with a grounded conductor, e.g. where you are wearing non-insulating shoes and standing on a conducting floor like damp concrete. This explains the possibility of getting a shock from a single conductor like a live mains wire.

    Coming back to the Tazer, if only one pole contacts flesh but the other hangs nearby, there will be no shock unless there is enough voltage to strike an arc - which may well happen, and possibly the current may then take a wider path. I can imagine this leading to a much more dangerous situation if a single contact struck the upper body or the head , and the other pole went to the ground, especially in a wet location. The current could then take a path through the heart or the brain, possibly with lethal results.

    I would imagine therefore that the output circuit of a Tazer would be designed to provide galvanic isolation, come to think it would really have to avoid discharging current into its immediate environment, namely its operator!
     
  15. ke5nnt

    Active Member

    Mar 1, 2009
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    To the source for info on safety: http://www.taser.com/research-and-safety/science-and-medical

    I believe the newer models of Taser products also have the capability to simultaneously monitor heart rhythm while delivering shock to prevent cardiac issues. These are very safe devices.

    I'll also add that the arcing by a taser after a subject has been sprayed with a chemical agent like OC Spray/Mace/Pepper Spray can cause the subject to catch fire because sprays have a flammability factor.
     
    Last edited: Sep 9, 2011
  16. Adjuster

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    Dec 26, 2010
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    I started to speculate about whether a non-lethal device would always be required, but on reflection that's not such a good idea. Some things are better left alone, so I've removed those comments.
     
    Last edited: Sep 9, 2011
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  17. dataman19

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    Dec 26, 2009
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    Tasers are dangerous....
    Even more dangerous when not used properly...
    ...
    Usually when someone is killed by a Taser it is because the so called "trained" law enforcement officer is misusing the device..
    ..
    Tasers are not silencer - just because someone is anoying doesn't warrant being tased...
    Tasers are not a replacement for authority, just because someone doesn't agree with an officer and disputes a statement, tasers are not an answer....
    Tasers have varying effects upon one person vs another person.
    ...
    I have seen numerous cases where tasers are consistently used improperly. Here in Arizona officers tend to reach for tasers for almost every occaision. Suspect is loitering outside a diner, Owners call police - police sho=w up and the loitering individual argues and starts to walk away. "Don't walk away from me...." ZAP Taser..... Individual is put into cardiac arrest by multiple taser blasts (becasue a Taser has the ability to re energize by just pressing or holding down the button.
    ..
    Taser have the potential to be lethal... therefore anyone who is trained to use a taser is supposed to be tasered to get qualified (Phoenix Police quit this test because several officers went into cardiac arrest while qualifying). So it is obviously all right to taser a homeless person, just not a police cadidate...
    ...
    I'm oppinionated on this issue, yes. 24+ years in Federal Service and I never used a Taser. Pepper spray and a gun yes, taser? Get real. Next they will be giving police men acid spray to permanently disfigure....
    ...
    Dave
    ....
     
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  18. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Has any one had an hands on incident involving a taser?
     
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