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William K.
User Rank
Platinum
Re: Fence chargers and "liitle old ladies"
William K.   2/13/2014 9:53:22 AM
NO RATINGS
If I shock a carjacker so that they stop threatening me with their gun I certainly will not stay around long enough for them to do anything else. And if it knocks them out, so much the better. Perhaps you don't understand that pointing a gun at somebody indicates that they are willing to shoot them. So at that point all the rules for polite discussion are suspended. The bad guy with the gun does not deserve my courtesy.

a.saji
User Rank
Silver
Re: Stun Gun and other devices?
a.saji   2/13/2014 4:33:57 AM
NO RATINGS
@kingDWS: That is interesting. It shows that there are some interesting facts about health and effects on electronics towards it. Wondering what sort of an effect it has on rays in my working area on a daily basis. 

etmax
User Rank
Gold
Re: Fence chargers and "liitle old ladies"
etmax   2/12/2014 10:50:26 PM
NO RATINGS
They refused to consider that a carjacker with a gun is dangerous.

Yes that's the problem with the world, a person breaks into your house and trips on a roller skate and he can sue you. They need to change the law considerably.

Electric fences certainly pack a wallap and I've experienced them first hand. The risk profile to people is low because the pulse repitition rate is quite low you may well know exact figures but I believe it's in the order of 2-5 seconds.

I don't think a car jacker would let it deter them, or they might take a tyre iron to the car if they don't figure out how to bypass it.

etmax
User Rank
Gold
Re: Stun Gun and other devices?
etmax   2/12/2014 10:39:32 PM
NO RATINGS
We did a session on the effects of electrical current on the human body at engineering school and what we were told was that:


1. DC doesn't cause ventricular fibrilation.

2. Frequencies below ~20Hz and above about 200Hz don't cause ventricular fibrilation.

3. The AC current required to cause vetricular fibrilation is around 60mA to 200mA.
 Below 60mA that it isn't sufficient to overide the heart's own timing and above 200mA the heart is clamped similar to DC because of overload. There may be burns but no fibrilation.

Obviously someone with a heart pacemaker will have a different set of risky conditions and tests have shown that inductive cook tops can be risky for them.

BTW, items 2 and 3 are why the telecom ring signal was 17Hz at 100V peak back in the day.

KingDWS
User Rank
Gold
Re: Stun Gun and other devices?
KingDWS   2/12/2014 4:05:39 PM
NO RATINGS
Perhaps the reason its not available is that it only takes 5-7ma not 10 to kill someone. It's not enough to stop the heart which can happen over 10ma but what it does for a fair amount of certain people is cause multiple fibrilations that sort of override the natural beat. So instead of stopping it and the person dies the heart looses its ability to pump as all the chambers get out of sync. Same dead result just 30-50% lower ma levels. The volts can go up much higher but then you get skin charing and internal scar tissue if your really concerned that much about your potential attacker. ;-]

Gaffer Gaggs
User Rank
Iron
Circuit current kills
Gaffer Gaggs   1/9/2014 4:33:00 PM
NO RATINGS
There was a receint article in one of the electrical trade magazines that explained the "kill voltage" for electrical systems was based on 13-15 WATTS through the body. The well researched article was based on some work in the 50's that RCDs and GFCIs standards are based upon that to kill a "normal" person that 13-15 watts of power had to go through a person's heart disrupting the normal sineous rythem. The article went on to explain the various resistances and impeadances areas; and pathways of the human body. They explained why (in this Country USA) GFCIs are required in "wet" areas such as kitchens, bath & laundry rooms, pool, ponds,docks and fountain areas where electricity is being used.

The US/UL reasoning of 6mA at 120VAC will prevent anyone (from a baby crawling across a floor to a 90 year old oriental woman blow drying her hair in the shower) from having a life ending shock ie. electrocution. The EU/IEC- RCD reasoning of a higher "trip" current of 20mA at 220VAC will prevent most people (98+%) from electrocution while allowing for fewer false trips of the personel portective devices. There were more lawyers in the US's litiguoes society than in the EU and the difference between the way the neutral/ground bonds are done in the various power systems. The baby and the 90 year olds were picked because they are the worst case senerios for electrical schocks.

If you want the full skinny, read "The Effects of Electrical Current Through the Human Body" its 800+ pages of research from worrld wide studies that set the standards; oh yeah it'll make your skin crawl when you read about some of the "test methods".  

William K.
User Rank
Platinum
Fence chargers and "liitle old ladies"
William K.   10/1/2013 8:12:10 PM
NO RATINGS
Electric fences deliver a whole lot more than 70 volts. On the more standard units that I have worked on the primary voltage is about 100 volts, and the secondary of the step-up transformer has a turns ratio of about 1:50, or possibly much more. The spark from a properly functioning fence charger will easily jump a quarter inch, indicating about 2500 volts. The "high powered" fence chargers, designed to electrify a mile of fence around a horse pasture, use a capacitor charged to about 700 volts to pulse the primary of a much larger transformer. The output of that device will jump over a half of an inch with a loud snap.

As for the possibility of injuring an innocent person, that is unlikely since the system is only turned on when I would press and hold the button. Releasing the button switches the system off immediately. So unless some old lady points a gun in my direction and grabs the door handle there is no way they could get a shock. But, of course, the "Black Max" was taken off the market because somebody felt that it dould be dangerous. They refused to consider that a carjacker with a gun is dangerous. Bottom line: YOU CAN'T FIX STUPID. (note that I did not invent that phrase, but it certainly fits.)

bob from maine
User Rank
Platinum
Re: Stun Gun and other devices?
bob from maine   10/1/2013 4:16:21 PM
NO RATINGS
The Black Max is/was a good idea; except - when the bad-guy tried to open the drivers door and got zapped his immediate response was to jump backwards - into traffic. A satisfying end to a potential car-jacker, though tragic to granny who approached the wrong car. I think they have been outlawed. I built a zapper to disuade squirrels from using our bird feeder using a flyback transformer from a TV, a capacitor, resistor, relay and a push button. It never killed a squirrel - quite - but it took them several minutes to recover. Output was in the 12-18KV range and produced just one pulse. Squirrels can fly! But they learn quickly. I think electric fences are 70V open circuit and limited to 60mA. Considering how unpleasant an electric fence is, I can't imagine how painful a Taser must be.

etmax
User Rank
Gold
Re: Stun Gun and other devices?
etmax   9/28/2013 10:52:53 PM
NO RATINGS
Absolutely :-) BTW I was sitting on my chair writing my previous post with my ear plugs in and as I rolled the chair back a little I could hear eletrical noise in the ear plugs and there was an electrifying sensation as sparks flew from me (my ear canal :-( )) to the metal parts of the ear plugs which got stronger as the chair moved more. That was a deterrent too, I didn't move my chair the rest of the night! We've had a very dry gusty northerly the last few days and the humidity is down below 40%.

William K.
User Rank
Platinum
Re: Stun Gun and other devices?
William K.   9/28/2013 7:35:47 PM
NO RATINGS
The Black Max system as I would implement it would be controlled by a normally off momentary switch. So it would never be active unless it was intended to be active, even safer than a gun because it would not be able to go foo accidentally. It would only be activated when I saw a person with a gun approaching, or attempting to pull the door open. So the little old lady would be perfectly safe unless she pulled a gun. It is intended to be an active response to a specific threat, not a burglar alarm sort of function. Big difference there. Besides that, the system would be installed in a manner such that it could be removed and disposed of in a hurry, being replaced by an electronic siren of similar dimensions.

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