capacitors and stun guns

a fine line between stupid and clever

capacitors and stun guns

Postby nyazzip » Mon Sep 08, 2008 10:19 pm

all the worry about capacitors on here...i am still morbidly curious about them. i have yet to even discharge one( i use the waiting technique).
aren't stun guns just a capacitor bank? i understand the basic stun guns operate at many tens of thousands of volts, whereas a guitar amp may push 500 volts or so. so why is the amp considered so lethal whereas, as we sit here reading this right now, there are probably hundreds of people getting "stunned" worldwide, some even for fun, to make a Youtube video or something.
sure, i have heard of a token few police fatalities, but there is usually struggling and drugs and adrenaline and hidden cop brutality involved in those cases as well.
do the capacitor banks in amplifiers really store that much more current than the juice in a stun gun? i'm just wondering if maybe the capcitor thing is a bit overblown.
certainly i would bet getting popped is painful and surprising, but if your work is unplugged, then what more could it entail....?
and i know everyone is going to yell at me, but i have never read of a case of anyone being killed by an unplugged home appliance, be it TV, amp, whatever, and i have been reading the news since 1980 or so. so whats the deal, why the hype...?
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Postby erichayes » Mon Sep 08, 2008 11:25 pm

Voltage doesn't kill; current kills. If voltage was capable of killing, there would be thousands of deaths per year from people shuffling across carpets and grabbing doorknobs, or sliding out of the car and closing the door, or accidentally hooking up with an electric fence.

Current (or intensity, which is why it's symbolized by "I") is the worker in Ohm's law, for better or worse. Current's what burns out resistors, blows fuses, and makes funny smells and smoke.

40 mA at 350 VDC can kill you--values not uncommon in tube amps. Static electricity and Tasers/stun guns are low current sources, although I will concede that getting hit by a bolt of lightning probably interferes with ones life expectancy.
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Postby nyazzip » Mon Sep 08, 2008 11:33 pm

right, after i posted that i did a bit of browsing, and i saw one model operates at only 3 milliamp. so is this correct: the higher the Farad rating, the higher the amperage...?
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Postby Gingertube » Tue Sep 09, 2008 12:20 am

nyazzip,
3mA sound right - for your possible interest:
When I did my electronics training in a major public hospital there were considered to be 3 Classes of electrical safety.
Class Z - ordinary domestic appliances etc., safety can be guranteed by residual current devices (earth leakage breaker).
Class B - for when there is a an external connection to a person which they can't get away from - like if you have ECG electrodes strapped to, or stuck on your body.
Class A - for when there is a direct electrical connection to the heart via a blood pressure monitoring system, an external pacemaker or similar.

If you are shooting electrodes into a person Class B would seem to apply.
The limit for Class B was 5mA.

For info IIRC the limit for Class A was 20 uA.

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Postby BudP » Tue Sep 09, 2008 4:59 am

Right on, Ian! And to clarify, 20 uA (microamps) is .02 mA (milliamps) - so that 3 mA figure previously referenced would be 3000 uA - quite a bit higher than the IIRC limit mentioned!

I'd never really considered the capacitor rating (uF) equating to current flow, but it makes sense... normally the current "flow" from a cap is determined by the circuit it's in, but when shorted, a larger cap would tend to deliver more amps than a smaller one (charged to the same voltage).

My personal physiological current limit is ... zero!

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Postby EWBrown » Sun Sep 14, 2008 6:56 pm

Back when I was doing product safety testing, we had a saying that "3 milliamps leakage current can make you pee your pants". We used 3 mA as the safe limit for most applications that used a normal "removable" power plug, and 30 mA if the EUT was hard-wired ( no plug) into the electrical distribution.

Stun guns generate from 50KV up to 300KV, but at microamps, the instantaneous capacitor discharge gives it more "punch" and the effects on the nervous system are well known :o

Anyone who ever worked on a 1960s -1980s vintage color TV probaably felt similar effects from coming into unintentional contact with the HV connection on the CRT... See my "best zap" story about the 20 inch color Tempest CRT, and just how the "spark" exited my body to ground :o Yellow_Light_Colorz_PDT_09

/ed B lucky to still be alive... Yellow_Light_Colorz_PDT_11 Yellow_Light_Colorz_PDT_07 Yellow_Light_Colorz_PDT_08
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Postby mesherm » Fri Sep 19, 2008 1:45 pm

Stun guns are very similar to strobes, photoflash circuits, or even switching power supplies.
You have a DC current source (batteries), a solid state oscillator to convert the DC to AC so the voltage can be be stepped up through a transformer and again rectified back to DC but at hundreds of volts to charge a capacitor, and finally a trigger that discharges the capacitor through another transformer to give the final voltage boost to the electrodes.
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TASERs and swifties

Postby EWBrown » Fri Sep 19, 2008 5:38 pm

The Stun Guns / Tasers use a Cockroft / Walton voltage multiplier (a string of multiple HV disc caps and rectifiers to step up the AC from the inverter to the 50-300KV "zap" voltage). Their predecessors were called "cattle prods" and these used a simple vibrator type power supply and the voltage multiplier string. THe body of the prod held a number of D or C size batteries, and gave the device quite a bit of "heft". :o

A close relative is the "electric fly swatter" which contains an HV generator, the aforementioned diode / cap HVDC multiplier, and the working end looks like small tennis racket, with three layers of approximate 8 mm mesh screening, with the center being "common" amd the othe two screens on the outside, all spaced about 6 mm apart. Whwn a bug or skeeter gets swept inside, the spaark jumps and the big dies Yellow_Light_Colorz_PDT_07 THese often show up at flea markets and as with most "made in China toys" the price , and overall quality, is quite low, but they are FUN!!!

Trivia Time:

The letters in TASER stand for Thomas A. Swift's Electric Rifle. (This was covered in a recent "Modern Marvels" program on History Channel).

One probably has to be at least 50 years old to know what an "electric rifle" Yellow_Light_Colorz_PDT_02 Think of it as being the Star tTek phaser's grandfather Yellow_Light_Colorz_PDT_01

The Tom Swift series of books , was a series of sci-fi / wild west lost in space stories aimed at teenage boys I enjoyed many of the books back in the 1950s, and the books were popular from the 1920s through the early 1960s. They were more or less around the same era as "The Hardy Boys" books. Long before video games and I-pods took over our youts' lives Yellow_Light_Colorz_PDT_11

The Tom Swift stories contained a quantity of crafty little puns, often refered to as "Swifties", like this example:

"Take the prisoner downstairs to the dungeon", Tom said condescendingly.

or

"The lights have gone out", Tom said darkly.

want more? sure you do... Yellow_Light_Colorz_PDT_05

http://thinks.com/words/tomswift.htm



/ed B
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Postby mesherm » Fri Sep 19, 2008 9:07 pm

For those of you tired of tube amps but still longing for high voltages and such:
http://hackedgadgets.com/2007/01/27/top-5-coil-guns/
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Postby munoz » Wed Apr 13, 2011 8:09 pm

Ohh I see a video on your link and I'm amaze on that......
Is there a stun guns design like a cellphone?
A man with a briefcase can steal millions more than any man with a stun gun.
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Postby EWBrown » Wed Apr 13, 2011 9:07 pm

I was at a gun show a few years ago, and one supplier of "police equipment" the two sellers were playing a game of "chicken" with a stun gun, by sticking one finger into the "lightning bolt". When they got "hit" they jumped, and there was a bit of creative cussing >:o ;) (lol)

I politely turned down an "opportunity" to engage in their game..... =:o

The "great grandfather" of stun gun technology is the jet engine igniter. A roughly 4X4X4 steel box, with two inputs for 24-28VDC, and a ceramic insulator bushing output terminal. The output voltage was 130KV, and was designed to fire up 8 or more "burners" inside a jet turbine engine.

I know from personal experience, these things definitely kick like an angry mule =:o :'( (lol)

/ed B in NC
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Postby lynxx » Fri May 13, 2011 11:22 am

Hey Ed.
I read the Tom Swift series during the 60's and 70's. Still have some stashed somewhere.
Back in my electronics class it was considered a lethal dose if it was .03A(3ma or higher). I have been attacked by HV in old TV's also. Makes you hurt yourself instead of hurting you. You get a healthly respect for 40KV real fast. I can remember when a gentleman(that was like my on Dad) and taught me a lot of electronics, we were working on an old Magnavox console, on that still had the lead Hi voltage output tube. I would play fine and then the picture would fade out. When we checked the voltage it was at 96KV. My friend got bit when he reached around and turned of the the TV at the switchl. OUCH (sick)
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Postby Geek » Fri May 13, 2011 1:08 pm

lynxx wrote:... .03A(3ma or higher).


.003. ,03, 30mA will definately kill.

Oddly enough, most GFCI's I've tested only trip at 5mA (beware - look for "Leviton" instead of "Leveton" on the electrical device - the latter being a cheap knockoff).

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Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Postby EWBrown » Sat May 14, 2011 6:05 pm

When I was doing product safety for a living (mid 90s) we used to have a saying; "anything over 30 milliamps will make you pee ypur pants" ;) (lol) =:o

It all depends where the current flows through the body. Worst case is when it passes through the heart, either hand to hand, across the chest, or from (especially ) left hand to either foot (don't stand on damp basement floors in bare feet when working on anything which is plugged into the AC line).

The least dangerous shock is through a single hand or finger, it will still hurt and make you say things which would embarass grandma, but it won't cause any ral damage, except for possible skinned knuckles from the pull back reflex.

Don't become a "world famous conductor" in your electronic endeavours...

/ed B
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