stungunX

RAOIO-ELECTRONIC8

OG- *—THE STIWIG JN S CIRCUIT is a multi-slagc yottsge step-up e >rcuit The Ol O? cifcurt praduces a so<ułnwe ou(put of about 10 kHŁ and 03 produce* iS-_s (Sscharge putses ac a ratę o* about 20 ppm. Tboae puises tire SCSI. wbicft induen a voftage m the wntnę; o* saep-up trsnslormers T2 and

T3.

Physiological effects

So that you may umlerstafid ihe danger inhcrcnt to thc siun gun. Ictjs discuss the physiological cflecis tirst When a high soltage i> discharged on ihe suriacc uf thc \kin. thc omem prodiHcd travds thn»ugh rhe iKT\ł>u^v' system by cxciting single cdls ans! fhe myeltn shrtnhs that encłosc ihcm. When that currcnt njachcs a synapso conneetcd to a muscicJ it causes thc muscle to contract violcntlv atu! possibly to go into spusms.

The kwiger conlact with ibc high wlt-jgc b. nuintjincd. thc morc rouscles wili be atTcclcd If thc high wltagc maintains oontact with fhe skin king enough to ca&sc musclc spasms. it may takc ten or fiftecn minutes befbrc tho hrain i,s ahle to re-cstablish contml over tho nerve and mus-cutar systems.

How much power is tetjuired to cause soch spasms ^ł That s not an casy qoestion to aoswer becausc. jlrhough it is rela nsdy casy to make precisc mcasurements of thc power produced by a high-soltagc devicc, ir is diflicult to ratę thc human body*s snsceptibility to shock aceuratcly. Somc obvious factors mcludc age and dis eases soch .ts epilepsy But the hottom linę is simple The omły one footi unturul nirh a stun gun is a font.

The amount ofcncrgy a dnricc defWers is actuaWy the amooiu of power deluered in a given period of łimeJ Kir our pur* poses, it makes sensc to talk ahout cncrgy in joulcs i watt-scconds). Using a frcsh 9.8-wh Ni-Cd bal tery. thc stun gun is eapable of dełiscring peak ptiwer polses of 25.000 watts. Actu.illy. pulses stan out at peak power and then dcc as esponcn tially. Ihe length of rhe decay limę dc pends on the componcnt?; used in the Circuit, the ambient tcmpertaturc. thc bat-tery s capacity. and thc positioning of the outpul euntaets with nrspect to cach olher

Assummg that the decay ratę is putely etponcniul. the stun gun can producc ahout 0 5 joulcs of cncrgy, prmidcd that thc battery is fully charged. Ixt s put that number m pcrspcctive.

Both thc Underwntcr s Laboratory (in Kullctin no. 14) and thc UJ S. Consumer Product Safery Coinmission state that sentrieular fihrillation (heart artack) can bc caused m humans by applying 10 joulcs of energy- Since the stun gun only gcncraics ahout half a joule. ynu might think that a device that produces only one twcnticlh of the critical umount has a more-fhan adwjualt* marsin of safety. Don i bet on it. A brief coniact with the stun-guns dischargc hurts a grcat deal. but it takes only ahout trvc seconds of contmuous dischargc ló immobih/c someonc complctely.

lx't’s comparc thc stun gun‘s outpul with a similar devicc. called a Taser gun. which appcanrd on thc market a few ycurs ago. You may havc scen a film demon-sirating just h« »w efleeti ve thc Taser could bc as a deterrent. A foolhardy voluntccr was pajd an cnormous sum of rnoney to have thc Taser fia*d al him. No rnattei how big. strong, (and stupid) thc person w:in. as soon as the Taser’s “darts" hit him. hc would a>llapsc to thc grnund and go into unconimllahlc consulstoas.

Ihe energy produced by thc Taser is only 0.3 joulcs—ahout 60% of what our stun gun pniduccsf Even so. the Taser has bccn oflicially elassified as a tircarm by thc Burcau of Tobacco and Rrcarms be-cause >t shoots iis electrodc "darts” ihrough the air. Lscn though our stun gun docsn’t operatc (hal way. thc Taser put.s out considerably less energy thun thc stun gun. Keep thosc facts and figures in iniiul as you asscmble and use thc device.

How it works

The schematic diagram of thc stun gun is shown rn Rg. 1 BasicaJly. it's a multi-stage power supply arrangal so that each succcctling stage multiplics thc vołtage produced by thc prcceding stage. The finał stage of thc Circuit Icetls two op-positcly phascd transformers that producc cxticmcły high wiltage pulses. If that dc-scriptKm snunds familiar. you vc próba-Wy studictl capacir«ve dtschargc ignitkm systems—the stun gun works on thc same principlcs.

The first section of thc power supply is a switcher u)mposcd of Ql. Q2. and thc primary windings (connectcd to leads li. F. G, and I!) of TI When hrl switch SI is ckisćtl. RI unhalanccs thc Circuit and that causes >t to stan oscittaiing. Since basc currcnt is prmidcd by a separate w mding of Tl (connectcd to Icads C and D), thc Iwo transistors are drivcn out of phasc with cach other, and that kecps thc circuit oscillating. Kesistor R2 limits basc ilrivc to a safc value, and diodes Dl and 1)2 arc steering diodes that switch basc currcnt from one transistor to thc other. Oscilla-tion occurs at a frequcncv of about 10 kHz.

The sw itching action thc first stage gcncraics an AC mfcagc in Tl s high-vi*łr-age sccondary (icads A and B). The amount of sottage depends on thc battery used. but a battery of scven to ninc volts should producc 250 (o 300 volts across Tl \ secondary.

That voltagc is n^ctificd by the full-wavc bridge composed of di<xles D3 D6 Capac«orC2 char ges through D7 at a ratę that is comrotled by R3

The value of capacitor C2 aJfect.s thc (Mitput of the stun gun. The greater thc capacitancc. thc morc energy that can be stored, .so thc morc powcrłul the dischargc will bc. A larger capacitor givcs higger sparks. but tcqu<res morc charging limę. and that givcs a lower dischargc raić. On the other hand. a smali er capacitor giwes smalicr sparks. but a taslcr dis-charge ratc. If you wish to etperiment with dilTcrcnt values for C2. try 3.9 p.|- (as shown iii l ig. I). 7.K and I 95 p,F.

*sc values wcrc arriscd at by using one 3.9 pK capacitor ałonc. Iwo of thc same capacitors m scrics. and łsw> m para lici

Mcanwhdc. UJT Q3 pmduccs 15-p.s pulses at a ratc of about 20 ppm. That ralc is conlrolled by C3 and thc scrics com-binalion of R6 and R7. ^"hen a pulse arrives at thc gatc of SCRI. it fires and discharges C2 That induccs a high-woh-age pulse in thc primary w indings of T2 and T3. whose priwuwcs musi hc wired out of phasc with cach other. The resuh is a nnging wave of AC whose negatisc component then rcachcs around and forces thc SCR to tum olf. WTien thc next pul.se from Q3 arrives. the cyclc rcpeats.

The outputs of thc stun gun appear across thc sccondarics of T2 and T3. The hot Icads of diuse transformers conncct to

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