| Exploding wires This post is prompted in response to the post here http://www.sciencemadness.org/talk/viewthread.php?tid=11756 much of this is informatively discussed at length in the reference given by damn2 here _ http://www.sciencemadness.org/talk/viewthread.php?tid=11756&... Succinctly outlined here _ http://www.teledynerisi.com/0products/8td/page06.html http://www.teledynerisi.com/0products/8td/index.html http://www.teledynerisi.com/0products/index.html It was my understanding the notion of exploding electronic board resistors was put to rest in this other thread _ http://www.sciencemadness.org/talk/viewthread.php?tid=7266&p... here we go again _ First some definitions and misconceptions. There are two applications of electric firing and these are mutually exclusive, ignition, or alternatively , detonation ( of secondary explosives ) 'Xenoid' describes above an elaborate apparatus to ignite rocket motors. I can't help thinking so much effort for so little gain. I can't think of any reason to do so in quite that way except that is just how he likes to do it. One can very expediently make a single use improvised " Hot Bridge Wire " squib ignitor made from a flashlight or torch light bulb. Heating it with a blowtorch to poke it open with a nail , and fill it with powdered match heads. The flashlight itself is the only power supply needed and an arbitrary length of hookup wire. Bulbs are manufactured with small values of resistance, which of course increases many fold when turned on , limiting the working current. This complicates calculation of adding the measured ohms of the firing cable. To determine the voltage needed to obtain the working current its easiest to just test the bulb connected to the firing cable to light it before making it into an ignitor. Using one more 1.5 volt battery than what is normally required should be sufficient. Moderately higher voltage drives excessive current through the bulb lessening it's life in normal use , but as it burns brighter that may be advantageous in this application. http://www.bulbtown.com/1_0_2_99_Amp_Light_Bulbs_s/665.htm http://www.bulbtown.com/1_4_9_Volt_Light_Bulbs_s/764.htm [url]  [/url]Primary ( initiating ) explosives ( substituted for match heads ) can be detonated in this same way. http://en.wikipedia.org/wiki/Blasting_cap Multiple charges are routinely connected by detonation cord set off from a single blasting cap. Apart from wearing high impact resistant eyeglasses and face visor , ballistic vest , and tongs or forceps for handling , thoughtful precaution is necessary when making an electric blasting cap as the wire leads are effectively a dipole antenna and as such susceptible to radio frequency broadcast in the vicinity which could resonantly induce current sufficient to heat the bridgewire ( filament in this case ). From the time it is first loaded with explosive and initially been tested for continuity ( read the following procedure ) to the time when it will be used , the exposed lead ends must remain twisted together. To ensure there is no hangfire , immediately prior to use ( by having the cap inside a pit dug into the ground covered with a sand bag ) it is tested for continuity , a tricky feat that requires a milliampere low voltage source of just under 1 volt. The cap lead ends are then connected at this time to the cable or wire that will be used for firing it, which is also first tested for continuity being already shorted and disconnected at the power end. The final act is to bring the cap from under the sandbag to the main charge of secondary explosive and inserted into a previously formed opening there , then promptly leaving the scene to a safe area. The last thing before firing is to un-short the cable end and test again for continuity before hooking up to power for firing . This is to distinguish an electrical failure mode from a dud hang fire which may perhaps be still smoldering , ready to explode , in that case a wait of 15 minutes or more is warranted before approaching the item for inspection. For a high degree of safety one could instead electrically light a fuse first to then set off the blasting cap. ( Individuals who snicker and think all this is excessive , are by definition kwels ) [url]  [/url]__________________________ The EBW ( exploding bridge wire ) is an altogether different device that initiates detonation of secondary explosives in direct contact without the use of primary explosives. This is accomplished by vaporizing a small metal wire by the rapid Joule heating produced by a nearly instantaneous ( very low impedance ) applied electric current. Immediately evident by the very L O U D bang it makes , note there will be little sound if the wire only melts and drips away much as a fuse. ( See here fusing current ) - http://www.ndrr.com/rmr_faq/Introduction/Fusing-Currents.htm and also this - http://www.litz-wire.com/New%20PDFs/Fusing_Currents_R2.011609.pdf * Note that both the above references omit to state that the wire diameter must be C U B E D . before taking the square root , so , √ ( D X D X D ) , only then multiplied by the coefficient " A " EBW devices must be within arms reach of the pulsed power source and supplied by a short low impedance cable typically within 40 - 50 cm. This can be : Solid copper core RG-8U Coaxial cable , [url]  [/url]Braided or Rutherford Litzendraht ( Litz ) wire [url]  [/url]http://en.wikipedia.org/wiki/Litz_wire , http://www.litz-wire.com/applications.html , http://www.hmwire.com , http://www.hmwire.com/sm.html , Goertz flat ribbon cable , [url]  [/url]similar available plain and much cheaper from _ http://www.alphacoredirect.com/contents/en-us/d53.html or 2 plys of 12AWG from http://www.decorp.com [url]  [/url][url] [/url]http://www.flatwirestore.com/mm5/merchant.mvc?Screen=CTGY&Store_Cod... http://www.tycoelectronics.com/catalog/cinf/en/c/11930/1486 http://www.tycoelectronics.com/catalog/minf/en/152 http://www.ampnetconnect.com/product_groups.asp?grp_id=1660&path=0,... http://www.ampnetconnect.com/product_cut_sheet.asp?grp_id=2285&path... even 2 edgewise parallel flat cross section solid grounding strap would do. http://www.keison.co.uk/furse/conductors_flat_tape.htm Fralock transformer coil copper tape http://www.surplussales.com/RF/RFSilv-CoppS.html _____ Perversely , the uninitiated continue to believe that the bridge wire itself is a resistive element , - - W R O N G - - A bridge wire is just that , an UNINSULATED wire having as low a DC current resistance as possible. Due to the extremely short time rise of the current , initially conduction occurs only along the surface , known as " skin effect ", as the wire heats up the resistance increases, then as the wire melts the resistance drops again and conduction resumes now through the entire cross section and continues to increase as it becomes vapor. High resistance material inhibits this progression so that the surface is cooked off forming a vapor boundary layer which is more conductive , dissipating the discharge as a heat flash , not shock.* Note this is a principle reason why very fine wire is used in pulses of very short time frames , the current simply cannot penetrate into the depths of the wire where it needs to be to rapidly heat the wire. The applicable equation of state is , I = V / R , current I = amps , V = volts , R = ohms Arithmetically R must be as small as possible to maximize the current. This is why kilovolts are typically applied , to assure a huge current surge and rise time. [url]  [/url]Another misconception is the available energy provided to the wire. A capacitor's stored energy according to E = CV^2 /2 , E = Joules , C = farads , V = volts 83 Joules = (.00082 F X 450 X 450 ) / 2 may be adequate to the task were it all to arrive instantaneously - which it cannot , being a function of time and restrictive circuit characteristics. The determinant will be Power , the rate at which the energy can be delivered by the cable to the EBW. Because this is a rate per second , at initial discharge apparent power seems as if megawatts are on tap. Read Overview here _http://en.wikipedia.org/wiki/Pulsed_power Dividing 83 Joules by the discharge time .000160 sec = 0.518 Megawatt average power discharge time is calculated as follows : see - RC time constant , below [url]  [/url]- RC time constant Determining the time during which the initial discharge occurs is given by TC = RC , R = ohms , C = farads , TC means Time Constant , a factor which relates the rate at which the capacitor discharges. Specifically , 63 percent of charged voltage during the first TC leaving 37 percent remaining , 86 percent of the original after 2 X TC , leaving 13 percent of the total remaining , after the third TC 95 percent discharge has occurred. Complete discharge is assumed after 5 X TC. See middle of page here - http://www.kpsec.freeuk.com/capacit.htm also bottom of this page - http://www.bcae1.com/capacitr.htm RC TC in depth - http://www.electronics-tutorials.ws/rc/rc_1.html RC Time Constant Calculator - http://www.cvs1.uklinux.net/cgi-bin/calculators/time_const.cgi Capacitors exhibit resistance which limits their rate of discharge, known as ESR ( Equivalent Series Resistance ). Smaller ESR means a shorter RC Time Constant and more power ( energy delivered per unit time ). For the capacitor type and size range applicable typically around 0.1 ohm or less. Reducing ESR shortens the TC and the current rise time without needing to have higher voltage to compensate for higher resistance.Very short pulse durations are only acheived by capacitors having exceptionally low ESR. As these do not have large capacitance, they must have a very high voltage to store significant energy. What is a Capacitor ? - http://www.sofia.usra.edu/Edu/materials/activeAstronomy/sec5_capaci... http://www.bychoice.com/capacitor_DF.pdf http://www.illinoiscapacitor.com/uploads/papers_application/F8CD49C... http://www.cartage.org.lb/en/themes/sciences/physics/electromagneti... http://www.cartage.org.lb/en/themes/sciences/physics/electromagneti... Equivalent Series Resistance (ESR) of Capacitors - http://www.low-esr.com/QT_LowESR.pdf Equivalent Series Resistance of Tantulum Capacitors , Both the following PDF's are the same - http://www.avx.com/docs/techinfo/eqtant.pdf - http://www.avxtantalum.com/pdf/EQTANT.PDF - In the opening post of this thread -> http://www.sciencemadness.org/talk/viewthread.php?tid=11756 given 820 uF or .00082 F, assuming a 2 cm 28 AWG EBW Resistance of EBW = .004 ohm , plus Resistance of cable = .0267 ohm ( sum of core and shields resistance of 3 meters 10 AWG RG-8U coax , see footnote ## ) , estimated ESR 0.1 ohm ( note that ESR is 3 times greater than the rest of the circuit resistance ) the total circuit resistance = .131 ohm then TC = RC = (.131 )(.00082 ) =.000107 ~ 107 microseconds - discharged at 450 volts after one TC the remaining voltage is 167 ( 37 % ) , so by E = CV^2/ 2 ( .00082 X 167 X 167 ) / 2 = 11.5 Joules , dividing by the rating of 83 Joules ( 11.5 / 83 ) = 13.8 % 100 % - 13.8 % = 86.2 % of the energy is delivered during the first 107 microseconds. The magic factor is 1.5 times the TC when the remaining charge is 100 volts ( 22.2 % ) 95 % of the energy of the capacitor has gone into the line in just 160 millionths of a second. What this means is if conduction is still occurring only along the surface of the EBW , there will be no loud B A N G ! http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Effectiv... - Given that frequency is the reciprocal of time , f = 1/ t , then the 160 millionths of a second translates to a frequency of 6.25 kHz. Well below the 170 kHz where skin effect reduces cross sectional saturation. Look up 28 AWG , here -> http://www.powerstream.com/Wire_Size.htm Note that this value would be a mere 2.6 kHz for the 10 AWG coaxial core were it just bare wire instead of coaxial cable. _____ Joules needed for vaporization of a 2 cm 28 AWG wire = ( weight of EBW / molar weight Cu ) X ( * *Enthalpy of vaporization of Copper 300 KJ / mol + Heat of fusion 13.1 KJ / mol ) = ( .0145 gm / 63.546 gm/mol ) X ( 313100 J/mol ) = 71.4 Joules By comparison an equivalent weight of TNT yields 65.5 Joules (.0145 X 4519 Joules/gm ) * * From http://www.webelements.com/copper/thermochemistry.html weight of bridge wire is easily obtained from this applet here _ http://circuitcalculator.com/wordpress/2007/09/20/wire-parameter-calculator Resistance of EBW = .004 ohm , Resistance of cable = .0267 ohm ( see footnote ## ) The energy is consumed along the entire circuit's resistance. The portion which will act on the EBW is: .004 / (.004 +.0267 ) = 0.03 , alternatively a 25 cm length of cable is .0022 ohm recalculating , .004 / (.004 +.0022 ) = 0.645 , then .645 X 83 Joules = 53.5 Joules An 83 Joule rated capacitor will not be adequate with inherent circuit losses , and still be marginal with somewhat thinner wire. A thinner wire has less mass and will require less energy to vaporize while presenting more resistance and consume a greater portion of the available energy in the circuit. Worth a try with an aluminum foil ribbon and very short cable run ~ 25 cm. Remember it must make a very loud bang , if it does not sound like a rifle shot you have not achieved detonation status. 12AX7 observed in this other post http://www.sciencemadness.org/talk/viewthread.php?tid=6032&p... the only energy that matters in a system is that which actually achieves the intent. _____ Capacitive reactance and Inductive reactance the two components of circuit impedance behave as an additional form of resistance which interferes with rapid discharge of the capacitor and transmission of that power as a short pulse. Coaxial power cable limits this to a maximum of it's characteristic impedance of 50 ohms regardless of length. This value is only a transmission line design parameter , whereas the actual line impedance of your particular firing cable depends entirely on the wavelength of the discharge waveform relative to the cables length , and what is attached on the ends. Given that wavelength is the speed of light ' c ' divided by the frequency , λ = c / f, or alternatively multiplying by the time of discharge , wavelength = λ = c X t = ( 300,000,000 X .00016 ) = 48000 meters. The actual wavelength within the cable is always shorter than this because it slows down ( similar to light when it enters a denser medium ) known as " velocity propagation factor ". For RG-8U it is 0.84 of light speed. A pulse that is lengthy due to a long discharge time becomes shorter by the propagation delay inherent to the cable. A cable of just 3 meters behaves here as a short circuit , exhibiting practically no line impedance to or attenuation of the discharge pulse. See footnote below - IMPEDANCE EXPLAINED - Xc = .159 / f C , Xc = capacitive reactance of the capacitor expressed as ohms f = frequency , C = farads. So , Xc = .159 / ( 6250 X .00082 ) = .031 ohm ( vanishingly small ) * Note the absurdly overpriced Goertz " speaker cable " exhibits a characteristic impedance of just 2 to 4 ohms by further reducing line induction. Unrelated to the present topic , a rational perspective on such expensive attributes. http://www.leedsradio.com/technical/snakeoil-cables.html Ideally the EBW will have melted by full discharge as the current surge drives through the lowering resistance and vaporizes the wire. We have observed that the ESR of the capacitor is the most pronounced inhibitor of circuit performance , throttling the power available. By the end of the next post it will be evident how the effect of ESR can be minimized to improve the response and performance by at least two fold. _____ The power feed cable as selected below must be of large gauge to minimize resistance ( ## 3 meter length of RG-8U coax ) or a braid of Litz cable. Welding cable can suffice for only very short lengths but the induction becomes significant in the circuits performance. This is because it acts as a transformer primary , magnetically coupling with anything electrically conductive even moist ground. Given everything going for it one can see why this has no application other than for use in ordnance where the EBW can be snug up against the pulse generator. A setup for outdoor use will need to have the pulse generator close by which puts it at hazard if used to detonate explosives. Charging and firing control can be done from a distance with a 3 wire extension cable. ( See the circuit diagrams - next post - below ) * 28 AWG is a common size used in " wire wrap " electronic board prototyping. Click thumbnails then click again the pictures here -> http://en.wikipedia.org/wiki/Wire_wrap My suggestion of 28 AWG is 3 to 4 times thicker than what is usually used for an EBW, and with much bigger caps. Given that the 1 mil to 3 mil wire otherwise used is AWG 40 and smaller which is much finer than hair one should not stray too far from 28 AWG wire as selected above. Much smaller wire size as noted requires less effort to explode but becomes increasingly more difficult to physically work with and prepare. Larger wire naturally requires greater energy to explode but more importantly the lower frequency at which skin effect becomes significant will affect cross sectional current saturation. Fine wire is cheaply obtained from ordinary stranded electric line cord. Count the number of strands in the wire bundle of a known gauge ( 14 AWG being common ) to derive the single strand size verified here _ http://www.interstatewire.com/WireTable.htm http://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/swc.pdf ==> One experimenter's results with videos http://members.tm.net/lapointe/Wire_Explosions.html Viewing this setup one immediately can see despite success with fine copper wire that such a large loop of single conductor must sap considerable energy by inductive losses. This can't be stressed enough , the faster the current rise time , the greater the need to minimize induction in the circuit ! Viewing the following videos I ask myself what's wrong with this picture. The widely separated cables is what , which is in effect a single turn solenoid the induction of which is responsible for the mediocre results observed. Capacitor like woelen's - explosion - http://www.youtube.com/watch?v=CY8bkf7QcVE same guy with new General Atomics capacitor http://www.youtube.com/watch?v=QMWRvAI4o2E Banks of capacitors in parallel have one fatal flaw : ALL of the energy will discharge into the capacitor that fails destroying it and perhaps damaging those that are alongside. [url]  [/url]It's essential to design a capacitor bank so that the individual caps can have at least one terminal disconnected from the common conductor with the other caps so that it can be individually tested for "leakage current" and signs of impending failure. http://www.fullnet.com/~tomg/esrscope.htm Invest in a good RCL bridge meter that can measure this. Better yet get it all in one package , the most prized of all , Sencore LC 75, 76, 77, 101, 102, 103 ( may be seen on EBay for ~ 150 to 250 dollars and up ) These can even re-form deteriorated aluminum electrolytics. The oxide insulating layer will tend to deteriorate in the absence of a sufficient rejuvenating voltage, and eventually the capacitor will lose its ability to withstand voltage if voltage is not applied. A capacitor to which this has happened can often be "reformed" by connecting it to a voltage source through a resistor and allowing the resulting current to slowly restore the oxide layer. ( See my attachment Equivalent Series Resistance & Maximum Leakage.rtf next post below in Pulse Power - Firing circuits ) http://bama.edebris.com/download/sencore/lc102/LC102.pdf Cheaper expedient methods (with oscilloscope ) are available http://octopus.freeyellow.com/esr.html http://octopus.freeyellow.com/99.html All the way at the bottom see ' Scope ESR ' here _ http://www.anatekcorp.com/ttg/tiptrick.htm _____ - IMPEDANCE EXPLAINED - http://www.eskimo.com/~ddf/Theory/Char_Z.html http://www.speedingedge.com/PDF-Files/BTS002_Characteristic_Impedan... The activity in a 3 meter cable at the discharge frequency of 6.25 kHz being very much less than a quarter wavelength is seen at the extreme right side of this diagram here_ http://www.tpub.com/content/neets/14182/css/14182_150.htm http://www.allaboutcircuits.com/vol_2/chpt_14/5.html http://www.epanorama.net/documents/wiring/cable_impedance.html , See the following - Cables characteristics at high frequencies - Why attenuation figures tend to increase with increasing frequency ? Impedance calculations ( scroll down ) http://ocarc.ca/coax.htm http://www.mantaro.com/resources/impedance_calculator.htm http://hamradio.arc.nasa.gov/coaxcableloss.html http://74.125.93.104/search?q=cache:xfy31beGKowJ:hamradio.arc.nasa.gov/coaxcableloss.html+%22Belden+9913%22&cd=58&hl=en&ct=clnk&gl=us FOOTNOTE ## 3 meter length of Belden 9913 10 AWG solid copper core RG-8U coax , .0089 ohms / meter ( sum of both core and shield resistance ) RF9913 - $ 0.76 cents ft ( recommended vendor ) - http://www.radiobooks.com/products/rf910.htm - http://www.radiobooks.com/rwcoax.htm 25 ft cable + UHF connectors, or custom size ready made - $39.95 - http://www.radiobooks.com/products/ca9913.htm An RG-213 stranded conductor 7 X 21 AWG + UHF connectors, ready made cable may be suitable to sustain a multi kilojoule pulse for modest power throughput ( rated for 5 kilowatt ( 250 V X 20 amp ) due to the effective cross section being half that of solid core RG-8U, is cheaply available here _ http://www.buckscom.com/catalog/index.php?main_page=popup_image&pID... http://www.buckscom.com/catalog/index.php?main_page=product_info&cP... This one is preferable for applications at kilovolts having a very short time pulse. Belden 9913 - 0.79 cents/foot ( alternative more expensive vendors ) http://www.theantennafarm.com/catalog/index.php?main_page=product_i... http://www.signalpros.com/index_files/Page3071.htm http://www.progressive-concepts.com/info/item.html?id=68 RG-8U Cable specifications and data - http://www.contactcables.com/products/Belden/Belden9913datasheet.pd... http://www.alliedelec.com/Images/Products/Datasheets/BM/BELDEN_WIRE... http://sigma.octopart.com/30985/datasheet/Belden-9913-010500.pdf http://www.belden.com/pdfs/03Belden_Master_Catalog/06Coaxial_Cables... ( page 6.70 ) Fusing current http://www.ndrr.com/rmr_faq/Introduction/Fusing-Currents.htm http://www.litz-wire.com/New%20PDFs/Fusing_Currents_R2.011609.pdf http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/wirefusin... http://www.interfacebus.com/Reference_Cable_AWG_Sizes.html http://www.interfacebus.com/Aluminum_Wire_AWG_Size.html Wire chart Solid conductor http://amasci.com/tesla/wire1.html http://www.powerstream.com/Wire_Size.htm Stranded conductor http://www.interstatewire.com/WireTable.htm http://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/swc.pdf Wire calculator http://circuitcalculator.com/wordpress/2007/09/20/wire-parameter-calculator Unit conversion http://www.allconversions.com __________________________________________ | |||||||||
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| Pulse Power - Firing circuits All the previous analysis presupposes the capacitor is a stand alone power source connected in a closed loop with the EBW. Energy storage capacitors as these below, while suitable for exploding wires , are large and unwieldy. A high voltage power supply is also needed to charge them. 240 uF 5000 Volts - 3000 Joules http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350128516137 [url]  [/url]http://www.gaep.com/capacitors.html To provide a large power pulse , a current surge generator is a better arrangement. By intentionally causing the a.c. power line to short circuit through the EBW , this enables a very large power pulse to be directly applied with minimal , relatively inexpensive hardware. In this scheme the capacitor voltage discharges through a spark gap to complete a circuit with the a.c. power line , resulting in conduction of a huge current surge ( termed " in rush current ") through the firing cable. This is known as '" Power OR " mode of operation , a " shunt " diode channels this " follow current " from the a.c. line conducted by the arc. See F O O T N O T E S bottom of the next post following Also read here beginning the 3rd paragraph at left _ http://img11.imagevenue.com/img.php?loc=loc284&image=05761_Magnetizing_.jpg A current surge of hundreds of amps during one half cycle of the a.c. power line frequency can be tolerated only as a self terminated transient event to prevent damage to the firing circuit and in particular the a.c. power line. The EBW additionally serves as the circuit protection fuse , taking only just the power used to explode. A 300 amp surge through a 2 cm 28 AWG wire by P = R I^2 = .004 ( 300 X 300 ) = 360 watts , more than 5 times what was determined necessary to be vaporized. Note that much more power is consumed by the rest of the power line circuit which heats up considerably though manageably in a single shot event. Line transients as these are commonly handled by commercial surge suppressors discussed here - http://www.zerosurge.com/PDF/PQ94.pdf _____ Drawing ' A ' ( attachment ) restricts the capacitor current to only the firing circuit by having the capacitor ' C ' parallel with the a.c. line. Synchronizing a.c. line commutation to occur in phase with the capacitive discharge is facilitated by a triggered spark gap or gas tube ' gg ' as part of the capacitor EBW circuit - Drawing ' B ' See footnote - Triggered Switches , in the post following this one and - http://www.angelfire.com/80s/sixmhz/trigatron.html This allows the peak voltage of the a.c. line to trigger the gas gap into conduction. A diode ' d ', restricts triggering to the phase when the a.c. line voltage has the same polarity as the caps. This arrangement does not receive the power boost provided by having the capacitors in series with the a.c. line and will not be considered further. 3 terminal gas tube - 2 to be used in parallel & need to have leads thickened - $ 3.02 each - http://www.mouser.com/Search/Refine.aspx?Keyword=871-B88069X8440B20... - http://www.epcos.com/inf/100/ds/t81a90xx8440b202.pdf Drawing ' C ' shows the capacitor ' C ' in series with the EBW and the a.c. power line. The problem of a.c. commutation synchronization is solved by a spark gap ' G ' which conducts in phase at peak a.c. power line voltage. Having the a.c. power line in series with the capacitor has an additional benefit that the a.c. line voltage and capacitor voltage add together increasing the voltage to the EBW , improving the current rise time. A large diode ' D ' provides a path for the resulting current surge generated in the firing circuit. _____ * * * Note that all the following circuits are divided into a charging and switching part shown on the left side of each drawing , and the power storage part shown on the right side of the same drawing. The entire circuit is interconnected across some distance with a 3 conductor cable serving as an extension cord. Each conductor is labeled ' Top ' , ' Mid ' , ' Bot ' ( Top , Middle , Bottom ) This arrangement also charges the extension cable to the same static voltage as the capacitors. which adds the cable's capacitance to the firing circuit , reducing the damping at discharge. ' Top ' and ' Mid ' conductors flow electron current to the left. ' Bot ' conductor flows current to the right. ( This is true for all these circuits , although charging phases may have different current paths. ) Suitable cable is of the type used for connecting RV ( Recreational Vehicles ) and trailers to the electric utility main grid , RV 30 Amp Generator Cord , 10/3 ( The leading number is the gauge AWG followed by the number of conductors ) Characteristic impedance for twisted pair of this type would be somewhere 100 to 200 ohms See http://www.mantaro.com/resources/impedance_calculator.htm Conductor inductance calculations ( nice to know not really all that useful here ) http://www.kolb-net.de/pulsedpower.html - - scroll down A very good price is less than a dollar a foot. 500 foot loop circuit resistance = .509 ohm http://wesbellwireandcable.com/PortableCord.html http://wesbellwireandcable.com/SOOW/SOOW10-3.html - 250 ft - $ 247.50 http://www.americord.com/bulk-cable/prod_537.html - 250 ft - $ 217.50 Cord Nomenclature http://www.americord.com/glossary http://www.cables.com.tw/yuefeng/glossary.htm Crimped and soldered terminal lugs with screws are to be used to hook up the 3 conductor connecting cable. Plugs and receptacles to connect the charging and switching circuit to the a.c line. http://en.wikipedia.org/wiki/IEC_connector , IEC 320 C19 / C20 , cords are not available ready made in 30 amp rating, but can certainly be wired with 10 AWG wire and provide a secure connection , the pins are robust enough and provide better moisture seal. [url]  [url]The following rewireable plug must have the 2 piece mating seam sealed with epoxy http://www.mouser.com/Search/Refine.aspx?Keyword=4789.1200 http://www.schurterinc.com/pdf/english/typ_4789.pdf http://www.mouser.com/Search/Refine.aspx?Keyword=4797.0015 http://www.schurterinc.com/pdf/english/typ_4797.pdf http://www.apcmedia.com/salestools/SADE-5TNRML_R0_EN.pdf http://www.feller-at.com/English/Feller-GP-E.htm NEMA Standard connectors ( If you must , use these , but are comparatively very large ) http://www.hubbellcatalog.com/wiring/catalogpages/section-b.pdf see B-17 to B-19 _____ Drawing ' D ' shows a practical circuit having the minimum components. Single Pole Single Throw / NO ( normally open ) switch ' S ' connects power to charge the capacitor(s) ' C '. Electron current flows through resistance ' R ', and parallel resistor ' r ' with series ' LED ' light emitting diode , through diode ' dx ' and ' Mid ' conductor , collecting in the negative ( - ) terminal of the the capacitor(s) ' C ', displacing current out of the positive ( + ) terminal flowing back through ' Top ' conductor and shunt diode ' D ' to the a.c. source. As it is charged , light emitting diode ' LED ' momentarily flickers on then darkens indicating that charging has occurred. Resistance ' R ' is to protect the small diode ' dx ' from excessive current when charging starts ). * * * For added safety a 10 amp fast acting circuit breaker ' X ' provides redundant protection for domestic wiring , serving also as a switch it now does the actual firing when turned on. The charging circuit is F I R S T switched off by normally open switch ' S ' before the charged circuit can be fired. Circuit breaker ' X ' fires the circuit by applying the a.c. line voltage in series with the cap(s) , effectively doubling the circuit voltage which arcs into conduction the Gas Gap arrestor ' gg ' near the peak of the a.c. sine wave. ' Top ' conductor channels the resulting current surge left and down shunt diode ' D ' to the a.c. source. In practice the 325 volt peak is minimal and very marginal to produce an arc across a spark gap , better is a " Gas Gap Arrestor " ( use 2 or even 3 in parallel and solder thicker leads on each ) ' gg ' - Gas Gap Arrestor - 444-GT-230L - $ 3.09 http://www.mouser.com/Search/Refine.aspx?Keyword=444-GT-230L http://www.mouser.com/catalog/specsheets/XC-600002.pdf ' gg ' - Gas Gap Arrestor - (RMO) CG2-230L , middle of this page - $ 2.75 http://www.surplussales.com/Semiconductors/SemiCTransSup.html [url]  [/url]http://sigma.octopart.com/510848/datasheet/Littelfuse-CG2230L.pdf http://octopart.com/search?q=CG2-230L , cheapest at Mouser http://www.mouser.com/Search/Refine.aspx?N=254139&Keyword=CG2-230L - $ 1.89 ' X ' - Single Pole circuit breaker - $ 10.99 http://www.mouser.com/Search/Refine.aspx?Keyword=845-1BU10R http://www.altechcorp.com/PDFS/R-Series.pdf http://www.mouser.com/catalog/637/1795.pdf - @ $2 each set of 3 breakers held by pins this has two 15 amp breakers which can work and is cheap enough to try out but needs to be dismantled http://www.sciplus.com/singleItem.cfm/terms/348 [url]  [/url]' S ' - Switch SPST / no - (SWP) 1175 , lower third this page - $ 3.75 http://www.surplussales.com/Switches/SWPushB-1.html [url]  [/url][url] [/url]' R ' - 30 ohm 5% 15W Power Resistors - $ 0.63 cents X 8 resistors ( 2 sets of 4 are to be wired in series for a total equivalent resistance of 15 ohms ) http://www.mouser.com/Search/Refine.aspx?Keyword=280-CR15-30-RC http://www.mouser.com/catalog/specsheets/XC-600041.pdf ' r ' - 8.2 kohm 5% 1/4W - $ 0.22 cents http://www.mouser.com/Search/Refine.aspx?Keyword=30BJ250-8.2K ' LED ' - Green LED - $ 0.26 cents http://www.mouser.com/Search/Refine.aspx?Keyword=351-5502-RC ' LED ' - Green LED - (SDI) LTL-4233 - $ 0.15 cents http://www.surplussales.com/Bulbs-Incan-Panel/LEDDisplay.html _____ Available capacitors that have a higher working voltage than the ~ 162 Volt peak that comes from the wall socket , require this voltage to be stepped up. Drawing ' E ' has the capacitor charged to a higher voltage with a transformer included in the circuit. Switch ' S ' flows electron current through diode ' dy ' into primary coil ' p ' of transformer ' T ' and ' Bot ' conductor back to the a.c. source , inducing a current in secondary coil ' s ' of transformer ' T '. Current flows through diode ' dx ' into ,' Mid ' conductor collecting in the negative ( - ) terminal of capacitors(s) ' C ' charging the elevated voltage , displacing current out of the positive ( + ) terminal flowing back through ' Top ' conductor down resistor ' R ', and parallel resistor' r ' with series light emitting diode ' LED ', into 'secondary coil ' s ' of transformer ' T '. ( * * where the wire crosses ' Mid ' conductor there is N O connection ) Light emitting diode ' LED ' momentarily flickers on then darkens indicating that charging has occurred. Firing as already explained is done by circuit breaker ' X ' with the charging circuit F I R S T switched off by normally open switch ' S ' before the charged circuit can be fired.. _____ Alternatively as explained in Drawing ' F ' using another capacitor as a half wave voltage doubler , ramps up the charging voltage to 2 times the a.c. line voltage. In phase - 1 - the capacitor is charged , then in phase - 2 - the reverse voltage of the a.c.line and the just charged capacitor add together in series aiding effectively doubling. Illustrated here _ http://www.gallawa.com/microtech/doubler.html Motor ' start ' capacitors are bipolar electrolytics , also called Non-Polarised or NP capacitors and are the most suitable for use in voltage doubling as they are designed for a.c. operation , but only if run briefly. Those with a Voltage rating higher than the ~ 125 VAC minimally necessary can be run for just a little longer before overheating ( over 85º C , impairment will occur ) (Cy) ' 270-324 uF, 250 VAC ( the range specifies plus or minus 10% variance from 300 uF ) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200326166634 http://www.amazon.com/dp/B000LERFO4 , ( the point here is shop around ) These here are perfectly adequate _ http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230281260691 - $ 4 each http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370198861276 Motor ' run ' caps can operate continuously but have much less capacitance, or are much more expensive for equivalent capacitance, and larger. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310028799378 - $ 12 each Capacitor testing - http://toad.net/~jsmeenen/capacitor.html U.S. a.c. power lines typically achieve a peak of ~ 162 volts which provides the equivalent of 115 volts direct current, called R.M.S. ( root mean square ). You may wonder why a.c. capacitors have the seemingly odd rating of 125 volts. 60 cycle a.c. is 120 half cycles of alternating polarity, voltage rises from zero to peak voltage after 1/240 of a second (.004167) ( yellow portion shown below ) and over the next 1/240 of a second drops back to zero again ( green portion ) repeating this rise and fall but in reverse polarity for the following half cycle. ( orange and lime ) [url]  [/url]This sets the time available for the percentage of the supplied line voltage a capacitor will charge up to during the rise of one half cycle. It is not instantaneous. Re-arranging the folrmula : Xc = .159 / f C , C = farads f = frequency , Xc = capacitive reactance of the capacitor expressed as ohms , thus : XcC = .159 / f , = .159 / 60 , = .00265 , which is effectively the minimum RC time constant ( TC ) for any capacitor at this frequency ( without considering additionally the ESR which will make the time constant longer ) It does not matter what size capacitor or what voltage is applied to it, this value is set in stone, it is characteristic of 60 cycle a.c. and cannot be changed. Dividing the rise time .004167 by .00265 , = 1.57 TC ( Time constants ) works out to 79 percent of peak a.c. line voltage , or 128 volts. This in practice will never be seen due to the resistance present in the capacitor, this despite that the capacitor will still be charging slightly even as the a.c. line voltage is dropping , until both are equal. As the applied a.c. voltage decreases the capacitor will discharge through the a.c. source. The capacitor will not be completely discharged when the a.c. line voltage reverses polarity, but as the polarity is now the same as the capacitor polarity, the voltages aid, quickly discharging the capacitor the rest of the way. When the applied a.c voltage reverses direction, the capacitor is charged again, and the entire process is repeated with the next half cycle of the a.c. waveform. The waveform of an applied sinusoidal a.c.voltage will remain unchanged and only its amplitude ( peak value ) will be affected. Hence when measuring the voltage pole to pole on a capacitor in series with an a.c. line you detect a voltage drop, just as though it were a resistor, this is the capacitive reactance. http://www.electronics-tutorials.ws/capacitor/cap_8.html In a half wave voltage doubler , diodes are used to block one phase of the a.c. waveform so that the capacitor remains charged when the polarity is reversed. When the polarity again changes , charging continues where it left off incrementally raising the voltage charged in the capacitor ever closer to the a.c. supply voltage. _____ Drawing ' G ' shows this scheme. - In the first a.c. phase current flows up from ' Bot ' conductor through resistor ' R ', and parallel resistor ' r ' with series ' LED ' light emitting diode , to motor start capacitor ' Cy ' , diode ' dy ', and switch ' S ' back to the a.c. source. ( Resistance ' R ' is necessary to protect the small diodes ' dx , dy , dz ' from excessive current when charging starts ). - In the next a.c. phase switch ' S ' flows current through diode ' dx ' , into ' Mid ' conductor, collecting in the negative ( - ) terminal of capacitor(s) ' C ', displacing current out of the positive ( + ) terminal flowing through ' Top ' conductor , and down diode ' dz ' ( * * NOTE where the wire crosses ' Mid ' conductor there is N O connection ) into motor start capacitor ' Cy ' where the a.c. line voltage acts in series aiding , to raise the charging voltage on capacitor(s) ' C ' to double a.c. line voltage. As it is charged , light emitting diode ' LED ' momentarily flickers on then darkens indicating that charging has occurred. Firing is as before done by circuit breaker ' X ' and switch ' S ' turned off F I R S T before the charged circuit can be fired. When fired , the a.c. line voltage applied in series aiding effectively raises the circuit voltage to 3 times the a.c. line voltage , enough for spark gap ' G ' to arc into conduction , current surges into the positive ( + ) terminals of cap(s) ' C ' displacing current from the negative ( - ) terminals of capacitor(s) ' C ' left through ' Mid ' conductor and circuit breaker ' X '. ' Top ' conductor channels the current surge left and down shunt diode ' D ' to the a.c. source. ' dx , dy , dz ' - Small ~ 6 amp diodes - (SDI) MR756 - $ 0.30 cents ( 2 of these are to be wired in parallel for each of ' dx , dy , dz ' a total of 6 diodes ) found down a bit from the top , use the " find on this page " function of your browser http://www.surplussales.com/Semiconductors/Diodes-Rectifiers-5.html ' G ' - Air Gap - 350 to 600 volts - (RMO) WP438 - near the bottom of this page - $ 3 http://www.surplussales.com/Semiconductors/SemiCTransSup.html [url]  [/url]Using Rectifiers In Voltage Multiplier Circuits http://www.eettaiwan.com/ARTICLES/2001JUN/2001JUN14_AMD_AN2009.PDF _____ Drawing ' H ' Omitted for clarity but an essential part of any such devices is a means for safely discharging the stored energy of a bank of capacitors. This must be attached and operable before the capacitors are ever charged . Under no circumstances E V E R handle any part of these devices when charged except to fire ! Until after you have completed the ritual described in the next 2 paragraphs the circuit must be considered to be charged even if it has been fired - there may still be residual charge. Attached to ' Top ' conductor parallel with the shunt diode ' D ' is a 2 meter length of wire with it's other end soldered to a strip of metal on one edge of a small wood block ' B '. On the opposite edge of wood block ' B ' is another strip of metal soldered with a wire that's hooked to one terminal of an otherwise unconnected a.c. plug ' E ' ( kept safely inside of a glass jar ) this will be inserted instead of the power cord into the surge generator. Wood block ' B ' is to be weighed and submerged in a small bucket of water acidified with a supermarket bought pint bottle of lime juice ( citric acid ). This water " resistor " will harmlessly dissipate the charge. To discharge by using this circuit instead , the entire device must F I R S T be powered off by disconnecting from the a.c. line altogether and instead connected to plug ' E 'Switch On circuit breaker ' X ' to conduct the charge through the corresponding terminal of the a.c. plug into the receptacle wired to the water bucket. This above is simply a very cheaply implemented expedient contrivance to obviate more elaborate alternative permanent wiring to the circuit which will be outlined in the closing post. A circuit can include instead a compact drain resistor network. Wire wound power resistors can withstand Intermittent loading 10 times their rated power for short pulse durations provided duty cycle limitations are observed. The best compact size and price per watt is for wire wound cement types in 15 or 25 watt rating. Remember that 95 % of the energy will dump during the first 1.5 RC time constant. The reciprocal of capacitance 1/C is the resistance value for an RC time constant of one second. This means that 95 % discharge of energy will occur in 1.5 seconds. To provide an equivalent resistance that gives a discharge time long enough to stay within the power handling capabilities of the resistor network first calculate capacitor bank energy. An example using 6000 uF charged at 450 volts , E = CV^2/ 2 = 607 Joules = ( .006 X 450 X 450 ) / 2 . Divide 607 Joules by the maximum excess loading factor 10 , to obtain the combined watt rating of the resistors to be used. 60.7 is most closely 4 X 15 watt resistors. Now divide " 10 " by the capacitance thus 10/.006 , to give a value of 1667 ohms ( 1600 nearest manufactured value ). Alternatively , r.m.s. discharge voltage (.707 X 450 ) is 318. Using P = V^2/ R re-arranging to R = V^2/ P , ( 318 X 318 )/60.7 = 1666 ohm , same thing * Dividing V^2 by full value , 607 Joules , resistance is 167 ohm same as with 1/C . 1600 ohms will discharge 95 % in 15 seconds , total discharge after 50 seconds, why it is advisable to overload the resistors and use much less ressitance value, by choosing instead to divide 1.5 or 2 by the capacitance . A series of 4 groups , each with 4 resistors in parallel , 16 total , costing from $ 9.12 to $ 15.84 - See Mouser catalog link below _ can be secured on both sides of a thin aluminum plate ( If all resistors are the same value then that value will be the equivalent combined resistance ) and will give adequate heat sinking 10 times the actual 240 or 400 watt rating. Using P = V^2/ R ( 318 X 318 )/62 = 1631 watts , what a hair blower/dryer consumes per second. Choosing a 62 Ohm resistor , one group of 4 in parallel can serve double purpose as the current limiting resistance for the charging circuit. http://www.mouser.com/Search/Refine.aspx?N=4141191+4294966099+42945... http://www.mouser.com/Search/Refine.aspx?N=4141191+4294966099+42945... http://www.mouser.com/catalog/specsheets/XC-600041.pdf _____ Aluminum electrolytic capacitors provide the highest energy pulse for their size. Capacitance and voltage vary inversely , you will find those sizes having optimal energy storage occurs at a few thousand uF at a few hundred volts. Select one specifically designed for Strobe and Photoflash applications, these are made with very low ESR ( Equivalent Series Resistance ). Larger capacitance has lower ESR , in the range of interest typically around 0.1 ohm or less. This type can best provide the firing pulse. Price and sizes vary greatly, shop around. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260350709930 - 2 X $ 35 This one here is 150 Joules in 100 cc ~ ( 40 X 80 mm ) ' C ' - Electrolytic Power Capacitor - 1500 uf 450 VDC - $ 5 , salvaged * * Marx Generator made up of 10 of these = 1500 Joules http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140322028747 * Note if this auction has ended, scroll down to the original offer and . . select " View seller's other items ". This offer is regularly repeated. Observe dummy terminal pinout-code VRD pg 13(pdf) , guidelines pg 19 , 20 , 21, (pdf) http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-all-e1001i-090126.... available new from United Chemi-Con Caps - http://www.ucccaps.com http://www.ucccaps.com/detail.aspx?ID=103647 http://www.ucccaps.com/detail.aspx?ID=105567 Described as " snap mount " usually implies " spade " type terminals for mounting with spade wire lugs for easy replacement when servicing appliances. These are not that kind and are best mounted on a board with terminals soldered. - As we shall see , output of these caps can be doubled to 300 Joules per 100 cc. _____ Hi Energy Cap http://www.gaep.com/tech-bulletins/large-high-energy-density-capaci... Electrolytic Technology & Design http://www.elna-america.com/tech_al_principles.php Aluminum Electrolytic Application Guide http://www.cde.com/catalogs/AEappGUIDE.pdf Electrolytic Capacitors - Testing, Care & Storage http://www.jammaboards.com/guides/Capacitor_Testing.pdf also online here - http://www.repairfaq.org/sam/captest.htm ESR http://www.gaep.com/tech-bulletins/capacitor-engineering-bulletins.... http://www.faradnet.com/deeley/book_toc.htm Capacitor Service Life http://www.liebert.com/common/ViewDocument.aspx?id=1210 These electrolytics are polar and cannot stand reverse bias , but can be discharged while connected in series aiding , providing there is a diode ' D ' parallel , serving to prevent reverse charging as described before. This is the most expensive item of the circuit selling for 30 to 55 dollars U.S. A 600 volt 300 amp ( or better ) chassis mount stud type Diode with flag terminal. one of this -> ' D ' Stud Diode - ( 300 amp - 600 volt ) - $ 30.44 http://www.mouser.com/Search/Refine.aspx?Keyword=844-300UR60A http://www.vishay.com/docs/93508/93508300.pdf http://sigma.octopart.com/12038/datasheet/Vishay-300UR60A.pdf, similar to these [url]  [/url][url] [/url]A diode of lesser current rating ( and therefore cheaper ) can withstand brief surges , but it won't last for very long through repeated firings of this type. Alternatively several cheaper lesser rated diodes may be used in parallel , for example , 4 of these -> ' D ' Stud Diode (SDI) 70HF40 - ( 70 amp, 400 volt ) - $ 0.50 cents salvaged for anything higher than it's 400 volt rating , 2 in series 4 times , 8 total. look down near the bottom , use the " find on this page " function of your browser http://www.surplussales.com/Semiconductors/Diodes-Rectifiers-3.html http://sigma.octopart.com/511589/datasheet/Vishay-70HF40.pdf or 3 of these -> ' D ' Stud Diode - ( 95 amp - 800 volt ) - $ 6.82 http://www.mouser.com/Search/Refine.aspx?Keyword=844-95PF80 http://www.vishay.com/docs/93532/93532.pdf General information on diodes. http://www.kilowattclassroom.com/Archive/DiodeRec.pdf _____ The seller of the 1500 uF cap listed above , correctly observes that 10 of those arranged into a Marx generator , ( a device to charge caps in parallel and then discharge them together in series ) will produce a 4500 volt output ( 450 volts each, times 10 ) but at only 150 uF equivalent capacitance ( 1500 uF / 10 ) for a total 1500 Joules. http://www.allaboutcircuits.com/vol_1/chpt_13/4.html http://home.earthlink.net/%7Ejimlux/hv/marx.htm http://www.kronjaeger.com/hv/hv/src/marx/index.html http://www.electricstuff.co.uk/marxgen.htm Greinacher Cascade Multiplier _ http://www.instructables.com/id/High_Voltage_Power_Supply_For_Marx_... see parts (CFP) YE-TW-3 and (CFP) YE-TW-6 , here _ http://www.surplussales.com/Capacitors/motorstart.html http://www.techlib.com/files/voltmult.pdf http://www.amazing1.com/download/MARXIU1045.pdf http://www.celnav.de/hv/hv3.htm http://www.celnav.de/hv/hv4.htm Here is a real big one ->http://skyfi.org.ru/photos/2008/marksgen/005.jpg http://skyfi.org.ru/photos/?path=marksgen Drawing ' I ' shows this with just 4 caps , gaps and diodes in place of resistors, ( anyone of the already outlined charging circuits can be used here ) switch ' S ' flows current through resistance ' R ', and parallel resistor ' r ' with series light emitting diode ' LED ', up diode ' dx ', into ' Mid ' conductor, through diodes ' d1 ' collecting in the negative ( - ) terminals of capacitors ' C ', displacing current out of the positive ( + ) terminals flowing through diodes ' d2 ' and out diodes ' dy , dz ' into ' Bot ' conductor back to the a.c. source. ( one 600 volt diode as ' dx , dy ' in line , per every 3 capacitors to resist reverse breakdown during firing if caps are charged at just a.c line voltage , add more diodes as needed if caps are charged at higher voltage and substitute spark gaps for the gas gaps ). As it is charged , light emitting diode ' LED ' momentarily flickers on then darkens indicating that charging has occurred ( this is also necessary to protect the small diodes from excessive current when charging starts ). The charging circuit is to be switched off F I R S T before the charged circuit can be fired. A normally open switch accomplishes that. Circuit breaker ' X ' fires the circuit by applying the a.c. line voltage in series with the caps ' C '. Current is drawn back through ' Mid ' conductor from the negative ( - ) terminal of the left cap ' C ' which arcs into conduction the left Gas Gap ' gg ' , in an avalanche cascade , current surges from the negative ( - ) terminals of all caps ' C ' across Gas Gaps ' gg ' into the positive ( + ) terminals of cap(s) ' C ' to arc into conduction Spark Gap ' G ' where from current surges into the positive ( + ) terminal of the right cap ' C '. ' Top ' conductor channels the resulting current surge to the a.c. source down shunt diodes ' D1 , D2 ' in series to resist reverse brealdown during firing. ______ Given the example of the 1500 uF 450 Volt cap , it can be charged at 3 times the peak domestic U.S. a.c. value of 162 volts (* 115 volts X √2 ) to 486 volts ( note that overcharging slightly ~ 8.5 % is perfectly alright providing it is discharged promptly and since it is static and not subjected to cyclical deep discharge at a.c. line frequency which will cause overheating and breakdown failure ). Voltage of the ten caps ( 10 X 486 ) + 162 peak a.c. line voltage add to 5022 volts By E = CV^2/ 2 , E = Joules , C = farads , V = volts 1891 Joules = (.00015 F X 5022 X 5022 ) / 2 , , or as Dirty Harry ( Clint Eastwood ) would say - " will blow your head clean off " - , this is not an exaggeration , 1891 Joules is equivalent to 1395 foot pounds of muzzle energy , a proof load for the .44 caliber remington magnum , and nearly the equal of the large heavy power cap shown above. Loud blowing up of fruit http://www.youtube.com/watch?v=aWf-V2-kr9Q Here is what happens with 9 kJ - equivalent to a .50 caliber Browning Machine Gun round. from http://www.powerlabs.org Just think , that could be you all over the street.  9kJ is what a hair blower/dryer consumes in only six seconds The short time interval of the pulse makes all the difference. Read Overview here _ http://en.wikipedia.org/wiki/Pulsed_power - This is continued in the following post - ___________________________________________  | |||||||||
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| - continued from the post above - If 2 capacitors ' C ' are placed in a circuit so that both are in series , as in the Marx layout , equivalent capacitance then becomes 750 uF , but the voltages in series add 486 + 486 , plus the a.c. power line voltage of 162 peak comes to 1134 volts at firing. By E = CV^2/ 2 , (.00075 F X 1134 X 1134 ) / 2 , = 482 Joules Drawing ' J ' - T H I S . I S . T H E . O N E . T H A T . M A T T E R S Alternatively if both capacitors are placed instead in parallel as in circuit Drawing ' J ' , the equivalent capacitance is the sum of both , 3000 uF. The firing voltage remains the same , charged to 486 volts ( 3 times peak a.c. line voltage ) plus the a.c. power line voltage boost at firing comes to 648 volts. By E = CV^2/ 2 , (.003 F X 648 X 648 ) / 2 , = 630 Joules THE LESS ELABORATE CIRCUIT OUTPUTS . 1 4 8 . JOULES MORE POWER ! Employing the higher voltage rated caps ~ 450 volts requires a voltage tripler circuit and an additional charging a.c. motor start capacitor. This is outlined in Drawing' J ' Single Pole Single Throw switch - SPST / no ( normally open ) ' S ' connects the charging circuit of a.c. motor start capacitors ' Cx , Cy ' & diodes ' dx , dy '. ( * * NOTE where the wires cross ' in between ' Cx , Cy ' there is N O connection ). Half cycle ' 1 ' charges the caps and half cycle ' 2 ' applies both voltages in series with the a.c power line voltage to diodes ' d1 , d2 ' and the firing capacitors ' C ' charging them in parallel to 3 times the a.c. voltage. Electron current flows through diode ' d1 ' into ' Mid ' conductor collecting in the negative ( - ) terminals of caps ' C ' displacing current out of the positive ( + ) terminals flowing through ' Top ' conductor and down into diode ' d2 ' ( * * NOTE where the wire crosses ' Mid ' conductor there is N O connection ). Resistance ' R ', is necessary to protect the small diodes from excessive current when charging starts. Parallel with ' R ' is an a.c. voltage rated light bulb ' B ' to provide visual indication when it momentarily flickers on then darkens indicating that charging has occurred. Firing as before is done by circuit breaker ' X ' with switch ' S ' turned off F I R S T before the charged circuit can be fired. Circuit breaker ' X ' fires the circuit by applying the a.c. line voltage in series with the cap(s) , which arcs into conduction the Spark Gap ' G ' near the peak of the a.c. sine wave. ' Top ' conductor channels the resulting current surge left and down shunt diode ' D ' to the a.c. source. I want to emphasize that it is possible to achieve equally high energy and power surge levels using fewer components than for the Marx generator mentioned above. Compared to the 1891 Joule Marx generator of 10 - 1500 uF caps , just 6 of these caps in parallel as in Drawing ' J ' would be 9000 uF , then By E = CV^2/ 2 , 1890 Joules = (.009 F X 648 X 648 ) / 2 EQUIVALENT OUTPUT OF JOULES USING FEWER COMPONENTS ! The circuit performance is improved by eliminating the extra resistance that is present with the extra components and wiring. By having a bank of capacitors in parallel , just as with resistors in parallel , equivalent resistance is greatly diminished , ( the exact opposite of series resistance! ). http://www.electronics-tutorials.ws/resistor/res_4.html http://www.electronics-tutorials.ws/capacitor/cap_6.html http://www.electronics-tutorials.ws/capacitor/cap_7.html The same as with batteries , for capacitors in series the voltages add , for capacitors in parallel the currents add. The RC time constant remains unchanged for either configuration because the ESR of individual caps does not change. TC = R X C = ( 0.1 X .0015 F ) = .00015 sec - | - For six 1500 uF caps in series the errected capacitance is ( 1500 / 6 ) = 250 uF, the ESR value of each adds so that 6 X 0.1 ohm = 0.6 ohm , TC = R X C = ( 0.6 X .00025 F ) = .00015 sec. - | - For six 1500 uF caps in parallel capacitance adds totaling ( 1500 X 6 ) = 9000 uF, equivalent ESR of the bank reduces to ( 0.1 ohm / 6 ) = .0167 ohm , TC = ( .0167 X .009 F ) = .00015 sec. also By graphing power relative to time as it appears on an oscilloscope, energy is represented by the area under the power trace. Capacitor ESR establishes how brief the RC time constant is and how narrow the pulse. By varying the voltage , the only thing that can be altered is the leading slope of the pulse ( and the height ) not its width ( the area remains constant because the energy is the same ) Very short pulse durations are only acheived by capacitors having exceptionally low ESR. As these do not have large capacitance, they must have a very high voltage to store significant energy.The increased resistance of the series circuit depletes more power and is less efficient. More importantly with lower voltage one can dispense with heavy high voltage insulation requirements to obviate systemic breakdown ( arcing ) which occurs at kilovolt levels. At kilovolts everything is huge http://www.celnav.de/hv/hv1.htm Of course lower voltage produces comparatively longer current rise time ( all things being equal ) but it won't matter given the following current surge. The rated energy per cap at 450 volts is 150 Joules times ten caps is 1500 Joules. By slightly overcharging to 486 volts plus the boost from a.c. line voltage applied in series during it's discharge , output is increased to 3149 Joules = (.015 F X 648 X 648 ) / 2 slightly more than the 165 pound 240 uF high voltage capacitor mentioned at the beginning of this post. Yet this device is small enough to fit into a shoe box and weigh less than a 3 liter bottle of soda. How to size a capacitor bank , specific for ultracapacitors but generally applicable. http://www.powerdesignindia.co.in/STATIC/PDF/200807/PDIOL_2008JUL31... See attachment below - Equivalent Series Resistance & Maximum Leakage.rtf - One can determine all the values for one capacitor and then simply - - multiply by the number of caps to obtain the output of all. Thus: By E = CV^2/ 2 , (.0015 F X 648 X 648 ) / 2 = 315 Joules - - 315 X 6 = 1890 Joules ESR of one 0.0015 Farad cap is ~ 0.1 ohm R in value TC ( Time Constant ) by R X C = TC , 0.1 X .0015 = .00015 sec Average power of a single cap is ( 315 joules / .00015 ) = 2,100,000 watts - - times 6 ( caps ) is 12.6 megawatts combined average power. Mean voltage is close to the RMS ( Root Mean Square ) value ( Peak voltage is ~ 648 ) X 0.707 = 458 volts Dividing 2,100,000 watts by 458 volts = 4585 amps average current - - 4585 X 6 caps = 27510 amps. A related thread on this topic http://www.sciencemadness.org/talk/viewthread.php?tid=6032 Pulsed power has many varied applications. http://www.nessengr.com/links.html A pulse can serve to energize a laser, or a maser ( its equivalent in the microwave region ). Jolt a coil generating intense magnetic flux or provide the feed current to a magnetic flux compression generator. This remains an area of endeavor into high energy physics within the means of shoe string budgets. http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator Coin shrinking - http://205.243.100.155/photos/shrinker5.pdf applying the data just derived above on a 20 turn coil of 1/2 inch ( 12.5 mm ) using flat tape conductor as this _ http://www.keison.co.uk/furse/conductors_flat_tape.htm The more squat the coil the higher the induction Flux Density (in Gauss ) = N I / (2.02 × L) Where: N = # of turns of wire on coil I = current flowing in coil ( Amperes ) L = length of coil ( Inches ) Flux Density (in Gauss ) = ( 20 )( 27510 A ) / (2.02 × 0.5”) = 54.5 Teslas 54.5 times the 10,000 gauss a Neodymium magnet has in a closed armature , which is 5 times what the 2000 gauss open air or gap flux will be , 272 times more. In other words, the field of a rectangle of Neodymium magnets 16 by 17, 272 total, compressed into the space of one Neodymium magnet. No wonder the coils explode. Due to the rapid rise and fall of the field , the induced eddy current in the coin will be far greater. Which is why you do not want the induction from a wide loop of connecting cable to couple to the surroundings where it does nothing but subject the tape collection you keep in the room above the garage to an EMP , : -O The energy must remain in the wires all the way to where it has to act. More than you probably want to know _ http://www.mse.eng.ohio-state.edu/%7EDaehn/metalforminghb/tabofcont... - V E R Y , V E R Y , I M P O R T A N T - It is not my responsibility to protect you from your irresponsibility. If you do not understand what is detailed here which is as basic as it gets , or what a ground fault is and how not to create one , you are at serious hazard of electrocuting yourself when you become an unwitting part of the circuit. ( " Electrocute " is a word derived from the invention of the electric chair, meaning electro - execution , if you auto - electro - execute , you are automatically eligible for a Darwin award. ) A 20 kilovolt discharge when it is the result of static buildup from walking on a carpet is merely startling due to the miniscule power. A several hundred Joule pulse at this same level will kill you instantly if received in one hand and out the other hand. If only one arm or leg is affected it will knock you out cold and due to the resulting nerve damage you may never be able to use that arm or walk well again. Standing on a dry rubber mat when outside is good practice. Not directly touching the firing switch is life saving practice , use a stick. http://www.repairfaq.org/sam/safety.htm In order not to cause havoc and collateral ruin , the a.c. branch line used must be directly wired to the main service panel power transfer switch, from the utility. Nothing else will do. Preferably with its own circuit breaker since you W I L L trip a circuit breaker. Do not bypass the utility meter, it's surge arrestor safely adds another cutoff point. There cannot be any lighting or running domestic appliances even in standby mode , such as televisions , air conditioners , refrigerators , including ones you have not thought of such as the water heater , kitchen stove ignitor ( without gas pilot ), timers , clocks , or alarms. Everything off on that branch line , preferably disconnected. If you have any doubts at all consult an electrician first. Finally, house wiring of aluminum is not suitable for this method, nor if it has been de-rated from original installation, is more than 40 years old or is cotton asphalt insulated. All these pose potential risk for starting fire. ____________________________ Triggered Switches Below is collected wisdom from the internet on over-voltage gaps The spark gap length / voltage relationship varies with electric field distribution, but spark lengths usually range roughly from .28 to .9 mm. per kilovolt of peak voltage at voltages in the 4 to 35 KV range. Significantly longer spark lengths in millimeters per kilovolt can occur at peak voltages near or above 50 KV. This is for air at normal sea level atmospheric pressure. Longer sparks can occur at high altitudes. A spark gap can be triggered in many ways, but there are two main types, those which trigger via localized ionization ( via a secondary spark, point corona, UV laser, ionizing radiation, flame etc.) and those which trigger via altering the breakdown potential of the gap along the Paschen curve ( such as spark gaps which are initially pressurized and then bled to provoke conduction ). The x-axis of the Paschen curve is measured in mBar-mm ( the product of pressure and separation ), with the y-axis being in kV. If the separation is constant and the pressure is reduced the breakdown potential decreases until the gap fires, likewise if the pressure is constant and the separation is reduced the breakdown potential decreases until the gap fires. Being that such a gap triggers itself by lowering the separation ( but not touching ) it can be said to fall into the latter of the two types. If the contacts touch to conduct then it would be a mechanical switch. Gas discharge tubes are filled with special gases with low dielectric potential designed to arc-over ( that is, start conducting electricity ) at predictable low voltages. In other words, the gas-tube is a closed environment that allows lightning-like pulses of electricity flash through. By selecting the right gas and separation of electrodes in the tube, engineers can set a precise flashover voltage. Gas tubes can conduct a great deal of power--thousands of kilowatts--and react quickly, typically in about a nanosecond. They are faster than MOVs ( Metal Oxide Semiconductors ) and less likely to be damaged by large surges. On the negative side, a gas tube does not start conducting ( and suppressing a surge ) until the voltage applied it reaches two to four times the tube's rating. The tube itself does not dissipate the energy of the surge; it just shorts it out, allowing your wiring to absorb the energy. Moreover, the discharge voltage of a gas tube can be affected by ambient lighting ( hence most manufacturers shield them from light ). Worst of all, when a gas tube starts conducting, it doesn't like to stop. Typically, a gas tube requires a reversal of current flow to quench its internal arc, which means that the power going to your PC could be shorted for up to 8.33 milliseconds, the length of a single half cycle of utility power. Sometimes gas tubes continue to conduct for several AC current cycles __________________________ F O O T N O T E S TM 5-692-2 Maintenance of Mechanical & Electrical Equipment http://www.army.mil/usapa/eng/DR_pubs/dr_a/pdf/tm5_692_2.pdf From top page 28-2 A lightning stroke to a power system develops very high surge voltages across equipment and line insulation systems. If these voltages exceed the insulation strength, a flashover occurs. Once lightning enters a power system, the surge current is unlikely to cause any damage. Although the current may be extremely high, it is very short lived and can easily be handled by a small conductor. The largest recorded conductor to be fused or vaporized by a direct stroke was an American Wire Gage (AWG) No. 10. The size of conductors, installed expressly for conducting lightning currents, is usually determined by mechanical strength considerations, rather than by current-carrying capacity. On some rare occasions, overhead ground wires have been severed by lightning at the point of contact. This is probably due to the stroke channel heating the conductor at the point of impingement, rather than from simply conducting the lightning current. _______________________ Transient Overvoltages In Electrical Distribution System & Suppression Techniques http://www.nalanda.nitc.ac.in/nitcresources/ee/lectures/VoltageTran... From middle paragraph page 12 In applications where there is a normal operating voltage, as in the AC mains, there is a possibility that the gas tube will not reset itself once it has fired and suppressed the transient. This condition is known as " follow on " current and is defined " as the current that passes through a device from the connected power source following the passage of discharge current ". Follow on current will maintain conduction of the ionized gas after the transient has disappeared and the concern is that the follow on current may not clear itself as the a.c current drops to zero and will result in a permanently destroyed gas tube. In an AC mains application it is not sufficient to rely solely on the crossings of the sinusoidal voltage to extinguish the follow current. _______________________ Grounding, Bonding, & Shielding For Electronic Equipment Vol II & I http://www.tech-systems-labs.com/books/grounding.pdf From middle page 1-68 , Vol II (1) Follow current. The typical discharge (arc) voltage across a spark gap is 20 to 30 volts while it is in full conduction. Because of the low arc voltage, the voltage and current available from the ac power supply would maintain the spark gap in an on state after a transient was dissipated until the first zero crossing of the power supply or until a supply line fuse opened, a line burned open, the spark gap burned open, or the service transformer burned open. __________________________________________ Attachment: Equivalent Series Resistance & Maximum Leakage.rtf (264kB) This file has been downloaded 1300 times | |||||||||
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| GoatRider |
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I blew up a switching power supply regulator when I misread the pinout and hooked +V to ground. It had a ceramic package, there were bits of ceramic thrown across the room. | |||||||||
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| zed |
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Interesting. My friend Dr. Crazyfingers built an exploding wire device many years ago. Folks like Magicians and the special effects people from the Lucas related "Industrial Light and Magic" where interested in the effect. Unfortunately, he was trying to achieve the effect with a very small gauge, round, copper wire(nearly invisible).....and his results were inconsistent. During development, his potential clients found a string form of chemical explosive that was reliable and easy to handle, and he reluctantly abandoned exploding wire experiments. He did however, impart a little high voltage wisdom to me, while the project was ongoing......."Don't point at that giant capacitor....Damn it" "This stuff points back!" [Edited on 23-6-2009 by zed] | |||||||||
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| franklyn |
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| Available again - Get'em while they last ! ' C ' - Electrolytic Power Capacitor - 1500 uf 450 VDC , 150 Joules in 100 cc ~ ( 40 X 80 mm ) - $ 5 , salvaged -> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140330869...  . | |||||||||
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| 12AX7 |
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Electrolytic? Pffifle. Too much inductance. http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank.ht... I estimate this bank has 20.0uF capacitance, 0.1uH ESL and around 0.003 ohms ESR. That's a time constant of about 2.3 microseconds. The caps are rated 630VDC max, 1.5 x overload for short periods, so could in principle run up to nearly 1kVDC. (That's all of 10 joules stored energy.) A short directly across the terminals would take 2.3us to turn that 1kV into 0V at approximately 14kA (minus losses). If voltage falls linearly while current rises linearly during this event (a gross approximation to the damped sinusoid of reality), then the peak power will be on the order of 3.5 megawatts. (After the first 1/4 cycle, most of the energy (about 8-9J) will be in magnetic form, then after another quarter cycle it'll be back in the capacitors; etc.) Tim
Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout. Need engineering assistance? Drop me a message! | |||||||||
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| franklyn |
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| @ 12AX7 See the detailed explanation in the opening post a bit down from the top where it says Joules needed for vaporization of a 2 cm 28 AWG wire on how to determine the joules needed to blow the volume of metal comprising a bridgewire. You can calculate the weight with this _ http://circuitcalculator.com/wordpress/2007/09/20/wire-param... Knowing this you can now proceed to the next phase , of determining the capacitance and voltage to provide the needed energy You stated ~ 4 Joules = {( 20 uf ) X ( 630 volts ) X ( 630 volts )} / 2 10 Joules at 1000 volts is not realistic , if the rating is substantially exceeded the caps will fail , count on it. Of course you can get around this by placing 2 caps in series to withstand 2 X 630 volts. The energy will remain ~ 4 joules for the reduced equivalent capacitance of 5 uf Discharge time will not change , although the actual output certainly will be less. Read my third post above for why that is. The ESR ( Equivalent Series Resistance ) of the capacitor(s) determines what the discharge time will be. By your numbers the ' RC ' time constant has to be (.003 ohm ) X (.00002 farad ) = 60 nanoseconds , where 2.3 microseconds comes from I don't see. If you don't know or have a ' reasonable ' idea of what the ESR is ( from the manufacturer perhaps ) any ' surmise ' of a discharge time is just that, surmise. Voltage is irrelevant to anything but the determination of what the energy of the capacitance is. Higher voltage will only squash more of the energy into the leading part of the discharge profile. For the established ESR the pulse width remains unchanged regardless of any other changes. A higher energy pulse may be inferred from the truncated leading portion from what follows. Extremely short ( a few millionths of a second ) discharge times unless there is some other need besides just exploding a wire, is wholly uncalled for and unnecessary. A very big problem which rears up with short discharge times is the skin effect which overshadows any stray inductance by at least another 2 orders of magnitude. ( 100 times or greater ) You cite 2.3 usec ( I'll humor you for the moment ) frequency is the reciprocal of time , f = 1/ t , then the 2.3 millionths of a second translates to a frequency of 435 kHz. You will need at the very least a 32 AWG wire or much preferably smaller to lessen attenuation of the pulse. See this chart - http://www.powerstream.com/Wire_Size.htm posted just above this - Joules needed for vaporization of a 2 cm 28 AWG wire or calculate it here yourself _ http://www.mantaro.com/resources/impedance_calculator.htm#sk... also attached below _ True all of this is classic EBW technology and practice. The prevailing school of thought is a minute EBW subjected to a very brief pulse, which serves as a choke point to the pulse, thereby condensing the energy. The problems with this is that it requires very careful engineering with no ' wiggle ' room. If something is off by just a bit due to unforeseen parasitic losses , either because of lowered voltage reducing the needed energy, or stray inductance sapping it, then there is no bang. In my view and the point of starting this thread is that everything is wrong with this established approach and that it may work at all is a wonder. .  | |||||||||
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| 12AX7 |
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I know what my capacitors are rated for. From the data sheet, DC test voltage -- 1.6 * V_R (2 sec.) Operating voltage for short periods -- 1.25 * V_R (2000 hr.) They are 630VDC (250VAC) units, so they are safe to use at about 1008V for short periods (probably with reduced capacitance as a result, because these are self-healing type capacitors.) The datasheet also claims 60mohm typical ESR, which is around 3mohm for the 200 in parallel. (SRF is claimed as around 5MHz, but the hardware connecting them drops that noticably, to about 0.1uH total and a bulk SRF of 114kHz.)
No, the energy doubles because capacitance halved and voltage doubled. Or even more obviously, energy doubled because stuff doubled.
Actually, it will probably be longer, but how much depends on geometry.
Not at all certain. In fact, the two reasons capacitors are connected in series are these: one, to provide higher voltage capacity than otherwise available; two, to increase dI/dt (that is, rise time, and peak power as a direct result).
I would be quite impressed if you could suspend Ampere's law during a test fire of my capacitor bank. Sadly, Maxwell's equations come in fours, so this cannot be. As I clearly stated, my bank has a measured 100nH series inductance, thus forming a series resonant RLC circuit. As time constants go, the L dominates over the R, which is why your RC figure is absurd.
It is my understanding that EBWs require sharp rise times in order to produce a shockwave per se. Is that correct? A shockwave at 10km/s crosses a 28AWG wire (about 10 mils = 0.25mm diameter) in 25 nanoseconds, so it stands to reason that the wire must explode about as fast in order to produce a complementary shockwave. That's something you certainly will not accomplish with an electrolytic. If "shockwaving bridgewires" are, in fact, unnecessary, and mere "turning to an arc bridgewires" are sufficient, then yes, you could get away with an electrolytic. This is something else I do not know.
Non sequitur. Skin effect is due to self inductance. Skin effect also has no effect, given this kind of wire (you need significant energy beyond 10MHz to make 28AWG wire look futile; my cap bank will have little beyond 1MHz). If stray inductance is a problem (for instance, it is entirely the reason my cap bank has 100nH ESL -- although that's much better than the 500nH to 1uH a more naive layout would yield!), it can be shielded to some extent. Transmission lines, ground planes and coaxial fixtures are all worth considering in this regard. This is precisely how the atom bomb makers delivered nanosecond pulses to the slappers.
Again, as clearly stated in my post, 2.3us is the quarter wave time. This is the time it takes to transfer all the energy from one store to the other, i.e., from capacitance to inductance or back again. As you can readily calculate from circuit values, actual series resonant frequency (complete cycles of energy transfer) is around 110kHz. Please read my posts in their entirety -- it's not at all a chore, as my posts are generally short and concise (although I am making an exception in writing this one).
The only thing that I gather from your reply is that your established approach is wrong. I am sorry to say this makes four people* I have met on this forum who inextricably seem to know more electronics than myself, despite showing no proof of their talents, meanwhile attempting to proclaim their dangerously lacking knowledge as incontrovertible testament. I do not know much about exploding bridgewires, but if you are attempting to apply your present electronics knowledge, it does not surprise me in the least that you are drawing conclusions like "everything is wrong with the established approach". Instead of attempting to invalidate someone or something with much more experience than yourself, perhaps you should check yourself first. Tim * Four screen names, that is. Has anyone else wondered how you type exactly the same as Rosco? Oh, and it's still really badly formatted.
Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout. Need engineering assistance? Drop me a message! | |||||||||
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| franklyn |
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| @ 12AX7 I was going to add this opening bit to the item you're replying to by all means don't take my word for it. " Electrolytic? Pffifle. Too much inductance." http://www.bychoice.com/capacitor_DF.pdf Bottom of page 6 In the case of a capacitor, particularly in the low frequency range (30Khz and below), the XL term is extremely small compared to XC and can be ignored for computation purposes. http://www.avx.com/docs/techinfo/eqtant.pdf Read first 3 paragraphs page 1 , ending with the following _ " ESL is partly associated with the body of the capacitor and partly with the leads: the value of the latter part is proportional to the length of lead left on the capacitor when it is mounted in its circuit location. Provided that these leads are kept short, the effect of inductance can be ignored at frequencies below about 100kHz." From this we see that inductance is mainly a property of the connecting circuit rather than contribution from the electrolytic capacitor itself. General atomics has perhaps the best overview of ESR http://www.gaep.com/tech-bulletins/capacitor-engineering-bulletins.... _____________________________________ As to your rambling response - I have absolutely no idea what you are going on about. My take is that you are getting lost in math (which you do not disclose ) that has no bearing on pulse discharge physics, as you say " resonant RLC circuit " , is not really applicable. For example: capacitors in parallel are figured thus 10uf + 10uf = 20 uf capacitors in series thus : 10uf X 10uf = 5 uf 10uf + 10uf 100 pairs of 2 in series gets you to the same result. You didn't state it but I'm guessing 100nf caps , ( 20uf / 200 ). If you want 10 uf equivalent capacitance you would need 400 capacitors 200 pairs 2 in series. Yes double energy for double stuff. The original 20 uf bank would need to be 800 caps 400 pairs 2 in series. _____ Induction is the direct result of current, the more there is the greater the induction. Skin effect is just the result of rapid change in current. Taking an RC time constant as the reciprocal of frequency as I do is more of a rule of thumb approximation since the discharge is a spike and not a repeating waveform as such ( another reason circuit math doesn't mean much applied to this ) _____ I've been involved In electronics manufacturing all my adult life. I never got my EE, personal circumstances compelled me to drop out. I did get as far as partial differential equations and Fourier transforms all of which I have since forgotten. Maybe that's why. I'm reminded of Dorothy Parker, member of the Algonquin Round Table here in New York, who playing a parlor word game was once asked to make a sentence with the word horticulture and quipped, " You can lead a whore to culture but you can't make her drink " , alas . | |||||||||
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| Hennig Brand |
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My ESR meter(which I just dug out), says the cap I have(25uF@2KV,oil filled cylindrical can) is very close to zero esr. My meter is not very good for this at it is mostly used for testing to see if caps are fried or not. It looks to be around 0.05 ohms, which would give me a time constant(for the cap alone) of 1.25 microseconds right? Assuming everything else to be zero in the "perfect circuit", then this cap could potentially deliver 33 joules in that first time constant, since 2/3 roughly of the charge is delivered in the first time constant right? Assuming the ESD curves do look the same proportionately, more or less for the different capacitors(even electrolytics), would it be possible with the super fast, HV capacitor banks to build up more energy in the metal wire? Higher voltage caps with smaller capacitance will have a smaller time constant, since esr is usually smaller and capacitance is smaller. My feeling from common electrical laws is that the higher voltage will give less speed and power losses in the hook-up lines if done right(I think). This could maybe cause a more violent explosion of the wire from more energy being built up before the inertia of the wire is overcome(before explosive vaporization)? The higher tension caps could maybe also provide more umpf were it counts directly following, and during explosive vaporization? Maybe most of the overall speed differences are caused by the blast machine circuit and not the capacitors though usually? I will read more since I have the feeling you will point out something, about how the differences can be dealt with by using thicker bridge wire, different cable and circuit etc(I think you may have already once or twice). One thing I have noticed though is that electrolytics usually won' t cut the mustard if one wants the most tough reliable bank(they won' t take the abuse the others will). The rise time in the discharge curve is much longer, and can be more unpredictable, largely because of the more delayed and drawn out rise(greater error potential). They are just often very cheaply made to, even for what they are. One of the biggest reasons(commercially) for using these devices(EBW) is for multiple point, simultaneous, accurate detonations. There is not many fractions of a usec to spare many times before best results are not obtained and the system impractical. It does seem though that the high voltages of commercial units is not necessarily advantageous for single shots(single point), for the hobbiest as you have shown, which I didn' t understand before(took it for granted HV was neccessary). [Edited on 9-7-2009 by Hennig Brand] | |||||||||
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| franklyn |
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| @ Hennig Brand The .05 ohm ESR you measured is an expected value for paper oil caps. Don't dwell on charge, a capacitor's energy is in its voltage, work from that. I explained above that after 1.5 ( R X C ) time constant, 95 % of the energy has been discharged, and this can be considered the useful pulse width. Yes there remains another 3.5 time constants until the capacitor has completely discharged, but the remaining 5 % is very low grade energy, similar to the hot exhaust from an engine after most of the work has already been done. The energy is not proportional to the voltage , it is a square function of voltage. After 1 ( R X C ) time constant the remaining voltage is 37 % , but energy just 14 %. The 63 % drop in voltage accounts for 86 % of the energy. by ( C x V x V )/ 2 , = (.000025 uf ) X ( 2000 volts) X ( 2000 volts) / 2 , = 50 Joules so 50 X 0.86 = 43 Joules , expended after the first 1.25 microsecond. The physics of this are , ESR will determine the time constant , and to a lesser extent manipulating the capacitance and voltage relation to have the energy needed to explode a particular wire. Because , to have a short time constant you really also need a small capacitance , ( remember R C is R and also C ) In order to have meaningful energy this then has to be charged to very high voltage. You could instead work at half that voltage with four capacitors of equal value in parallel instead. But why stop there ? The quarrel I have with this approach apart from the ancillary headaches of dealing with high voltage and skin effect of hyper rapid current rise , is a short pulse only matters if you need high precision in timing a pulse. Any ordinary application of pulsed power requires no more precision timing than can be had with a doorbell push button, so why bother if you have no application for it. The question then too is do you have a Krytron available and the resources of a NIST certified calibration lab to take full advantage of this potential precision. This is power switching not small signal electronics , any ordinary gating scheme will trigger variably plus or minus in tens of microseconds , this is known as jitter. A few nanosecond pulse can occur anywhere along within that time frame. It is as if you use an atomic cesium clock to time the boiling of eggs, or drive a world land speed record holding jet car to the local convenience store. . | |||||||||
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| 12AX7 |
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And inductance simply doesn't matter? I ask again, are you able to suspend Ampere's law at will?
Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout. Need engineering assistance? Drop me a message! | |||||||||
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| watson.fawkes |
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This discussion, though, brings up a couple of questions for me.
[Edited on 11-7-2009 by watson.fawkes] | |||||||||
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| Hennig Brand |
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I did make a math boo-boo, it does change things for sure. I can' t remember what I did exactly, but I may have been calculating for coulombs then said joules(thats what it looks like I did), tricky, tricky! Will try and avoid charge and stay with joules and volts from now on. I am starting to think that it is pretty difficult to tell exactly what is taking place in this EBW senario, even with a good command of the electronics laws. Even normal electronics, at slower speeds etc, is studied mostly by looking at the effects of things changing that we can see, or using relatively simple instruments(except maybe by high level people). I sense, that to get a good feel, or any degree of accuracy would take some special doing. The easiest thing is to probably test, by trial and error, as is the case with a lot of hobby science experimenting(If the goal is infact to initiate explosives). The really small things probably come into play, and make huge differences. I am not trying to say we should abandon trying to understand as much as we can theoretically however. I think you may be right about the over-emphasis on the super short pulses, and it may not be as necessary as many tend to feel it is. We may be drawing some false conclusions, based on information regarding specific uses differing from ours for EBW caps. The amount of energy that goes into the before, and during explosive vaporization phase must be different for the different speed pulses though. Maybe this is not significant, but I am interested, and others may be able to provide some insite that I cannot. There must be a very limited portion of that first 1.5 TC that has the most impact on initiating ability. I would think as with chemical explosions, that not all are created equally, but it may be different in some ways for EBW. Maybe the differences aren' t that great, it would be fun to test maybe. In a lot of blasting manuals it describes EBW technology as being not too uncommon as a way of initiating multiple point source explosions(I don' t know what kind of accuracy and precision they get, or how much is needed for their purposes, but it is apparently used). The Germans apparently used this technology as well during the last World War, for mining and demolition(I think I read this awhile back). I would love to find some detailed information about their machines and how they were used in blasting. [Edited on 10-7-2009 by Hennig Brand] | |||||||||
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| dann2 |
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Hello, Paper here (my favourite communication tool as it gives the impression I actually know WTF they are saying  ).What is the length (approx.) time period involved when we declare that an EBW is actually able to detonate secondary explosives? (assuming we have enough Joules in that time period). There must be some (approx. ballpark) time period where time greater that this maximum period are considered simple too slow no matter that the pulse energy. From the paper (it's about making nano powders and has pulse times in the order of 2 to 4 micro seconds) there is a graph below and some text. It is a worthwhile read. _________________________________________ The copper wires used in our experiment are 196 micro m in diameter and 85 mm in length, which yields an equivalent inductance of 0.11 micro H calculated using Eq. (1). Figure 2 presents the waveforms of the discharge current and voltage measured in the experiment in which the energy storage capacitor was charged to a voltage of 20 kV. It shows a typical picture of exploding wire. The voltage begins to rise strongly when the current reaches its maximum of about 10 kA and then falls down, which means that the vaporization of the wire begins, leading to a rapid increase of the wire resistance. After the current falls down to a value of 3 kA, it rises up again, which represents an arc breakdown through the wire vapor, a shunting of the current by this low resistance arc. It should be noted that the experimentally measured voltage shown in Figure 2 is not the voltage of the wire resistance but rather the voltage across L2 and R2 in addition to the wire voltage. The voltage of the wire resistance is important for us to make an estimation of the energy deposition in the wire before the explosion. __________________________________________ Fig 2 below. L2 and R2 are the resistance and Inductance of leads inside vacuum chamber (unavoidable).  [Edited on 11-7-2009 by dann2] | |||||||||
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| watson.fawkes |
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This leads to the vaporization transition. If this transition is slow enough, escaping vapor will similarly escape through whatever gas channel is available. But when, in the correct option, vaporization is fast enough, simple gas kinetics retard outflow well enough to create a shock wave, which is the whole point. The upshot is that the basic operation of this device requires a short pulse. | |||||||||
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| Hennig Brand |
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I don' t know exactly were the limits are with this, because I haven' t studied it enough, but this is mostly my feeling as well. I am going to try and find some more information, or try and possibly do a little testing. With explosives anyway, not all shockwaves are equal, and the more brisant make a much more dense, fast and powerful shockwave(if I have said this right). What different secondaries require from the EBW could be wildly different as well. For the sake of arguement I guess PETN is normally the standard though in EBW technology(thought I should say so, so as not to confuse the issue). [Edited on 11-7-2009 by Hennig Brand] | |||||||||
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| dann2 |
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Hello, Doing some reading myself on time frames (my own link!) at this url http://www.teledynerisi.com/0products/8td/page03.html (this was posted before BTW) it seems to give the ball park figure of needing a rate of current rise of 1000 Amps per micro second. The capacitor is close to the bridge wire using a short transmission cable with a spark gap between the capacitor and bridge wire. The cap is charged relatively slowly and when the spark gap fires (at some kilo Volts) the charge is dumped into the bridge wire. You would need a heavy transmission line. Perhaps two flat Copper conducting planes seperated by the appropriate insulation layer. Multiple firing points could be set off at the same time with a control line to the 'spark gap'. The spark gap being replaced with a solid state trigger of some sort. (I guess). Regarding using Gold or Pt for the bridge wire. Perhaps it is these metals ability to avoid corrosion etc that they are used. Silver or Copper is more conductive but much less inert. The (variable depth depending on age etc) oxide layer that may form on them may be considered unacceptable. edit: According the manufacturers they use Gold as it is very stable for years. (its in one of the pdf attached). Attached file(s) (in zip) 0298.pdf gives inductance values etc for detonators and cables used in firing and books. 0792.pdf using longer cables @ Hinnig Brand 0592.pdf for delayed firings (sound weird to me but I guess it must work) see page5.pdf for some stuff on times and what happens as the pulse progresses. If you Google technical site:http://www.teledynerisi.com you will gets lots of PDF on technical stuff on the systems that they sell. I Google and downloaded and attached the lot. Its a bit of a hod podge but good reading IMHO. Dann2 Dann2 [Edited on 11-7-2009 by dann2] Attachment: ewb.zip (873kB) This file has been downloaded 356 times | |||||||||
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| 12AX7 |
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Referring, perhaps, to an oscilloscope? Those are fairly standard equipment, and a must-have even for mere repair techs. I wouldn't at all consider a 'scope "high level".  You can get a fair base model DSO (that's Digital Storage Oscilloscope) for $500 or so new, or a better, older one for $100 on eBay pretty easy. You pretty well need a DSO for this, since you only get one shot of waveform, kind of hard to observe on a live analog scope (although they did make analog storage scopes!).
I don't think it's nearly as imposing. Now, trial and error is nice for a test, but if you're making more error than success, you don't get much from it. The good old combination of theory, test and verify is much more effective, and produces a lot more data a lot quicker. Of course, that requires theory and instrumentation, but these are not hard to come by either: even the basic RLC circuit tells one a lot about the general circuit parameters to expect. Tim
Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout. Need engineering assistance? Drop me a message! | |||||||||
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| franklyn |
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@ 1 2 A X 7 " And inductance simply doesn't matter? I ask again, are you able to suspend Ampere's law at will? " Inductance matters to what ? The time constant chart above _ http://i41.tinypic.com/35mgob5.jpg is the same for RC as it is for L/R. You either have one or the other not both together. If the energy is in capacitance being discharged it cannot also be in inductance , though this may acquire an induction from the others discharge much the same as in a parallel tank circuit. Inductive reactance will only serve to delay the onset of the pulse at the terminals , not affect the discharge time , as only resistance can. Capacitive reactance cancels Inductive reactance at the self resonance frequency of the capacitor given by f = .159 / √ LC this is where only R , remains , but all this is moot since the manufacturer has thoughtfully provided this data in a lump sum value typically as dissipation factor. I outlined here http://www.sciencemadness.org/talk/viewthread.php?tid=5064#p... how ESR may be obtained from DF thus E S R = DF / ( 6.28 f C ) This is the 3rd time I have given this reference - twice to you http://www.gaep.com/tech-bulletins/capacitor-engineering-bul... Read on page 7 "How the ESR is applied" on into page 8 Depending on method , the contrived value for ESR can vary some but not so much that the calculated discharge will be far off from the actual discharge time that would be measured. @ watson.fawkes "Now that I understand more about how these things works, I can say with confidence that this is just wrong. The upshot is that the basic operation of this device requires a short pulse." Pulse width is irrelevant to whether explosion occurs or not. Pulse amplitude is what matters since the area under the power curve is the energy delivered. Knowing what energy is necessary to make vapor of a known amount of metal , it is then a matter of delivering that in excess. If you just send the exact amount success is uncertain. Inertia and theta pinch guarantees the current converts the metal into a supercritical fluid at which point the mechanics of the gas laws predominate. I'm continuously baffled as to the insistence that power supplied must cut off abruptly in order for the wire to be rendered into gas. Which is what is done by making a pulse short. . | |||||||||
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| watson.fawkes |
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According to your argument, it doesn't matter at all how long it takes to deliver the excess of energy. So I'll build a circuit to deliver it over a day. Hell, I'll pump in 1000 times the total energy-to-vapor over that day. I most certainly will not get an explosion. If, on the other hand, I deliver that same amount of energy in 1 μs, I certainly will. | |||||||||
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| watson.fawkes |
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| 12AX7 |
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That is because you get an RC or L/R time constant precisely when the other element does not show up in the circuit. Both are most certainly present in this circuit! What must I demonstrate to you to prove that this is the case? Wire has inductance, resistors have inductance, capacitors have inductance, it is most certainly a mandatory part of modelling this circuit's response!
Blatantly wrong! PLEASE read up on RLC series resonance!
Dissipation factor is another representation of ESR and has nothing to do with ESL. It is precisely because inductive reactance "cancels" with capacitive reactance that the complete RLC circuit must be considered.
Ah yes, then how do you explain my capacitor bank discharging in microseconds? It is an empirically measured, indisputable fact that it discharges in microseconds. How, then, are you able to construct a figure of 60ns, a figure which is blatantly wrong by two orders of magnitude? The only explanation is that your method is wrong. Tim
Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout. Need engineering assistance? Drop me a message! | |||||||||
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| Hennig Brand |
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@franklyn I see what you are saying, it is not that the kinetic self confinement is not important, or that pulse width is not important, and that the power under the power curve is all that matters. It is that they are the same thing essentially, or describing the same phenomina(shape of curve and the timing). The first power spike before the dip, tells use exactly how much energy is going into the bridge wire, and/or bridge wire circuit(depending on where taking readings), before the explosive vaporization. This is so because(as has been stated and verified by reputable sources), the first current rise is during the time the wire heats up(resistance becomes more on heating), then current drops(resistance becomes greater still,vaporization takes place, but vapor held in place by inertia), then after current goes higher again after explosive vaporization(shockwave) since resistance goes down(plasma very conductive). Observing these waveformes, will give a good picture of what takes place at the bridge wire during the explosive vaporization. It also tells how much energy goes into each stage(pre vaporization, vaporization, post vaporization), by using area under the curve(curves), and calculus normally, or computer(I think I said this approx right). I would think that for normal purposes, even if you had to use a laquer, shellac or some kind of plastic coating on your bridge wire, even if a little more power and/or a thicker BW had to be used it should still be workable I would think. I just took some 40gauge wire(0.0799mm diameter) and made a bridge of approx 5mm length(arbitrarily). I used one of those $2-3 racket bug zappers to charge up my 25uF(oil filled) cap to 600 volts, giving me about 4joules in first 1.5 time constant(1.25usec). I have done it 6 or more times now, and it is a pretty healthy bang for sure, even with that small amount of power. It seems like it could initiate(just opinion), similar to silver fulminate or something in effect(just opinion based on observation and sound). By the way I believe when elctricity is studied at higher levels they have a little more gear than just a multimeter and an oscilloscope. Even when just discussing oscilloscopes, there is horrendous differences in there sophistication. It also says in that Wiki article under "mechanism of operation", that a current rise rate of 100 amperes per micro second is required, to develope a shockwave(at least under their conditions). If I can do this correctly now. charge=CV, so 600V times 0.000025F, so 0.015 coulombs. In first time contant(1.25usec) I will get about 63% of this, so 0.00945 coulombs. 1/1.25=0.8, 0.8x0.00945=0.00756 coulombs per usec. 0.00756coulombs/0.000001sec=7560 amperes for first microsec. It would seem that I have lots, especially if one doesn' t count the losses from the circuit and switch, etc. It still seems that I have lots to play with, even at only 600V, with this small 0.0799mm diameter bridgewire. I noticed in the Wiki article about EBW it states that all it takes is a current rise rate of 100A per usec, in order to get a shockwave. This doesn' t say anything about that shockwaves ability to initiate secondaries though. In the Teledynerisi article it shows graphs with 5x this amount and calling it a marginal firing, and thats with their (perfect) blasting cap. That article also talks of inductance, and says that if the inductance is too great, because of too long a line or improper line or configuration, that the pulse will be drawn out so much as to not explode the bridge wire properly"reducing the magnitude of the shock wave". It gives a flatter more gradual curve(not what we desire).Doesn' t a bigger time constant give us a much more gradual curve as well in general. Those high capacitance caps can' t perform like the small capacitance caps, for the same energy. I wonder what the difference in losses would be like between the high voltage(2000+volts) and the lower voltage caps(several hundred volts) in circuit? [Edited on 11-7-2009 by Hennig Brand] http://www.sciencemadness.org/talk/viewthread.php?tid=12414 |
Sunday, December 10, 2017
How to assassinate Trump, Dark Web? like Hariri...don't forget their convoys have big jammers incorporated...another question the delay fuse, that you only get on the russian blackmarket. Like Hariri means this : Exploding wires. What is it...really very interessting, if you find people able to have university do to make it
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