Has anyone made a EBW setup.

I like your sense of humour

Seems you need to read a lot more on this topic.

A Guide to Explosives Firing
www.dtic.mil/dtic/tr/fulltext/u2/a322055.pdf

If you want a second opinion _
www.amateurpyro.com/forums/topic/414-ebws-capacitor-discharg...

_______________________________________________________


While on the topic I thought this an interesting development , it's a device that
amplifies the power from a normal blasting machine producing a pulse to fire EBW's.

Blasting Machine Power Multipliers for EBW's
www.teledynerisi.com/1techtopics/pdf/0295.pdf
www.teledynerisi.com/products/0products_2fs_page43.asp

The above would be used for example with a blasting machine like this_
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=26117...

.

http://www.youtube.com/watch?v=IXMDltOiNpU

With this I detonate ETN directly

The energy stored in the capacitor is 8J, from that you can transfer about 0,5-1J into exploding wire
(see http://www.dtic.mil/dtic/tr/fulltext/u2/609449.pdf).

Reliability is 100% for me; at the moment more than 50 test never failed.
Unfotunately I never tried with others primary.
In the future I will try to detonate a very insensitive material like AN-AL.
(see patent US 3,156,186)
If it works I can remove every type of primary

Nice, I'd use azide with the wire for critical applications to be sure. Interesting, 1J makes that thing explode, and with enough force to initiate the ETN. I wonder how will it perform in winter at -20, specially if the ETN has previously been a little melted from the heat of the sun near a window

EBW HV Power Supply from Handheld Bug Zapper Rackets

I have two hand held bug zappers that were given to me which had mechanical problems of some sort but the power supplies still work fine (is it a bad sign that people keep giving me their old junk?). I also have 6 X 1000V, 1uF film capacitors which I removed from a large burned out VFD (variable frequency drive) for large induction motor speed control found at a scrap yard years ago. I discovered that once the ca. 400V capacitors were removed from these bug zapper power supplies that they could easily charge a several uF capacitor up to 1000V and that two of these in series could easily charge up to 2000V. I haven't tried going much higher except by accident the 3X2 capacitor bank of 6X1000V, 1uF capacitors (total 2000V, 1.5uF) was charged up to about 2200V once. Another 1000v, 1A diode (1N4007), was added in series with each of the two rectifier diodes present on each PS output.

So far I only have 40 gauge copper to make bridge wires and only RG6 coax (cable/satellite television cable) and/or speaker wire for transmission. Charged up to 2000V the 1.5uF capacitor bank can easily detonate ETN through 1ft of 18 gauge speaker wire, however, attempting the same thing with 12ft of RG6 coaxial cable resulted in failures.

I am just getting my feet wet with this, but decided to post since I think it is interesting.





I know I should have bypass resistors in parallel with the two sets of series connected capacitors and on the rectifier diodes to ensure even distribution of charge/voltage. I ordered some high voltage, high ohmic value, bleeder resistors today but they will be a while getting to me.

Ideally 4 or even 6kV would be much better than 2kV and if the bridge wire was closer to 50 gauge the power requirements would be much less than they are now using a 40 gauge bridge wire. I think I have some heavy coaxial stored in a shed that was used by someone for Ham radio, which could be a big improvement in the transmission department.

Another couple of bug zapper rackets and I am good to go for 4kV.

Does anyone know exactly what type of capacitor this is? The warning on it is a bit ominous and for good reason I guess. A couple of these in series would be 12uF and could be charged to about 4kV. Now that is one hell of a jolt! I came into possession quite a few years ago of a lot of used 1970s electronics and electrical equipment from personnel carriers, etc, when they were being refurbished; a certain piece, of which I had a few dozen I think, had one of these big HV capacitors buried deep inside.




[Edited on 9-4-2015 by Hennig Brand]

24uF Capacitor Charged To 1600V Discharged Through 12ft RG6 Coax Into 40 Gauge Copper Bridgewire Initiates ETN

I hooked up the big 2kV, 24uF capacitor this morning to the bug zapper HV power supply. A 40 gauge copper bridge wire, about 1.5-2mm long was connected at the other end of 12ft of RG6 coaxial cable. Wrapped around the bridge wire in a bit of plastic wrap was about 50mg of loose, crystalline, ETN. The 24uF capacitor was only charged to 1600V because the bug zapper power supply took almost a full minute to even charge it up that much (batteries are old, so replacing them could make a big difference). There was a huge bang when the wire was touched to the charged capacitor and on inspection the plastic wrap was seen to be blown away and the bit of circuit board/spacer which held the bridge wire was broken away from the solder joints.

Capacitor Energy = 1/2CV^2
Energy = 1/2*0.000024F*1600V^2
Energy = 30.7 Joules

If two were hooked in series and charged to 4000V:

Energy = 1/2*0.000012F*4000V^2
Energy = 96 Joules !!!

I am still just learning, but this amount of capacitance is likely way overkill even with a 40 gauge bridge wire, also, at least 4000V would be much better than 2000V for long cable runs. It should be no problem initiating ETN through 100ft of cable with the right capacitor(s) and cable. I used a half to a full foot of 18 gauge speaker wire on either end of the RG6 coaxial for this test, so a section of consumable wire of some sort could be made as part of each EBW cap assembly with the idea that it would be consumed/destroyed in the blast.



I suppose three of these capacitors hooked in series, with appropriate bypass resistors, would have 8uF of capacitance and could be charged as high as 6000V which would be about right probably.

Energy = 1/2CV^2
Energy = 144J !!!


Remote Control of EBW Power Supply Charging and Firing

The big limitation to these systems is the transmission cable, which must be kept as short as possible for practical purposes. I see no reason why heavy cables need to be run all the way back to the operator/shot firer. The power supply, capacitor(s) and firing switch/mechanism could all be fairly close to the blast in a tough enclosure or even buried. Small signal, light gauge, wiring could be run to the distant operator/shot firer so that charging and firing could be controlled as well as voltage/charge monitoring all from a distance. In fact if desired all that needs to be relatively close to the blast is the capacitor(s) and the firing mechanism, the power supply could charge the capacitors through a fairly light copper pair from a distance.


[Edited on 9-4-2015 by Hennig Brand]

You need a beefier power supply for the cap. Using this bug zapper is like trying to fill a pool with a bucket

E.g. a topology like this one:

http://www.hvlabs.hu/inverter/fcsinverter.gif

The IR2153 or 21531 are selfresonating drivers that can be tuned in on the sweet spot of the transformer and operated in halfbridge or push pull mode. They are cheap and quite reliable, requiring very limited amount of external parts, but one has to limit the current through the chip Vcc leg to max 5mA. This can be done via a resistor of appropriate size if the supply voltage is fairly constant. With a battery though, I would suggest a sepic converter for that job. It is very annoying when the circuit draws big amps from the battery dropping the voltage below the UVLO treshold of the driver chip (9,5-10V) and the circuit starts to softswitch itself on and off. Then one tries to decrease the limiting resistor value and the chip gives off the ghost when a fresh battery with higher voltage is connected...
A sepic converter will feed a stable voltage of appropriate value to power the chip independent of the input voltage from the battery and eliminates the overcurrent problem very efficiently.
The output of the transformer can be driven through a simple voltage multiplier to get the required kV.

Thanks, not a bad idea. You know though, the two series connected bug zappers have no problem charging up 1.5uF to 2000V, from just a couple of 1.5V AA cells, in well under 10 seconds. The last capacitor used really is a beast at 24uF and 2000V. Would be pretty funny to have an EBW power supply made with eight or ten series/parallel connected bug zapper power supplies. They are only $3-4 dollars each new IIRC and the first two were given to me broken so they were free. Pretty sure the transformers in them could handle more current so I could probably crank them up some.

Here is a power supply I have used in the past that works great and is not picky at all about component choice (pretty much any transistors that can handle the voltage and current within reason). I built a stun gun eight years ago or so and used the front half of one of these circuits when I built it (up to and including T1). It made a simple and tough little HV supply.






The circuits were taken from the following website which also has some assembly instructions.

http://chemelec.com/Projects/Stun-Gun-1/Stun-Gun.htm

I think it was probably the second one I used, but like I said before component choice is flexible. I wound my own transformers, or rewound I should say T1 from a salvaged switching supply transformer. Some voltage multiplier stages after T1 and you have everything you need. What you suggested could be a better solution, but it doesn't have to be too sophisticated and I kind of like working with garden variety discrete components such as transistors, capacitors, resistors, etc.


[Edited on 9-4-2015 by Hennig Brand]

I'm sure both options will work just fine....and usually whichever one is simpler will do a better job.

And then there are the days when simple stuff gets kinda out of hands :

Looks very nice. Is that an EBW power supply?

Also, forgot to mention that there were high ohmic value bleeder resistors across the original HV storage capacitors on the bug zappers' outputs. These resistors as well as the original ca. 400V capacitors were removed so that the zapper supplies could be used to charge 1000V capacitors.

As was mentioned already, with two AA, 1.5 volt cells, the two series connected bug zapper power supplies took about a minute to charge the 24uF capacitor up to 1600V. The two AA batteries (3V total) were replaced with a small sealed lead acid battery (4V) which enabled the bug zapper supplies to charge the 24uF capacitor up to the full 2000V in 30-40 seconds. I was just going to add more AA batteries in series/parallel to get higher voltage/current capability, but this lead acid battery was sitting right on the table looking at me already. Components (transistors and transformers) were monitored for excessive heating during charging and were found to get only slightly warm if at all. These bug zapper supplies could probably be run from even higher supply voltages.

Almost like my brother knew what I needed when he dropped off the battery a couple of days ago which he said came out of a junked handheld spotlight (like the ones used for jacking deer).





I have some RG-213 stored in a shed, but will have to dig it out to know for sure how much. It can be bought for $1/foot or less sometimes if you can make a deal with some of the Ham radio nuts (have heard of it being sold sometimes for as little as 50 cents per foot). Here is a picture of RG-213. It is a very heavy coaxial with 12.5 gauge center conductor I believe and very heavy braided shielding. According to the literature RG-213 is very suitable for use as EBW transmission line. The table was taken from "Explosives Engineering", by Cooper.




[Edited on 10-4-2015 by Hennig Brand]

High Voltage/High Current Relay

This relay which I built in the last hour or two is extremely crude, but something much more refined could be easily built. Other than the foot long piece of 1/2" brass rod purchased for $5 everything else was from the junk pile. The idea is that the capacitor(s) can be charged through the low current normally closed contact (brass wood screw) and then once charged the solenoid could be activated which would dump the high current pulse through the 1/2" brass contact and into the transmission line and bridge wire thereby initiating the cap. Of course the relay could also connect the capacitor(s) to some other more efficient switching mechanism which could then dump the stored charge into the transmission line and bridge wire. The relay can be operated remotely using a length of light gauge wire.

Here is a picture of the crude high voltage/ high current relay and also a tiny video of it in operation.



Attachment: Relay in Action.mp4 (9.2MB)
This file has been downloaded 1375 times


The solenoid is much bigger than it needs to be. It is rated for 120V and when kept mostly retracted it generates lots of force even when powered by only an 18V cordless drill battery pack (as was done in the video). Also from reading some of the Tesla coil sites, it seems that contacts with large, smooth surfaces with the right curvature can really reduce inductance and losses at a spark gap. I tried for 1" brass rod for contacts, but all I could locate yesterday was 1/2".


The pivot screw has been replaced with a pivot bolt which looks a little less foolish and will work better and for longer too. The spring was also positioned so that a little more tension was put on the contacts in the normally closed position. Picture below.




[Edited on 11-4-2015 by Hennig Brand]

Triggered Spark Gap Switch

Screw Triggered Spark Gap

Thanks, that site looks interesting. There are also at least a few sites online with peoples' descriptions of how they have built their own. They aren't terribly complicated and I probably will eventually build one.

Here are a couple pictures of the "Screw Gap". It works, but I have not tested it yet with proper transmission cable, proper EBW and explosives in a cap.




Thanks for the reading material Jock88.

edit:

Static Gap

A plain old static gap with a threaded adjustment for width would be the simplest thing, however, at these relatively low voltages the spark gap is very narrow especially with large curved electrodes which are used because they are much more efficient than fine point contacts. A very narrow gap and slight changes in the surface of the contacts (any kind of roughness or buildup) could make the gap fire early and wear or other changes could cause the gap to fail to fire. Since energy is proportional to the capacitor(s) voltage squared the gap would need to be very carefully adjusted in order to get good results.

I used the calculator from the following site, which is apparently based on empirical data, to get data points for the attached graph which was made in Excel. The other graph, showing higher voltages, came from the site linked to above regarding stun gun HV PS circuits.

https://www.cirris.com/learning-center/calculators/50-high-v...






Here is the same graph as above, but this time with extrapolated values from 3000-6000V.






Ok, I just found the following appendix from the article, "Electrostatic Discharge: Understand, Simulate, and Fix ESD Problems, Third Edition
Published Online: 22 SEP 2009", which has tables giving break over voltages for spherical and pointed contacts. This looks like a decent reference.


Attachment: Spark Over Voltages (Wiley).pdf (429kB)
This file has been downloaded 1085 times


[Edited on 14-4-2015 by Hennig Brand]

Simple Trigatron Trigger Pulse Generator From Bug Zapper Power Supply

Yeah, I knew you meant Cooper. Thanks for that compressed file, it has a lot of good stuff in it. I have been mulling the triggered switch thing over for the last couple of days. Just about ready to give something a try.


I already linked to this page earlier, but after looking at the one-shot trigatron pulse generator on that page I got a couple of ideas.

http://hotstreamer.deanostoybox.com/ross/projects/Pulse/puls...

Here is an image of the one-shot pulse generator from that page:






In order to keep things really simple the SCR was replaced with a static spark gap and the AC input and voltage doubler stage were replaced with the ubiquitous bug zapper power supply. A single bug zapper supply, with proper adjustment, can easily charge a suitable capacitor to over a 1000 volts if needed. The capacitor is charged through the primary winding of the transformer until the breakover voltage of the spark gap is reached which then arcs over and dumps the stored charge through the transformer primary very rapidly which transfers the pulse by electromagnetic induction to the transformer secondary and the trigatron trigger electrode.





If more precise firing times are required replace the static spark gap with an SCR. Multiple circuits like this could be fired simultaneously using SCRs. SCRs are sensitive to overvoltage, with ones I have commonly seen being rated for max 400V or sometimes 600V, so the capacitor and charging circuit would need to be designed carefully so as not to create an over voltage situation unless very high voltage SCRs could be obtained. A pulse capacitor charged to a lower voltage and a transformer with lower turns ratio (more voltage gain) would be needed.

I avoided winding a transformer by taking one from a switching supply, which seems to have a couple windings with a turns ratio (# turns in primary/# turns in secondary) of 1/2-1/4 (estimated by spark gap length at secondary). This transformer is not designed to be used at several thousand volts, but so far it seems to be holding up just fine. When I actually get it put together more properly I will post a picture or two.

BTW, a couple people have mentioned capacitor charging current limiting resistors. They are not needed when using the bug zapper supplies, since the transformers themselves are made to be current limiting (or it just happened that way maybe).

I am pretty sure I can get by with just three bug zapper power supplies, as long as I go no higher than 3-4kV and a few uF of capacitance. Two in series to charge the capacitor bank and one to fire the trigatron. If I was more clever, or motivated, I probably wouldn't even need the third one, but they are only $3 each at the local dollar store anyway.


[Edited on 15-4-2015 by Hennig Brand]

pcb bridge wire

I think the bridgewire should be up on posts with low density fine secondary explosive all around it. I was thinking along similar lines as you for a while though. The other thing is that the bridge wire is normally 0.001 inch to 0.003 inch in diameter; 40 AWG is actually slightly bigger than 0.003 inch in diameter and that is tricky enough to deal with. Gold has less than half the tensile strength of copper, so it must need very special handling equipment especially when it gets down to 0.001 inch.




Then again maybe I am not right, here is a document showing the bridgewire positioned more or less right up against the plug.




Attachment: High Temperature EBW Detonator.pdf (317kB)
This file has been downloaded 900 times


[Edited on 17-4-2015 by Hennig Brand]

Quote: Originally posted by markx

The last "single pulse" circuit with the spark gap will generate a very high frequency hv ac on the transformer secondary (the capacitor and primary winding form a LC resonant circuit as the gap fires and shorts the cap through the inductance)....it is actually the most classic setup for spark triggered tig welder arcstarters. The high frequency ac is transferred to the welder circuit by an air core transformer. In fact the resonant ac is usually of such high frequency that it will flow by the semiconductor junctions (paracitic capacitance of the junction will conduct it) and will not harm them. It will also not produce a classic electric shock in you body if you should touch the secondary while the gap fires. Actually one can barely feel it due to the skin effect....it still can burn your skin if enough power is applied.

The bug zappers have a tiny flyback transformer in them, which produces AC, but the output is rectified to DC with HV diodes (the diode(s) also come with the zappers). It has to be DC because the energy is stored in a capacitor like a coiled spring waiting for the unsuspecting bug to get between the conductive mesh contacts and then to ride the lightning.

0.3g of ETN Initiated With 40 Gauge Copper EBW

EBW Head:

A half inch or so of hot melt glue stick was sliced off on a cutting board, drilled once and then drilled a second time, for lead wires, using a previously made jig/spacer made from a piece of circuit board to give precise hole spacing. The bridge wire was ca. 40AWG copper of about 2 to 2.5mm length. The white-out solder flow retardant worked beautifully preventing any solder from flowing out onto the middle of the bridgewire. It could also be easily removed with acetone which made it very soft so that it could be gently wiped away. A fine cotton swab soaked in acetone would likely be effective and gentle. Once a few tricks are learned EBW head construction is not that difficult. The EBW head was pressed into the fluffy ETN with light finger pressure only.


Charge:

0.3g of ETN pressed in three increments into a 7.6mm Al casing; 0.1g at about 30lbs, 0.1g at about 15lbs and 0.1g with only finger pressure to remove voids and settle the ETN. The ETN was very light and fluffy, the result of rapid precipitation from dilution of a well mixed solution in methanol with water.


Transmission Line:

12ft of RG-6 coax (satellite/cable television coax) and 1ft of 18AWG speaker wire. Total 13ft of transmission line.


Capacitor Bank:

6X 1uF, 1000V connected to give 0.67uF and 3000V. The bank was charged to only 2300V for this test. The voltage divider allows a much lower and very safe proportional voltage to be monitored with a regular multimeter/volt meter and from a distance with a fine sensing wire if desired. The voltage divider also doubles as a bleeder resistor ensuring that the capacitor bank is fairly quickly discharged after use.


Switching:

Switching was accomplished by the very crude and inefficient method of touching the center conductor of the coax to the speaker wire connected to the capacitor bank.


Target:

Ca. 2.6mm steel plate.


Results:

It was a very loud boom, which I could tell clearly even though I was wearing earmuffs (I was only 10ft away of course). The result, in terms of steel penetration & shattering, would have been better if the bottom increment(s) of ETN had been pressed to much higher density with a press and of course if more ETN had been used. This test was simply proof of concept.

Very large capacitors are not needed at all. The most important thing is to have low impedance cable that isn't too long, good low inductance & resistance connections and high voltage. I have 100ft of RG-213 ordered which I will have soon, as well as enough new pulse capacitors to make a low ERS capacitor bank of 1.2uF and 4000V. I don't think I will have any trouble initiating these homemade EBW detonators through 100ft of RG-213 since it is a very low loss cable.


BTW, a good source of ca. 40AWG copper magnet wire is the little door and window alarms which are often available at dollar stores and hardware stores, etc. Don’t let the small size fool you, the inductor that is in them holds a lot of magnet wire. About ten years ago I decided to make a 2-3V relay from a reed switch and the magnet wire on one of those inductors. It seemed like I was winding for hours though I guess it couldn’t have been; it was really surprising how long the wire was that makes up those windings. The insulation can be easily burned off with a low flame of a small butane torch. Even a mini butane torch can melt the fine copper wire if care is not used.






[Edited on 18-4-2015 by Hennig Brand]

Hi I've drawn up a drawing of how I see the bridgewire head made from a fiberglass pcb cheers nuxy

Energy Injected to the Wire During the First Current Pulse

The following snip-it and table were taken from, "Electric Explosion of Wires as a Method for Preparation of Nanopowders" by Yu A. Kotov. The article is attached below as well.

"
The energy W injected to the wire during the first current pulse was found to be

W = (hb * W0 * S^2 * Z)^0.5


where W0 = 1/2CVo^2 is the stored energy, J; Vo is the capacitor charging voltage, kV; Z = (L/C)^0.5 is the circuit characteristic impedance, Ohm; L is the discharge circuit inductance, μH; C is the capacitance, μF; S = 1/4 * pi * D^2 is the wire cross-sectional area, mm2 (D being the wire diameter, mm); hb has the dimensionality of A^2 * s / mm4 and represents the pre-explosion specific ‘action’ or thermal toughness of the material heated with a current pulse (Anderson&Neilson, 1959; Cnare & Neilson, 1959; Cnare, 1961). This notion was used earlier (Rudenberg, 1950) for calculation of safety fuses. The obtained hb values (Anderson & Neilson, 1959; Cnare&Neilson, 1959; Tucker&Neilson, 1959; Cnare, 1961; Kotov et al., 1990) are given in Table 1."






Attachment: Electric Explosions of Wires as a Method of Preparation of Nanopowders.pdf (208kB)
This file has been downloaded 1196 times


hb(Copper) / hb(Gold) = ca. 4

All other things being equal, it seems as though it takes roughly four times the energy to explode a copper bridgewire than it takes for a gold one. Of course, all other things being equal, a change in the diameter of the bridge wire by a factor of two would change the burst energy by a factor of sixteen.

Quote: Originally posted by jock88

You can purchase very fine Nichrome wire. It may the more resistant to corrosion for a more long term device. Copper is somewhat reactive with a very thin wire(or is it?). The extra resistance of the tiny piece of Nichrome would be irrelevant.

I see you still refuse to show mercy to this mangled corpse of a witness plate....hasn't the poor bastard suffered enough already?

Cool capacitor bank btw...

I am going to use it for a strainer when I am done.
No, seriously, it seems when I go looking for a witness plate that one keeps turning up. Just like a bad penny!


Here are a couple snip-its which show how even relatively small increases in explosive density make initiation of secondary explosives by EBW much more difficult. The first snip-it is from Cooper and the second is from "Exploding Wires Vol 4".





[Edited on 21-4-2015 by Hennig Brand]

EBW Failure using 0.67uF cap Charged to 2400V fired Through over 51ft of RG-6 Equivalent Cable

I was fairly sure that this wouldn't work, but I tried it anyway. A half gram of ETN was pressed in a 7.6mm aluminum casing with over 100lbs of force with a lever press and then another 0.2g was added loose on top. The copper bridgewire EBW head was made in the same way as last time and was gently pressed into the loose ETN just enough to remove voids and lightly compact it. Fifty feet of RG-6 and 1ft of 18 gauge speaker wire was used as transmission line. The 0.67uF capacitor bank was charged to 2400V and wires touched together to fire the EBW. There was no detonation and on closer inspection about 1/3 to 1/2 of the ETN was gone and the EBW head, which had been lightly glued in place, had been blown out of the cap. It seems as though the ETN was ignited and built up just enough pressure to pop out the EBW head. It was a fairly long run of fairly light cable and the capacitor bank was only charged to 2400V, so this is to be expected.

In the last day or so I made a graph generating spreadsheet in Excel using what I think are the appropriate pulsed power equations. According to "Explosives Engineering" by Cooper, EBWs typically require several hundred amps at very fast rise rate, in the neighborhood of 200A/usec. Using the numbers from each test I made a couple of graphs, one for the successful attempt from earlier and one from this past failure. It is very clear why this last test failed when looking at the graph. So far change in bridgewire resistance was not accounted for when making the graphs. I may post the spreadsheet soon so that others can use it. I think it could be a great tool for analysing EBW systems and should lead to greater understanding, control and reproducibility. BTW, one of the key equations from Cooper is incorrect.

Ironically the RG-213 came in about an hour or so after I did the test with the RG-6. As can be seen from the images, RG-213 is a much heavier coaxial cable than RG-6. The white cable below is 50ft of RG-6. The black cable in the box is 100ft of RG-213.

I also made the main electrodes for a trigatron a couple of days ago which are shown below.





[Edited on 21-4-2015 by Hennig Brand]

Burst Action of EBWs

Distributed-Parameter Method for EBW System Analysis

The equations given in Cooper are for the common lumped-parameter method for analysing pulsed power systems. Besides the fact that one of his equations is wrong, according to what I have been reading this method is very inaccurate except for cases with essentially no transmission line. So what I have presented above is likely very inaccurate. I found a good article yesterday in "Exploding Wires Vol. 2" outlining a simplified distributed-parameter method that is reported to provide analytical results very close to actual results in most cases. I am not going to attempt to explain it here, because it would be a waste of time since the author did such a great job of it. I have attached the section from the text below, as well as the Excel sheet I spent the day working on which is based on the final simplified equations from the article.

It is a work in progress, but the results produced by the spreadsheet seem reasonable at this point. When values are input for the same type and length of wires, the reflection times seem to agree fairly well with the times from the graphs in Cooper's book, but the currents still seem a bit high. This method does assume a constant voltage source, which the author states is normally a reasonable assumption for the short times (considerably less than one RC time constant) normally involved to bring a wire to explosion. An assumption used in this method that also could result in at least slightly higher currents, "For most purposes, the wiring and transmission lines used in exploding wire work can be treated as lossless lines, that is, R~0 because provision is made for carrying very high currents and G~0 because good insulating materials are used between the wires to prevent high-voltage breakdown." Another factor which results in higher currents, especially in the early stages before wire explosion, is the constant high value for bridge wire resistance used. According to the article maximum resistance is normally used for this method. Five ohms was used throughout for bridgewire resistance, since maximum values for gold bridgewires can apparently go as high as 10 ohms. Lowering bridgewire resistance does bring the currents closer to what is seen in the graphs in Cooper.

The new graphs are attached.





For the 13ft RG-6 graph, burst action (0.45A^2s) is reached in about 0.62 microseconds with a burst current of 1240 amps. This test was of course successful in practise as well. For the 51ft RG-6 graph burst action is reached in about 1.41 microseconds at a burst current of about 800 amps. The time was longer until burst and the current was also lower at burst in comparison to the first graph. The second test was a failure in practise, but the switching losses could have been huge since switching was accomplished by the very crude method of touching too small gauge (18 gauge) wires together by hand.



Attachment: Effects of Transmission Lines in Applications of Exploding Wires (Section from Exploding Wires Vol.2).pdf (719kB)
This file has been downloaded 707 times


Attachment: EBW Current Versus Time (Distributed Parameter Method) - Spreadsheet and Graph.xlsx (65kB)
This file has been downloaded 771 times


[Edited on 23-4-2015 by Hennig Brand]

Comparing Gold and Copper EBWs - Bridgewire Inertia and Resistance

The resistance of copper, gold and platinum starts out very low and then increases very rapidly in the final fraction of a microsecond before biridgewire explosion. I have attached the resistance versus time graphs from "Initiation of Explosives by Exploding Wires" for gold and copper. Those documents have other graphs for several other metals if you want to look as well.


Increase in resistance with temperature (wiretron.com)

°F .......°C......NiCrA........NiCrC

68 .......20.......0 .............0
600.....315 .....3.3% .......5.2%
1000....538 ....6.3% .......8.6%
2000...1093....6.0% .......10.5%


So ironically it looks as though nichrome ends up having too little resistance when it counts. Higher resistance at the start is only part of the problem, what is even worse is that its resistance rises only slightly with temperature. Inertia again plays a major role. Nichrome wire will tend to rise in energy level more gradually instead of explosively. With proper function, gold and copper bridgewires obtain most of their energy in the last few tens of nanoseconds before wire explosion (P=I^2R). Also, nichrome's density is even a bit lower than copper which is undesirable (inertia again). I believe nichrome may have other problems too, but I would need to look into it more.

I have never tried it, so I don't know for sure, but nichrome doesn't come highly recommended from the few things I have read. It will undoubtedly work, but it might require a blasting box that is very large (more power). Platinum is used commercially from what I have read, but gold is more common. The amount of gold is so small in an EBW that commercially the cost is not a big concern. It is much harder for an average experimenter to obtain gold in a cost effective way though.

I am in the process of trying to collect the four volumes of "Exploding Wires". They were published in the 60s, as was a lot of the reading material on EBWs.





[Edited on 25-4-2015 by Hennig Brand]

Comparing Gold and Copper EBWs (Revisited) - Heats of Vaporization

Something else of significance which I am still trying to wrap my head around is the effect of bridgewire material heat of vaporization on bridgewire energy/current rise requirements.

If comparing bridgewires of equal volume a copper bridgewire takes about 26% more energy to vaporize (if my calculations are correct).

edit:
So far this actually doesn't look to be of great significance. The area under the gold and copper power versus time graphs from "Initiation of Explosives by Exploding Wires V & VI" were found. At least from their tests, it turns out that the fraction of total energy used up in the phase change is only different by about 2-3% between gold and copper. The phase change energy was higher for copper, but then so was the total energy. They more or less cancelled each other out, at least for those tests.

Here is the excel sheet were that was used to compare the two graphs from the articles:


Attachment: Energy to Bridgewire Gold versus Copper.xlsx (14kB)
This file has been downloaded 810 times


Here is something a little humorous. I picked up four bug zappers at the local dollar store for $3 each. It turns out that they are of the lower voltage variety only putting out about 850-900 volts. For fun I hooked all four in series with at least 4kV worth of diodes on the output terminals. The capacitor bank was made from salvaged pulse capacitors. The eight of them hooked together give a capacitance of 0.5uF and a voltage of 4000V. The four series connected bug zapper supplies can charge the bank up to about 3200V in about 10-12 seconds. I guess I need another bug zapper so I can charge them up to 4000V. Actually, the 4000V bank probably shouldn't be charged much over 3200V anyway. In any case these bug zappers are really the weakest I have seen so far. Three of the zapper supplies I had before would easily produce more voltage than four of these. Anyway $15 in these weak bug zappers can get you a 4kV supply. I guess I really should just build a decent HV supply, other than winding the transformer there really is nothing to it. Actually a suitable transformer could likely be ordered very easily if the tedious process of (re)winding a transformer was preferred to be avoided.




[Edited on 25-4-2015 by Hennig Brand]

I believe break time is referring to when the wire bursts. It can be very violent if enough energy is dumped in fast enough or it can be very gently like a hot wire igniter if not enough energy is dumped into the wire in a short enough time. In order to make a shockwave capable of initiating secondary explosives the rate of energy deposition has to be high enough that the inertia (mass) of the bridgewire can hold it back enough to build up to a very energetic release/shockwave.
From Cooper, " The attainment of burst does not depend on the shape of the current trace, but occurs at the time and current where the area under the current squared versus time curve equals the burst action. Attainment of burst is necessary but not sufficient to form the shock that will detonate the initial pressing." So wire burst or break is necessary but it can happen at too low an energy level to initiate the explosive.

With a big enough HV power supply anything is possible probably, even no wire at all. Maybe with a big enough Tesla coil we wouldn't even need transmission line.
It really isn't that hard to get a good approximation of what is going on if a few reasonable assumptions are made. It does take a bit of time and a little math knowledge to go through it, but that article I posted with the first version of the spreadsheet explains it very well. I am definitely not a math wiz, but I am not too bad either and I spent a day sorting through it.

You are referring to voltage drop across the bridgewire which gets very high as the wire approaches explosion because the resistance spikes and current pulses have stepped up to a high value too (Ohm's law, V=IR). If you look at the first test results, from a few posts ago, the model gave a peak current of 1356A and if we assume a peak resistance of 4ohms we get V=1356A*4ohms= 5424V across the bridgewire before burst. As you can imagine, much higher voltages are easily possible as well, such as when higher voltage capacitors are used, shorter and/or more efficient transmission line and also if a different bridgewire material is used which has a higher final resistance such as gold (about double the final resistance of copper).

A couple people have mentioned small consumer grade inverters with added voltage multipliers, such as a Cockcroft–Walton generator, which would likely be one of the simplest alternatives with the most complicated part being "off the shelf". Even the smallest automotive inverters are way overpowered though for any normal sized EBW capacitor bank. I suppose that being a little bit overpowered is not a big concern though.

Regarding bug zappers, I think what they may have done is reduced the voltage and made the capacitance larger. I could compare the capacitors later. The sparks from these zappers seem weaker as well though.

0.5uF, 4000V Capacitor Bank Charged to 4000V in Under 10 Seconds From 2 Bug Zapper Supplies

I went back to the two older bug zapper supplies, because they put out more voltage and current. Four of the pulse capacitors from the other bug zapper supplies were used to make two voltage doubler stages, one on each bug zapper output. Separate halves of the main 4000V capacitor bank (2000V) were connected as C2 for the two voltage doubler stages. Each bug zapper supply now charges up half of the capacitor bank to 2000V for a total combined capacitor bank voltage of 4000V. These two bug zapper supplies can now easily charge the 0.5uF, 4000V, capacitor bank up to 4000V in under 10 seconds. Two bug zapper supplies can be made to function as an effective EBW system power supply.





Observation:
Replacing all tiny gauge wiring that typically comes with these zappers with even the small solid conductors from telephone cable greatly increases performance.

Quote: Originally posted by Hennig Brand

I believe break time is referring to when the wire bursts. It can be very violent if enough energy is dumped in fast enough or it can be very gently like a hot wire igniter if not enough energy is dumped into the wire in a short enough time. In order to make a shockwave capable of initiating secondary explosives the rate of energy deposition has to be high enough that the inertia (mass) of the bridgewire can hold it back enough to build up to a very energetic release/shockwave. From Cooper, " The attainment of burst does not depend on the shape of the current trace, but occurs at the time and current where the area under the current squared versus time curve equals the burst action. Attainment of burst is necessary but not sufficient to form the shock that will detonate the initial pressing." So wire burst or break is necessary but it can happen at too low an energy level to initiate the explosive.

0.6g of ETN Initiated by 1.5mil Cu EBW using 3700V, 0.5uf, capacitor discharged through ca. 51ft of RG-6 Coaxial Cable

The 0.6g of ETN was pressed into the 7.6mm Al casing in three increments. About 0.2g was pressed with a lever press at about 100lbs of force, about 0.2g was pressed firmly by hand and about 0.2g was poured in loose and then only very gently compressed just to settle and remove large voids. The copper bridgewire was ca. 1.5mil in diameter and ca. 100mil in length. The 0.5uF capacitor bank was charged to ca. 3700V before the small capacitor (0.15uF, 800V) on the third bug zapper supply was discharged through the primary winding of the trigger transformer sending a HV trigger pulse from the transformers secondary winding to the trigger electrode of the trigatron thereby discharging the main stored charge through the firing leads and bridgewire almost instantaneously. The trigger transformer used is a repurposed switching power supply transformer, salvaged from an old power supply. The trigger electrode/conductor and insulation/spacing were provided by a section of high voltage wire (40kV) connecting the flyback transformer and CRT anode from an old television. About 150 ohms worth of resistors were put in series between the trigger pulse generator and the trigger electrode to isolate the generator from the main electrical charge. The trigger circuit was fired by simply touching two wires together, connecting the capacitor to the primary winding of the trigger transformer. The target the EBW detonator was sitting on (held in place by tape) is 1/8" steel. Even from 40+ft away it was a nice boom, however the damage to the witness plate was a bit less than hoped for. There was, however, a significant dent in the top side and a substantial scab blown off the back side proving that there was definitely a detonation. A significant amount of the 0.6g of ETN may have been used up during the time it took to accelerate from low velocity to high velocity detonation.

The fireset can obviously be made much more compact. The three bug zapper supplies could be made to fit into something not much bigger than a large package of cigarettes probably. The trigatron could be made 5-10X smaller; when I get around to it I am going to make a nice compact trigatron in a small (plastic?) enclosure.

Found a good use for the tiny vise that was given to me a while back. It really makes soldering the bridgewires much easier. I kind of wish I hadn't spent over $100 on 100ft of RG-213 since for my purposes RG-6 seems to be adequate. To get similar results as this test at 102ft, instead of 51ft, the RG-6 coax could simply be doubled (connect shield to shield and center conductor to center conductor at both ends). Connecting two lengths in parallel basically halves the inductance and resistance.






Here is the graph produced using the previously posted, distributed parameter method, spreadsheet.




Here are the numbers from the last test, which failed, and this successful test for comparison purposes.

For 2400V, 0.67uF, 51ft RG-6, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 876 A
Time at or above Burst Action = 1.54 usec
Average rate of Current Rise = 876A/1.54usec = 569 A/usec
No detonation from test

For 3700V, 0.5uF, 51ft RG-6, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 1039 A
Time at or above Burst Action = 1.15 usec
Average rate of Current Rise = 1039A/1.15usec = 903 A/usec
Detonation confirmed

Of course this test used a trigatron, triggered spark gap, while switching for the previous tests was done by simply touching two 18gauge wires together, so it is really not a fair comparison.


[Edited on 29-4-2015 by Hennig Brand]

[Edited on 25-9-2015 by Bert]

10g of ETN Putty Explosive Initiated With Custom Made EBW Detonator

Well the bug zappers are no more. After about three successful tests I noticed that the bug zapper supplies were charging the capacitor bank up to lower and lower voltages until they wouldn't even charge the bank up to 2000V anymore. The amount of current being drawn from those zapper supplies was really a lot more than what they were designed for. I am currently working on a compact switching supply operating at fairly high frequency, but for now I came up with a simple solution for a power supply that is very tough and basically free. I located four discarded microwave ovens which provided me with everything needed to make a power supply. I obtained a transformer, four HV capacitors and four HV diodes. The transformer was run with a hundred watt light bulb in series with the primary to limit current which was latter changed to two 75ohm, 50W, resistors in series. The four diodes and capacitors were configured as two voltage doublers with the diodes run in opposite directions. This gave one output that was 2000+V and one output that was -2000+V. The two outputs together gave a potential difference of well over 4000V (without load). This supply is very robust and free, but the efficiency is low especially since half the power going to the system is dissipated in the current limiting resistors. A properly matched transformer could double the efficiency. Efficiency is not a big concern for me at the moment, anyway, since the amount of energy used is so small and this isn't a commercial product. The system draws about 50W of which about 26W is dissipated in the current limiting resistors. It can charge the 0.5uF capacitor up to 4000V in under ten seconds. A small automotive inverter fed by a 12V lead acid battery was used to feed the transformer, though the unit could have just as easily been plugged into a standard wall plug for this test.

The detonator was made about a week ago. The 7.6mm casing contained about 0.7g of ETN, 0.5g pressed at 100lbs, 0.1g hand pressed, 0.1g left almost loose. The ca. 1.5mil copper bridgewire was about 100mil long. The blasting cable used was 50ft of RG-6 and 2-3 feet of 18 gauge speaker wire. The main charge was 10g of 80% ETN putty explosive. The target was 1/8 inch wall thickness square tubing. The 0.5uF capacitor bank was charged to about 3800V before the trigatron was fired. Detonation was immediate, as it has been for all the successful tests. Both 1/8 inch sides of the tubing were penetrated.

I am going to get a tough little plastic toolbox to house the whole fireset. Much bigger and heavier than a commercial fireset, but it is tough as nails and free. Still working on a more compact version.

A safety note: None of the capacitors stay charged for more than a few seconds after power is removed from the circuit. The main pulse capacitor bank has 10Mohm bleeder/bypass resistors across each capacitor in the series string. The microwave oven capacitors have internal bleeder resistors, which drain them in a few seconds. All in all it is a fairly safe system....did I mention free.

Note, all microwave oven capacitors may not have internal bleeder resistors, but I think most do.





[Edited on 8-5-2015 by Hennig Brand]

I've managed to get my setup up and running but I still need to make some etn this weekend to fully test it most parts are from fleabay the high voltage generator looks like its meant for a tazer cos it produces nice sparks between the electrodes at 3 volt supply.
I used 10 400v 10 uf capacitors in series for 4000 v 1 uf and a spark switch to fire them I also like found that a peizo bbq igniter will fire the switch ok so that realy simplifys that part now I just need the new router bits to turnup so I can mill some mini pcb,s cheers nuxy.

Nux Vomica,
I like what you did with the housing for the sparkgap switch. I will do something similar when I get around to miniaturizing my fireset. Those capacitors you have are not the right thing though, unless I missed something. They are high ESL and ESR and not designed for pulse applications. Also when you add capacitors in series ESL and ESR increase just like resistance with resistors. I know I have caps in series too but they were salvaged and they are pulse rated caps. It is best to get high voltage, low capacitance pulse rated caps with low ESL and ESR and put them in parallel as much as possible. Your setup might still work with a short low inductance blasting cable but they are relatively slow caps from what I have seen. Interested to see how your charging circuit works out. If it is for a tazer it will put out very low current but you may be able to do somthing with it still. Some good ideas you have there. Yeah, if properly adjusted even very weak sparks will fire the gap. Interesting that a piezo igniter works. I though about using one and then decided not to try it. It may work but it is very underpowered. I think there are advantages to more trigger pulse power.

Those poor bug zapper supplies, after doing a couple of simple calculations after the fact it was obvious that I was seriously abusing them. The 60Hz stuff is working great but it is just so big and heavy. A much smaller 60Hz transformer than the MOT could be used but I used what I had. If I wanted to charge to 8000V or even 10 000V this system could easily be made to do it too. I am trying to learn about modern switching power supplies. They are small, light, powerful and efficient.


Jock88,
That is starting to look like a drawbar isn't it.


[Edited on 8-5-2015 by Hennig Brand]

The capacitors were advertised as low impedance and low esr I suppose you cant trust sellers on ebay though, the power supply doesnt seem to have any trouble pushing the voltage over 4000v i have to shut the power off quickly cos it shoots up fast, im trying to think of a voltage limiting circuit that shuts the power off at a set voltage.
yeah a pezio dosent seem to have much spark in it but it will fire the switch every time that i have clicked it.
cheers nuxy.



[Edited on 8-5-2015 by nux vomica]

I spent the last few hours making a smaller trigatron. The tubing used is food grade vinyl I believe (it was part of a wine/beer brewing kit) and is an excellent insulator. Not exactly sure how well the tubing is going to respond to high voltage discharges, but it should be fine I think especially since it is only one discharge every now and then, not constant repetitive discharges. The tubing fits the electrodes like a glove, in fact it is a little difficult to get them apart once together. Half inch brass rod was used as the starting point. Here are a few pictures.








I have been calling the caps I purchased metal film type when actually they are metal foil type which are far superior from what I have read. Here is a data sheet for the caps I bought. They are the same ones many of the Tesla coil people love to use. Probably bigger and tougher than they need to be for this application.


Attachment: High Pulse Capacitors Data sheet Type 942C.pdf (134kB)
This file has been downloaded 874 times


[Edited on 10-5-2015 by Hennig Brand]

I am waiting for the home brew krytron design...



Or your LASER pulse switched sprytron?

Now you're just getting fancy. I am just a meat and potatoes kind of guy.

For non repetitive, low demand, applications such as these I think the trigatron is just fine. Some of these other devices do give lower delay and jitter and operating life from the bit I have read. Operating life is not a big concern for us though, since EBW triggering is not a high frequency application. Unless doing multiple shots where the shots need to be timed perfectly, the small amount of delay and jitter of a well made and adjusted trigatron is likely more than accurate enough for us. I guess the laser triggered devices are extremely precise with very low delay and jitter.

Quote: Originally posted by Hennig Brand

That is not a radio controlled EBW it is a radio controlled hot wire igniter. However, yes, it would be possible to remotely charge and trigger an EBW fireset. I enjoy that particular YouTuber's videos, but I don't think I like how he made a switch from the vibrator motor. I would have taken the vibrator motor right out and used the power wires to drive a relay or transistor. Wires are safer than radio control, especially if the radio control system is not well designed and encoded. Heavy wires are only needed between the fireset and detonator, the fireset can be controlled by fairly fine wires. To be honest, I don't think it is fair to call the wires heavy anyway in many cases. The RG-6 coaxial I have been using it not heavy at all and it tends not to tangle much either.

Quote: Originally posted by Spartan

Has anyone try to connect a mobile phone to the EBW detonator something like this video: https://www.youtube.com/watch?v=LrSdQjlUND8 Do you think it's possible? If it is safe i think it's a good idea, you avoid to use to long wires.

EBW Capacitor Bank Charging Circuit (555 Inverter Based)

Thanks for the radio control encoding tips. I was aware that a lot more sophistication and safety could be added, but to tell the truth I never made it past using two tones at once. Always meant to go back and make it more sophisticated though. Electricity/electronics is just one of my hobbies, I went through Chemical Engineering.

First off I will say that Markx was right when he said I needed a beefier power supply than those bug zappers and his suggestion for a circuit was a good one. The post by Markx earlier in this thread can be found here:

http://www.sciencemadness.org/talk/viewthread.php?tid=23466#...

I have ordered some of the IR2153 and 21531, but they will take a couple of weeks to get to me (paid a lot more for the 21531, oh well live and learn). In the mean time I have been working on a 555 inverter circuit. The IR2153 is superior as a mosfet driver, but the 555 can be made to work and it is a much more common IC.

I used the circuit found here:
http://www.eleccircuit.com/220-volts-power-inverter-using-ne...

However, I was not interested in driving a big, heavy, slow 50 or 60Hz transformer or using a voltage multiplier with big capacitors as is required with such low frequencies. In order to bring the frequency of the astable circuit from 50Hz up to about 15kHz C1 was changed to 1nF, R1 was changed to 1kohm and R2 was changed to 47kohm. This also kept the duty cycle just slightly over 50%. The only part I used that was exactly the same as specified was the 555 timer IC. I was hesitant to go higher in frequency because I was only using a regular 555, not the faster cmos variety and I was only using slow 1N4007 diodes not one of the faster types such as UF4007.

The transformer was wound on a plastic bobbin which came with the salvaged pot core used. The ferrite pot core is 3019P, 3C8 material (presently called 3C81 from what I have read). The primary is 18 turns 26AWG bifular wound in two layers to give a center tap. The secondary was wound in 10 layers, with each layer having about 40 turns of double insulated 40AWG magnet wire. A layer/strip of printer paper just slightly wider than the bobbin winding surface was wrapped on between each layer which added insulation between layers and also gave a nice flat, smooth, surface to wind on. There are better commercial insulating papers available for winding. Apparently I had the primary hooked up out of phase yesterday because it took about 15seconds to even charge the capacitor bank up to 2000V and I was having some trouble with the upper transistor heating, but the heat sinks I was using yesterday were also tiny and the run times were longer so I am not sure that it is related. Today I changed the transformer primary winding wiring around and now the circuit charges up the 0.5uF capacitor bank to 4000V in about 5 seconds. I should also mention that there is 40Mohms of resistance across the capacitor bank as a bleeder and bypass network and that there is 1Mohm (10X 100kohm resistors) between the capacitor bank and the power supply. So the supply is putting out much more than what would be needed to charge the capacitor bank without these extra loads.

The heat sinks are just what I could find lying around and are not even matched. More than big enough for the 5 second run time though. The pot core was found on a piece of industrial electronics in a scrap yard. It looks to have been sitting out in the snow and rain for several years. The old windings were removed before the new windings were put on.

The battery pack I am using is made up of a mix of old AA batteries and so is not ideal. The circuit draws about 0.7-0.8A, from the little battery pack, which pulls it down to about 7-7.5Volts. The output from the transformer is about 500-550V which is fed into two six stage half wave voltage multipliers made up of 3kV 10nF ceramic caps and 1N4007 (1A, 1000V) diodes. The diodes for the two multipliers are run in opposite directions from one another. The voltage across the two multiplier outputs is greater than 6000V with no load.








Found some mounting hardware. It looks a little less amateurish without the pink elastic band.




[Edited on 15-5-2015 by Hennig Brand]

Quote: Originally posted by Varmint

Henning: The rectifiers aren't at odds with the chopping frequency, but the conduction to off recovery time.

Ferrite Transformer & Voltage Multiplier Design Guides

105ft of Blasting Line, 10g of ETN Putty Explosive Initiated With Custom Made ETN EBW Detonator

This test was performed nearly exactly the same as the last test, except that a new homemade power supply was used. The 0.5uF capacitor bank was charged to ca. 3800V before the homemade brass trigatron was triggered dumping the electrical charge through the blasting cable and bridgewire. The detonator was made using a 7.6mm id Al casing and 0.7g of ETN; 0.5g was pressed at 100lbs of force, 0.1g was hand pressed and 0.1g was put in nearly loose. The bridgewire used was 1.5mil diameter copper, about 100mil long. The witness target was 1/8 inch wall thickness square steel tubing. The blasting cable was made up of 100ft of RG-6 (standard cable, satellite, TV coaxial) and 5-6ft of 18 gauge speaker wire. The main charge was once again 10g of 80% ETN putty explosive.

The test was a complete success. Both 1/8" sides of the steel tubing were perforated in a very brisant detonation.

Right now this system is a bit inconvenient because it takes about 15 minutes to set up the modular fireset and run the line to the charge. Once all fireset components are assembled together permanently in a suitable small enclosure it should only take a couple of minutes to set up.

Being 105ft away is normally far enough for my purposes, but the distance could be doubled to 210ft with the same setup by simply using two 210ft lengths of the same cable type. Two 210ft pieces in parallel basically have half the inductance and resistance compared to a single cable of the same length and should perform similarly as a single piece 105ft long. There are also much better cables available, which would allow much longer cable runs to be made. In my opinion, however, 100ft is enough for most normal small scale blasting. If more distance is needed the blasting box could be sandbagged 100ft away from the blast and the operator could control the blasting box through long thin cable at a much greater distance away.

I used the old trigatron, in the wooden block, because I wanted to keep everything as much the same as earlier tests as possible.






Here is a current versus time graph generated using the "Distributed Parameter Method" Excel sheet attached earlier in this thread.



The theoretical numbers for the earlier failed test look better than this test, however the theoretical model assumed fast efficient switching. A trigatron was used in this successful test, and simple touching of 18 gauge wires was used as the method of switching for the earlier failed test. Fast efficient switching appears to be very important, but I am unable to quantify it exactly at this time.

For 3800V, 0.5uF, 105ft RG-6, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 853 A
Time at or above Burst Action = 1.85 usec
Average rate of Current Rise = 462 A/usec
Trigatron Switching
Detonation Confirmed

For 2400V, 0.67uF, 51ft RG-6, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 876 A
Time at or above Burst Action = 1.54 usec
Average rate of Current Rise = 876A/1.54usec = 569 A/usec
Switching accomplished by touching two 18gauge wires together
No detonation from test


[Edited on 22-5-2015 by Hennig Brand]

Much Better Cables Are Available

Just did a theoretical comparison between RG-6 coax and the "C" cable sold by RISI using the distributed parameter method. Using "C" cable could easily double the distance that my system would function effectively, compared to when using RG-6, everything else being equal. I would like to get some of this cable or something similar.

RG-6 Coaxial
For 3800V, 0.5uF, 105ft RG-6, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 853 A
Time at or above Burst Action = 1.85 usec
Average rate of Current Rise = 462 A/usec
Trigatron Switching
Detonation Confirmed

"C" Cable Coaxial
For 3800V, 0.5uF, 210ft RISI "C" Type Coax, Cu BW 1.5mil D, 100mil L
Current at or above Burst Action = 763 A
Time at or above Burst Action = 1.44 usec
Average rate of Current Rise = 531 A/usec





[Edited on 25-5-2015 by Hennig Brand]

Quote: Originally posted by Hennig Brand

These documents give a feel for what is possible with commercial gold EBW detonators. Results would likely be somewhat different with my homemade copper EBW detonators and fireset. The specs of the capacitors used in the RISI firesets are normally 1uF and 4000V from what I have seen. It looks as though quite a few commercial detonators can be fired simultaneously in various series parallel configurations depending on cable length, etc.

I'm getting the closer to being able to do some proper testing now ive got new capacitors, there Epcos 5uf 1300v radial metalized polypropylene film with 0.006 ohm ESR I bought 4 so that gives me 5200v and 1.25 UF.

I had issues with mach3 on my cnc router that took time to work out so I just finished routing the board on the weekend but every thing seems to fit on okay , I built the spark switch into the board to tidy things up a bit and keep it close to the capacitors.

I've taken a short video of the piezo fireing the spark switch but thats about it so far , cheers nuxy.






[Edited on 9-6-2015 by nux vomica]

Looks very professional, well done. Those capacitors are far superior to what you had before for this purpose. You did a nice job of making a small tidy spark gap switch. Your setup will be quite compact that is for sure, which is a good thing.


I have a bunch of 2153 chips now so I should probably make at least one inverter using one. The inverter based on the ubiquitous 555 is working well enough for my purposes already though, at least in this application. The 2153 inverter circuit diagram below was taken from the following webpage:

http://danyk.cz/menic230_4_en.html

The 2153 datasheet has a graph allowing component choices to me made for a desired operating frequency.





Attachment: IR2153 Data Sheet.pdf (156kB)
This file has been downloaded 551 times


[Edited on 9-6-2015 by Hennig Brand]

Just had a successful test used 0.030 mm dia x 1.6mm long copper bridgewire with .8 grm etn, dont know compression figures as in a rush but compressed .7 then used .1 grm loose alloy tube 8mm id x20mm long at the end of 7 meters of rg6 coax and 200mm speaker twin core.

Charged capacitors for 11seconds volt measurement would be over 4500 volts didn't have gauge just used times tested in shed then hit piezo button nice bang and a dent nearly through the 2mm s/s plate nice




[Edited on 10-6-2015 by nux vomica]

[Edited on 10-6-2015 by nux vomica]

[Edited on 10-6-2015 by nux vomica]

[Edited on 10-6-2015 by nux vomica]

edit: Oh I see, the power supply is low current as suspected, which could also mean that it won't take too much abuse before it becomes damaged. Good news it that it is fairly easy to build a decent power supply. It makes a nice little project in itself too.

Use a voltage divider which gives a lower proportional voltage for measuring. Even regular 1/4watt resistors can be used if enough of them are connected in series. Often times they are only rated for a few hundred volts each IIRC, but if you add ten in series the series string can easily handle a few thousand volts. High voltage resistors are also available, such as thick film resistors, if you want to go that route. I made a voltage divider that has about 40Mohms resistance and my multimeter is attached to it at the appropriate place so that 4000V on the capacitor bank reads as 25V, but it could be any voltage you choose. The meter I am using is only rated for 1000V DC so there was no way I could use it to measure the 4000V directly.




[Edited on 11-6-2015 by Hennig Brand]

Quote: Originally posted by Hennig Brand

A positive result is nice. So the bridgewire was around 0.63 mils in diameter or 54 AWG right? Seems extremely thin, but if it works it works. Must be very difficult not to break when handling. Was the bridgwire copper? It would have been nice to know more about the specifics of the test, such as capacitor bank voltage prior to firing. Your assumption about the voltage could be right, but maybe not.

I should listen to the quote about assumption being the mother of all fuxkups.

I have made a few assumptions in my time too and reaped the rewards.

From the above picture it looks as though your power supply is being supplied by only two AA batteries. That in itself tells a lot about the limited current supplying capability of the power supply. Power supplies have losses, usually quite significant especially with small power supplies, but lets assume for a minute that yours has no losses (Power In = Power Out). Lets assume you can pull 1A from the two AA batteries at 3V. Using conservation of energy, power in is 3V * 1A = 3W, so at 4500V the current drawn could be a maximum of 3W / 4500V = ca. 0.67mA. At 4500V the 5 Mohm Volt meter would draw, 4500V / 5 000 000 ohm = 0.9mA (0.9mA > 0.67mA). I went through these same problems when I was using the bug zapper supplies.

Had another test also successful l used same setup with copper bridgewire 0.030 x 1.6mm long .7 grams etn compressed to 1.49 grams cc and .1 gram loose on top, 7 meters coax and 200mm twin speaker wire.
Haven't been able to get to electronic supply shop so don't have accurate voltage levels just charged for 11 seconds as before and pushed pezio button detonation was instantaneous and plate was more damaged than last shot nuxy

[Edited on 11-6-2015 by nux vomica]