Sciencemadness Discussion Board

Has anyone made a EBW setup.

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Grantr - 19-10-2015 at 07:29

Aurium,

Thanks. I am very aware of the dangers of HV. I am working on a new schematic.

I want to build the Circuit like Nux built using those eBay high voltage generators. That is what it appears he is using on page 3.

I have a working Microwave oven Xfomer as well but would rather have something lighter and compact and portable. The MOT would need a voltage multiplier to get the voltage up since I think these are all output around 2100 volts.

Nux,

Do you have any idea how much voltage that generator produces? The info on ebay is crap.

Grantr - 19-10-2015 at 18:14

Attached are two schematic I have been working on. All diodes are the same value. Lower voltage resistors will be chained together in series or either HV resistors will be used. I plan to use the same caps referenced earlier.

The one using the Microwave oven xformer MOT has a resistor on the AC input to limit current.

The voltage divider circuit would be the same for both. I only have it in one drawing. It should give me 450 volts on a volt meter when the caps are charged to 4500 volts.

Attachment: Bridge wire.doc (71kB)
This file has been downloaded 480 times

nux vomica - 19-10-2015 at 20:57

Grantr I didn't bother measuring the voltage of the eBay units but I think all the resistors are going to put too much load on the hv unit and it wont charge high enough to fire the ebw bridge wire.

I think that if you want bleeder resistors and a voltage divider you need the 12/220v inverter and the diode cascade setup, I use it and it works perfectly every time. Nux

Aurium - 20-10-2015 at 08:19

I agree nux. I used those HV modules for my SGD and I found even a 10Mohm bleeder resistor to be too low.
As for max voltage from the module, I connected it to a 6V battery, that got shunted to 3.5V (maximum input is 6V). Then I used two parallel metallic plates to measure arc breakdown distance and got a max voltage of around 15kV, at the 3.5V input.

Grantr - 20-10-2015 at 15:00

I did not realize you could charge a bank of caps with much higher voltage than their rated volts. I knew that could overcharge them but didn't know they could withstand the higher voltage charged that way.

The two 1 M ohm resistors would draw 10 watts. That does seem to be high considering that would be about 2.2 amps at 4.5V


What is a SGD Aurium?


Thanks,

Aurium - 20-10-2015 at 16:19

http://www.sciencemadness.org/talk/viewthread.php?tid=63840

Gargamel - 20-12-2015 at 12:52

Hi guys,

I'm about to order some extra thin copper wire for experimenting.

Commonly the wire is coated with insulation, HPN enamel for example, which can be soldered through.

I wonder how the coating might affect the behaviour of the wire when it is vaporised....?
Do you have an opinion on that?

Bear in mind that most of the coating will be charred from the soldering action before.



The wires you guys used in your successful tests - did they have insulation coating?

The_Davster - 20-12-2015 at 13:11

The coating will be inconsequential for an EBW setup.

nux vomica - 20-12-2015 at 13:15

There are plenty of electronic equipment that have copper wire fine enough for what you need ,eg the small 12v relays that mount on pcb boards, camera flash trigger transformers.
I don't remove the coating on the wire and the ebw always works ok for me.

Gargamel - 23-12-2015 at 09:39

Thanks you.

Yes I know there are sources for salvage of such wire.
But i find it hard to determine what i'm actually working with. 0,02, 0,04, or 0,06...?
Hard to say...

But a critical factor, especially if the shooting wire is quite long.

I'd like to know excactly what i'm working with.

Sulaiman - 23-12-2015 at 10:37

A few comments on the two circuit diagrams;

Upper schematic

I think that the 6kV 200mA diodes (microwave oven type?) are too slow to be efficient at rectifying the high frequency output of the little eBay inverters.

Diode D6 can /should be replaced with a direct connection.
It does no harm but removing it will make things easier (e.g. earth = 0V load wire)

The voltage divider for the voltmeter would be 10:1 IF the voltmeter has infinite input resistance.
DMMs are usually 10 MOhm and analogue 10 or 20 kOhm per fsd volt.
For a 10 MOhm dmm R9 should be (10 x 3)/(10 - 3) = 4.2857 kOhm, use 4.3 kOhm.

Rather than stressing R5 and R6 by having half of the high voltage across each
you could use four 1 MOhm resistors, one across each of the h.v. capacitors.


Lower schematic

D4 is not only redundant, it is the wrong way around

D3 and C1 are redundant

as above for R2 and R3

Edit: if you measure the resistance of a few meters (or feet/yards/furlongs) of your unknown wire
with a cheap dmm on resistance range (corrected for the resistance of the dmm leads etc.)
by comparing the Ohms/meter with common tables you will get very close to the actual wire gauge.
Easier is a micrometer or digital caliper to measure o.d. with insulation and look up the gauge.
As a chemist you should be able to determine the gauge by titration !

[Edited on 23-12-2015 by Sulaiman]

nux vomica - 23-12-2015 at 19:30

Ok here's a random relay pulled off a circutboard wire measures 0.07 mm .

20151224_141338.jpg - 1.8MB 20151224_141328.jpg - 1.9MB

[Edited on 24-12-2015 by nux vomica]

CrazyC - 30-1-2016 at 10:36

Hello just to give an idea you guys could try.

Use a glow plug from a model glow engine. It's ready made with a wire in it that will glow red hot to start the engine from just a 1.5v battery or completly blow out from 12v car battery.

I know because I had a model and not the right tools when I was young and dumber:D This would set off SADS for example.

Remember line loss and I don't know if wires can easly be hooked to them or how much you want to spend on caps.

Just giving ideas to be helpfull use it if you want.

hissingnoise - 30-1-2016 at 12:26

This ignitor on instructables, a variation of which I've been using for years, is easy 'n cheap!


XeonTheMGPony - 30-1-2016 at 12:32

I make my own with steel wool and 22 guage copper solid core, the more simpler ones I use either solid or multi strand and a single wrap of nichrome around a match head.

99% are the nichrom method, but for timed circuits or rockets I use a capacitor discharge through a 1.5mm length of steel wool that's been glued onto a match stick with nitro cotton and crimped into the copper leads, usual cap bank is 600uf at 250v driven by basic photo flash style circuit (Parts obtained from a photoflash of disposable cameras)

lysander - 12-3-2016 at 20:16

Nux and Hennig: Can you post some schematics of your "preferred embodiments?"

I spent some time digesting this older thread by Franklyn on EBWs -- lots of great theory, and clever designs for mains/AC-driven firing. But I like the idea of running off a battery, as well as the safety of having self-balancing and draining capacitor networks. Based on the results you folks are getting I think he might have overspecified things. Granted, he advocates firing 28AWG bridge wires with 83J.

Anyway, it looks like your general design involves:


  1. Battery driven flyback transformer
  2. Rectifier
  3. Voltage limiter (and some sort of charge maintenance switch to compensate for the cap bleeders)?
  4. Self-draining and balancing capacitor network
  5. Voltage divider to monitor charge status
  6. Trigatron (or other gap arc trigger?)
  7. RG6 (or better) to bridge wire


And nux has a bunch of this on a PCB now?!

I might be able to piece the segments together by rereading the last nine pages enough times, but once you've got a design as reliable and inexpensive as you're reporting it merits a schematic! Heck, send me a sketch and I'll do it in SPICE.

As for actually building it: I've done HV but nothing in the kV range. Are there special protoboards to prevent arcing? Or do you just get cheaper ones without through-plating and drill the surface contacts around connection points?

[Edited on 13-3-2016 by lysander]

Hennig Brand - 13-3-2016 at 02:55

Back on page 4,

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

I described the simple 555 timer IC based inverter design I eventually settled on (at least so far). I used very basic techniques, through hole components and protoboard. I have done hobby electronics off and on for years but never got into making PCBs. The circuit I built was so simple, and I wasn't mass producing it, so even the simple methods I used are fine I think. Nux made PCBs and it does make a very neat, high quality, finished power supply circuit.

I put quite a bit of time in learning about transformer design and voltage multiplier design and wrote very straightforward guides for others to use. Nux was able to order a small power supply which worked well coupled with a voltage multiplier. There isn't much fluff in this thread, but at the same time it covers most of the important points while not going into a bunch of overly complicated (and unnecessary?) theory. I read that other thread, and found it made the topic very overwhelming, especially for the amateur, and much of what was stated was actually incorrect in my opinion. Simple is usually better, unless there are really good reasons to complicate things. Anyway, do yourself a favor and read this thread since it is well worth it and most of the hard work has been done for you. I believe the information provided to be correct for the most part and unnecessary complication has been avoided so that all that is needed is a very basic understanding of electricity and physics to make it work.

Arcing? Lots of space, or components can be potted. Read the thread please!

lysander - 13-3-2016 at 06:53

Quote: Originally posted by Hennig Brand  
I read that other thread, and found it made the topic very overwhelming, especially for the amateur, and much of what was stated was actually incorrect in my opinion. Simple is usually better, unless there are really good reasons to complicate things. Anyway, do yourself a favor and read this thread since it is well worth it and most of the hard work has been done for you.


I agree. This is a 5-star thread, and I have read the whole thing once and thought it well worth while.

It's just that one gets to the end and isn't quite sure which things that were tried were discarded in favor of which alternative (or would be if you were starting from scratch). But you folks have done the hard work: I'll spend some time summarizing, and would appreciate it if you correct anything I misunderstand!

Hennig Brand - 13-3-2016 at 09:41

Thanks for the compliment. Something to keep in mind, in general there was a progression towards more and more suitable components and designs as the thread and understanding grew.

PHILOU Zrealone - 13-3-2016 at 12:42

Quote: Originally posted by hissingnoise  
This ignitor on instructables, a variation of which I've been using for years, is easy 'n cheap!


Usually I work with very efficient drink straw fuses but I have also tested the electric systems...
So I also have a lot of christmass-tree tiny light bulbs/ampoules.
I cut the head off the tiny glass recipient with a dremel cutting disc. I check the resistance of both wire to see if filament is stil integer.
The plastic base holder can be taken away and you are left with a glass tube with two free external copper wires that goes into the ampoule (about 1.5 cm long and 0.5 cm large) and are connected to the resistant filament.

Then I fill the ampoule with whatever I want:
For ignition:
-Black powder
-KClO3/S/C/CaCO3 black powder

For flash or detonation:
-Ni(N2H4)3(NO3)2 --> this flashes-bang
-Ni(N2H4)3(NO3)2 / Silver acetylide nitrato complex (2/1 by weight) --> this detonates > 5 km/s
-Silver acetylide nitrato complex --> this detonates > 3 km/s

The last two are true detonators because the ampoule can hold a detonating material up to 1.2 cm long and 0.4 cm large.
I insert the powder with a tiny paper cone and slight vibrations...I also hit smoothly the ampoule sothat the powder self confide to a higher density.
When everything is inserted, I check for the integrity of the resistance of the filament, I press a little more the powder from above and insert even more powder.
--> I try to get as much into the ampoule at the max density.

I recheck for the integrity of the resistance of the filament and finally I put a tiny drop of concentrated nitrocellulose/aceton on top to seal the ampoule and leave to dry. The NC cap cover is active material and can transmit the detonation wave to a secondary material...

Those devices can be inserted as such for ingitors or detonators in sensitive mixes or in larger/longer copper pipe detonators with a secondary (avoiding contact of the wires with the pipe of course --> use of glue to fix the glass to the pipe).

[Edited on 13-3-2016 by PHILOU Zrealone]

lysander - 13-3-2016 at 15:04

PHILOU et. al.: This thread is about exploding bridge wires, not electric matches.

It looks like Nux has settled on a piezo spark triggered spark-gap "trigatron." Hennig, do you prefer your spark-gap or did you end up going with a thyristor?

OK, here's first try. Using COTS components wherever possible, current BOM:

  1. 12V battery (e.g., SLA)
  2. 40W 12V-220V DC/AC transformer ($5 Ebay). (Note that this is a high-frequency output, and peak voltage should be over 300V.)
  3. 10x 100kOhm resistors for supply isolation
  4. 10x 10nF 3kV capacitors (for voltage multiplier)
  5. 10x 1N4007 (1kV, 1A) diodes (for voltage multiplier)
  6. 4x 5uF 1300V EPCOS capacitors ($3/ea. Ebay)
  7. 2x .5W 10MOhm bleeder resistors
  8. 4.3MOhm and 27MOhm resistors for voltage divider
  9. LED Voltmeter
  10. RG-6 cable from capacitor output to bridgewire.
  11. Piezo spark ignitor (for spark-gap trigatron)
  12. Nuts, bolts, and insulating sleeve for trigatron

Basic design is:

  1. 220VAC Power supply connected through isolation resistors to stacked Villard cascade producing ~3000VDC.
  2. 4 capacitors connected in two parallel groups with HV bleeder resistors to produce a roughly 2600V 5uF capacitor circuit.
  3. Voltmeter circuit using 10x voltage divider to monitor capacitor charge.
  4. Trigatron dumps capacitor bank to bridge wire through RG-6 cable

So something like this?

hFQ3BLG.jpg - 285kB

[Edited on 13-3-2016 by lysander]

nux vomica - 13-3-2016 at 16:37

Hi Lysander it looks like capacitor c11 and c14 wont be connected when the trigatron is conducting the trigatron acts as the gap in a dead short, the charge will flow through the voltage multiplier and destroy that instead by the looks.
If you want to simplify things a bit the voltage divider will discharge the caps pretty quickly and lower the work that the voltage doubler circuit has to do.
The sketchup file is the one the spark gap and caps are mounted on , the voltage multiplier and 240 volt supply are separate parts

Cheers nux


ebw board 4000v.png - 15kB

Attachment: ebw board 4000v.skp (68kB)
This file has been downloaded 614 times

ebw.jpg - 13kB

hFQ3BLG.jpg - 295kB

[Edited on 14-3-2016 by nux vomica]

lysander - 13-3-2016 at 17:16

Oh yeah, these supplies are floating. We want to fire the bridge wire through a ground. What do you use for ground when you're firing?

[Edited on 14-3-2016 by lysander]

Hennig Brand - 13-3-2016 at 17:52

The bridge wire and blasting line only "knows" or "sees" the potential difference (voltage) across it. The pulse capacitor(s) are what supply the pulsed current to the blasting line and bridge wire not the power supply used to charge the capacitors. I chose the negative charge side of the pulse capacitor(s) as common or circuit ground just because of convention, but it should work fine either way (I think).

edit: The pulse capacitors are not polarized


[Edited on 14-3-2016 by Hennig Brand]

lysander - 13-3-2016 at 17:56

Wait, you both feed the pulse back into the capacitor block (as shown on nux's correction to my first schematic)? And you don't isolate your voltmeter from it?

I guess that could work because the bridge wire is sort of a fast-blow fuse. But only sort of: I would have guessed that the ionized airgap would conduct a good amount of the remaining voltage in the capacitor bank as a surge even after the bridgewire has blown. Of course, I haven't actually done it and you two have plenty of successful shots, so if you haven't fried anything downstream of the bridgewire then I guess it works!

nux vomica - 13-3-2016 at 19:01

Quote: Originally posted by lysander  
Wait, you both feed the pulse back into the capacitor block (as shown on nux's correction to my first schematic)? And you don't isolate your voltmeter from it?

I guess that could work because the bridge wire is sort of a fast-blow fuse. But only sort of: I would have guessed that the ionized airgap would conduct a good amount of the remaining voltage in the capacitor bank as a surge even after the bridgewire has blown. Of course, I haven't actually done it and you two have plenty of successful shots, so if you haven't fried anything downstream of the bridgewire then I guess it works!


Its all about the cap + - potential as well as the caps low internal resistance the fireing of the circuit balances the potential in the caps while the gap is still conducting .
The voltage divider gives a high resistance so only a small current can flow so the voltmeter is well isolated .


[Edited on 14-3-2016 by nux vomica]

lysander - 13-3-2016 at 20:56

@nux, I can't tell from the Sketchup and photo how you're actually wired. Are you doing two pairs of caps in series, as in my diagram? Or are you going for the full series 5200V?

Here's an updated schematic. If this is right then it looks like the trickiest part is tuning the trigatron. @nux: in the video where you were testing your trigger something flashed each time but I couldn't tell what it was. Were you just dumping the pulse back into the capacitor bank?

U1DD7QW.jpg - 312kB

nux vomica - 13-3-2016 at 21:13

Quote: Originally posted by lysander  
@nux, I can't tell from the Sketchup and photo how you're actually wired. Are you doing two pairs of caps in series, as in my diagram? Or are you going for the full series 5200V?

Here's an updated schematic. If this is right then it looks like the trickiest part is tuning the trigatron. @nux: in the video where you were testing your trigger something flashed each time but I couldn't tell what it was. Were you just dumping the pulse back into the capacitor bank?



Full series 5200v 1.25 UF. in the video I was letting the charging circuit run and just firing the spark gap with the piezio, the flash is the spark in the gap as it travels to the other side of the capacitor.

PHILOU Zrealone - 14-3-2016 at 06:38

Quote: Originally posted by lysander  
PHILOU et. al.: This thread is about exploding bridge wires, not electric matches.

Unless I'm wrong detonation is a fast explosion...
Before putting others on the line read carrefully what they wrote!

*********************************************
Then I fill the ampoule with whatever I want:
For ignition:
-Black powder
-KClO3/S/C/CaCO3 black powder

For flash or detonation:
-Ni(N2H4)3(NO3)2 --> this flashes-bang
-Ni(N2H4)3(NO3)2 / Silver acetylide nitrato complex (2/1 by weight) --> this detonates > 5 km/s
-Silver acetylide nitrato complex --> this detonates > 3 km/s

The last two are true detonators because the ampoule can hold a detonating material up to 1.2 cm long and 0.4 cm large.

I insert the powder with a tiny paper cone and slight vibrations...I also hit smoothly the ampoule sothat the powder self confide to a higher density.
When everything is inserted, I check for the integrity of the resistance of the filament, I press a little more the powder from above and insert even more powder.
--> I try to get as much into the ampoule at the max density.

I recheck for the integrity of the resistance of the filament and finally I put a tiny drop of concentrated nitrocellulose/aceton on top to seal the ampoule and leave to dry. The NC cap cover is active material and can transmit the detonation wave to a secondary material...

Those devices can be inserted as such for ingitors or detonators in sensitive mixes or in larger/longer copper pipe detonators with a secondary (avoiding contact of the wires with the pipe of course --> use of glue to fix the glass to the pipe).
*********************************************
Here is a picture of a EBW and of my light-bulb version...you are very strong if you can tell me a difference...


EBW.jpg - 120kB

lysander - 14-3-2016 at 07:44

Quote: Originally posted by nux vomica  
Quote: Originally posted by lysander  
@nux: in the video where you were testing your trigger something flashed each time but I couldn't tell what it was. Were you just dumping the pulse back into the capacitor bank?



In the video I was letting the charging circuit run and just firing the spark gap with the piezio, the flash is the spark in the gap as it travels to the other side of the capacitor.


Why is the flash visible? It looks like you have the gap inside an opaque insulated tube.

Microtek - 14-3-2016 at 08:28

Philou:

The difference is that in a true EBW, the bridge wire takes the place of primary explosive: The electrical discharge dumps so much energy into the wire, so suddenly that it vaporizes and then even more into the ionized plasma so it explodes and causes the secondary base charge to detonate.
So an EBW is an example of an NPED, but much more reliable than the ones relying on DDT of something like specially treated PETN.

Herr Haber - 14-3-2016 at 14:06

Quote: Originally posted by PHILOU Zrealone  


-Ni(N2H4)3(NO3)2 --> this flashes-bang

Errrm? Isnt that disappointing? I was planning on trying NHN because it looked like a promising primary.
I'm surprised it doesnt detonate. Any idea why?

Quote: Originally posted by PHILOU Zrealone  

I insert the powder with a tiny paper cone and slight vibrations...


Ah, here I can offer a massive improvement I believe. Go to your closest "cooking supplies" store and find the bits they put in the "cones" that are used to make meringue or writing on top of cakes. You'll find many shapes (we only care for round of course) and many diameters. If you dont understand what I'm talking about I can send you a picture.
You wont bother with miniature paper funnels that dont keep their shape and always have some composition adhering to the sides. Better still, if you are working with a static sensitive primary, they're made of metal ! From there, you can weld them to wire if you dont like having them in your hand or even ground them if you feel the need :)

nux vomica - 14-3-2016 at 21:58



Why is the flash visible? It looks like you have the gap inside an opaque insulated tube.

Yes its a plastic rod drilled out so the spark electrodes are inside i also have the piezo spark electrode tapped into the plastic rod to insulate it from the spark gap electrodes , you dont want any chance of the electrodes conducting until you are ready.

PHILOU Zrealone - 15-3-2016 at 03:31

Quote: Originally posted by Microtek  
Philou:

The difference is that in a true EBW, the bridge wire takes the place of primary explosive: The electrical discharge dumps so much energy into the wire, so suddenly that it vaporizes and then even more into the ionized plasma so it explodes and causes the secondary base charge to detonate.
So an EBW is an example of an NPED, but much more reliable than the ones relying on DDT of something like specially treated PETN.

Thank you Microtek,
I did forgot that the metal is vapourized by the electric pulse and that it is an electric arc and the resulting shockwave that initiate a secondary in close contact...just like a Al/CuO nanothermite would do with plasma Cu gas...
Maybe with this Al/CuO nano mix would it enter the category of NPED?

Anyway my device works with much lower current ;-) but it is as effective if you overdrive it and vapourize the filament creating an electric arc :-° ... just a little shorter delay before detonation.

PHILOU Zrealone - 15-3-2016 at 03:47

Quote: Originally posted by Herr Haber  
Quote: Originally posted by PHILOU Zrealone  


-Ni(N2H4)3(NO3)2 --> this flashes-bang

Errrm? Isnt that disappointing? I was planning on trying NHN because it looked like a promising primary.
I'm surprised it doesnt detonate. Any idea why?

Quote: Originally posted by PHILOU Zrealone  

I insert the powder with a tiny paper cone and slight vibrations...


Ah, here I can offer a massive improvement I believe. Go to your closest "cooking supplies" store and find the bits they put in the "cones" that are used to make meringue or writing on top of cakes. You'll find many shapes (we only care for round of course) and many diameters. If you dont understand what I'm talking about I can send you a picture.
You wont bother with miniature paper funnels that dont keep their shape and always have some composition adhering to the sides. Better still, if you are working with a static sensitive primary, they're made of metal ! From there, you can weld them to wire if you dont like having them in your hand or even ground them if you feel the need :)

NHN or Ni(N2H4)3(NO3)2 is not very reliable as a detonating stuf for tiny detonators on its own...you need confinement and larger quantities for the D2D to occure.
This may be circumvented by the admixture of silver acetylide nitrato complex (SANC/SADS) what is compatible with NHN.
I use 2/1 mix by weight of both ultrafine compounds; then the NHN benefits from the ultrasensitivity of SADS and reliability of D2D in minute amount and the SADS benefits from the higher energy output and VOD of the NHN --> kind of complementary mix.
You may also use SADS pellet as initial detonating stuff and NHN as secondary detonating stuff prior to the "secondary" (here ternary charge).

Thank you for the kitchen cone idea...I never had troubles with paper...no adherence of the powder onto it...depends certainly of the smoothness of paper you choose (sand paper :P ? - just kidding ;) )
You can also use the end of a plastic drink straw to insert completely the straw with 1cm of loose powder at the end into the bulb sothat the powder falls into the bulb without loosing a grain of initiator outside; then you refill the end of the straw and repeat until bulb completely filled.

lysander - 15-3-2016 at 05:39

Quote: Originally posted by nux vomica  


Why is the flash visible? It looks like you have the gap inside an opaque insulated tube.

Yes its a plastic rod drilled out so the spark electrodes are inside i also have the piezo spark electrode tapped into the plastic rod to insulate it from the spark gap electrodes , you dont want any chance of the electrodes conducting until you are ready.


So is the flash visible because the plastic is actually translucent?

And the piezo electrode does discharge its spark into one of the gap electrodes, right? I.e., the electrode tip is exposed to the airgap inside the rod, and the only "insulation" is the air gap?

Aurium - 15-3-2016 at 07:54

I imagine that a SGD of mine could also be piezo triggered.

By using 3 electrodes, cap +, cap -, and a third piezo trigger in the middle.

This is a bit more complex than just a spark gap but it may be worth the engineering to have instant det on command rather than having to wait for the caps to charge.

Hennig Brand - 15-3-2016 at 10:19

The spark gap is normally used to ignite (detonate?) a primary explosive very fast (with almost no delay), but in some cases it can obviously be used as a detonator for secondary explosives as well and in this case is another example of just how sensitive ETN can be to some stimuli. The exploding bridge wire, EBW, is a different animal entirely from a resistive element electrical heater/igniter, or even the spark gap detonator. It may be hard to believe at first glance but given the extremely small amount of time involved that tiny bit of gold, platinum, or copper wire is actually a very effective energy storage device because of its mass, heat capacity/sensible heats, latent heats: heat of fusion, heat of vaporization, (also heat of plasma?) and also electrical resistance and how that resistance changes with temperature. Its mass also aids the transfer of energy (I think) once the inertia of the wire is overcome and the extremely rapid explosive expansion and shockwave takes place. A great deal of energy is stored in the wire, with the correct application of energy, which is released explosively and can very effectively and reliably initiate many secondary explosives.


[Edited on 15-3-2016 by Hennig Brand]

nux vomica - 15-3-2016 at 21:11

Quote: Originally posted by lysander  
Quote: Originally posted by nux vomica  


Why is the flash visible? It looks like you have the gap inside an opaque insulated tube.

Yes its a plastic rod drilled out so the spark electrodes are inside i also have the piezo spark electrode tapped into the plastic rod to insulate it from the spark gap electrodes , you dont want any chance of the electrodes conducting until you are ready.


So is the flash visible because the plastic is actually translucent?

And the piezo electrode does discharge its spark into one of the gap electrodes, right? I.e., the electrode tip is exposed to the airgap inside the rod, and the only "insulation" is the air gap?


Yep its only a standard 3 electrode spark gap switch with airgap between the two main electrodes the piezo electrode is close enough to fire the gap but far enough away so the electrodes wont bridge across it and fire .
The plastic is white but the spark is so bright it still is visable on the outside

Hennig Brand - 20-3-2016 at 05:31

I have a couple other things to add to my last post. The spark gap detonator is interesting and useful in some applications, but I have to pick on it a little.

With enough power (edit: energy) delivered quickly enough to the gap a spark gap could probably be used to detonate anything an EBW could, but I think the EBW is much more efficient, reliable and safer. Everything else being equal (fireset/capacitor(s), wire type and length, explosive to be initiated, etc) an EBW should be able to provide a more energetic, more intense impact/shock making it more effective as an initiator. I have not tested a spark gap detonator, but it seems that variables effecting performance and reliability are more difficult to control. I can say from experience that with even modest care EBWs can be made very reliable.


[Edited on 21-3-2016 by Hennig Brand]

Aurium - 20-3-2016 at 17:05

The novel interesting feature about a SGD is that the coupled capacitor can be made at least 10x smaller than with an EBW.
I'v had repetitive success with ETN at just 0.1uF (5kV) and some meters of wiring, which is much less than the 1uF~2uF capacitor rule of thumb for an EBW. So I can have a smaller cap and equal cable length, or an equal cap and larger cable lengths.

In terms of firing energy the SGD is much cheaper. ~10x less cap energy is needed.

Oh, and no dealing with hair-thin wires and soldering, its of very simple construction.

But you are right Hennig, I found that the ETN must be very low density for the SGD to work, and I haven't tested it with any other explosive other than ETN.

I'd be great-full if you could provide some free readings on the physics of EBWs.
My idea of an EBW is that the goal is just to super heat the wire, and the expansion and explosion initiates the explosive, I never imagined an energy accumulation mechanism in the thin wire.

IMO its like the EBW is a cannon ball and the SGD is a sniper bullet.

With the EBW one has to super-heat the whole thin wire to a plasma and from then on, involving a few mg of copper to be heated.

In a SGD one only has to heat a superthin air path at first.

Air is ~1000x less dense than metal, so its allot less material to be plasmafied. ~1000x less material + the same energy dumped means x1000 hotter temperatures and x1000 faster expansion, but with x0.001 the mass involved in an EBW. (say in the ug range)

Which is best is a matter of further experimentation.


[Edited on 21-3-2016 by Aurium]

Hennig Brand - 21-3-2016 at 01:16

The spark gap is used for very little commercially or by the military from everything I have read, with the most notable exception being the very famous RPG-7 system which uses it, fired by a piezoelectric impact fuse crushed on impact, to instantaneously ignite a primary explosive at the rear of the shaped charge. This should indicate some things about a spark gaps suitability for most purposes.

Yeah, EBWs generally use a 1uF capacitor bank or larger even in their systems but they often fire many shots simultaneously and from much more than a few meters away in cable length (the capacitance used is by no means the minimum in most cases with commercial systems). The bridgewire in an EBW is a very easily controlled, well defined, energy dissipation medium/element whereas what is between the spark gap is more difficult to control. If in fact EBWs take more power to fire this would likely be seen as a good thing from a military and commercial perspective (the main reason to go with slappers over EBWs from what I understand is that they require much more power again to fire making them even less likely to be involved in an accident).

Can discuss more later maybe. No time at the moment.


[Edited on 22-3-2016 by Hennig Brand]

yobbo I - 21-3-2016 at 08:11

There is an attached .rar on page one of this thread around 13 / 4/ 15

[Edited on 21-3-2016 by yobbo I]

Rosco Bodine - 21-3-2016 at 08:25

IIRC the spark gap from a Wimhurst static generator and Leyden jar "accumulator" is the historically original "first embodiment of a practical detonator" and was used to detonate nitroglycerine before later attempts to replace the SGD scheme using detonating caps ultimately settling for a mercury fulminate blasting cap as the simpler replacement for the original practical means which was the SGD. On the old google explosives newsgroup it was reported that a ball of cotton soaked in NG in the base of a fired .22 rimfire could be reliably detonated by a spark across the cut end of a piece of coaxial cable butted against the NG soaked cotton and crimped to secure, fired directly one shot pulse discharge by an automotive ignition coil.....kaboom, presto high order detonation.

I think I have seen this concept mentioned in literature possibly a biography on Sobrero or Nobel but am not finding any search hits about it, and I have not tested the idea which appears to be obscure information. But ETN is about as near to NG in a solid form as will be found and definitely a bit less stable than NG so it makes sense a SGD would or should work for ETN and function simply by thermal shock alone augmented by any local shock wave from expanding air in the "pop" of an arc. If it is pure thermal shock then an intense IR laser pulse should do the same to cook off the HE high order.

[Edited on 3/21/2016 by Rosco Bodine]

Aurium - 22-3-2016 at 08:25

I love the random pieces of explosive tech trivia you guys know ahahah. Ya ol'times kaboomer.

I bet it's all about that local shockwave caused by the expanding plasma because:
1- A lower energy spark will not detonate the ETN. All plasmas are several thousands kelvin which is more that enough to overcome any activation energy.
Maybe it takes a minimum shockwave intensity to cause a detonation.
2- The ETN does not detonate when exposed to a very hot flame, it just decomposes. It only dets when wrapped in aluminum foil, behavior that I can only
attribute to a catalyzing effect by the Al.

A SGD is just as safe as having the ETN sitting in a plastic tube.
If one is concerned about static detonating accidentally one simply link the two input wires and unlink them moments before use.
Also it takes a heck of static jolt to cause a detonation or any activation.
It won't happen in a billion years.
Still, I understand that it is a tiny bit less safe than an EBW, hence unsuitable for use in nuclear detonators. And one can never be too safe about nukes.

Will have to keep on testing them, maybe with different energetics.
If a SGD takes x10 less energy to fire ETN, perhaps it also takes x10 less energy to fire RDX or TNT or other true secondaries.
If not well yea it makes little sense to use it commercially, those guys aren't worried about the price or size of the capacitors.

yobbo I - 22-3-2016 at 16:04


If you want small you go for slapper detonators. It's slappers in all nukes, most misiles etc

Hennig Brand - 23-3-2016 at 13:42

Wrapping in aluminum foil confines the ETN, which prevents heat from dissipating as quickly and pressure to rise more allowing the temperature to rise higher which in turn results in faster combustion which again raises the temperature even faster and higher. There may be some sort of catalytic effect as well, I don't know. It doesn't take much thermal shock to push ETN to detonation. I was getting good pops from little bits of loose ETN by simply touching it with the end of a hot soldering iron, with no confinement at all!

Temperature tells us about the energy level of a unit of something. A Bic lighter can apparently reach temperatures as high as 2000C, but good luck using it to solder a copper pipe with lead solder. Way more than enough temperature, but because the amount of heat/energy produced is so low it can't raise the temperature of the copper pipe enough. For thermal shock there needs to be a reasonable amount of energy, but more importantly it has to be delivered extremely quickly.

The higher the "energy density", and the faster the energy can be delivered, the more shock, the more intense impact, which can be produce and the more ability the energy donor will have at initiating a secondary explosive. The wire in the EBW is a type of energy concentrator, or accumulator, which stores and then releases the energy extremely rapidly and from a very small volume (highly concentrated/focused energy). As much energy as possible in as small a volume as possible in as small a time as possible is what we are after, well enough to be a reliable initiator anyway.



[Edited on 24-3-2016 by Hennig Brand]

nux vomica - 29-4-2016 at 03:47

Just had a successful test of a ebw detonator that uses a 1206 smt resistor unstead of a fine bridgewire, the reasoning is that you break the wire frequently while building the detonator, and a resistor wont be as delicate and should still be able to set off etn.

The resistance of the resistor is 2 ohms and it is recessed into the plastic holder to insulate the electrodes from the metal 9 volt battery caseing.

I used 1 grm of etn in the caseing and charged up to 4000 volts and had it fireing through 25 meters of coax , the s/s target is 2mm thick.


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PHILOU Zrealone - 29-4-2016 at 07:58

Quote: Originally posted by nux vomica  
Just had a successful test of a ebw detonator that uses a 1206 smt resistor unstead of a fine bridgewire, the reasoning is that you break the wire frequently while building the detonator, and a resistor wont be as delicate and should still be able to set off etn.

The resistance of the resistor is 2 ohms and it is recessed into the plastic holder to insulate the electrodes from the metal 9 volt battery caseing.

I used 1 grm of etn in the caseing and charged up to 4000 volts and had it fireing through 25 meters of coax , the s/s target is 2mm thick.

1g of detonating ETN should have made a neat/clean hole (of the diameter of the pipe holding the ETN) through your 2 mm plate...
I think it didn't detonate but simply deflagrated.

Aurium - 29-4-2016 at 12:32

Quote: Originally posted by PHILOU Zrealone  

1g of detonating ETN should have made a neat/clean hole (of the diameter of the pipe holding the ETN) through your 2 mm plate...
I think it didn't detonate but simply deflagrated.


I agree. Even 0.1g could do more damage than shown.

What capacitance are you using?

Using a resistor makes sense over a thin wire. Get more juice out of the capacitor during the first milisecond.
Still, why did you choose to go with an SMD resistor instead of a regular one?
Those are allot of work to solder.

XeonTheMGPony - 29-4-2016 at 13:02

Either type of of resister dampens the effect of the plasma shock you're trying to create.

The point of the fine wire is it creates a metal ion rich plasma that can generate tremendous pressure and heat, this is where you get the high order shock from.

Carbon just doesn't do it quite the same.

nux vomica - 29-4-2016 at 21:58

Gave it another shot today worked ok to me :D i think the first shot moved and tilted away from the 2mm plate if you look at the plate the caseing fragments only marked one side as if the detonator had moved .

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XeonTheMGPony - 30-4-2016 at 12:35

trick I used for fusing the wires to the lead wire I used basically a cap driven spot welder. I'd charge the cap to 6v and then hook the leads to the caps and press onto the bridge wire and it would fuse tot he lead wires, got to play with it to get it perfect, but it worked great with me, used the same system to spot weld leads on to batteries.

Good results though surprising the carbon is allowing you to get a good pulse into it.

[Edited on 30-4-2016 by XeonTheMGPony]

yobbo II - 30-4-2016 at 17:46

Home produced very fast discharge capacitors here

http://laserkids.sourceforge.net/eng_capacitor.html#top

nux vomica - 30-4-2016 at 18:36

Quote: Originally posted by yobbo II  
Home produced very fast discharge capacitors here

http://laserkids.sourceforge.net/eng_capacitor.html#top


They would give you satisfaction as there self made but a bit too big, i would still use these as they are the ducks nuts. http://m.ebay.com/itm/291095298708?_mwBanner=1

nux vomica - 7-5-2016 at 01:42

Managed to video the ebw unit chargeing up and fireing a 16 grm shaped charge into a100mm target also had a seperate camera filming the charge going off about 4 meters away.

Dont know results yet as i will have to cut the target up at work next week.


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nux vomica - 10-5-2016 at 03:01

Ok the results were not as good as i hoped only 32mm penertration,it looks as i should have used more standoff than 3x as the enterance hole looks extra large might have to go 5.5 x standoff.

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lysander - 12-6-2016 at 11:35

How can we protect the voltage source from the pulse? I finally got to wire this up and the first shot fried most of the diodes on the top cascade.

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nux vomica - 12-6-2016 at 15:26

Quote: Originally posted by lysander  
How can we protect the voltage source from the pulse? I finally got to wire this up and the first shot fried most of the diodes on the top cascade.


Looks like only put a diode one one output of the cascades , you need to put one on both.
Nux

The Plutonium Bunny - 20-6-2016 at 09:25

This is my first post, so hello everyone! I will say before I begin that I have no honest-to-goodness high explosives to test my EBW with, so I am not sure if it will actually detonate high explosives like ETN.

That said, I made some nitrocellulose and have experimented with it and some simple bridgewires I made. My bridgewires are just ~1cm long single strands of fine copper wire from alligator clip test leads, crimped on each end to thicker wires. These thicker wires go to a normal 120V electrical extension cord which goes to my capacitor bank/detonator button (the extension cord is so I can be far away from the explosion). My capacitors are five 330V disposable camera flash capacitors wired in series for more current. I have two bolts held apart by a spring that can be pushed together to act as a high-current detonator button. I made a YouTube video about my EBW setup, which may be viewed here: https://www.youtube.com/watch?v=KD2RTMVT8qQ

When I charge my cap bank to 300V and press the button, a very loud noise and a bright blue flash ensue. The copper wire is nowhere to be found. I have achieved what I believe to be a nitrocellulose detonation by initiating pressed nitrocellulose with one of my EBWs inside a crimped-over brass shell casing. The explosion may be viewed in this YouTube video: https://www.youtube.com/watch?v=OmjHgaalygU

Hopefully this information is helpful. On a side note, do any of the experienced experimenters on this forum have any input as to whether this EBW setup would actually initiate ETN and other high explosives?

nux vomica - 25-4-2018 at 19:23

Underground wanted a circuit diagram from my ebw setup



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[Edited on 26-4-2018 by nux vomica]

underground - 26-4-2018 at 19:16

Ty bro, but still got few questions:
1) How does actually works the spark gap button ?
2) Bank is 1mf ? 1mf is enough for capacity ?
3) I saw on other posts that you use some dividers(resistors) for measuring the current from the bank and for discharging it after the spark, can you saw me where they were connected please?

Also i am thinking to use a 9v battery to make things a bit smaller and lighter

underground - 21-6-2018 at 08:40

After rading the thread, i was thinking to trigger the EBW with a single channel remote control switch. Since high voltage relays are very expensive, i thought the following swith as you can see the attachment. There would be a spring that will always reset the 2nd electrode to its starting position and when current pass through the motor, the electrode will pass close to the other electrode triggering the EWB with an arc. What do you think, would be reliable ?

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