Sciencemadness Discussion Board - Has anyone made a EBW setup.

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.

I see what you say about the power supply not being able pushover 2800v with the meter connected that's why I've been charging with the negative wire connected then touching the positive wire to get a reading, after 11 seconds from fully discharged the reading averages 4200v when I've tested it multiple times on the bench not accurate I know for data collection but its the best that I can do for now. cheers nuxy

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

jock88 - 11-6-2015 at 17:00

Most commercial ebw detonators are made with PETN (AFAIK). This PETN has to be very small crystals to increase sensitivity.

On sensitive is ETN compared to normal PETN and the very fine crystal PETN?

Succsess with Petn

nux vomica - 12-6-2015 at 01:01

Managed to get Petn to detonate with my ebw the first time I tried.

The Petn acetone mix was poured into cold water that was being stirred rapidly , the precipitated Petn was vacuum filtered then left to dry ,the dry Petn was fine and free flowing powder.

I used the same setup as last time 7 meter coax 200mm twin core, copper bridgewire 0.030mm dia x 1.6mmlong 8mm id alloy tube with the main charge 0.70 grams compressed to 1.31 grams cubic centimetres and 0.10 grams loose on top.

Capacitor bank was charged for 11 seconds and pezio button pushed detonation was instantaneous and it did seem louder than etn.

[Edited on 12-6-2015 by nux vomica]

Hennig Brand - 12-6-2015 at 04:08

Good job, yeah, PETN is at least a little more insensitive to initiation than ETN all other things being equal. However, either PETN or ETN can be easily initiated by EBW as long as the packing density is kept low around the bridgewire and yes the finer the crystals the greater the sensitivity also. There are specialized techniques used commercially to get the PETN particle size extremely small. ETN works fine, but PETN is much more storage stable and at least a little less sensitive to initiation both of which are advantages for a commercial product. In extreme environments with high temperatures ETN's low melting point (60-61C) would be a real problem too.

BTW, on the last page when I suggested putting resistors in series to make a high voltage resistor divider out of lower voltage resistor types, be aware that the voltage drop across each resistor will only be the same if the resistance of each resistor in the series string is the same. The voltage drop across a higher value resistor, and therefore also the power dissipated, will be greater than for a lower value resistor in a series string and could be enough to damage or completely destroy the resistor if not of the appropriate type with adequate voltage and power ratings.

[Edited on 12-6-2015 by Hennig Brand]

Ebw shaped charge

nux vomica - 13-6-2015 at 20:52

I think I can get a shaped charge to work with my Ebw setup I formed a cone with a file in a piece of delrin on my lathe then pressed 0.70 grams of etn on top then 0.10 loose on top same alloy tube and bridgewire setup but instead of soldering the lead wires to the coax I used jst connectors I used them in rc helicopters and planes so I've got a good supply on hand.

I didn't form a copper cone to fit so the charge was unlined and touching the 2mm s/s plate but it blew a nice hole clean through so it seems to detonate and focus the waves to form a copper liner into a penetrator even in such a short explosive length (calculated 8mm long ).

hopefully next post will be a successful shape charge shot cheers nuxy.

[Edited on 14-6-2015 by nux vomica]

[Edited on 14-6-2015 by nux vomica]

EFP shaped charge.

nux vomica - 16-6-2015 at 03:31

Just had a awesome result using my ebw setup to fire a EFP shaped charge.
I saw some 10mm s/s rivnuts at work and thought they would be a great shaped charge outer container, I used 1.2 grams of etn compressed to 1.3 grams c/c plus 0.1 on top for a total of 1.3 grms of etn the copper dish was 6.25mm rad, 0.8mm thick and 11.5 mm dia ,bridge wire 0.030 dia x 1.6mm long, coax 7 meters with 200mm twin core on the end connecting with a jst to the shaped charge I don't have voltage level but counted to 15 seconds then pushed the piezo button and detonation was instantaneous.
I used 50mm standoff from the 6mm thick mild steel plate and the dia of the hole measured 3.48mm next time I will use thicker plate cause it punched through 6mm very easily

Cheers nuxy.

Exit side

This is the shaped charge side

[Edited on 16-6-2015 by nux vomica]

Hennig Brand - 16-6-2015 at 06:31

Very professional looking again and I also like those "rivnuts", they look like they make great casings. With the amount of curvature you are using I think you may be starting to get into the transition zone between Munroe effect and EFP. At the very least you will have a very narrow and elongated projectile, which is a good thing from a penetration perspective. From what I have seen an EFP liner would normally have a depth of curvature somewhere around 20% the diameter of the liner, or often much less even, while yours is reported to be (6.25mm - sqrt(6.25mm^2 - 5.75mm^2)) / 11.5mm * 100% = ca. 33%.....(if I haven't messed up). The standoff used also tells a story, it is only about 4 & 1/3 times the charge diameter, which is a very short distance for an EFP to form. The hole produced is also quite small in diameter for an EFP, especially at such close range. It is an interesting test all things considered.

If something works it works, but still you are flying blind with your charging circuit since you have no way of telling what the capacitor bank voltage is. Here is a circuit I found online a while back on the following site somewhere I believe:

http://www.sebaseraelettronica.altervista.org/

Capacitive Discharge Igniter Circuit.jpg - 213kB

Overall the design is not suitable for an EBW system, especially since he was using huge slow electrolytic capacitors of fairly low voltage and high capacitance. However, the voltage indicator part of the circuit, built around an lm358 operational amplifier used as a comparator, looks like it would work well. In conjunction with a voltage divider it could light an led when the capacitor bank voltage rose above a set point value.

Alternatively one of these could be ordered. I ordered one so that I could stop using a multimeter. These little panel meters are small and can be installed permanently in the blasting box. They can be used in conjunction with a suitable voltage divider to measure high voltages.

http://www.ebay.ca/itm/201130716977?_trksid=p2057872.m2749.l...

If you want to prevent putting an extra load on the little power supply, you could have the voltage divider circuit & voltage meter only in circuit when a momentary push button switch is pressed. This also gives you a safe way to discharge any remaining charge in the capacitor bank and prevent shocking experiences.

[Edited on 17-6-2015 by Hennig Brand]

nux vomica - 16-6-2015 at 22:34

I actually have some of those power meters but they are two wire 30volts , I am getting around to a working voltage measuring setup but as always time and trying to do to many other things gets in the way.

I cut the 6mm plate in half through the shaped charge hole the entry side is from the top, I like the copper coating on the inside looks cool , might call it a Dolezal charge cause it identifies itself as a efp charge.

cheers nuxy.

[Edited on 17-6-2015 by nux vomica]

Hennig Brand - 17-6-2015 at 04:46

I see you have a voltage multiplier constructed, looks good. I went with the three wire meter so that the sensing input and the power input for the meter would be separate. Not sure exactly what kind of load those panel meters present even with just the sensing line, but a two wire will also draw current to run the meter from the sensing wire and with a very low current, high voltage, voltage divider current draw needs to be kept to a minimum.

If keeping the power supply as physically small as possible is a priority using lower voltage ceramic caps would make a huge difference. The voltage multiplier takes up a large portion of the total size of the supply. I just received 200, 10nF, 2kV ceramic capacitors which cost me about $4.50 Canadian. I used 3kV, 10nF, ceramic caps when I made my voltage multiplier, but 2kV, 10nF, caps would have been more than enough since the supply voltage to the multiplier is only around 500-550V. Look at the size difference between these two! (3kV, 10nF on the left & 2kV, 10nF, on the right in the image)

HV Ceramic Capacitor Size Comparison.jpg - 269kB

[Edited on 17-6-2015 by Hennig Brand]

nux vomica - 19-6-2015 at 03:14

Just had a awesome result using my ebw setup to fire a EFP shaped charge.
I saw some 10mm s/s rivnuts at work and thought they would be a great shaped charge outer container, I used 1.2 grams of etn compressed to 1.3 grams c/c plus 0.1 on top for a total of 1.3 grms of etn the copper dish was 6.25mm rad, 0.8mm thick and 11.5 mm dia ,bridge wire 0.030 dia x 1.6mm long, coax 7 meters with 200mm twin core on the end connecting with a jst to the shaped charge I don't have voltage level but counted to 15 seconds then pushed the piezo button and detonation was instantaneous.
I used 50mm standoff from the 6mm thick mild steel plate and the dia of the hole measured 3.48mm next time I will use thicker plate cause it punched through 6mm easy

Tried the same setup at 50mm standoff but with 10mm thick m/s plate, punched through the 10mm plate and the carrot travelled 65 mm into the pine wood block but it broke up into small fragments in the wood. :mad:

The entry hole is quite messy and if you look there is a round ring where the front edge of the rivnut impacted, but the jet hole is offset to the ring mark, I didn't think when I was drilling the bridgewire wire pin holes but they were a little offset from centre and I think its made the jet slightly malformed and offset so I didn't get a cleaner entry hole cheers Nuxy.

[Edited on 19-6-2015 by nux vomica]

[Edited on 19-6-2015 by nux vomica]

Hennig Brand - 19-6-2015 at 05:05

You are getting excellent penetration, really almost too good for a regular EFP from what I have seen and especially at that amount of standoff. I am interested in the depth of curvature of your liner. I know I calculated something above, but if you had a liner handy could you measure the depth of the dish with a depth gauge? I have a depth gauge rod on a Vernier caliper, not sure what you have for tools.

No Voltage Multiplier?

An option to keep the power supply as small as possible could be to use no voltage multiplier stage at all and wind a HV transformer capable of putting out the required output voltage all by itself. This option is more difficult for the amateur, however, since special techniques and materials are required to wind transformers at several thousand volts or more. Winding a 400 or 500V transformer with regular techniques is no big deal, but more than that can get tricky. A several thousand volt transformer would need to be vacuum potted in an insulating epoxy or something similar to prevent internal arcing and shorting between windings. Special formers/bobbins are also normally used which likely would need to be made.

LCR Meter

Have a look at my new LCR (inductance, capacitance, resistance) meter. It is a fairly low priced model out of China, but so far it seems very good. They can be a very useful piece of test equipment when doing these sorts of projects. The inductance meter can be very useful when designing transformers and obviously inductors. The capacitance meter can be used as a test, along with other tests if available, to help determine the condition of capacitors (e.g. usually one cap goes bad at a time in a pulsed power capacitor bank and a capacitance meter can usually be used to identify it). As long as they are not overcharged, or repeatedly shorted into a very low impedance load (e.g. screwdriver across charged capacitor, short blasting lines also put a lot more strain on the capacitors), I think our pulse capacitors will last a very long time given the very low usage. Tesla coil capacitor banks, on the other hand, do occasionally have capacitors "die" from what I have read. There are many uses for an LCR meter, I recommend one.

[Edited on 20-6-2015 by Hennig Brand]

nux vomica - 19-6-2015 at 21:46

Took some measurements for you hennig I made a mistake with the copper thickness its actually 0.6mm not 0.80mm there must have been a burr on the edge I didn't see.

Diameter is 11.41mm overall height is 3.17mm and weight 0.60 grams the ball diameter is 12.50mm.
Cheers nuxy.

[Edited on 20-6-2015 by nux vomica]

nux vomica - 19-6-2015 at 23:34

Couldn't help myself just had to try and shoot that liner through something, managed to make it through 16mm m/s plate just :cool:

.The standoff was 50mm and the shell s/s rivnut.

Used 1.2 grams PETN as im still waiting for my batch of etn to dry +0.1 PETN on top, 0.030mm dia copper wire and I've made the length 2mm, I have tested this length and I haven't had a misfire yet and it makes it a bit easier to solder the wire on the pins, sorry I promise to work on voltage measurement soon

so I charged the cap bank for 15 seconds and pushed the piezio detonation was instantaneous (as usual) funny thing is the support pole for the charge is only screwed on and its never blown off and there is hardly any fragment damage to it ?

I wonder if I change the standoff whether it will give better penetration or maybe 1.2 grams of PETN can only just penetrate that far.

Cheers Nuxy.

[Edited on 20-6-2015 by nux vomica]

Hennig Brand - 20-6-2015 at 02:44

Interesting, the depth of curvature is in the upper range for an EFP but still within from what I have seen. The penetration is too much for an EFP though and the target looks like it has been hit by a SC jet not a EFP. I am going to have to try a stronger casing for my next EFP test. I suppose you are using pure nitric ester too which would make a difference.

Ok Nuxy, stop messing around, where is the picture of the actual liner you used?

nux vomica - 20-6-2015 at 03:19

Honestly it was the one in the vernier caliper photo no point letting it sit around

Hennig Brand - 20-6-2015 at 10:06

Here are a couple commercially produced EBW initiated mini shaped charges. The commercial model is getting no where near the penetration you are getting and with much more explosive. The kind of penetration you are getting is more consistent with a jetting shaped charge not an EFP. I guess it could be somewhere in between which I think is possible.

Attachment: Mini EBW Initiated EFP.pdf (29kB)
This file has been downloaded 550 times

Attachment: Mini EBW Initiated Shaped Charge.pdf (29kB)
This file has been downloaded 592 times

It just occurred to me that the optimum depth of curvature for an EFP liner would also be dependent on the velocity and pressure of the explosive. You are using straight nitric ester, so of course the center of the liner has been accelerated much more than when slower explosives are used, stretching and narrowing more before the detonation wave makes it to the bottom outer edge of the liner. The amount of pressure applied to the liner, work done on the liner, per unit time is much greater with the pure nitric ester explosive. The deeper the dish the more contact time there is between the explosive and liner for transfer of energy to the liner, also the more the explosive force will be directed towards the center of the liner and towards the target, stretching and narrowing the projectile. The more stretched out, narrower, faster moving projectile will penetrate more steel, which is the same as what is observed for Munroe effect SC jets when more powerful explosives are used for basically the same reasons. You are also using a fairly deep dish, by any EFP standards. I think you have something closer to a Munroe effect shaped charge.

EFPs are typically a longer range type SC device with much less penetrating ability than a close range Munroe effect shaped charge. As a generalization they normally make a much wider shallower hole than a Munroe effect SC, but can be used at great distances from the target.

[Edited on 20-6-2015 by Hennig Brand]

nux vomica - 20-6-2015 at 16:10

I don't know anything about the mechanics of what is going on with shaped charges but I am pretty happy with the result, I've spun liners up on my lathe and didn't get as good penetration as I am getting with hitting a ball bearing into the copper sheet.

Ive made a small batch of plastic ebw holders yesterday amongst assembling and firing that last charge I routed a new work holder for drilling the pinholes in the threaded plastic its also good for holding the bridgewire when your soldering the connector wires on to the head . cheers nuxy

[Edited on 21-6-2015 by nux vomica]

Hennig Brand - 20-6-2015 at 16:59

Looks good, the way it all threads together is great. Using exploding bridge wire technology really is a pretty effective way to initiate explosives. There are a few things to know, but after that the technology is pretty accessible.

Edit: I just wanted to add that a thiner liner would also be easier to accelerate (less inertia) and its resistance to being "shaped" would be less too. So you have a very fast powerful explosive, a thin liner with deep curvature and a strong casing. It is more and more understandable what is going on. Still impressive tests btw, glad you did them. I think I understand what has been happening with mine more now.

[Edited on 21-6-2015 by Hennig Brand]

nux vomica - 20-6-2015 at 19:15

I feel that useing the ebw setup is safer from a assembly point of view as in not having to use azides etc, you can still have a accident but it lessens the risk.

[Edited on 21-6-2015 by nux vomica]

Hennig Brand - 21-6-2015 at 07:10

I agree at this point. Especially for the amateur the explosive and poison dangers associated with primary explosives is certainly much higher than when only using secondary explosives and a EBW. The high voltage capacitor could be dangerous especially to the careless or uneducated, but only when it is charged. Also my capacitor bank is only 4J when fully charged which I think is only mildly hazardous (unlikely to be anywhere near lethal) as capacitor banks go.

Commercially is a different story, my perception is that for every primaryless EBW detonator used there are likely 1000 or even many more regular electric detonators with primary explosives being used. For a blaster the regular commercial electric detonators are quite safe. Commerially EBW detonators are mostly used in applications where precise timing and simultaniety is required. Even very good regular electric detonators are not very fast and the timing varies a lot from one detonator to another compared to EBW detonators. For the amateur who is synthesising and loading his own primaries, however, there can be considerable dangers. EBW detonators do eliminate a lot of dangers for the amateur in my opinion.

[Edited on 22-6-2015 by Hennig Brand]

jock88 - 21-6-2015 at 13:39

I think the nonex (spelling) tubing system is used alot.

nux vomica - 21-6-2015 at 18:30

Looks good, the way it all threads together is great. Using exploding bridge wire technology really is a pretty effective way to initiate explosives. There are a few things to know, but after that the technology is pretty accessible.

Edit: I just wanted to add that a thiner liner would also be easier to accelerate (less inertia) and its resistance to being "shaped" would be less too. So you have a very fast powerful explosive, a thin liner with deep curvature and a strong casing. It is more and more understandable what is going on. Still impressive tests btw, glad you did them. I think I understand what has been happening with mine more now.

Quote:

No probs I enjoy a challenge and its always nice when things work out hopefully other people can use the information .

Problem is that you always think you have climbed to the top of the mountain but the is always another peak in front of you , I'm getting a itch to try and make a working foil slapper setup next.

Nuxy.

[Edited on 22-6-2015 by nux vomica]

Hennig Brand - 23-6-2015 at 13:33

A slapper might be interesting, however, for regular blasting I think EBWs already have a high enough power requirement and are safe and reliable enough for any regular blasting purposes. It would be interesting just for the hell of it though. Now if we can just separate the U-235 from the U-238.......just kidding.

From the little bit I know about it they normally use plutonium in the implosion devices anyway.

I just got one of the little three wire LED display voltage meters in the mail today. The one I have is drawing about 14.5-14.6mA through the power line at 4.18V, and about 84uA through the sensing line at 4.18V which means the sensing circuitry has an input resistance of about 50kohms. The three wire meters will work fine when used with a suitable voltage divider.

Here are a couple of images of the LED voltage meter. They did not focus well, but in reality the meter display is extremely clear and easy to read. Since it is LED and not LCD it is very easy to read in the dark too. Not bad for about $1.70! I have one coming in green too.

[Edited on 24-6-2015 by Hennig Brand]

nux vomica - 23-6-2015 at 21:51

A slapper might be interesting, however, for regular blasting I think EBWs already have a high enough power requirement and are safe and reliable enough for any regular blasting purposes. It would be interesting just for the hell of it though. Now if we can just separate the U-235 from the U-238.......just kidding.

From the little bit I know about it they normally use plutonium in the implosion devices anyway.

Meanwhile in my secret lab .

852fdd1bc9adc9981de3418bc16527cc.jpg - 492kB

Hennig Brand - 24-6-2015 at 04:02

Nice poster! I just checked and my laboratory centrifuge isn't large or powerful enough to enrich the uranium.

I guess our plans for world domination will have to wait.

nux vomica - 24-6-2015 at 04:24

Old marvin is a classic i remember watching him on a black and white tv as a kid

delays__delays_by_behindtg-d5osdfv.png - 139kB

[Edited on 24-6-2015 by nux vomica]

Hennig Brand - 26-6-2015 at 07:34

Giving away your age I see.

I am not one of the old and wise here, but I am not one of the kids either, I am about half way in between at this point I guess.

You mentioned using Delrin on the last page, it is excellent material for making bobbins for high voltage transformers, IIRC. Instead of layer winding (one on top of the other), like how I wound the 500V transformer for my power supply, a bobbin can be made on a lathe from Delrin round stock by cutting sections out along its length for the windings and leaving insulating dividers. After winding it is vacuum potted in epoxy resin or some other suitable insulator that can be applied as a liquid, will cure and hold up well. Here is a picture of the type of bobbin I am talking about. The picture is of a HV (ca. 50kV) output transformer for a stungun.

edit: I just remembered that it was glass filled Delrin that was suggested to me by an electronics designer for making high voltage transformer bobbins. I can't remember any more specifics.

[Edited on 27-6-2015 by Hennig Brand]

nux vomica - 26-6-2015 at 18:05

Giving away your age I see.

Hey dinosaurs ruled the earth once

Ive seen round ferrite cores before on transformers but why split the secondary up , phasing , winding density . nuxy

[Edited on 27-6-2015 by nux vomica]

Hennig Brand - 26-6-2015 at 18:16

This would only be if you were going to omit the voltage multiplier and make a 5 or 6 thousand volt transformer. Yeah, the core in that picture is a ferrite rod and the transformer is meant to act in flyback mode I believe. A different core could be used, such as an E-Core. The special bobbin, winding style and vacuum potting in epoxy allows much better separation and insulation between windings which is designed to prevent arcing between windings, especially between the primary and secondary. I am not a transformer expert and have done most of my learning online.

I meant no disrespect with the comments about your age. We are all getting older, I feel like I blinked twice and I went from being a teenager to closer to 40. How the hell did that happen? If I could go back knowing what I know now I would, but to go back and be as ignorant as I was then, no thank you. "Youth is wasted on the young." - George Bernard Shaw

[Edited on 27-6-2015 by Hennig Brand]

nux vomica - 26-6-2015 at 18:56

I just got a result with my inverter voltage multiplier I was stuck on 2000v reading when I remembered about using larger capacitor values for slower frequency's so I joined 3 more rows underneath and if I take out the voltage from the end of the fourth row I get 5438v .

I am lazy these days and bought the inverter on fleabay http://www.ebay.com.au/itm/221596931989?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT and I run it on 12v

The voltage divider is r1 40,000,000 ohms, r2 250,000 0hms to give you 31.056v at the measureing point ,the voltage calculation is 5000v divided by 31.056v to gives you 160.9 volts so 33.8 x 160.9 =5438 volts.

Now to try it out

Cheers nuxy.

[Edited on 27-6-2015 by nux vomica]

Hennig Brand - 27-6-2015 at 06:25

Well that certainly is a cost and labor effective way to go. I am tempted to order one of those myself. I wonder what the operating frequency is for your inverter. If the frequency and capacitor values are too low the output voltage will drop out when even a small load is applied.

nux vomica - 27-6-2015 at 17:05

I meant no disrespect with the comments about your age. We are all getting older, I feel like I blinked twice and I went from being a teenager to closer to 40. How the hell did that happen? If I could go back knowing what I know now I would, but to go back and be as ignorant as I was then, no thank you. "Youth is wasted on the young." - George Bernard Shaw

[Edited on 27-6-2015 by Hennig Brand]

Don't give it a second thought I don't mind a bit of shit stirring the politicaley correct thought police are wasting there time on me.

yeh to know what I know now and go back, id probably go back slap myself around and then tell myself to pull my socks up and try harder at school you dum shit.

nux vomica - 28-6-2015 at 04:34

Whent and connected the epicos capacitor bank to the inverter setup was getting 37v could only get to 30v for picture ? so it work's but I think I shorted something out cos got a loud bang thst scared the crap out of me :mad:

bugger wil check it out tomorrow .

[Edited on 28-6-2015 by nux vomica]

Hennig Brand - 28-6-2015 at 04:56

Seems like you might be overcharging, 37V across R2 would be close to 6000V on the capacitor bank. The other thing to keep in mind is that series connected capacitors even of the same type are not perfectly identical and will not share the charge/voltage equally. One of the functions of bleeder resistors on the capacitors is to function as bypass resistors which act to even out the charge/voltage and help keep a balance. If you capacitor bank is rated for 5200V, then only going to 80% of that or maybe even less especially when connected in series would probably be wise. Regarding the loud bang it could have been on the board somewhere with the voltage multiplier. I ground the copper traces off of my board between the two voltage multipliers, etc, because I was getting arc over at high voltages.

nux vomica - 28-6-2015 at 05:25

Seems like you might be overcharging, 37V across R2 would be close to 6000V on the capacitor bank. The other thing to keep in mind is that series connected capacitors even of the same type are not perfectly identical and will not share the charge/voltage equally. One of the functions of bleeder resistors on the capacitors is to function as bypass resistors which act to even out the charge/voltage and help keep a balance. If you capacitor bank is rated for 5200V, then only going to 80% of that or maybe even less especially when connected in series would probably be wise. Regarding the loud bang it could have been on the board somewhere with the voltage multiplier. I ground the copper traces off of my board between the two voltage multipliers, etc, because I was getting arc over at high voltages.

Yes letting it get to 37v was probably pushing it, the multiplier network was where I suspected the bang came from as well ,when you play with electricity you will always get the magic smoke sometime

What value are your bleeder resistors hennig?.
cheers nuxy.

[Edited on 28-6-2015 by nux vomica]

Hennig Brand - 28-6-2015 at 08:02

I have four pairs of capacitors in a series string with a half Watt, 10Mohm, HV resistor across each capacitor pair for a total of 40Mohms. There are formulas and rules of thumb for selecting bypass resistors. If the resistance is too high is doesn't even out the voltage/charge as well and if too low it puts a large load on the power supply, drains the capacitors very quickly and wastes precious battery power. It isn't really that critical as long as a reasonable value is chosen though. The 10Mohm resistors I am using are a fairly standard value used by the Tesla coil people for this same purpose on their capacitor banks. Since the charging rate is fairly slow even higher value resistors could easily be used though. The other benefit is that the bypass resistors act as bleeder resistors and drain the capacitors completely within a reasonably short time after charging is stopped.

[Edited on 28-6-2015 by Hennig Brand]

nux vomica - 28-6-2015 at 19:50

Hennig am I right in saying your bleeder resistors only go between each pair of capacitors so if I only have 4 in series do you need a resistor in series with the capacitor series?
Woh thats a tounge twister .

[Edited on 29-6-2015 by nux vomica]

Hennig Brand - 29-6-2015 at 05:22

One across each pair in the series string, in parallel with each pair. You would have one in parallel with each capacitor. I also have 10X100kohm resistors in series (1Mohm total) between the power supply and the capacitor bank to limit charging current and to provide isolation between the power supply and capacitor bank at discharge. I also have the voltage divider of course for voltage monitoring, which I believe is about 40Mohm as well. The resistance values I have chosen are likely not ideal, but it should give you an idea. Higher resistance values would put less load on the power supply and depending on how much higher might work nearly as well.

nux vomica - 29-6-2015 at 05:38

One across each pair in the series string, in parallel with each pair. You would have one in parallel with each capacitor. I also have 10X100kohm resistors in series (1Mohm total) between the power supply and the capacitor bank to limit charging current and to provide isolation between the power supply and capacitor bank at discharge. I also have the voltage divider of course for voltage monitoring, which I believe is about 40Mohm as well. The resistance values I have chosen are likely not ideal, but it should give you an idea. Higher resistance values would put less load on the power supply and depending on how much higher might work nearly as well.

Thanks hennig for the info cheers nuxy.

nux vomica - 30-6-2015 at 00:34

Decided to rebuild and permanently pot the voltage doubler as I blew a diode when I had the bang earlier ,I only need 4 stages and don't need the extra caps as I thought before so I machined a piece of delrin at work on the milling m/c then hot glued the assembly in the H section to insulate it from further mishaps ,I also need to put in the 1meg resistor as the epicos caps charge in 3 to 4 seconds, I would like to slow things down so its a bit easier to just go over what voltage you want then let the bleeders drop the voltage to what you want.
cheers nuxy

[Edited on 30-6-2015 by nux vomica]

PHILOU Zrealone - 30-6-2015 at 07:51

I'm sure sortly you will come to those

500 kV switch

I know that video for decades now, but it is still fascinating to me how the electricity flows not by the shortest way...if follows the ionisation channel of arc warmed air...reason why it lifts up and elongates before shutting down.

Hennig Brand - 30-6-2015 at 18:31

Very interesting video, good demonstration, thanks for sharing.

Gargamel - 8-7-2015 at 04:42

Concerning your capacitor banks:
Do you think it's OK to put them in series and charge them to almost their tested voltage?
I mean, you never know if the voltage is distributed evenly. Maybe some have a greater leak current then others.
Or one of them fails, in this case it will ruin the others too.

Concerning the bugzappers:

Quote:

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

Any idea why they loose power that way? Normally I would assume a sudden death if semiconductors die, not a slow decrease of power.

If it's capacitors or resistors, those could be replaced by stronger/better quality types.

OT:

Quote:

Weak bug zappers are outlawed when I come from from an animal welfare point of view. Only bug zappers of a minimum 1/2CV^2 are allowed on sale. The cheap one leave the bug riding the lightning too long before death and are very cruel!

IMHO there's only one kind of insect I like to kill with these, and that's culex mosquitos in the home or workplace. For these you don't need much power. Just so much that they stick to the racket. Dump em in the sink/toilet - goodbye. To much power and you'll burn them in a way that their residues spoil the racket over time.

Hennig Brand - 8-7-2015 at 04:58

Concerning your capacitor banks:
Do you think it's OK to put them in series and charge them to almost their tested voltage?
I mean, you never know if the voltage is distributed evenly. Maybe some have a greater leak current then others.
Or one of them fails, in this case it will ruin the others too.

Putting the capacitors in series is not ideal, but with reasonably well matched capacitors, suitable bypass resistors and by not overcharging it works quite well. It is common practice by many of the Tesla coil enthusiasts to put these kinds of capacitors in series strings much longer than we have done. The big thing to prevent capacitor damage is to not overcharge the capacitor bank. Discharging the capacitor bank into very low inductance, low resistance, loads can put a lot of strain on the capacitors too and will cause accelerated degradation (very short blasting line or blade of screwdriver, etc). I have been probably pushing the limits a bit by charging my 4000V bank to 3800V, but these types of capacitors can normally handle considerably more than their rated voltage. It would probably be best to charge to a somewhat lower voltage however.

Regarding the bug zapper supplies, they were not able to supply a suitably high current and I also believe they were fighting against each other (outputs out of phase) to some extent when hooked up together in series. I imagine the tiny windings in the tiny transformers were becoming damaged when they eventually started to fail, but I didn't put much energy into investigation. They really weren't very suitable for the application, too puny.

[Edited on 8-7-2015 by Hennig Brand]

Gargamel - 8-7-2015 at 10:52

Quote:

Regarding the bug zapper supplies, they were not able to supply a suitably high current

And if you increase your bleeders? And my add another multiplier stage?
This will take very long to charge though...

I'm just lazy that's all. I know there are better solutions, but I'd like to have something small, portable.

Kemo M062 with additional multiplier would be another idea.

I just searched the hell about suitable capacitors, this really expensive.
The combination nux vomica has choosen - 4x Epcos 5uF 1300V is really the cheapest I could find, ~13€. Every other combination is much more expensive.
If that is not enough, one could put another 4 in parallel.

Thank you for posting all this appetizers. You just made me hungry

edit:
Hennig, do you have an ESR value for your 1µ/1000V caps?

[Edited on 8-7-2015 by Gargamel]

nux vomica - 8-7-2015 at 18:46

Quote:

Regarding the bug zapper supplies, they were not able to supply a suitably high current

edit:
Hennig, do you have an ESR value for your 1µ/1000V caps?

[Edited on 8-7-2015 by Gargamel]

You can use these http://www.ebay.com/itm/DC-3V-to-7kV-Boost-High-voltage-Generator-Booster-Ignition-Coil-Power- to get your high voltage.
4 of the epicos caps are enough you don't really need over 1 uf.
This is a link for further back in the thread http://www.sciencemadness.org/talk/files.php?pid=404525&... about the esr of hennigs capacitors.
cheers nuxy

Hennig Brand - 9-7-2015 at 00:11

Using a lot of capacitance is pointless. The energy that is delivered to the bridgewire has to be delivered in well under a microsecond normally. It is power (energy delivered / time) that is important not a huge amount of stored joules/energy. If you look at the ESR of the capacitor bank and add it to the resistance of the switch, the cables, connections and bridgewire (all circuit resistance) and know that the time constant for capacitor discharge is the product of the capacitance in Farads and resistance in Ohms (tau = RC) or the time in seconds it takes to discharge to 37% of full charge it becomes clear. Charge on the capacitor bank is equal to the product of the capacitance in Farads and the charge voltage (Q = CV). Of course it is more complicated than this because there is not only resistance to consider but also circuit inductance and capacitance (impedance), but even just looking at the RC time constant, and charge equation, shows that what is needed is high voltage and low ESR, not huge amounts of capacitance. I am only using a 0.5uF capacitor bank and most of the commercial models use 1uF and those commercial models are designed to be able to fire multiple caps simultaneously in series/parallel configurations. Not only are these types of capacitors expensive, but storing large amounts of joules in high voltage capacitors can be just plain dangerous too, never mind the fact that it is pointless from a performance perspective. There has to be a certain amount of capacitance, but the point of diminishing return is reached very quickly much more quickly than most people imagine.

I actually haven't used the capacitors that I bought yet, I am still using the snubber capacitors that I salvaged from old variable frequency drive (VFD) motor controllers found at a scrap yard. They likely have very similar specs to the ones in the data sheet though, since they are of the same general type.

[Edited on 9-7-2015 by Hennig Brand]

Gargamel - 9-7-2015 at 02:15

I'm aware of that.

The idea behind putting another string parallel is to halve ESR and ESL.

Quote:

If you look at the ESR of the capacitor bank and add it to the resistance of the switch, the cables, connections and bridgewire (all circuit resistance)

Have you ever calculated if the ESR of the capacitors itself is so critical?
I mean, if the rest is of rather high resistance, what's the point...?

Where's the most serious bottleneck for the sharpest possible rise?

Hennig Brand - 9-7-2015 at 03:14

The most important resistance variable other than the capacitor(s) in a reasonably well designed system is the transmission line and unless a very poor choice is made when selecting a cable its resistance is so low, and more difficult to change, as to not be nearly as much of a factor as that of the capacitor(s). The switch and connections, etc, can also be significant, especially if designed poorly. Choosing the right type of capacitor is by far one of the most, if not the most, important variable. Of course if so determined, or as the result of a serious lack of understanding, high resistance and high inductance could be added to a system which would prevent the system from functioning properly even with a capacitor bank with the lowest ESR and ESL possible. It is of course a system with all components contributing, but capacitor selection is an area where by far some of the biggest overall effects on the system can be made.

Inductance is normally the biggest limiting factor to current rate of rise in actual systems, from what I have seen.

Have a look at this, from earlier in this very thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=23466&...

edit:
Yeah, once you are into pulse rated type capacitors the difference from one type to another may not be that great overall. Going from an electrolytic with 5 ohms of ESR to a pulse cap (e.g. metal film or foil) with 5 milliohms of ESR makes a huge difference, but going from a pulse cap with 10 milliohms to one with 5 milliohms when the blasting line has 0.5 ohms of resistance is not nearly as significant. Low ESR is important for capacitor longevity as well though, not just speed, since the current and current rate of rise involved is massive. Low ESR capacitors dissipate less heat/energy and will not get destroyed nearly as easily or quickly in pulsed power applications as capacitors with significantly higher ESR. Even relatively small amounts of resistance in a capacitor can cause great mechanical stresses and damage with large currents and fast current rise.

Low ESL is also very important for fast current rate of rise.

[Edited on 9-7-2015 by Hennig Brand]

Blasting Line / Transmission Line / Firing Line

Hennig Brand - 9-7-2015 at 10:18

Even regular lamp cord and speaker wire seem to have reasonably suitable specifications, especially since both are so common. The following was taken from Wikipedia:

"Ordinary lamp cord has an inductance of 0.1–0.2 μH/foot, likewise for shielded cord,[6] so a run of up to about 5 feet (10 total feet of conductor) will have less than 1% inductive loss in the audible range. Some premium speaker cables have lower inductance at the cost of higher capacitance; 0.02-0.05μH/foot is typical, in which case a run of up to about 25 feet (50 feet of conductor) will have less than 1% inductive loss."

I collected a few datasheets on some common coaxial cables a while back, but never bothered to post them. It is good information to have when one is trying to make system comparisons. I see that I have saved the Wiki article on speaker wire as well as a pdf, hopefully as long as I give credit it is ok to post it.

There are better cables as well, not listed here, that the commercial people sometimes use.

Attachment: RG-6U Data Sheet.pdf (99kB)
This file has been downloaded 485 times

Attachment: RG-8U Data Sheet.pdf (95kB)
This file has been downloaded 431 times

Attachment: RG-8X Data Sheet.pdf (95kB)
This file has been downloaded 477 times

Attachment: RG-11U Data Sheet.pdf (96kB)
This file has been downloaded 419 times

Attachment: RG-58U Data Sheet.pdf (92kB)
This file has been downloaded 450 times

Attachment: RG-59U Data Sheet.pdf (93kB)
This file has been downloaded 427 times

Attachment: RG-213U Data Sheet.pdf (94kB)
This file has been downloaded 417 times

Attachment: Speaker wire - Wikipedia, the free encyclopedia.pdf (424kB)
This file has been downloaded 588 times

[Edited on 9-7-2015 by Hennig Brand]

Gargamel - 11-7-2015 at 07:25

Quote:

5 milliohms of ESR

Rather 20 or more, most caps simply don't have the voltage rating needed, so one has to put several in series.

And capacitors with higher voltage rating than 1xxxV are much more expensive.

My feeling is that a lot of small capacitors with high voltage in parallel is better than a lot of big capacitors in series. But the price...

Did you ever think about some kind of regulation?
My worry would be that due to some uncertain factor like a battery a little stronger ect. the output voltage gets to high, destroying the expensive capacitors.

edit:
concerning typical coax cables:
Any experience about how the behave after some rough handling "in the field"? Most of these are meant to be placed somewhere permanently, like in a satellite TV installation ect. and not moved around hundreds of times.

edit2:
How about these paper/oil capacitors, like this one here:
http://www.ebay.co.uk/itm/HUGE-Russian-K41-1a-Paper-PIO-capa...

I've never found any ESR/ESR informations about these types...
Any idea how good they are compared to MKP or FKP types?

[Edited on 11-7-2015 by Gargamel]

[Edited on 11-7-2015 by Gargamel]

Hennig Brand - 12-7-2015 at 07:08

I would spent a little money and get suitable capacitors with suitable voltage, ESR, ESL and current ratings. We are limited somewhat by capacitor availability and price I guess. It is obviously much better to put the capacitors in parallel as much as possible, but we make do as best we can with what is available. These are not single use items either and should be good for thousands of shots if not abused (I think). The capacitors I bought, which Nuxy linked to a little earlier, are 2000V and 0.15uF with 5mohms of ESR, so for a 0.6uF bank made up of 16 (8 parallel strings of 2 in series) the ESR would be about 1.25mohms (unless I messed up somewhere). The 16 capacitors I bought cost me about $130 Canadian (including delivery), so yeah they are expensive but keep in mind there are cheaper albeit often less durable options available. I bought the type I did because they are greatly favored by the Tesla coil enthusiasts and are supposed to be incredibly tough.

The big thing is to monitor capacitor voltage when charging and stay under the rated voltage for maximum life, probably even as much as 20% under for best longevity and prevention of overcharging accidents would be wise. Yeah, some type of overcharge prevention circuitry could be employed. I was thinking of using an op-amp used as a comparator to monitor the charge voltage via the voltage multiplier. A small circuit could be used to send small pulses to simply maintain the level of charge once the capacitor was charged to the desired set point.

I have found RG-6 to be incredibly tough, at least so far. Why would anyone need to be excessively rough with the cable? I am careful not to pinch or put hard bends or kinks in the cable, but other than that the cable doesn't seem to require any special treatment.

That capacitor you linked to would likely be better suited to starting or stopping someone's heart than a practical EBW system. It is a very scary capacitor at 4000V and 160J !

[Edited on 12-7-2015 by Hennig Brand]

Gargamel - 12-7-2015 at 13:01

I'm ignoring the inductance here, but imagining a setup with 2 strings a 5 of the 5µ/1300V caps would give 12,5mOhm for 2µF -> a time constant of 25ns. So the capacitors alone should have finished the bulk of their business in that time, if the rest of the circuit lets them.

The RG213 Cable has about 300mOhm DC Resistance, back and forth for 100feet. Even with shorter cables much more than the caps.

Quote:

The capacitors I bought, which Nuxy linked to a little earlier, are 2000V and 0.15uF with 5mohms of ESR, so for a 0.6uF bank made up of 16 (8 parallel strings of 2 in series) the ESR would be about 1.25mohms (unless I messed up somewhere)

One question:
My feeling is that it's easier the transmit the energy through a higher voltage. Why didn't you choose something like 3 in series and 5 strings parallel?

After all the cable is the bottleneck...? Only to have a little less strain on the caps?

And also wonder:
These dV per time ans peak ampere reatios - arent't these rather ment for continous operations? Like every cycle of a switching PSU ect.
We only do single cycles every once in a while. As long as nothing is damaged in this few hundred µs it can cool down literally forever...?

-> so it's even pointless, to some extent...?

-> why not rather use 6000V or even 8000V? I would also assume the switch to be easier to set up at higher voltage.

Quote:

I have found RG-6 to be incredibly tough, at least so far. Why would anyone need to be excessively rough with the cable? I am careful not to pinch or put hard bends or kinks in the cable, but other than that the cable doesn't seem to require any special treatment.

The DVB-C Cables I know are some kind of stiff... I don't know, just some thought. The central conductor is not a flexible strand, but rather a rod. If you roll this out hundreds of time I would assume it to break some time.

Since 1 M

Quote:

That capacitor you linked to would likely be better suited to starting or stopping someone's heart than a practical EBW system. It is a very scary capacitor at 4000V and 160J !

I mentioned it as an example for the type. The large capacity of this one is overkill for our needs of course.

[Edited on 12-7-2015 by Gargamel]

markx - 12-7-2015 at 13:40

The K-41 type are an ancient soviet oil/paper design....usually the smaller ones could be found in the phase shifting circuits of asynchronous electric motors. A rather mediocre type of caps. I would be quite surprised if they held up to the ESR ESL standards of contemporary designs.
The one in the ebay picture is a deathtrap if stored like that...with unshorted leads that is. These huge bastards tend to gather charge all by themselves if left in storage in an unshorted condition and can give you a really nasty surprise if you do not know the danger.
I still remember the hit a 720pF hv cap gave me when I was constructing a TIG welder arcstarter years ago. It's not an experience I intend to repeat

nux vomica - 12-7-2015 at 15:43

You dont want to be lugging around anything that is too big as well here is my setup in a temporary box .

dangerous amateur - 13-7-2015 at 06:32

Interesting stuff!

Say what kind of metal do you use on your spark gap switches? Bronze?
They must withstand enormous currents, wont they burn down after relativly few shots?

Won't the plastic tube surrounding the electrodes burn away too?

I'd also be afraid the HV finds a way into the piezo switch, and into the finger operating it

[Edited on 13-7-2015 by dangerous amateur]

Hennig Brand - 13-7-2015 at 07:05

Nice compact looking fireset you have there!

Since the trigger pulse is very low current and high voltage some resistance can be placed between the trigger electrode and the trigger pulse generator without reducing the effectiveness of the trigger pulse significantly. I have about 150 ohms between the pulse transformer and the trigger electrode IIRC, which helps ensure that the firing line and bridgewire present a much lower impedance load for the main discharge across the switch (provides isolation). I think he is probably alright with the piezo igniter, but it doesn't hurt to be careful. An extra rubber insulator or cover could be put on or over the piezo igniter button if more insulation/isolation between finger and high voltage switch was needed.

Yes, higher voltage results in higher di/dt, but why is that necessarily better? My system already works great even through over 100ft of RG-6 when charged to 3800V. It will cost more for capacitors to get the same amount of capacitance at higher voltage and the capacitor bank will be much bulkier. The danger of and from an accidental shock will be greater. It will put more strain on the capacitors; the current through a series string of capacitors is the same, while parallel strings share the current between them. As voltage increases all system components generally get bigger and bulkier and more expensive. Once the system works well and is reliable, why increase the voltage, system size, expense and danger? There are some good reasons why the commercial systems are normally 3000-4000V, and I am sure I have not thought of all of them.

[Edited on 13-7-2015 by Hennig Brand]

dangerous amateur - 13-7-2015 at 13:31

Can somebody please write an opinion about my trigatron question?

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.

How did this brass and the insulation survive the firing?
Did you experience erosion and how severe was it?

Do the electrodes have to be re-adjusted very often?

And will not the rapid expanding hot air around the plasma rip away the insulation hose?

I used to "play" with HV a few years ago and i built a trigatron simply with 3 Nails and a bugzapper. But that was before my interest in energetics...

I never had such high currents.

[Edited on 13-7-2015 by dangerous amateur]

Hennig Brand - 13-7-2015 at 14:28

Sorry about that, I noticed your post earlier and then got side tracked by something else.

The brass should stand up quite well. Brass electrodes are commonly used by the Tesla coil enthusiasts which is a much higher demand application with repetitive discharges whereas an EBW switch is only fired once per explosive blast normally. I have only fired my trigatron about 15-20 times now, but I did just check and there doesn't appear to be any noticeable damage to the electrodes. The electrodes, if not too small and easily damaged, shouldn't need adjustment very often in my opinion. I haven't used the trigatron in the plastic hose yet, but I think it will be fine. It is a very rapid discharge and the resistance of the spark gap drops to quite a low value which should keep heat dissipation to a minimum (I don't know for sure though). The thing I was worried about was arc over across the plastic tubing, which would simply mean that the switch capsule would need to be made bigger, or change its shape or change material of construction, etc. Efficient spark gap switch electrodes are of a large enough size and are shaped properly. The Tesla coil people normally use spherical or hemispherical electrodes (e.g. rounded end on a rod electrode).

BTW, a bug zapper is the heart of my trigger pulse generator at the moment too.

nux vomica - 18-7-2015 at 19:22

Thought I'd try something different today by useing 0.55 mm stainless steel as the liner, exactly same size as my copper one's in the rivnut setup , 1.2 grm + 0.1 etn ebw voltage 3500 volts 40 mm standoff into a 10 mm plate

Penertrated through plate no probs with a little bit of spatter around hole but hole seems slightly bigger in dia.

There seemed to be more shrapnel damage to the support post as well and there was a burnt wood smell from the pine block underneath the plate as well as more wood debries in the hole in the plate ,think I will split the pine to see what is inside.
cheers nuxy

retrofit - 19-7-2015 at 13:56

nux vomica and Hennig, re: the voltage multiplier:

I tried using 10nF caps but the capacitance was so low that the voltage drop was excessive, to the point of being less than the input. Each subsequent stage read less voltage than the one before it! Putting more capacitance in parallel helped somewhat, but not enough.

I put in 4.7uF capacitors and then it worked properly (in a single stage), but that makes for an excessively (physically) large multiplier, and your pictures both showed those little 10nF, 3kV caps. I could drive it off a higher frequency (currently 60Hz), but I don't have the parts on hand to rig up a high frequency inverter.

I've been relying on the equation V_drop = (I_load/(fC))(2/3*n^3 + 1/2*n^2 - 1/6*n) where f is frequency, C is capacitance, and n is the number of stages. Clearly, increasing my frequency would help quite a lot, but so does increasing the capacitance. Large current draw (a milliamp and up) seem to suggest an excessively large voltage drop.

I'm planning on driving it off a 2kV transformer, so I shouldn't need more than a single stage, but that looks like I'll need to rig up a second transformer as ballast (and the system is already quite heavy). nux vomica, are you using a high frequency inverter like Hennig or a HV transformer?

[Edited on 19-7-2015 by retrofit]

nux vomica - 19-7-2015 at 18:29

Quote: Originally posted by retrofit

nux vomica and Hennig, re: the voltage multiplier:

I tried using 10nF caps but the capacitance was so low that the voltage drop was excessive, to the point of being less than the input. Each subsequent stage read less voltage than the one before it! Putting more capacitance in parallel helped somewhat, but not enough.

I put in 4.7uF capacitors and then it worked properly (in a single stage), but that makes for an excessively (physically) large multiplier, and your pictures both showed those little 10nF, 3kV caps. I could drive it off a higher frequency (currently 60Hz), but I don't have the parts on hand to rig up a high frequency inverter.

I've been relying on the equation V_drop = (I_load/(fC))(2/3*n^3 + 1/2*n^2 - 1/6*n) where f is frequency, C is capacitance, and n is the number of stages. Clearly, increasing my frequency would help quite a lot, but so does increasing the capacitance. Large current draw (a milliamp and up) seem to suggest an excessively large voltage drop.

I'm planning on driving it off a 2kV transformer, so I shouldn't need more than a single stage, but that looks like I'll need to rig up a second transformer as ballast (and the system is already quite heavy). nux vomica, are you using a high frequency inverter like Hennig or a HV transformer?

[Edited on 19-7-2015 by retrofit]

Retrofit I am useing this 12/220 inverter off fleabayhttp://www.ebay.com.au/itm/221596931989?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT it supposably puts out 40 watts and I am not sure of the frequency but I assume it would be 60 hertz.
I am measureing the voltage with a voltage divider reading 30 volts at 5000 volts, with a analog sanwa multimeter which has 20 k ohms per volt and I max out at 3500 volts with four stages just to give you a idea . Cheers nuxy

[Edited on 20-7-2015 by nux vomica]

Hennig Brand - 20-7-2015 at 04:31

Here is the product description with that Ebay add:

"
This product is the latest 2nd generation booster module, step-up transformer. Input 12V DC, 220V AC and the other end can be obtained. Frequency of high-frequency, higher output power, can drive 40W energy-saving lamps.

•This paragraph Module Specifications: length 4.2, width 3.6, high 2.3
•Does not meet the requirements of the appliances should not be used:
•First; can not be used: the iron core of the transformer!
•On a non-electronic products; second; you can not use!
•Third: This baby is a high frequency, the multimeter is not accurate voltage measurement
"

From the description you can tell that it is not 60Hz, but is much higher frequency (this is a very good thing for our purposes). Also, since you are only using four half wave multiplier stages and still getting 3500V the inverter is obviously putting out much more than 240V (something closer to 500V I would say). Since the inverter is very simple, and probably has essentially no regulation, at very low loads the voltage will float much higher than what it would under a load closer to its rated output. The inverter putting out more than 240V is also a very good thing, since higher multiplier input voltage means less multiplier stages. Voltage multipliers are quite inefficient and bulky especially if the number of stages is not kept to a minimum. However, if the output current requirement is low and the frequency is kept high they work reasonably well and are simple and cheap to make.

At 240V I would not have seriously considered the above inverter (especially if it was only operating at 60Hz), but now that I know that it puts out much more voltage than that at low load, and operates at high frequency, it is actually a fairly suitable power supply/inverter to feed a voltage multiplier for our purposes. Seems like a simply and cheap power supply solution that should work quite well.

[Edited on 20-7-2015 by Hennig Brand]

nux vomica - 20-7-2015 at 07:55

Here is the product description with that Ebay add:

"
This product is the latest 2nd generation booster module, step-up transformer. Input 12V DC, 220V AC and the other end can be obtained. Frequency of high-frequency, higher output power, can drive 40W energy-saving lamps.

•This paragraph Module Specifications: length 4.2, width 3.6, high 2.3
•Does not meet the requirements of the appliances should not be used:
•First; can not be used: the iron core of the transformer!
•On a non-electronic products; second; you can not use!
•Third: This baby is a high frequency, the multimeter is not accurate voltage measurement
"

From the description you can tell that it is not 60Hz, but is much higher frequency (this is a very good thing for our purposes). Also, since you are only using four half wave multiplier stages and still getting 3500V the inverter is obviously putting out much more than 240V (something closer to 500V I would say). Since the inverter is very simple, and probably has essentially no regulation, at very low loads the voltage will float much higher than what it would under a load closer to its rated output. The inverter putting out more than 240V is also a very good thing, since higher multiplier input voltage means less multiplier stages. Voltage multipliers are quite inefficient and bulky especially if the number of stages is not kept to a minimum. However, if the output current requirement is low and the frequency is kept high they work reasonably well and are simple and cheap to make.

At 240V I would not have seriously considered the above inverter (especially if it was only operating at 60Hz), but now that I know that it puts out much more voltage than that at low load, and operates at high frequency, it is actually a fairly suitable power supply/inverter to feed a voltage multiplier for our purposes. Seems like a simply and cheap power supply solution that should work quite well.

[Edited on 20-7-2015 by Hennig Brand]

Hennig do Canadians use the expression "dumb luck" cause I think that nuxys nose has sniffed out a winner.
I know the canadians and our lot have the same pommy background but use different expressions but that one should be universal nuxy.

Hennig Brand - 20-7-2015 at 10:52

Yes we use that expression. I think you had some idea of what you were looking for though, so it probably wasn't completely luck. I actually ordered a couple of those maybe a week or two ago when you first told me about them. I don't really need them at the moment, but I will add them to my collection of "toys" for possible later use.

nux vomica - 20-7-2015 at 16:35

I did have a backup plan I drew the IR2153 schematic on eagle and was going to rout it out but a stepper driver board blew so waiting for a new one at the moment.
All of the bits are organized got a fx2240 fp4 transformer pot core and bobbin + a 10x25 round ferrite rod to try and make a 4000v transformer I pulled apart one of those ebay hv units and they are 20 primary 1800 secondary windings was a bit of a job counting the windings coming off the former.
Cheers nuxy.

Edit. I looked at the 12/220 inverter transistor markings looks like they are a chinese copy of 2sb1274 transistor it is pnp ,20 watts, and 100mhz frequency , I have also attached the data sheet . nuxy

Attachment: datasheet.pdf (88kB)
This file has been downloaded 517 times

[Edited on 21-7-2015 by nux vomica]

nux vomica - 20-7-2015 at 20:17

Yes we use that expression. I think you had some idea of what you were looking for though, so it probably wasn't completely luck. I actually ordered a couple of those maybe a week or two ago when you first told me about them. I don't really need them at the moment, but I will add them to my collection of "toys" for possible later use.

If you keep on doing a noah and collecting two of everything you will have a full ship soon. and don't they reckon were going to be flooded soon from global warming melting the icecaps.

[Edited on 22-7-2015 by nux vomica]

markx - 20-7-2015 at 23:31

I did have a backup plan I drew the IR2153 schematic on eagle and was going to rout it out but a stepper driver board blew so waiting for a new one at the moment.
All of the bits are organized got a fx2240 fp4 transformer pot core and bobbin + a 10x25 round ferrite rod to try and make a 4000v transformer I pulled apart one of those ebay hv units and they are 20 primary 1800 secondary windings was a bit of a job counting the windings coming off the former.

Looking at your pcb layout I see 2 problems :
a) pin 8 of the driver IC has to be connected to pin 1
b) pin 4 has to be connected to ground terminal (pin 6)

Also you might consider adding 10 ohm gate resistors to the fets. Also adding a 10k ohm resistor between gate and source of fets is a good idea. It will pull the gates down and keep switches closed in case the IC decides to malfunction or you switch the circuit on without the IC. The IR2153 is a pretty sensitive chip towards overloads and I have burnt a load of them before realizing that current limiting and keeping the gates from floating are essential for longevity of the circuit.
Considering the 100n snubber caps it is advantageous to add a series resistor to them (2-5ohm) it will provide current limiting for the caps and keep them from overheating. The snubbers will charge and discharge with every cycle of the switch and can easily overheat if there is only the esr of the cap to dissipate the energy.
With homewound transformers the snubber circuits can rarely be avoided as usually the parasitics are strongly present and voltage overshoot is heavy in push-pull topology. Especially if the windings have less than ideal coupling or the core has leakage flux. The overshoot can be expected around tree to five times the input voltage. So with a 12V source around 60V of overshoot on a mediocre transformer design is quite common. This will be on borderline avalanche mode for the IRF44 and is likely to kill the swithches quite soon. High frequency transformers are wound in some complicated ways by interleaving the primaries and secondaries and paralleling them (litz wire style) for improved electromagnetic coupling. So be prepared for some fried switches and driver ICs in near future

! Keeping that in mind I would suggest to use a dip socket for the IC and position the fets so that they can be easily desoldered for replacements. Also please add a fuse into the incoming dc bus....it will do wonders to save everything from burning down like a merry hell when the fets blow and short the battery through the transformer primary. Don't ask how I know this

nux vomica - 20-7-2015 at 23:50

Your quite right markx I missed 1/8 didn't rout and ive added the other earth wire, thanks I will look at the other suggestions nuxy

[Edit fixed points markx pointed out will work on other points.]

[Edited on 21-7-2015 by nux vomica]

markx - 21-7-2015 at 00:46

Your quite right markx I missed 1/8 didn't rout and ive added the other earth wire, thanks I will look at the other suggestions nuxy

Glad I could be of help before you routed the board...although it would have been an easy fix even so

But it is always great when things work on the first attempt.
I've been messing around with inverter designs quite a lot and know how easily they can blow up and how exponentially more complicated it all gets when the output power rises and stability becomes an issue. Transformer design and snubbing of the switches are key elements if any significant power output is needed. One can also choose more rugged switching elements with a higher voltage rating, but with mosfets this automatically means a higher on state resistance and hence lower efficacy with way more overheating issues. IGBTs are also a robust option with the same driver circuitry, but they tend to cost more than mosfets. And one has to keep track of the gate capacitance value as by using transistors with higher gate capacitance one may overshoot the driver IC current rating and blow it all to hell again. In that case an additional high current driver chip is needed....like IR2110 e.g.

Hennig Brand - 21-7-2015 at 17:28

If you keep on doing a noah and collecting two of everything you will have a full ship soon. and don't they reckon were going to be flooded soon from global warming melting the icecaps hennig what are you doing? control yourself.

I know what you mean, storage can be a problem. I really like to collect science and technology stuff. Any project I am working on, that works out well, I immediately want to stock up on the associated components and materials. Being able to do things gives me a sense of power and accomplishment I guess. Also, there are far worse things to spend one's time and money on.

Markx, thanks for the insights into homebrew inverters, I just learned a few things. So far that 555 based inverter I made is working fine, but the current draw is fairly low. Also the 15kHz switching frequency is low enough that even amateur standard parallel, layer, wound transformers normally work reasonably well (from what I have seen). Things do get tricky at much higher frequencies from what I have read and heard, as you have also stated.

nux vomica - 21-7-2015 at 19:43

Hennig if you have taken me the wrong way don't ,what you do with your life is your personal business so if I offended you I apologize and will keep the wisecracks to myself . Nuxy

markx - 21-7-2015 at 23:13

Markx, thanks for the insights into homebrew inverters, I just learned a few things. So far that 555 based inverter I made is working fine, but the current draw is fairly low. Also the 15kHz switching frequency is low enough that even amateur standard parallel, layer, wound transformers normally work reasonably well (from what I have seen). Things do get tricky at much higher frequencies from what I have read and heard, as you have also stated.

15kHz is way low for contemporary standards and really offers no advatages in terms of transformer or circuitry design. It only offers the disadvantage of saturating your transformer core at a rather negligible power output and overheating/blowing the switching elements and driver circuitry due to that. That is another point where the gate resistor can save a lot as a current limiter. If the junction blows and the IC is connected to the switch without the resistor, you basically short out the output of the driver chip and 99% it means that the chip gives up the ghost. If current limiting is provided then the driver circuitry has a good chance of living through it in my practical experience.
One can comfortably shoot for 40-50kHz of primary switching frequency without any further complications and gain a load of output power capacity from the same size ferrite core. Going into the >100kHz primary switching is where the complications tend to arise (litz wire, paralleling of windings and serious skin effect limitations), but there really is no need for such high frequencies. Most contemporary inverter designs do hover near the 50kHz primary switching speed....it tends to be the golden middle way between good efficacy, simple design and a broad range of affordable switching elements. For example most generic IGBTs are not really good for anything upwards 50kHz....the charge carrier recombination in the junction limits the turn on/off speed and you get high switching losses and cross conduction of the bridge by driving them too fast. Mosfets on the other hand do not suffer from that particular shortcoming and can comfortably go up into hundreds of kHz range.

[Edited on 22-7-2015 by markx]

retrofit - 21-7-2015 at 23:47

Edit: The capacitance values given here are wrong. C3 is 711nF nominally, C1 and C2 are each 237nF nominal. That means (1/2) * (711nF) * (3850 volts)^2 = 5.3 joules. 5.3 joules over 10uS is 530kW.

I finished putting together the voltage multiplier, constructing a trigatron (tube, electrodes, piezo igniter), and wiring all the pieces together. I haven't yet tested a discharge of the full capacitor bank (will do tomorrow). I just wanted to see if anyone had any comments or suggestions about the circuit.

The AC source is a small 12 VDC battery-powered inverter, putting out ~123 VAC at 60Hz (not ideal; as noted before, this requires a large capacitance in the voltage multiplier). The microwave oven transformer (MOT) has roughly a 16.6x step-up. After the single stage, half-wave voltage multiplier, the calculated voltage (extrapolated from lower voltage testing) is around 3850 VDC which charges up C3. R1 is a 50 ohm, 10 watt resistor (which, as I look at my board again, is actually on the bottom, between C2/D2 and C3/L1, not up top there). All caps are arranged to be rated for 4kV; all diodes are 12kV rated.

I didn't have a symbol in my parts library for the trigatron, so I just put a push button switch in the schematic. Not pictured is a 100 ohm, 10 watt resistor in series with the piezo igniter to encourage the capacitor bank (C3) to discharge through the load and not myself. The gap is set at 3mm (est. 9 kV breakdown voltage in air), and the piezo reliably sparks across the gap. I read that most trigatrons are operated within 80% or so of breakdown voltage. Is that gap too large for fast switching? If I take 3850 V to be 80% of the gap's breakdown voltage (giving 4813 V), then I might consider setting it to 1.6mm.

As an aside, I discovered that piezo igniter leads seem to be completely immune to my best attempts to solder to them. Improvisation of questionable quality followed.

The load for tomorrow's dry run (no bridgewire) is just the primary of another MOT to provide some inductance and take a bit of stress off the caps. In normal operation, that won't be present. I plan to use the primary because of the high surge current and thicker winding, but that will produce a high voltage pulse at the secondary windings. which might arc over. Perhaps it would be better to use the secondary, creating a high current, lower voltage pulse in the primary? All of this is irrelevant with a bridgewire in the system, because inductance appears to work against an EBW setup.

During normal operation, I was considering using that MOT to ballast the charging MOT--is it worth it?

As to energy/power output, 1/2 * 7.11uF * 3850 volts^2 ~= 52.69 joules. 52.69 joules over 10uS (pulled that out of thin air) should be 5.269 MW.

[Edited on 22-7-2015 by retrofit]

Hennig Brand - 22-7-2015 at 04:27

Retrofit, I used an MOT and full wave multiplier earlier in this thread and it works but is very inefficient and big and heavy. Also your capacitor has an awful lot of capacitance. Is it actually a pulse rated cap with low ESR and low ESL? Even with relatively low circuit resistance and inductance most of the charge on that capacitor will not be transferred before bridgewire burst.

Quote: Originally posted by markx

No advantages? There are massive advantages going from 60Hz to 15kHz. Markx, check the Magnetics ferrite transformer design guide I posted here:

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

With a 3019P pot core going from 20kHz to 50kHz increases the power handling capability from 48 Watts to 75 Watts. If the frequency is increased to 100kHz the power handling capability goes to 108W and at 250kHz, 210W. You are correct I could have used a higher frequency and reduced transformer size and gained efficiency, but since I only need 5W or less and for only a very short duration how much practical difference does it make? Even going with the relatively low frequency of 15kHz allows reasonably small capacitors to be used for the voltage multiplier and also reasonable efficiency at the required current draw. I suppose battery life could be improved with higher frequency which is a consideration. If I was designing a 500W power supply for continuous use I would be much more concerned with efficiency and keeping the component sizes as small as possible, but I am much less concerned with a 5W power supply that is only run for 5-10 seconds every once in a while.

I am fairly new to inverter design and what I built is definitely not optimized, but it works and so far seems reliable.

[Edited on 22-7-2015 by Hennig Brand]

retrofit - 22-7-2015 at 09:03

Quote:

Retrofit, I used an MOT and full wave multiplier earlier in this thread and it works but is very inefficient and big and heavy. Also your capacitor has an awful lot of capacitance. Is it actually a pulse rated cap with low ESR and low ESL? Even with relatively low circuit resistance and inductance most of the charge on that capacitor will not be transferred before bridgewire burst.

The capacitor C3 is actually a bank of metallized PE film capacitors sold as self-healing, low ESL/ESR/dissipation (cheap and ambiguous as to exact specifications, "no inductance", etc.). I condensed all the capacitors to their calculated values (including C1 and C2) rather than draw the wiring of each one. However, the LCR meter disagrees with the calculated values. I have 3 parallel strings of 2 capacitors each, all are 4.74uF. This should give 7.11uF, but I measure 691.0nF across the bank. The ESR value measured floats all over (no idea why), ~1.4-2.3 ohms at 100 Hz, and 0.09 ohms at 100 kHz. Measured series inductance is 3.655 H at 100 Hz and 3.316 uH at 100 kHz (with fairly long connecting leads).

Edit: Well, I pulled a bonehead. They're 474nF caps, not 4.74uF caps. The numbers seem much more reasonable now. Calculated capacitance is 711nF, actual is 691nF. Without the meter and your comment, I probably would have missed that. Thanks!

I edited my earlier post to make a note about incorrect values. (1/2) * (711nF) * (3850 volts)^2 = 5.3 joules. 5.3 joules over 10uS is 530kW. However, I'm still worried about that ESR value. It seems awfully high.

[Edited on 22-7-2015 by retrofit]

Hennig Brand - 22-7-2015 at 09:59

No problem, yeah, that makes more sense. Also I doubt the ESR is really that high and if it is there is likely a problem with one or more of the caps.

retrofit - 22-7-2015 at 11:35

Back to the drawing board for the trigatron. It wouldn't fire the gap with the capacitor bank in the circuit. I reversed the polarity, placing the positive electrode in the center of the gap and the ground to the ground side of the capacitor bank. A quick search of the literature suggested that trigatrons are sensitive to polarity. That yielded a small weak spark, so I closed up the gap to about 2mm, but it was no better (it appeared to fire once, but was not repeatable). Touching the wires together to discharge the bank gave a noticeably more intense spark (heavy rubber gloves and proper tongue angle required).

Nux vomica, how do you have your piezo igniter wired into your circuit?

Edit: Closing the gap to ~0.5mm and placing the positive electrode in the center and the ground on the negative side of the bank caused the gap to break down reliably. Perhaps too reliably, because it would occasionally spark over by itself and conduct continuously. Opening it back up to ~1.5mm worked for reliable breakdown, which coincides with the bank being charged to around 80% of theoretical breakdown voltage for the gap.

[Edited on 22-7-2015 by retrofit]

markx - 22-7-2015 at 11:39

I was a bit vague in my statement....pardon me. What I meant is that 15kHz design offers no advantages in hardware complication level compared to a 50kHz system. And of course a with a low power system one does not need to keep the efficacy sky high or the size as small as possible. Rather a stable and reliable system is what we are after. I was just trying to offer some insight on generic principles that I have gathered from my own experience

Hennig Brand - 22-7-2015 at 12:57

I see what you mean, that I could have gone to 50kHz with little extra trouble and got some benefits for doing so. I didn't have enough experience with it to know if going to 50kHz really wouldn't have caused extra complications, which was why I erred on the side of caution and kept the frequency low at 15kHz.

Hennig Brand - 24-7-2015 at 15:36

I just received a couple of printed circuit boards and a couple of mini trigatrons from Nux Vomica, like the ones used for his EBW fireset. He does very nice work. Since I have purchased some of the same capacitors a while back and inverters I could now easily assemble a fireset just like his. One can never have too many EBW firesets.

Thank you Mr. Vomica!

nux vomica - 24-7-2015 at 17:41

I just received a couple of printed circuit boards and a couple of mini trigatrons from Nux Vomica, like the ones used for his EBW fireset. He does very nice work. Since I have purchased some of the same capacitors a while back and inverters I could now easily assemble a fireset just like his. One can never have too many EBW firesets.

Thank you Mr. Vomica!

No problems henning enjoy, you are spoiled for choice now

, i am intrested to see what your thoughts are on the different setups.
If there is any interest I can post the sketchup file I used to rout my boards with, I'm also working on putting all the parts on one board which will make things more compact . Cheers Nuxy.

[Edited on 25-7-2015 by nux vomica]

markx - 1-8-2015 at 08:46

Was bored this saturday and decided to slap together a power converter based on the cheap chinese hf transformer from ebay. Turned out really well I must say...about 300W of output power with adjustable output voltage from 12-500V dc. Can also be used as a powerful EBW charger if output is fed into a voltage multiplier.
The switches are four irf3205 mosfets in a push-pull configuration. The "brain" is TL494 coupled with IR2110 to keep up with the relatively high gate capacitance of the particular mosfets. The IC-s are powered by a separate SEPIC converter to keep the ic power voltage independent of battery voltage. Output voltage is controlled by a non isoated feedback loop (through resistor bridge and smoothing capacitor) into error amp 1 of the TL494. There is also the option to use error amp 2 as a current limiter to keep the circuit from overstressing itself in case of a shorted output. I did not implement the current sense option yet, but it probably is a good idea now that I think about it

Scope shot of voltage on mosfet drain (left) and on the gate (right) 33kHz:

There is basically no voltage overshoot on the drains....snubbers and fine tuned driving frequency do an excellent job

Going higher with the switching frequency did produce considerable distortion in the drain waveform and a loss of output power. I guess for 5$ the transformers' core is not one of the brightest stars in the magnetic materials heaven

[Edited on 1-8-2015 by markx]

Hennig Brand - 1-8-2015 at 12:11

Well that is definitely a power supply and a fairly sophisticated one at that especially for an amateur, well done. Major overkill for an EBW fireset power supply though I would judge, but to be honest I have never actually seen a power supply from one of the commercial models so I don't know for sure.

markx - 1-8-2015 at 12:56

Well that is definitely a power supply and a fairly sophisticated one at that especially for an amateur, well done. Major overkill for an EBW fireset power supply though I would judge, but to be honest I have never actually seen a power supply from one of the commercial models so I don't know for sure.

It is a step forward from the bug zappers for sure

For a simple HV capacitance charger it is perhaps overkill, but I don't mind the extra zap.

Hennig Brand - 2-8-2015 at 11:01

Poke fun at those bug zappers if you want to but they were merely stepping stones and part of a learning process that ended with a fairly basic but reasonably good understanding of HV power supply design and of EBW technology in general. You should set up a EBW system yourself. You already have a power supply and it really is a very reliable and safe way to go. It also seems to appeal to technology nuts like us.

The whole concept is very interesting, or at least I find it so.

TGT - 3-8-2015 at 00:21

Is it possible to heat a small wire for electric ignition with just a car 12 volt battery? Sorry for the simple question. I have made one out of a photo flash and it seems to work good, but wire distance is limited. May be more caps?

TGT

markx - 3-8-2015 at 01:37

The whole concept is very interesting, or at least I find it so.

Naaah...I'm actually thinking them electric tennis rackets were a pretty darn good idea. I mean "out of the box" solution for a fireset that only cost pennies

markx - 3-8-2015 at 01:47

Quote: Originally posted by TGT

Is it possible to heat a small wire for electric ignition with just a car 12 volt battery? Sorry for the simple question. I have made one out of a photo flash and it seems to work good, but wire distance is limited. May be more caps?

TGT

Of course it is possible...you just have to take into account the resistance of the cable itself and the voltage drop across it. At a certain length the voltage drop on the cable itself will be big enough to prevent the ignition element from sufficiently heating up. At that point you have reached the limit for that particular gauge/material cable. To increase the distance you have to use heavier cable or higher voltage. Adding parallel caps to input will not help as it will neither up the voltage, nor affect the resistance of the circuit.

Hennig Brand - 3-8-2015 at 17:20

Quote: Originally posted by markx

Naaah...I'm actually thinking them electric tennis rackets were a pretty darn good idea. I mean "out of the box" solution for a fireset that only cost pennies

Thanks, you know it could have been made to work too if the current draw had been reduced by current limiting resistor(s) or inductor and loads such as bleeder resistors and voltage divider were either taken out of circuit during charging or made much higher resistance. The truth is they were awfully puny and there are better choices. Yeah, it seemed like a good idea at first.

They could be used for a disposable/consumable system with no blasting line, since the capacitor(s) required to fire the EBW detonator can be quite small (lower voltage and capacitance) and long term power supply longevity is certainly not a factor since it will not survive the blast anyway.

Capacitors in series - voltage distribution OK?

Gargamel - 7-8-2015 at 14:11

Have you guys ever measured the true voltage distribution over your caps?

The resistance of my measuring equipment (cheapo DMM 1MegOhm+ devider network, giving 10MegOhm) would be enough to severely affect balance, but if the capacitance is large enough I could charge them without any bleeder and take the measurement quickly.

Capacitors in series suck. Only we have no (cheap) choice.

Besides, have you ever tried to match your capacitors, and if, how did you do it? My DMM has no capacitance function. I wonder if a cheapo capacitance meter in the 15-20$ range is of any use.

Hennig Brand - 9-8-2015 at 08:06

Nux and I have both been using series connected capacitors for a while now and it has been working quite well for both of us. Many Tesla coil enthusiasts, likely thousands, have been using series connected capacitors as well. It may not be ideal, but it can work very well. Why don't you try it? You may find that it works satisfactorily.

Good quality pulse caps, of the same type, are normally fairly well matched in terms of ESR, ESL and capacitance.

[Edited on 10-8-2015 by Hennig Brand]

nux vomica - 9-8-2015 at 20:15

Gargamel these are the capacitors I use they aren't particularly expensive for four of them. http://m.ebay.com/itm/2-EPCOS-5uF-1300V-1kV-275V-250V-100V-radial-polypropylene-capacitors-/291095298708?nav=SEARCH

Cheers nuxy

[Edited on 10-8-2015 by nux vomica]

Gargamel - 10-8-2015 at 02:50

I got a large batch of 1,6KV/330nF rather cheap, but I like to see what's going on with them. If you they suffer from overvoltage, this might happen slowly, loosing capacitance over time. I want something reliable.

Also my power source consisting basically of an enlarged bugzapper style blocking oscillator does not like all these loads, the voltage drops to much. I need something stronger first.

I've got a CCFL inverter ready, if this thing does not work the way I want it, I'll get a TV transformer.

One question concerning your trigatrons:

Do your trigger circuits and main circuits share a common ground?
Your batteries too?

nux vomica - 10-8-2015 at 03:27

If you put three 330nf in series you only get 4800 volts 110nf you would have to parallel up a lot of caps to get to a decent uf figure.

[Edited on 10-8-2015 by nux vomica]

aldofad - 11-8-2015 at 01:54

This is an EBW I made time ago.

http://youtu.be/Ks6GFzZj8Vc

4500 V DC, rectified from a 10.000 V AC neon transformer. 1 micro F capacitor. PETN exploded correctly every time.

Gargamel - 11-8-2015 at 02:32

Quote:

4500 V DC, rectified from a 10.000 V AC neon transformer. 1 micro F capacitor. PETN exploded correctly every time.

What kind of wire and capacitor did you use?

Don't worry Nux, I've got a box full of them.

How do you guys wire your trigger electrodes?
Right now I envision to put my main circuit and my trigger circuit on a common ground, so that there are only 3 electrodes. The spark would shoot from a trigger electrode sitting very near to the positive main electrode to the common ground eletrode. That way it could ionize a large part of the gap.

The ground elektrode leads through the EBW to ground/capacitor -.

I could also use 4 electrodes and a completely separated circuit, shooting a spark across the main path.

My feeling is that the 3 electrode version would be more reliable.

aldofad - 11-8-2015 at 03:37