Sciencemadness Discussion Board

High voltage Halloween display

Pyro_cat - 15-9-2019 at 18:56



Been years since I did any Telsa coiling, I don't know if I want to do all that again.

I would like to just do the Jacobs ladder and some noisy discharges using capacitors. People who have never seen high voltage in real life are always like WTF, no way !

Microwave transformers always over heat. I even tried keeping them cool by submerging in distilled water but that only bought a little time before meltdown.

Neon sign transformers are weak, can make some decent crackling with a glass and foil capacitor but its still weak.

I have never had success building my own step up transformer.


woelen - 15-9-2019 at 23:20

Look up "ZVS driver" on internet, but also here on sciencemadness. This can make high power high voltage from low voltages. You need a fat low voltage power supply to which you connect the driver. You can buy complete kits on eBay. There are many good kits, but I suggest you to add your own additional cooling to the transistors and use a small CPU fan or something similar to make the cooling even more effective.

Be careful though. Making mistakes with ZVS drivers can be lethal! Really, this is no child's play!!!

wg48temp9 - 16-9-2019 at 06:58

Quote: Originally posted by Pyro_cat  

Microwave transformers always over heat. I even tried keeping them cool by submerging in distilled water but that only bought a little time before meltdown.


I guess you were using the transformer without a primary ballast to limit the current drawn by the Jacobs ladder. Without a ballast when a spark occurs across the secondary output it is effectively a short circuited across the secondary so the current drawn will exceed the maximum for the transformer.

Most domestic microwave oven transforms are designed to run with forced air cooing and not necessarily continuously rated. Even when correctly ballasted a Jacobs ladder is hard duty for a transformer not designed for such service due to the transients induced in the transformer when the spark strikes. As in Tesla coil service an RC filter is recommended on the secondary output.

To limit the short circuit current the transformer can be ballasted with a primary or secondary ballast. A primary ballast tends to be more easily implemented as its not operating at 2kV. A convenient primary ballast is the primary of a second MO transformer. That tends to limit the current too much but that will reduce the transform temperature rise sufficiently that it can handle continuous operation even with out forced air cooling.


[Edited on 9/16/2019 by wg48temp9]

Pyro_cat - 22-9-2019 at 17:46

I tried limiting the current to the microwave transformers with a "salt water variac".

I was hoping to find a way to be lazy and use like 100 amps, the heck with efficiency just a lots of 60 cycle hum and plasma. Did some looking around the web and it seems DIY step up transformers are not something people are doing, even the Tesla coil enthusiasts.

Building a Tesla coil and the capacitors is easier task then the primary that powers it.

They sell "pole pig" distribution transformers on e-bay now under $1000 lol maybe next year.

I have a decent neon sign transformer, I could do a coil. Everyone liked that when I did it years ago. I just envisioned using alot of power and I wanted to have some incandescent bulbs dimming each time the Jacobs ladder did a cycle.

Going the microwave oven transformer route I could probably exaggerate that effect of dimming lights to give the illusion its pulling more power then it actually does with some dollar store bulbs and by using thin wire to power everything and increase the voltage drop.

Pole pig transformer, that could re awaken that really could re awaken the enthusiasm I used to have for messing with the electricity.

Pyro_cat - 22-9-2019 at 18:05

Quote: Originally posted by woelen  
Look up "ZVS driver" on internet, but also here on sciencemadness. This can make high power high voltage from low voltages. You need a fat low voltage power supply to which you connect the driver. You can buy complete kits on eBay. There are many good kits, but I suggest you to add your own additional cooling to the transistors and use a small CPU fan or something similar to make the cooling even more effective.

Be careful though. Making mistakes with ZVS drivers can be lethal! Really, this is no child's play!!!


I know, I did manage to get zapped by the Tesla primary. That sucked.

Interesting how that works a ZVS driver. Thanks. Those Marx generators look interesting too.

I should send for these things and re awaken that electrical experimenting bug I used to have really bad. Be up all night doing them. Now I just play internet too much :(


[Edited on 23-9-2019 by Pyro_cat]

Pyro_cat - 24-9-2019 at 20:54

Decided I am doing a coil.

I got a neon sign transformer 15kv 30ma.

Run 220 though it like I did with the old oil burner ignition transformers back when I first got into coiling. Thought maybe I would burn it out putting 220 instead of 110 but no. Oil burner ignition ignition transformers changed. I don't even know what they use now to spark off oil burners but back when I was doing coils they came out with these new light ones, you had to look for the old ones.

If I remember its all about the capacitor, already got one nice door size piece of glass got to get my buddies to keep a look out for glass in the trash. The best cap I ever made was shower doors and they were that cant see through not smooth glass but it worked anyway. The top layer on top of the foil was storm windows. My caps with storm windows I thought would be better cause the foil layers were closer but the shower door cap was the best.

Nobody I know now ever saw a live Tesla coil, even if it "sucks" compared to whats on YouTube its still science madness.

Got to find a top for it. My first coils I used the brass ball from fireplace stuff then the brass float ball from a sewage pump.

I am going to have fun with this.



yobbo II - 18-10-2019 at 11:24


Would discharging a large high voltage capacitor (dangerous) through a very long thin wire strung out between to poles make a good display. If you used copper you would get greenish? The wire will be an exploding wire if the cap is large enough.
Yob

Pyro_cat - 19-10-2019 at 11:53

Quote: Originally posted by yobbo II  

Would discharging a large high voltage capacitor (dangerous) through a very long thin wire strung out between to poles make a good display. If you used copper you would get greenish? The wire will be an exploding wire if the cap is large enough.
Yob


Not so sure. High voltage manages to get through wires without heating them much. The higher the voltage, the lower the current. The lower the current, the lower the resistance.

But putting jumper cables to the 200 amp breaker panel bars is plenty for exploding wires and strips of tin foil. Didn't notice any green because with the copper because its so bright you can't look right at it.

On the subject of bright haven't yet attempted to build a carbon arc lamp yet. That would be a fun project. Very Frankensteinish too.

Thought of another way to create the illusion of more power consumption then I am actually using by attaching the transformers to sheet metal, grounded of course, the sheet metal resonates and amplifies that 60 cycle hum.



[Edited on 19-10-2019 by Pyro_cat]

Pyro_cat - 24-10-2019 at 06:49

My coil sucks. 5 inch sparks only to pointy grounded objects. Its the cap, and its not so easy to find glass for the capacitor anymore. I guess everyone is done getting new windows, it used to be easy spotting old storm windows in the trash.

I also missed out on getting the Fresnel lens from old projection TVs, another thing you saw all the time being tossed out that's rare now. Learned about that too late.

DoctorPurple - 24-10-2019 at 17:19

i've used MOTs(microwave oven transformers) for a Jacobs Ladder before, yeah they do need a ballast or they'll either trip a breaker or overheat. I used a coil from a halogen lamp ballast and i could add more inductance by adding more iron core to the coil and i adjusted it till it stopped tripping the breaker, then the MOTs and the ballast were submerged in motor oil and had a pretty high volume fan blowing onto the oil pool for cooling, i also added several capacitors on the secondary circuit to give it resonance. The whole setup could make arcs that could grow at least a foot in length, they'd grow till they accumulated plasma at the top of the large bell jar it was in.

yobbo II - 30-10-2019 at 08:40


A large high voltage capacitor connected to a long very thin wire (use as thin as possible) gauge 40 copper will create a very long spark and bang. You will have to switch the hv via a spark gap or some contraption. You get an exploding wire.
Large hv capacitors are VERY dangerous.

Yob

yobbo II - 30-10-2019 at 08:59

Have a look at this type of thing.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1969001...

Perhaps its a bit more complicated than I thought. You could try a wire a few feet long.

Another type of electric flash might be doable.

https://en.wikipedia.org/wiki/Air-gap_flash

At Doc P.

What value were the capacitors approx.

Yob



[Edited on 30-10-2019 by yobbo II]

Vomaturge - 30-10-2019 at 20:39

Quote: Originally posted by Pyro_cat  
My coil sucks. 5 inch sparks only to pointy grounded objects. Its the cap, and its not so easy to find glass for the capacitor anymore. I guess everyone is done getting new windows, it used to be easy spotting old storm windows in the trash.

I also missed out on getting the Fresnel lens from old projection TVs, another thing you saw all the time being tossed out that's rare now. Learned about that too late.


About 6 years ago, I had a little handheld van de graff that came with a plastic sheet that was supposed to hold a static charge. Reckless experimenter that I am, I sandwiched it between two metal pans and charged it until a very loud white spark flashed over. When the sheet finally got damaged (can't recall if it was abraded or if I exceeded the breakdown voltage) I tried plastic sheet protectors. They are surprisingly efficient capacitors. Here is a photo of a sheet protector of unknown thickness that I overcharged a few weeks ago with an advertised 20 kv, measured 200ua ionizer power supply:


PhotoPictureResizer_191030_214117537_crop_1429x852-357x213.jpg - 12kB

The plastic had been scraped (while in use as a sheet protector) and when the power was turned on a rapid series of small low energy discharges broke through the weak point and melted a hole. When this was covered in electrical tape the voltage built to a point where around 1 cm discharges could be made to a wire with the frayed end bent back to prevent corona. Around 4 cm discharges could travel along the surface of the plastic, arcing around the side of the dielectric. I don't have a way to measure kilovolts, so I'm just giving these examples of spark length. Anyhow, when the dielectric broke down at full voltage, the burned part of the plastic evaporated so quickly that it shattered the surrounding material, causing the damage shown here. It didn't help that I peeled back the foil (all the edges were re folded to prevent coronas) and let it flash over into the damage a few times.

None of that was very scientific, but here are some calculations. these consist of two sheets of polypropylene 76 microns thick and each of around 600cm2 surface area. Assuming a dielectric constant of 2, that gives about 14nf, or 28nf if electrodes were sandwiched between the layers. Polypropylene is said to have a dielectric strength of only about 50kv/mm, giving a maximum possible storage for the whole pack of about 3.8kv, and 2.8 uf, and an energy of about 20j. Of course, it would be better to use the dielectric at half of its maximum voltage, so you could maybe make 10 packs into capacitors of 1.9 kv working voltage and 2.8 uf. You could put them in pairs, and then put those 5 pairs in series for a 1.12 uf capacitor easily capable of holding 9500 volts. They could be immersed in a container of oil and pressed together by some sort of plastic frame.That's just one of the many combinations you could make with these protectors. Not very cheap (about $100 in materials in this case), definitely not easy or quick, but very doable.

Other than physical defects in such a hand made plastic cap, the only other drawback I can see with this design would be if the high frequency high repetition rate ringing discharges of a Tesla coil caused dielectric heating and melted the protectors. I don't have a lot of experience with DIY capacitors being placed under this kind of load, so I don't know how it would behave.

I know that was wayy to long, but I'd definitely recommend trying to charge a single plastic sheet protector to it's breakdown voltage with a low current DC supply. You won't be disappointed.


Pyro_cat - 30-12-2019 at 20:18

van de graff , that's on my science to do list !


But this coil how would I know if my coil is efficient as there is no way I know to test the output.

The length of the spark I can measure voltage, interesting link I found https://hackaday.com/2016/12/08/measuring-high-voltage-in-mi...

But comparing input to output power I don't know where to start.

[Edited on 31-12-2019 by Pyro_cat]

Pyro_cat - 30-12-2019 at 20:22

I can sort of tell by comparing the sound of the primary spark gap compared to the secondary discharges to a ground but that's it.

These coils are so hit or miss if everything is going to resonate or not.