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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Perhaps i should not have told you to make those transparency capacitors :P At this point i would have to suggest buying some professional capacitors. I just remembered that when i used transparency capacitors i had about 3-5 inch sparks and now with professional capacitors i get 1 1/2 feet.... I use cornell dubilier .68uf 1600vdc capacitors. Though it took me 32 of them to get 22 nf, they work absolutely perfectly. With a 12kv 60ma neon transformer i can run for 5 minutes with absolutely NO warming at all whatsoever. I would suggest some cde or AKA 'geek group' capacitors that are .15 uf and 2000vdc.
You can get them on ebay for 47 american dollars(i dont know where you live:P) for 12 of them. If you do get them just use all 12 in series for 12.5nf which is perfect. It would be rated for 24kvdc in all which is good because your power supply is dc so you have a safety margin of 4 times the supply voltage about.
But is your coil very loud when running and is the spark bright and blue or, dim and red or orange or purple?
Registered Member #1630
Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115
Just hold on a second... About Microwave oven caps___ 1) They are rated in AC as they are used to ballast the MOT. They are not typical of most capacitors! 2) MOT caps are NOT rated for pulse discharge and will explode often with violent results. (lots of energy stored in one of those!!)
Registered Member #1630
Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115
Arcstarter wrote ...
Perhaps i should not have told you to make those transparency capacitors :P At this point i would have to suggest buying some professional capacitors. I just remembered that when i used transparency capacitors i had about 3-5 inch sparks and now with professional capacitors i get 1 1/2 feet.... I use cornell dubilier .68uf 1600vdc capacitors. Though it took me 32 of them to get 22 nf, they work absolutely perfectly. With a 12kv 60ma neon transformer i can run for 5 minutes with absolutely NO warming at all whatsoever. I would suggest some cde or AKA 'geek group' capacitors that are .15 uf and 2000vdc.
You can get them on ebay for 47 american dollars(i dont know where you live:P) for 12 of them. If you do get them just use all 12 in series for 12.5nf which is perfect. It would be rated for 24kvdc in all which is good because your power supply is dc so you have a safety margin of 4 times the supply voltage about.
But is your coil very loud when running and is the spark bright and blue or, dim and red or orange or purple?
For a 12-60 you would have needed 20 Capacitors 1600x20= 32Kv @ 34nF. (3x the supply volatge in DC rating is MORE than enough) Of course the capacitor will only charge to half way and thats fine. later you can upgrade to another XMFR and still run the same cap.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Seoul_lasers wrote ...
Arcstarter wrote ...
Perhaps i should not have told you to make those transparency capacitors :P At this point i would have to suggest buying some professional capacitors. I just remembered that when i used transparency capacitors i had about 3-5 inch sparks and now with professional capacitors i get 1 1/2 feet.... I use cornell dubilier .68uf 1600vdc capacitors. Though it took me 32 of them to get 22 nf, they work absolutely perfectly. With a 12kv 60ma neon transformer i can run for 5 minutes with absolutely NO warming at all whatsoever. I would suggest some cde or AKA 'geek group' capacitors that are .15 uf and 2000vdc.
You can get them on ebay for 47 american dollars(i dont know where you live:P) for 12 of them. If you do get them just use all 12 in series for 12.5nf which is perfect. It would be rated for 24kvdc in all which is good because your power supply is dc so you have a safety margin of 4 times the supply voltage about.
But is your coil very loud when running and is the spark bright and blue or, dim and red or orange or purple?
For a 12-60 you would have needed 20 Capacitors 1600x20= 32Kv @ 34nF. (3x the supply volatge in DC rating is MORE than enough) Of course the capacitor will only charge to half way and thats fine. later you can upgrade to another XMFR and still run the same cap.
I was suggesting him use the .15 uf capacitors, not the .68 uf. And the capacitor in microwaves are dc because they do not ballast, but they are used for a voltage doubler. That is what the diode is used for.
Even though that is true i am still not sure if they can take very prolonged ac or not, but they are used in a dc application in those microwaves.
Registered Member #1391
Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40
Spark gap got bright blue/yellow sparks, not very huge or loud. They make a craplot of noice but it is still a bit short before they starting to hurt in the the ears. (If it matters: When I where testing the PSU, not connected to the coil, without capacitors the spark gap makes weak and more silent sparks. With capacitors they make much louder sparks, and brighter. Enough to illuminate my yard, kinda.) Also, I placed the secodary coil like this: The lowest winding is an about an inch(3cm) bellow lowest parts of the primary. Is that right? Oh, you say the capacitors might be bad, to bad :( But, what makes these inferior to the profecional capacitors?
Also a thought struck me, the power from the DC supply, it is well smoothed right? I shoul not connect some microwave oven capacitors in series, in parallel with the output?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Estragon wrote ...
But if they dont heat up, and they dont got internal arcing, is'nt every thing okay then? High dielectric losses would be noticable at heat, right?
Pretty much i think... But the other factors are indutance(you don't want inductance) and esr or equivalent series resistance. You do not want resistance on the plates because that will just limit the discharge current and it would take longer to discharge, which a rsg will not allow the time for a full discharge because it will move to the next electrode, discharged or not.
Like tesladownunder stated on his website, the less inductance he had on his homemade capacitor the longer and thicker and hotter arcs he had from his tesla coil.
Registered Member #1391
Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40
Yeah, but its aluminium foil with a big pice of wire spread on the middle of it. So I dont think it got internal resistance. But it might have some bad inductance. (The foil is tapped on the middle so that kinda cuts the inductance in half) Yet, it is not a big roll of foil, just 7x14 cm rolled togher some times. Hmmm, if just a little is enough it shouldent have been rolled up, just a stacked plate capacitor. But then it would require a lot more work for the same capacitence XD Also, small crack/wrinkles on the foil would make inductance problems to? I think I did a good jobb smothing it out.
Still, now I'm gonna make a new spark gap with closer spaced electrodes and try to tune it some more, maybe it nothing wrong at all. :P
But, how could it work exactly the same without ground and with the grounding? Next time I need to find a better place to put the cupper tube, with more squishy and wet groud, maybe? I used a weird place who are kinda just build on the topp of a mountain. (the rod you saw sticking up, could no be smashed longer down to to rock being everywhere bellow 60cm on all of our property)
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Making my first coil, SGTC need help with powersupply.
