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Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Tesladownunder wrote ...
So does your spark initiate at 5cm or get drawn out to that?
TDU
It initiates at 5cm. It would be even impossible to pull a spark when 3nf cap is in parallel with the spark gap. The electrodes have sharp tips so probably it is less then 50KV. I'll take a picture and send it tomorow...
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Mates wrote ...
It initiates at 5cm. It would be even impossible to pull a spark when 3nf cap is in parallel with the spark gap.
Not impossible at all. I avoid short circuiting capacitors so I usually have a resistor sn the output. The current limitation will mean you can draw out the spark rather than draining the cap in one bang. If you can initiate at 5cm across the cap, then you will get twice the peak voltage ACROSS your diode, ie nearly 10 cm. Try it and you will understand why the diodes rating needs to be higher.
Banned on 02/27/2008 Registered Member #1326
Joined: Sun Feb 17 2008, 11:19PM
Location:
Posts: 49
Mates, very good work of sharing. Here is an idea. I know transparent oil looks really cool, but why not fill the tube with wax so you dont have to worry about oil leakage. The wax I am talking about is soft and ductile, and it can also be used as ends sealant as in your scheme just by dipping the tubing. Remember the old day induction coils before the enamels ? when they had cotton wound and insulated wires with cotton bonded by soft wax as in old radios ? thats the one i am talking about.
For oil, I recommend the reject from fast food places that many people are using instead of diesel. first it has little moisture. second, it will gum up due to breakdown and double bonds. The viscosity will increase and leakage will be less probable.
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Here is the promised picture for TDU (you have to zoom it for the scale which on the CD box).
BTW: I absolutely agree on overrating the diode strings. There is 70pc in the string and my experience is they can handle 5cm discharges (even little bit more). Of course, I could have been lucky for whatever reason and it is also the most extreme I plan to expose the diodes. 100pc would be probably better for my power source but is so PITA work to put them together
One more thing: The HV output of the coil at 6 KHz is relatively nice sine wave…That’s the distortion work of the iron core.
Regarding the wax idea by thermite: It would probably work fine, but I don’t have good experience with paraffin as an isolator (mean the white candle - I've never tried any other type). Oil is much better. Moreover, the diodes are planned to be coiled to be more compact and I'm not sure how easy this would be with wax filling. If the string is done like in the protocol, there will be no leaks.
Banned on 02/27/2008 Registered Member #1326
Joined: Sun Feb 17 2008, 11:19PM
Location:
Posts: 49
Mates: Use the kitchen gum to squeeze the PVC tube around the filling made by the hot-glue before. This will make hermetic enclosure of the oil. Make the same on both ends.
(1) What is Kitchen Gum ? (2) Are you using the silicone to mold end slug of glue? (3) Why not mold the end slug slightly bigger in diameter than the ID of the PVC and then use the oil to slide it in making a seal ? (4) while you suck oil, doesnt it coat the glue and inside of PVC with oil and prevent a good direct bond ? (5) what is the composition of kitchen gum?
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
I've been following this thread carefully. The peak voltage across the diode could be as high as twice the capacitor's DC voltage but it does not necessarily have to be that high. A transformer that is operated in "flyback" mode will develop a higher voltage across the secondary in one direction than it does in the other direction - only the volt-seconds need to balance, not the amplitude of the +ve and -ve voltage swings, so the waveform looks assymmetric. This significantly reduces the PIV rating required for the HV diode, and is how LOPT stages work in TV sets. Just thought i'd clarify that point.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Mates,
You state above that mineral oil is toxic. I assume you aren't talking about whats commonly referred to as 'Baby oil" in the US, a clear petroleum based oil?
Its sold as a laxative in US stores, and isn't toxic except in huge doses. It's also a fair insulator.
The only problem I see with using an organic oil (sunflower, corn, canola, or frying oil) is that its amazingly unpleasant stuff when it goes rancid. Granted if all goes well you won't ever come in contact with the stuff once the diode is constructed, but I'd hate for one to break open after a couple years. I also would wonder how the electrical properties could change after its gone rancid, as I think the bacterial action would make the stuff increasingly acidic.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
> Its sold as a laxative in US stores, and isn't toxic except in huge doses
Death by laxative overdose?!?! Gee that sounds like fun!
I beleive any oil is quite unpleasant if you manage to get a lung full of it too? Lipid pneumonia? Presumably because it doesn't naturally evapourate out of there like water would? ...so be careful sucking on that oil filled tube!
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
thermite wrote ...
(1) What is Kitchen Gum ? (2) Are you using the silicone to mold end slug of glue? (3) Why not mold the end slug slightly bigger in diameter than the ID of the PVC and then use the oil to slide it in making a seal ? (4) while you suck oil, doesn’t it coat the glue and inside of PVC with oil and prevent a good direct bond ? (5) what is the composition of kitchen gum?
1) Kitchen gum are those small practical rings of gum material you can get in every drug store for almost nothing (check the first picture and you will see it) 2) No, I'm using hot glue (that's kind of special plastic you load into a special pistol which heats it up make liquid and sticky) 3) You can try... 4) Yes it does, but the squeezing power of the gum and subsequent over-gluing is enough to protect from any leakage 5) It can be latex based, silicon based - it is not critical in this case
Dave Marshall wrote ...
Mates,
You state above that mineral oil is toxic. I assume you aren't talking about whats commonly referred to as 'Baby oil" in the US, a clear petroleum based oil?
It’s sold as a laxative in US stores, and isn't toxic except in huge doses. It's also a fair insulator.
The only problem I see with using an organic oil (sunflower, corn, canola, or frying oil) is that its amazingly unpleasant stuff when it goes rancid. Granted if all goes well you won't ever come in contact with the stuff once the diode is constructed, but I'd hate for one to break open after a couple years. I also would wonder how the electrical properties could change after its gone rancid, as I think the bacterial action would make the stuff increasingly acidic.
Dave
Gold words... I agree on everything.
The toxicity warning is just in case some troll finds some crazy unknown oil-like liquid and start to suck it up like on the picture. But I agree that most of the oils you can get in contact with are harmless.
The “rancing†problem of the organic oil - I think it is mainly a problem when you leave some air gap in the filling. I store all my HV devices in cooking oil and I've never experience any smell or other symptoms. But in case you have a source of cheap mineral oil - it is much better solution
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Home made HV diode 50KV, 30A peak - complete protocol
