Donald Smith Devices too good to be true

[TanTric]

thank you xee, there's some way i can be sure what kind is the one i have? thank you brother

Most will handle at least 500 volts, some will handle 2000 volts.

[drak]

hi guys, i found this pearl and have a doubt, how much voltage will this kind of variable caps handle without damaging it? colective hugs

Looks like an air variable cap. Meaning if you over charge it, it will just arc between the plates and no permanent damage should occur. Again, I don't claim to be an expert, but I have air variable caps and over charge them all the time and they still work fine.

[TanTric]

....

thank you so much great drak!! keep it up


best regards

Looks like an air variable cap. Meaning if you over charge it, it will just arc between the plates and no permanent damage should occur. Again, I don't claim to be an expert, but I have air variable caps and over charge them all the time and they still work fine.

[drak]

thank you so much great drak!! keep it up


best regards

The only way you can damage a cap is to ruin the dielectric between the plate/foil/metal. Or ruin the metal it self which is hard to do. For example if the plates were separated by paper and if you were to over charge them to where there is an arc through the paper, it will leave a little hole in the paper and reduce the maximum voltage the cap can handle. Self healing caps use instead liquids or gels that will form around the hole after the arc. Air of course, is self healing. So is oil, but it can explode if it gets too hot and is sealed.

[dunfasto]

@ j dove

here is a link to download image resizer

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since you took images from your digital cam/phone the image is very large and have larger kilobytes. you can reduce the size of your images with this software so you can upload more pictures as this forum can support.

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thanks and regards

dunfasto

[nutgone]

Air spaced variable caps & PTFE spray????

Thinking about air spaced variable capacitors (I've been toying with buying one), is there any way you could use some kind of PTFE based lubricating spray to improve the insulation between the plates?

I suppose it could be difficult with the plates sliding, which could rub it off, but once set up it could help to stop arcing.

You can also get spray-on insulating tape these days, as well as dry PTFE sprays. Any good???

[nutgone]

@ j dove

here is a link to download image resizer

Download resize.exe Free - Free Picture Resizer

since you took images from your digital cam/phone the image is very large and have larger kilobytes. you can reduce the size of your images with this software so you can upload more pictures as this forum can support.

when your capacity in your account for uploading images filled fully then you can use free image hosting site as below

imgon.net - Free Image Hosting

and then you can paste link of your uploaded image on this thread.

for example i uploaded this image and pasted its url

http://imgon.net/di-EE2U.jpg

imgon is so simple no account needed and max upload image size is 10mb

thanks and regards

dunfasto

I use Photobucket, never had any trouble with them, although you do need an account, but it's free to sign up.
I find it handy as I an email pics straight from my phone into my PB account, then post up the links here into the "Insert Image" box & they appear.

AFAIK there's no limit to doing it this way, on this forum.

[DilJalaay]

hi guys, i found this pearl and have a doubt, how much voltage will this kind of variable caps handle without damaging it? colective hugs

I also got one like yours. i dip it in transformer oil. now it work in kilo volts.

[drak]

Thinking about air spaced variable capacitors (I've been toying with buying one), is there any way you could use some kind of PTFE based lubricating spray to improve the insulation between the plates?

I suppose it could be difficult with the plates sliding, which could rub it off, but once set up it could help to stop arcing.

You can also get spray-on insulating tape these days, as well as dry PTFE sprays. Any good???

Air variable caps don't have much capacitance at all. They would really only be good for high inductance coils (many turns). The plates never touch each other, so the spray would not rub off. I personally would just submerge mine in mineral oil if I needed higher voltage. But again, trying to drop a coil down to the Khz range requires a lot of capacitance, more then most variable capacitors can hold, or a really high inductive coil.

[Seeker2011]

hi guys, i found this pearl and have a doubt, how much voltage will this kind of variable caps handle without damaging it? colective hugs

Found online:
Usual breakdown ratings of common plate spacings

air gap in inches/ peak voltage breakdown

.030 1,000
.050 2,000
.070 3,000
.100 4,000
.125 4,500
.150 5,200
.170 6,000
.200 7,500
.250 9,000
.350 11,000
.500 15,000
.700 20,000

Another:
From the ARRL Handbook

Gap
inches V_peak
0.015 ___1000
0.02 ____1200
0.03 ____ 1500
0.05 ____ 2000
0.07 ____ 3000
0.08 ____ 3500
0.125 ___ 4500
0.15 ____ 6000
0.175 ___ 7000
0.25 ____ 9000
0.35 ___ 11000
0.5 ____ 13000

[dragon]

Thinking about air spaced variable capacitors (I've been toying with buying one), is there any way you could use some kind of PTFE based lubricating spray to improve the insulation between the plates?

I suppose it could be difficult with the plates sliding, which could rub it off, but once set up it could help to stop arcing.

You can also get spray-on insulating tape these days, as well as dry PTFE sprays. Any good???

Submerge them in mineral oil....

[nutgone]

Air variable caps don't have much capacitance at all. They would really only be good for high inductance coils (many turns). The plates never touch each other, so the spray would not rub off. I personally would just submerge mine in mineral oil if I needed higher voltage. But again, trying to drop a coil down to the Khz range requires a lot of capacitance, more then most variable capacitors can hold, or a really high inductive coil.

Agreed, but they could make a very handy trimming device, when combined with some other HV caps, to get the coil(s) tuned just right.

I suppose it may also be possible to dismantle it & add your own dielectric spacers??? (or am I still barking up the wrong tree??)

Anyway, it's food for thought.

I've recently come by some very thin sheet aluminium, but it needs some cleaning, polishing & straightening (came out of a rubbish dump).
I'm having so much trouble getting hold of cheap (FREE) HV caps I may just have to make my own!

I've also put a wanted ad out in my local Freegle Group for microwaves, & I will probably ask my local dump if they will let me have a few (which is doubtful, rubbish dumps here are notorious for wanting cash for every little thing & are very heavy on "health & safety).

I took apart a TV recently, a quite modern one. I was very disappointed with the bits on offer. The flyback was tiny! & the caps were pitiful! What a waste of time! Honestly, it was not really worth the bother.

It's only HV caps & my new RCL meter (on it's way from Hong Kong) that are holding me up now, once I have them I can really start to get going!

[drak]

Agreed, but they could make a very handy trimming device, when combined with some other HV caps, to get the coil(s) tuned just right.

At first, but the lower you go in frequency the capacitance required goes up I believe in a tangent curve. Or maybe its not tangent, I don't know, but when I got down to lets say 100Khz I needed .02uF on one of my coils. To drop the coil down to 99Khz, I had to add .005uF. At this point (well way before then) a trimmer cap would make no difference, because they are usually in the picofarad range.

I suppose it may also be possible to dismantle it & add your own dielectric spacers??? (or am I still barking up the wrong tree??)

You could, but the dielectric spacers only increase the max breakdown voltage. To increase capacitance you have to move the metal pieces closer together, which will lower your voltage breakdown. Have to find a happy medium.

[dunfasto]

things about radiant energy

radiant energy

1. it lights higher resistance wattage bulbs more easily.
2. lower resistance bulbs dont light.
3. cannot be measured with digital multimeters(DMM)
4. to measure it use analog ammeter of 50micro ampere in series with 1kohm resistance then your ammeter becomes 50mili ampere meter. same one can do with voltmeter also.
5. radiant energy is maximum at the centre of coil of a bifilar wound coil.
7. back emf is radiant energy.
8. its completely opposite of the electricity we have in our wall outlet grid power.
9. shows completely reverse effects that are shown by wall outlet electricity.

thanks and regards

dunfasto

[dunfasto]

dunfasto

gave you suggestion a try but at last wont on it either so i will have to get it to you another way .thanks for the info on it will get back to you as soon as i get it figured out . may be a bit. cheers

jeff

@ j dove

here is a link to download image resizer

Download resize.exe Free - Free Picture Resizer

since you took images from your digital cam/phone the image is very large and have larger kilobytes. you can reduce the size of your images with this software so you can upload more pictures as this forum can support.

you can use mspaint to change format of your image from bmp to jpg just open image to convert format in paint then select saveas and select jpg from the list of formats then save and its done.

when your capacity in your account for uploading images filled fully then you can use free image hosting site as below

imgon.net - Free Image Hosting

and then you can paste link of your uploaded image on this thread.

for example i uploaded this image and pasted its url

http://imgon.net/di-EE2U.jpg

imgon is so simple no account needed and max upload image size is 10mb

thanks and regards

dunfasto