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Old 6th November 2012, 07:11 PM   #11
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Quote:
Originally Posted by sreten View Post
Hi,

They say ignorance is bliss.

A paper dielectric will give a relatively high voltage rating, and can be soaked
in oil to help prevent the ingress of moisture, water doesn't help here at all.
You'll end up with a non-polar capacitor with a small value for its size.

High value low voltage polar capacitors are a different kettle of fish,
and the above approach simply won't work for them at all.

rgds, sreten.
Ignorance is bliss. Water is no good in a capacitor, but it still does not conduct electricity on it's own.

If you go the foil and paper with oil or wax route, I recommend you bake the capacitor for maybe 1-3 hours (pending on size) at 80-100 degrees celcius (pending on size and chosen timeframe) to get it properly "set in" after rolling. You can use certain types of paper tape for keeping things together when rolling and adding the connectors, you need to make sure there is as little movement as possible, it needs to be very tight. Be careful with the connectors you use, they should be same material as the foil and be careful not to puncture the dielectric or foil when packing it together.

Last edited by KaffiMann; 6th November 2012 at 07:20 PM.
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Old 6th November 2012, 08:25 PM   #12
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by KaffiMann View Post
Ignorance is bliss. Water is no good in a capacitor,
but it still does not conduct electricity on it's own.
Hi,

True, pure water doesn't conduct very well, but damp paper
is hardly likely to be pure, things will leach out of the paper.

rgds, sreten.
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Old 6th November 2012, 10:16 PM   #13
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i used tap water if that makes any difference
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Old 6th November 2012, 10:37 PM   #14
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Whether you use it in real equipment or not (probably not) IMO building basic electronic components is one of the best ways to learn. Do some research on the various types of capacitor and what materials they typically use. You should have no trouble making solid dielectric caps like glass, paper, plastic film and mica. An electrolytic is a bit more difficult. The way manufacturers get high values of capacitance is to etch the aluminum plates for more surface area. The electrolyte is often ethylene glycol (antifreeze- poison) with ammonium borate and a small amount of water added. Salts, even in trace amounts, are deadly to electrolytic caps- you'll never find a salted peanut vending machine in a capacitor factory! A salty fingerprint is the difference between a cap that lasts a couple weeks vs a couple decades.
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Old 6th November 2012, 11:00 PM   #15
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ok big oops i got poison on my skin and hands what do i do?
it was like 2 days ago when i was taking a capacitor apart and i washed my hands really good afterwards
i havent noticed anything on my skin or anything..
am i possibly okay? or am i going to get skin cancer or something?
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Old 6th November 2012, 11:06 PM   #16
Enzo is offline Enzo  United States
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Kaffi, you are right, PURE water is a poor conductor, but unless he has distilled water coming out his plumbing, his water is not pure. So within the context of the OP's situation, I have to consider water a conductor, at least enough to be significant.

Realflow: WHAT poison? I don't recall anything you have mentioned being poisonous. Salt water is not poison, canola oil is not poison. Or are you talking about the electrolyte from a commercial cap? If so, just wash it off as you did. Don't put it in your mouth and you'll be fine.
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Old 6th November 2012, 11:09 PM   #17
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oh i never put it near my mouth eww
i did wash my hands so i think i'll be fine thanks
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Old 6th November 2012, 11:12 PM   #18
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by realflow100 View Post
ok big oops i got poison on my skin and hands what do i do?
it was like 2 days ago when i was taking a capacitor apart and i washed my hands really good afterwards
i havent noticed anything on my skin or anything..
am i possibly okay? or am i going to get skin cancer or something?
Hi,

Its a lot more difficult than you imagine to expose yourself
to genuinely hazardous substances nowadays, you'll be fine.

rgds, sreten.
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Old 6th November 2012, 11:25 PM   #19
AJT is offline AJT  Philippines
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looking forward to your homemade resistors realflow....
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Old 7th November 2012, 11:52 AM   #20
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[QUOTE=Enzo;3231372]Kaffi, you are right, PURE water is a poor conductor, but unless he has distilled water coming out his plumbing, his water is not pure. So within the context of the OP's situation, I have to consider water a conductor, at least enough to be significant.
QUOTE]

I concede to this point, but I would still argue that for voltages below 24v with a fast blow fuse on psu lead there is nothing wrong with experimenting with any kind of fluid in capacitors, provided you take the neccesary precautions. Voltages below 24v are generally considered non-hazardous, there is very little or no risk of shock. You can however, start a fire, or if using the wrong solution for dielectric in worst case scenario: toxic gas, hence the fast blow fuse is a must, as it will most likely prevent any sort of accident.

For voltages above 24v, do not mess with anything you are not 100% certain of, water being one of them. All initial testing should be done at lower voltage, use fuses on both leads from psu at higher voltages just in case.
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