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Old 29th December 2009, 04:00 PM   #1
Brit01 is offline Brit01  United Kingdom
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Default Oil filled caps - how are they made? DIY caps?

I'd be interested to see the processes involved in making oil filled caps. Visually would be great.

Crazy thought: Has anyone attempted or thought about making home made oil caps?

I imagine the process is quite complex and requires special machinery to seal them.
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Old 29th December 2009, 04:09 PM   #2
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Just making a capacitor is the challenge I think. Filling them with oil and sealing them should be trivial in comparison. The Obbligato caps are sealed with an epoxy or sometimes with a solder. Depends on the type.
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Old 29th December 2009, 05:01 PM   #3
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Handling the films can be tricky. The separator material can be so thin, it seems to float on air, especially polypropylene (PP) and/or polyethylene (PE). It takes a lot of practice and patience to maneuver films by hand - and in small pieces. The length and amount of films to roll a capacitor is a different matter.

A film capacitor would need two lengths of metal foil (for the two electrodes). Cutting the foil can be tricky, because the edges have to be pristine (so edge burrs don't poke through the separator), so you'd want the metal professionally pre-cut to your specifications. Then you need sandwich and roll the separator between the two electrode foils. The electrodes are offset, so the edge of one foil overextends the seperator on one side, and the other foil overextends the other side. Then the terminals are welded on to the overextended foils on each side. Welds have to be done carefully, as to not damage the separator at the edges.

To make one by hand, here's what you need:

1. a spool of separator (could be paper for PIO) cut to the desired width.
2. two spools of electrode foil cut to the desired width.
3. a precision winding machine or jig capable of three or four layer windings (two metal foils and one or two layers of separator).
4. electrolyte or oil.
5. vacuum chamber for evacuating air and drawing in the electrolyte or oil.
6. apparatus to dispense the electrolyte or oil into the vacuum-drawn cell body.
7. end terminals cut to the correct shape of the cell body windings.
8. welder to attach end terminals.
9. case, can, enclosure, or external wrapper.
10. end sealant.

I have much experience building electrochemical energy storage using foil & separators (including polypropylene, polyethylene, silica, and more). It's certainly not impossible to do at home, but would be expensive to setup and obtain cut foils, separators, electrolytes, oils, etc. It would also be an excellent learning opportunity.

Google it. I'm sure some guy has made capacitors using kitchen-grade aluminum foil, old newspapers, and vegetable oil ... although keep a fire extinguisher handy and don't leave the amplifier unattended because of the near-certitude of a fire.

EDIT: Here's a youtube video of what appears to be a paper-and-foil wrap fastened together with some zip ties. Some of the comments suggest soaking it in mineral oil. Here's a discussion thread on building a capacitor and discussing the use of a vacuum pump. The capacitor is apparently for high voltage Tesla experiments. I'm sure there's tons of resources.

Last edited by Kashmire; 29th December 2009 at 05:14 PM.
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Old 29th December 2009, 07:37 PM   #4
pointy is offline pointy  United Kingdom
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A nice pic of someone making caps in the USA..........(if the link works)

I do know that TCC used cartidge paper and Fulman car oil something like 15/35
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Old 29th December 2009, 07:44 PM   #5
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Quote:
Originally Posted by Kashmire View Post
Google it. I'm sure some guy has made capacitors using kitchen-grade aluminum foil, old newspapers, and vegetable oil ...
I was under the impression home-made capacitors were common in the early days of home electronics, most often wax types. Not that I see any reason other than challenge these days.
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Old 29th December 2009, 07:56 PM   #6
Arnulf is offline Arnulf  Europe
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Quote:
Originally Posted by rdf View Post
I was under the impression home-made capacitors were common in the early days of home electronics, most often wax types. Not that I see any reason other than challenge these days.
Or special purpose - say very high voltage capacitors for a "Tesla coil" or other HV experiments can be awfully difficult and expensive to come by yet they can be easily made out of common household items.

Those interested can find many ideas on the subject online, from making of capacitors ot making them look better ("modding"), which can be applied directly to produce "professional-looking" parts. I can't find the "modding" webpage right now, I do recall author using wooden cylinders and beeswax to repack industrial capacitors though.
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Old 29th December 2009, 08:34 PM   #7
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What about using a drying oil like linseed oil? Treat strips of paper, let dry, and then wrap?

Also, IIRC wax has a negative magnetic permeability or something like that. So using wax might decrease parasitic inductance.

- keantoken
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Old 29th December 2009, 10:08 PM   #8
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Quote:
Originally Posted by rdf View Post
I was under the impression home-made capacitors were common in the early days of home electronics, most often wax types. Not that I see any reason other than challenge these days.
Back in high school physics, we made capacitors using tin foil and toothpaste as an electrolyte.

I don't think we ever tested them however, and I'm not even sure if they would work at all... But if they did, some Colgate caps would be interesting to try out...
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Old 29th December 2009, 10:54 PM   #9
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My vote is castor oil.
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Old 29th December 2009, 11:45 PM   #10
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Nice picture, pointy!

You can clearly see she has the former prepared with a few wraps of separator material, but hasn't started the metal foil electrodes yet. The top metal foil spool has a bit hanging, which I suppose she is starting. Notice her neighbor is actively wrapping all parts ... you can see the top and bottom metal foils sandwiching several layers of separator.

Notice the winding machines have several spools of separator. It appears three spools are active, so this particular capacitor has three layers of separator between the two foil electrodes.
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