Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

DIY Capacitors
DIY Capacitors
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 15th June 2002, 05:17 PM   #1
tiroth is offline tiroth  United States
diyAudio Member
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Default DIY Capacitors

I'm sure that rolling your own film caps has been discussed before, but I wasn't able to find such a discussion in the archives. I did a little experiment today:

I cut a few 1.25"x12" strips of aluminum from a baking foil roll. Two of these I sintered together at one end, and then I attached leads to my new foil pair and to a third length of foil. I used an iron set to 450C (840F) and determined that the mechanical strength of the joint exceeded the strength of the foil itself, so I would guess that the electrical connection was quite solid.

I then created a stacked-film layer using saran-wrap (vinyl film) as my dielectric. After carefully smoothing the layers to eliminate folds in the film, I attached one end of the stack to a 0.5" wide tongue depressor, and wound the stack around it. To finish the capacitor, I wrapped the roll with electrical tape, which pulled the roll tighter and increased the capacitance.

I estimate the film to be 0.25 mils thick. Based on a figure of 160V per mil, I estimated the voltage rating of this capacitor to be 40V, but empirical testing determined that at least a 50WV rating is reasonable at DC.

Measured value: 22nF
Measured DA: 0.4%
DF: ???
Current handling: ???

I would expect inductance to be reasonably low because of the stacked layers and wide foil. I wonder if the "coaxially wound" Multicap is simply a wound stack like this?

Now, I doubt people will rush out to laboriously wind saran-wrap caps, especially when the resultant capacitance depends heavily on the construction. However, a better dielectric (teflon tape?) could be used, as well as tin or copper film. Suddenly, this seems more attractive.

Any thoughts from the forum?
  Reply With Quote
Old 15th June 2002, 05:46 PM   #2
phishead8 is offline phishead8  United States
diyAudio Member
phishead8's Avatar
Join Date: Sep 2001
Location: Los Angeles, CA
This is, in fact, how the boys of DIY Tesla Coil and DIY Rail Gun (and the like) make there own capacitors. Of course they use Aluminum Sheeting and Visqueen, and the whole roll is inside of a large PVC tube filled with Mineral Oil. They are usually constructing these because of a need for high voltage capabilities.
It seems to me that the little bit of money for a commercial cap is nothing compared to the labor of DIY caps.
  Reply With Quote
Old 15th June 2002, 07:20 PM   #3
JoeBob is offline JoeBob  Canada
diyAudio Member
JoeBob's Avatar
Join Date: Nov 2001
Location: Montreal, Canada
I'd say it ain't worth it, building all your caps. But even if it's laborous and long, it's still cool to have built your own. I think I'll give it a try. How about DIY resistors, heh .
  Reply With Quote
Old 15th June 2002, 10:54 PM   #4
tiroth is offline tiroth  United States
diyAudio Member
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
phishead, have you priced teflon caps lately?

Worth a try, maybe. Took me about 15 minutes.
  Reply With Quote
Old 16th June 2002, 06:33 AM   #5
Jocko Homo is offline Jocko Homo  United States
Join Date: Feb 2002
Location: As far from the NOSsers as possible
Unless they are a sealed unit, they are crappy.

  Reply With Quote
Old 17th June 2002, 12:00 PM   #6
SushiMasterX is offline SushiMasterX  United States
diyAudio Member
SushiMasterX's Avatar
Join Date: May 2002
Location: Detroit, "8 Mile"
Smile Yeah its fun to say you made your own caps!

Usually too much work, though.

The tesla-coil folks build their own because the price of buying a similiar rated cap from a manufacture would be Mega-expensive.

Try pricing or even finding a 100 farad cap with 100kv ratings, ha-ha. Even, 10 farad caps are in the few hundred dollar range. Car audio guys pay 3-400 for those. 1 farad's are ~$50.

If your going for economy or multiple farad-size, non-critical spec's, make your own. If you don't have time just buy it and save yourself the headache.

Compare the market price with the time required/fun-value to decide. Anything less than a couple of farad, tops, is where I think most would draw the line (a exception given-car audio amps). The caps in the less than a farad range are all reliable, consistent and cheaper, not too mention more time-saving then DIYing.

Giant caps are great for zapping things (e.g. rechargable ni-cd rejuvenator's) too.
They'll just pick up the current in the air and store it too, until you short it on yourself/someone, he-he! Yeooowww!

  Reply With Quote
Old 17th June 2002, 04:47 PM   #7
jackinnj is offline jackinnj  United States
diyAudio Member
jackinnj's Avatar
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
DIY Capacitors
Default Saran

is vinylidene chloride -- a relative of vinyl chloride -- I don't know that its dielectric properties are that great.
  Reply With Quote
Old 17th June 2002, 05:58 PM   #8
phishead8 is offline phishead8  United States
diyAudio Member
phishead8's Avatar
Join Date: Sep 2001
Location: Los Angeles, CA

What benefits does a Teflon capacitor yeild over a standard Mylar or polyester cap?

What makes an Al foil and Saran Wrap capacitor comparable to a Teflon cap?

A DIY cap has a certain amount of unreliability that I wouldn't trust. I prefer to use the well proven caps. But, if you are having success with your own, go for it. Good luck.

  Reply With Quote
Old 17th June 2002, 06:27 PM   #9
tiroth is offline tiroth  United States
diyAudio Member
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
I think people are confused about a couple of things.

1) I'm not a DIY capacitor evangelist. I just thought it was remarkably easy and worth considering. Reliability and stability are definitely major issues.

2) Aluminum foil + saran-wrap was just a proof of concept...no sense wasting expensive materials when cheap ones are available. The point was if you can do it with that, you can probably do it with better materials as well. I made a teflon cap later that day.

Why use teflon or polypropylene as opposed to mylar? I think that should be obvious: the dielectic has much more favorable properties.
  Reply With Quote
Old 20th June 2002, 01:59 AM   #10
GRollins is offline GRollins  United States
diyAudio Member
Join Date: Feb 2001
Location: Columbia, SC
Mark Finnis and I were discussing this in another thread a long time ago. If I recall correctly, we were talking about rolling them, as opposed to stacking them. No, I don't remember which thread, and I no longer have the time or patience to wade through the reams of stuff the search engine coughs up.
Three points in passing:
1) Cleanliness is a necessity. A bit of grit can puncture your plastic film and cause the cap to fail.
2) Kapton and other films are available surplus on the Web. Can't remember where offhand, but I'll try to wake up a brain cell and figure that part out if anyone is interested.
3) Jocko's point is a good one. You might consider dipping the cap in something--wax, perhaps, or some of this vinyl stuff that you use to recoat handles on tools. Another possibility would be to cast the finished cap in resin. I've potted guitar pickups in resin before with excellent results. Incidentally, ordinary tempra paints make perfect dyes for resin; I used black for the pickups, but there's no reason you couldn't use red or blue or whatever suits your fancy.
Go for it.

  Reply With Quote


DIY CapacitorsHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
what is the difference between silver mica capacitors and ceramic capacitors ?? prorms Solid State 1 6th May 2008 12:38 PM
Continental Capacitors' "Type-A" oil-filled capacitors? radical Parts 0 21st October 2004 08:39 PM
Oil capacitors Praudio Swap Meet 3 7th October 2003 03:00 AM
capacitors: panasonic FC vs elna RJH vs rubycon ZA capacitors costiss Parts 11 30th January 2003 09:32 PM
differences between computer grade capacitors and small can capacitors LBHajdu Pass Labs 0 22nd February 2002 01:29 AM

New To Site? Need Help?

All times are GMT. The time now is 12:26 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio