I slapped together a DIY cap today (I was bored, ok) and I pretty easilly got a velue of about 0.6uF or so. I'd like to one day build my own 100uF cap (I might settle for 50uF), any ideas how? I made my 0.6uF with about 5 feet of aluminium foil cut in half (about 4" x 60" sheets) and I rolled it up halfassed (really halfassed, watching tv, didn't even take my time) with saran wrap (it's for the cool factor, not quality, ok?) and clamped it between two pieces of metal (this greatly increased the capacitance (by a factor of three or so)) to get rid of even more air, looks ugly, but good enough for me. I was amazed how much capacitance it yielded, since I just did it as an experiment I was aiming for 100nF (that's why I did such a halfassed job). Now to get 100uF I guess I could do a better job, and use alot more foil. but even then it's getting really large, is there a better grocery store dielectric out there (nothing special, I like the idea of building these parts out of crap), or any other tips from those whove played around with rolling their own caps?
Last time I tried rolling a cap it was for my Tesla coil. 
I doubt you'd really get too much voltage out of your saran wrap...maybe 100V worth. Note also that the aluminum foil is several times thicker - it'll make for a high Q but will simply waste space at anything below several amperes of [resonant] current.
For 100uF, you might take a completely different tactic. Look up anodizing on the web, also take apart a few electrolytics, and try drawing your own conclusion.
Tim
I doubt you'd really get too much voltage out of your saran wrap...maybe 100V worth. Note also that the aluminum foil is several times thicker - it'll make for a high Q but will simply waste space at anything below several amperes of [resonant] current.
For 100uF, you might take a completely different tactic. Look up anodizing on the web, also take apart a few electrolytics, and try drawing your own conclusion.
Tim
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Joined 2002
Homemade caps will almost invariably be crappy; it's tough to wind them tight enough, and without the tricks of extended foil construction, they'll have a high inductance. But if your just doing it for spits and grins, try using polyethylene wrap (lower dielectric constant than Saran, but better soakage properties) or Teflon tape (where you'll get higher breakdown voltage). Oiled paper will give you a nice '40s ambiance.
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