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Homemade Capacitors



Original poster: Drbillpmt@xxxxxxx
Hi All,

I've been following the capacitor emails for some time. Maybe my capacitor making method will be of some help.

First: I use polypropylene as a dialectric. The source for it is the film used to tint vehicle windows. Not all of it is polypropylene, but much of it is. Some of it is as thick as .025 or even more. At 650 VDC per Mil, .024 would give you 15,600 VDC.

Second: I use brass shim stock for the metal. It is .005 thick and rolls quite easily. It is 2-Inches wide. Using 4-Inch strips of the poly, I leave one inch on both sides of the metal. For connections, I turn the shim stock 90 degrees and flatten it so I have a 2 inch strip coming out of each end of the roll. It is not easy to roll but it can be done.

Third: After the cap is rolled, I place tie-wraps around the assembly to hold it together. My first try was for a cap that needed to be around 0.004 UF for a 5 KVRMS output transformer with the spark gap across the transformer secondary. The capacitor went from one end of the spark gap, through a 20 Ohm non-inductive 75 Watt resistor to a spiral coil center. From the end of the spiral, I connected to the other side of the spark gap.

This setup now has over 20 hours on it with no problems. The cap stays cool. And the cap is dry - NO OIL!

I see no reson why one could not make a higher capacitance unit, for a higher voltage the same way, just scaled up.

Dr. Bill