THE OUDIN COIL
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The Oudin coil is a low efficiency curiosity in the world of tesla coils. It is an air core single coil transformer, with the bottom turns used as a part of a LC tank circuit, with a high voltage, very high frequency output at the top. Because of the low self capacitance of the coil, we need a low primary capacitance and high voltage input (in the past, best used were the Leyden jars and Rhumkorff coils). The top discharges are not spectacular, but the Oudin coil is a great high frequency source, for plasma discharge experiments (plasma balls). The d'Arsonval configuration of the primary tank (capacitors on each side of the coil tank connections) separate the top output from the main HV transformer voltage.

ELECTRIC SCHEMA
The coil is not grounded. This makes it a great jammer for the neighbour electronic stuff (a lot of electric interferences)
SETUP

COIL
- 14 cm diameter white PVC pipe, surounded by 8 columns (1.5 cm PVC pipes)
which sustain the turns
- 90 turns with bare 1.5 mm diameter copper wire. The turns are kept in position    by plastic separators on each column made with nylon tyes
- coil diameter = 6.68 inches
- total lenght = 45 cm
- calculated inductance = 436.186 microH
- calculated self capacitance = 9.3192 pF
- F res = 2.49 MHz

PRIMARY TANK
- mains transformer 220 V / 5000 V @ 15 mA (little 75 VA OBIT)
- filters on both outputs of the HV transformer ( ferrite toroids, 10 T each)
- simple spark gap: two Al heatsinks sliding on two rail leaders (plastic rulers)
- primary cap: at first try I used 2 x 470 pF @ 30 kV doorknobs in parallel on         each side of primary for a total Cp = 470 pF @ 30 kV
SETUP PICS
TURN SEPARATORS
COIL FORM
THE COIL
HV TRANSFORMER
PRIMARY CAPS
SPARK GAP


- Cp = 470 pF @ 30 kV doorknobs
- primary:
           Np = 7 turns
- secondary (the rest of the coil):
           Ns = 83 turns
The output is very high freq and give great plasma display in light bulbs (I used a 300 w light bulb). It would be interesting to use a more powerfull HV  xfrm.
LITTLE MOVIE
PLASMA PICTURES
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