As my son is now old enough and "sparked" too, we started a coil project together:
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HF Filter + Safety GapTo protect the HV source from surges and overvoltage I designed a combined HF filter and safety gap. The gap is adjusted to fire at approx. 10 kV. Additionally the filter is bridged by 2x7 VDRs rated 625 VAC (Epcos S20K625). The filter itself consists of 2x7 caps rated 4700 pF @ 2000 V balanced by 2x7 resistors rated 10 MΩ @ 1 W (Vishay VR68) and 2 resistors rated 549 Ω @ 50 W. The filter and the safety gap are symmetrical to ground.You can find the schematics here. |
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MMC CapacitorThe main capacitor consists of 6 pulse caps from a dismantled laser setup. Each cap is rated 50 nF @ 10 kV. As balancing resistors 22 MΩ @ 1 W types are used (Vishay VR68). The total capacitance is 75 nF.To protect the MMC against voltage surges the array is bridged by 6 surge arresters (Okaya RA-362M-V7; 3600 V / 3500 A). You can find the schematics here. |
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PrimaryMade of copper cable for car-hifi power supply (25mm²); 9 turns at 45° |