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I know this circuit is dangerous, but i made it anyway (probably a mistake)-https://www.instructables.com/id/Variable-voltage-ignition-coil-power-supply/

In my circuit, I used a small ignition coil with relativity little insulation, and a 5nf capacitor with 240v AC. The circuit did not create a spark, thus leaving it with an open secondary winding. I have heard that this is supposed to damage the coils, as the voltage builds up inside the wingdings and eventually shorts through the coils internal insulation (from primary coil to secondary coil). However, i'm not too sure if this would have been a problem, as the minimum capacitor rating for the circuit was 1uf, and I used a 5nf. I also only ran the coil for around a minute overall. Can someone tell me if the coil is likely significantly damaged, as it is a backup for the ones in my car, and I would still like to use it if any of my cars current coils were to die. Please anybody?

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  • \$\begingroup\$ You need a much bigger cap , such as those used in Microwave ovens \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 7 at 14:21
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    \$\begingroup\$ Wait, is this putting mains voltage on a 12V automotive ignition coil? \$\endgroup\$ – marcelm Oct 7 at 14:30
  • \$\begingroup\$ Yes, with a capacitor to limit the current \$\endgroup\$ – jerrytrey Oct 7 at 14:31
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    \$\begingroup\$ Ah, I missed that the cap was in series with the coil. The setup still makes me uneasy though. Also note that depending on the construction of the coil and the polarity of the mains connection, one of the output terminals could be live at mains voltage. \$\endgroup\$ – marcelm Oct 7 at 14:36
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    \$\begingroup\$ @jerrytrey I think your original instincts are correct "I know this circuit is dangerous, but i made it anyway (probably a mistake)-". It looks highly dangerous to me as well. In the Instructable there are several things I don't like (apart from the whole idea). The maker appears to have used thin, low voltage, wire throughout, even on the HT side of the circuit. The output terminals to become connected to the live mains. Using sunflower oil as an insulator because "motor oil as this is volatile and might explode." - has he ever seen a chip pan fire? My advice - don't do it!! \$\endgroup\$ – Peter Jennings Oct 7 at 15:58

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