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Increasing Voltage With Multiple Ignition Coils?

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powerpentode

Mar 22, 2021
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Hi all, I just joined and found this old thread. Let me offer some suggestions, as I have built Jacob's Ladders and Tesla Coils many times in my life. Disclaimer: These comments are my opinion and I take no responsibility for anyone else's decisions. Be careful, make your own choices, and apply common sense.
1. Staying away from mains voltage. This is a very good idea for those who are inexperienced with wiring protocols. However, please remember that it was not long ago that mains wires were openly exposed on walls and we used knife switches. If one is working directly with power mains, a local circuit breaker as on a power strip, is a great idea. I build circuits that use mains either in shielded and earthed/grounded, or code-approved plastic boxes. If I intend to expose mains wires, then I build on shellaced or varnished dry wood and I put the leads through insulated terminal barriers or standoffs. I also tend to cover those sections of the circuit with plexiglass mounted on standoffs (a piece was added over the capacitor in the photo attached. One only exposes wires now because of artistic reasons and even then great care is needed. You can apply an isolation transformer to separate your work from the power company's hot and neutral protocol, but it's still mains voltage, and of course, still dangerous. Keep everything clean and dry near the mains and near the high voltage outputs. No water, no dust, no fingerprints.
2. Working with high voltages. In general the current from a stepped up ignition coil might (I say might) be too small to clamp your heart, but you will probably jump and hurt yourself, knock your project on the floor and get a nasty burn, and cross some power wires. Therefore, I have secondary safety switches that must be set before any high voltage circuit is powered up, and the project itself is positioned in the center of wooden or laminated worktable with at least two feet of physical margin from the edge. Never, ever full hook up a high voltage experiment without first energizing it a few times to look for leak points and unexpected arcs. For example, before you put antennae on a jacob's ladder, turn it on and look for unexpected jumps.
3. The original circuit shown with a TRIAC type light dimmer and capacitor does in fact work and does not overheat, in my experience. That circuit has been known and published since the 1990s. You get a better spark than would be possible with a 12v interruptor. With a single coil I get about 5mm for a starting jump and it will hold out to 2.5cm easily. My advice, on 240V mains, use 5 mfd @ 480v (2x mains, or higher rating) for the capacitor and set the dimmer to its minimum level. You just want to use the peaks.
4. The two-coil circuit is also well-known and published. The positive leads are common because in some coils there is a 1.5 ohm resistor on the negative leg. But actually common negative should work just as well.
5. To use more than two coils? Yes the circuit will work with the two coils out of phase. HOWEVER, if the experimenter wants more voltage, s/he should just buy a neon sign transformer. I believe that I could put two sets of dual-coil configurations in series, BUT if and only if one set was placed on an isolation transformer and the phase was reversed. It would just be so much easier to buy that neon sign transformer. I had one rated at 30,000 volts and 40 ma.
6. Read some old hobby books from the pioneer days of high voltage and watch some YouTube videos. Maybe this will get the impulse to build high voltage circuits out of your system so to speak so that you can move on and do safer experiments! Suggested reading:
Morgan, Apfred P. The Boy Electrician, Lothrop,Lee & Shepard Co. New York, 1913 (updated), ISBN-13: 978-1626549814.
Adams, Joseph H. Harper's Electricity Book for Boys, Harper & Brothers Publishers, London & New York, 1907 (reprinted), ISBN-13 : 978-1559182065
Regarding the photo: Grounded power goes to the metal box, lower right. The capacitor has 3.5 mfd and 5 mfd sections, selectable at the power switch. The ignition coil cost about $10 at Amazon.
 

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Nikša

May 7, 2018
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4. The two-coil circuit is also well-known and published. The positive leads are common because in some coils there is a 1.5 ohm resistor on the negative leg. But actually common negative should work just as well.
5. To use more than two coils? Yes the circuit will work with the two coils out of phase. HOWEVER, if the experimenter wants more voltage, s/he should just buy a neon sign transformer. I believe that I could put two sets of dual-coil configurations in series, BUT if and only if one set was placed on an isolation transformer and the phase was reversed. It would just be so much easier to buy that neon sign transformer. I had one rated at 30,000 volts and 40 ma.

Yes, two coil circuit is well known and there are multiple videos on youtube.
They can be connected in series or antiparallel.
First image is the simplest and best diagram showing an IC circuit and some
explanation.

Now regarding series and parallel, it is easy to understand how output is taken between
two HV terminals in antiparallel circuit since primaries are connected in reverse,
BUT in series circuit they are connected in same direction. In other words, current in their primaries and
secondaries flows in same direction, thus it is like taking output between + and +.

Is second diagram wrong or, if not explain.

Or to rephrase, when you connect them in series, powerpentode,
do you connect polarities as in diagram below or reverse.

ignition coil.jpg
ap_coilcircuit.jpg sa_coilcircuit.jpg
 
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