12V battery to create spark gap?

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Discussion Overview

The discussion revolves around designing a circuit to create a spark gap using a 12V battery source. Participants explore the theoretical aspects of inductive circuits, capacitor charging, and the necessary voltage to achieve a spark between electrodes 3mm apart. The conversation includes considerations of circuit components and configurations, as well as safety concerns regarding high voltage generation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on building a circuit to generate a spark gap, noting the breakdown voltage required is 2334.24 V.
  • Another participant suggests looking up formulas related to circuits with coils and capacitors, emphasizing the need for a longer circuit period than the 1 ms switching time.
  • A participant mentions the equations for current and voltage in inductors and capacitors, indicating an understanding of their behavior in the circuit.
  • One participant proposes using a capacitor to build up voltage before discharging it to create a spark, while expressing uncertainty about the circuit design.
  • Another participant recommends studying photographic flash units as a reference for generating high voltage pulses safely.
  • One participant clarifies that they are designing a schematic rather than physically building the circuit.
  • A suggestion is made to use an oscillator, transformer, and rectifier to produce an intermediate voltage to charge a capacitor, followed by discharging through a resonating inductor.
  • Reference is made to automotive ignition circuits for additional techniques that could be applicable.

Areas of Agreement / Disagreement

Participants express various ideas and approaches without reaching a consensus on a specific circuit design or method to achieve the desired spark gap. Multiple competing views and suggestions remain present throughout the discussion.

Contextual Notes

Participants discuss the theoretical aspects of circuit design, but there are limitations regarding the practical implementation and safety considerations of working with high voltages. The discussion does not resolve the mathematical or technical steps necessary for the circuit design.

dadadeee23
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Hey okay, so I have a 12V source which can provide a max of 10 mA, and I also have a switch that can go from open to close in 1 ms, How can I create an inductive circuit that will create a spark gap between electrodes that are 3mm apart? I did the math and found the breakdown voltage to be 2334.24 V, so I guess I need to figure out a way to get my input voltage of 12V to my desired 2334.24V in order to ionize the air and have it actually jump. I just don't know how to build a circuit that would do that?

I think I would use a capacitor that would initially build up voltage until I reach my breakdown voltage and then release from the switch, and then I'm lost. Any suggestions? Thanks!
 
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Do you know the usual formulas for a circuit with a coil and a capacitor inside? If not, it would be useful to look them up.

I think you need a circuit with a period of much more than 1ms (so the switching time is not important). With capacitance and inductance, you can relate the current of 10mA to the peak voltage of the circuit, and find values for both elements which satisfy both constraints.
 
I know that iC=C(dVc/dt) and I know VL= L(diL/dt), so and inductor opposes instantaneous change in current and a capacitor opposes instantaneous change in voltage. I think I somewhat figured it out. I think maybe the 1 ms just is to confirm that the switch closes instantaneously. Thanks for the response!
 
dadadeee23 said:
Hey okay, so I have a 12V source which can provide a max of 10 mA, and I also have a switch that can go from open to close in 1 ms, How can I create an inductive circuit that will create a spark gap between electrodes that are 3mm apart? I did the math and found the breakdown voltage to be 2334.24 V, so I guess I need to figure out a way to get my input voltage of 12V to my desired 2334.24V in order to ionize the air and have it actually jump. I just don't know how to build a circuit that would do that?

I think I would use a capacitor that would initially build up voltage until I reach my breakdown voltage and then release from the switch, and then I'm lost. Any suggestions? Thanks!

dadadeee23 said:
I know that iC=C(dVc/dt) and I know VL= L(diL/dt), so and inductor opposes instantaneous change in current and a capacitor opposes instantaneous change in voltage. I think I somewhat figured it out. I think maybe the 1 ms just is to confirm that the switch closes instantaneously. Thanks for the response!

What do you want to make a spark for?
 
dadadeee23 said:
Hey okay, so I have a 12V source which can provide a max of 10 mA, and I also have a switch that can go from open to close in 1 ms, How can I create an inductive circuit that will create a spark gap between electrodes that are 3mm apart? I did the math and found the breakdown voltage to be 2334.24 V, so I guess I need to figure out a way to get my input voltage of 12V to my desired 2334.24V in order to ionize the air and have it actually jump. I just don't know how to build a circuit that would do that?

I think I would use a capacitor that would initially build up voltage until I reach my breakdown voltage and then release from the switch, and then I'm lost. Any suggestions? Thanks!

Why not look at how photographic flash units work? They will produce high energy pulses at several hundred volts. (The limit is only imposed by the fact that the flash tubes use that voltage.)
But you should really know what you are doing if you are planning to make sparks at high voltages. It could be wandering into the realms of what PF doesn't discuss. If you want 'safer' high voltage sparks, you may be better to try electrostatic methods.
 
I'm not physically building something, I am just designing a circuit schematic that would be capable of doing this with the parameters given haha. Thanks for the advice!
 
Ah well, as we're just thinking this one. . . . . You just need an oscillator, a transformer and a rectifier to produce a fairly high, intermediate voltage (a couple of hundred) and charge a Capacitor. You then discharge that capacitor through a resonating inductor to produce a seriously big 'ding' in Volts. This requires a fairly hefty solid state switch (SCR, for instance).
Look at motor car electronic ignition circuits for more techniques.
 

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