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Electric Ignition? Answered

So I have made two different versions of this spark generator, one used a Marx generator design and the other with a voltage multiple design. Both are working well, but when I expose a lighter fluid soaked wick to either one neither can start the fire. So the only thing I can think of is that while I am generating the spark it isn't hot enough or I am generating the spark before the vapors can achieve the correct oxygen/fuel mixture. Any ideas? Both use a modified Flyswatter circuit. 

Discussions

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steveastrouk

3 years ago

high voltage != high energy, necessarily. Think about a "static" shock - unless there's some energy storage, usually capacitive, sparks are weak.

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Jayccobsteveastrouk

Answer 3 years ago

That was my worries in this case. I wasn't sure if voltage or current was what ignited flammables. So I have worked out two thoughts on how to combat this with out becoming too crazy and using the components on hand.

The capacitors are 2kv 2200pF ceramics.

Ignore what the signal generator thing I put that there as a arbitrary power source for the purpose of the diagram.
So at this point I am wondering if you thing this a reasonble plan or if I need to just find something that has a higher capacitance.

Voltage multiplier.png
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steveastroukJayccob

Answer 3 years ago

You've got 8mJ of storage, if your bank comes up to 2kV, you can probably find tables of minimum energy to ignite mixtures of gases (look at "Flashpoint testing" perhaps)

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Jack A Lopez

3 years ago

Try a different gas mixture, like butane and air, from a butane lighter.

I know that's not the same thing as the fuel you want to want to ignite, but maybe getting your sparker to light something on fire, this might give you some insight. Maybe.

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JayccobJack A Lopez

Answer 3 years ago

I did try that out of a brainstorming block. Wouldn't light that but ironically if I separated the probe ends of the spark gap to the point it was unable to jump then held a light flame near it, the flame acted as a kick start for the spark. The spark would jump greater distances and it would make the flame bent and start to wrap around the spark.

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steveastroukJayccob

Answer 3 years ago

Yes, that's because the flame is a cloud of ionised particles. Its the basis of a a flame detector circuit.

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Josehf Murchison

3 years ago

Pass a peace of tissue paper between the probes.

It should scorch the paper but the paper won't burn.

The same thing is happening with your wick not enough heat to ignite a flame from any thing more solid than a gas.

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JayccobJosehf Murchison

Answer 3 years ago

Sorry wasn't hit the wrong button in case you get a notification.

Anyways it doesn't ever scorch paper or light butane.

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Kiteman

3 years ago

Where abouts, relative to the wick, are you generating the spark?

Could you post a close-up-ish photo of the wick & spark-gap?

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JayccobKiteman

Answer 3 years ago

Sorry it took me so long I have been out of town. So I have created the spark in three different locations on the wick. Currently for ease of testing purposes I have been using a permanent match, and the fuel I have soaked it in was Ronson lighter fluid. The gap is just too big for the spark to jump on its own so that it only sparks when something like the wick enters it. In the photo the red circles are the location I had the arc come across it.I also included a photo of the current set-up as Steveastrouk mentions up there I worry my current is too low.

RIMG0384.JPGRIMG0386.JPGRIMG0385ircled.jpg
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KitemanJayccob

Answer 3 years ago

My first thought is that your choice of fuel could be the issue - lighter fluid doesn't evaporate so easily as, say, methanol, white spirits or petrol.

The second thing it that you need the spark to pass through a cloud of vapour with the right amount of oxygen.

If I was setting this up myself, I would make sure that the spark jumped without anything in its path, so that the fumes ignite as soon as they reach the right density. I'd use a setup as simple as this:

SparkGap.jpg