NE555 variable frequency circuit 50kHz-1MHz

shortbus

Joined Sep 30, 2009
7,760
Sounds like a fuel issue, wonder if wax in the paper would act differently?The arc is so hot it needs to be defused somehow?
I'm pretty sure it is the low amperage of the arc. In the TS earlier threads on this he wanted such a low amperage that it won't start a fire. The volts burn through the paper but it needs amps to keep the heat going till the ignition point.
 

MisterBill2

Joined Jan 23, 2018
6,309
In response to post #36, it takes a certain amount of time for the current to rise to the point where the magnetic core is saturated, then there is a spike. Everything after saturation occurs just makes heat. The voltage is what forces the current through the resistance.
But we still have no mention of any details about the transformer, and that item is a very big deal, right from the beginning, because it determines the maximum power that can be delivered as well as the maximum voltage possible, and the amp-turns needed to provide the required power in the spark. In addition, the characteristics of the transformer control what frequency would be reasonable to use.
SO there is important information missing!!!
 

Thread Starter

-live wire-

Joined Dec 22, 2017
911
But we still have no mention of any details about the transformer, and that item is a very big deal, right from the beginning, because it determines the maximum power that can be delivered as well as the maximum voltage possible, and the amp-turns needed to provide the required power in the spark.
Sorry. I thought I specified the transformer somewhere. It's this but with the primary removed, and ~ 10 turns of stranded, insulated, 18 AWG copper wire. The primary inductance measures ~3uH on an LC meter, and the secondary is either so large it is out of range or it just has too high a series resistance (1k on meter). The whole thing is about 1" by 1" by 1".

With a 6V PS, at 140kHz, 50%, it draws an average of 1A (measured with meter), and the arcs get hot enough to ignite a piece of paper, if it's in there long enough. The same is true of the mosfet, if there is not a heatsink with fan. ;) Weaker arcs can go through insulation and through my hand, due to the capacitance. I tried shocking myself with it across one hand to get a sense of the mA, and I felt nothing. But if I put my hand too close then my skin gets burned a bit, but not in a painful way (just some black dots).

@Wendy, I don't want to use carbon rods due to the issues with UV light, and other carbon arc dangers.
 

shortbus

Joined Sep 30, 2009
7,760
I don't want to use carbon rods due to the issues with UV light, and other carbon arc dangers.
I think I asked you this before but I'll do it again. How old are you? It seems like you have many fears of things that are not really dangers if even the smallest amount of common sense is applied to.
 
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MisterBill2

Joined Jan 23, 2018
6,309
I do not recall seeing anything about the transformer, although there may have been a link at some time. Now that I see it I suggest adding another winding and making it into an oscillator. That is how a whole lot of simple circuits function, and they must have an adequate production yield to be happy with the profit that is made. And a simple power oscillator would probably use one or two capacitors, one power transistor, and 2 or three resistors, about as simple as could be. And the power MOSFET already on hand could be a good start. Cheap and easy!!!
 

Wendy

Joined Mar 24, 2008
22,145
What you are referring to as carbon arc danger is white hot heat, so you have dismissed out of hand one of the mechanisms that might ignite hard to start fuels. There are two ways of creating a hot arc, the biggest is current.The soft arc in a piezo arc hits fuel that is easy to ignite.Since you are trying to ignite fuel that is not easy you are going to have to evaluate what it is you want. Do you wear laser glasses when you play with a LASER pointer? That is much more dangerous than a bright arc. This is not a welding machine.
 

MisterBill2

Joined Jan 23, 2018
6,309
What you are referring to as carbon arc danger is white hot heat, so you have dismissed out of hand one of the mechanisms that might ignite hard to start fuels. There are two ways of creating a hot arc, the biggest is current.The soft arc in a piezo arc hits fuel that is easy to ignite.Since you are trying to ignite fuel that is not easy you are going to have to evaluate what it is you want. Do you wear laser glasses when you play with a LASER pointer? That is much more dangerous than a bright arc. This is not a welding machine.
The very most dangerous tool around is the plasma cutter torch. It sprays air, or some gas, at a temperature of at least 10,000 degrees, so as it works it is cutting steel by melting it with really hot air (plasma). And that air is heated by an electric arc. At least that is how our safety person explained it. Exactly the same heating method as lightning, except on a smaller scale. And of course the IR radiation can burn eyes or any other parts that are exposed to it.
But it is entirely possible to use a plasma cutter safely, by doing it correctly. Likewise a carbon arc. One must certainly understand what they are doing.
 

Wendy

Joined Mar 24, 2008
22,145
The one at my local Maker space uses an arc To minimize splatter collateral damage the piece part is immersed in a shallow pool of water Unfortunately it spends more time down than it does up Google Dallas Maker Space for some interesting reading.
 

shortbus

Joined Sep 30, 2009
7,760
The very most dangerous tool around is the plasma cutter torch. It sprays air, or some gas, at a temperature of at least 10,000 degrees, so as it works it is cutting steel by melting it with really hot air (plasma)
Dangerous how? To the metal being cut yes, but if you just point it out into the surrounding air it does nothing. Or at least my small one doesn't. It needs the ground back into the machine to do anything.

All of this talk about the sparking being "dangerous" to the eyes and ultra violet and UV is also applicable to looking into the sun too long. It comes down to "theoretical" and "practical", you can hurt yourself and others if you try. But for that matter the fire that you're trying to start caries the same risk.
 

MisterBill2

Joined Jan 23, 2018
6,309
Dangerous how? To the metal being cut yes, but if you just point it out into the surrounding air it does nothing. Or at least my small one doesn't. It needs the ground back into the machine to do anything.

All of this talk about the sparking being "dangerous" to the eyes and ultra violet and UV is also applicable to looking into the sun too long. It comes down to "theoretical" and "practical", you can hurt yourself and others if you try. But for that matter the fire that you're trying to start caries the same risk.
The plasma cutter that I am familiar with will spray a stream of glowing plasma several inches into the air, and it can ignite a wooden pallet from a foot away. THAT is why I call it dangerous!
 

MaxHeadRoom

Joined Jul 18, 2013
20,881
Plasma Arc used for cutting is H.V. DC with the material at +ve potential, and if there is a concern of being burnt, do the operation under water as many plasma machines do.
Also eliminates the need for dark 'shades'.;)
Max.
 
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shortbus

Joined Sep 30, 2009
7,760
Plasma Arc used for cutting is H.V. DC with the material at +ve potential, and if there is a concern of being burnt, do the operation under water as many plasma machines do.
Also eliminates the need for dark 'shades'.;)
Max.
It is also done to cut down on the noise and smoke.
 

shortbus

Joined Sep 30, 2009
7,760
The plasma cutter that I am familiar with will spray a stream of glowing plasma several inches into the air, and it can ignite a wooden pallet from a foot away. THAT is why I call it dangerous!
Got something from Youtube or somewhere else to back that up? All that I have been around need a ground to work. My small 1/4" cut one does and the 3/4" capacity one they had at work did too. If the 'torch' was triggered into open air you only got a few sparks in the cup over the nozzle.
 

MisterBill2

Joined Jan 23, 2018
6,309
Got something from Youtube or somewhere else to back that up? All that I have been around need a ground to work. My small 1/4" cut one does and the 3/4" capacity one they had at work did too. If the 'torch' was triggered into open air you only got a few sparks in the cup over the nozzle.
I am quoting witnesses including those who used it. I never used it and never watched it in use. And I try to avoid youtube. (==the cartoon channel)
 

shortbus

Joined Sep 30, 2009
7,760
I am quoting witnesses including those who used it
Yeah, some people don't tell facts though. I have one and have seen many big ones like Max is talking about in use. What you were told doesn't happen, sorry. Just like when Mig welders first came out, people that never used one said that they would throw an arc without the wire being pointed at the work. Not true.
 
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