Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Understanding electric sparks
Polesch
Harmless
*




Posts: 23
Registered: 9-7-2011
Location: Norway
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 04:42
Understanding electric sparks


I'm just another amateur that wants to attempt a small-scale Birkeland-Eyde process, if not only as a proof of concept. But as a chemist with very little knowledge in electricity, and the need to generate an electric arc or plasma to do this, I need some help.

As a source of the electric arc I opted for a small and simple "spark gap igniter", the one found here. As you can see it inputs 4.8-5V/3A, and outputs a spark that can traverse a gap through air of about 1.25 cm (<0.5"). I have no clue what technical device does this, and what that igniter is made of, capacitor? Transformer? Both? Marx generator? Cockcroft–Walton generator?

I made a quick video where I tested it and its ability to produce nitric oxides. Here you can see it connected to three 1.5V batteries in series. And it does seem to produce nitric oxides just fine, as detected by odor and the reddening of a moist litmus paper.

As my main concern here is safety, I'd like to know what type of voltage and current it outputs, and what sort of harm/damage that could do to me if struck/jolted. My naive views on electricity tells me that anything powered on three tiny batteries (AAA) has to be harmless, and an input of ~15W. But I have received warnings by others that it could potentially be lethal, with that voltage and a few milliamps.

For me it looks identical to what is used in electroshock weapons, contact tasers, as used by police in some countries. For what information I've managed to find on some of them, they generally output voltages in the 200-300 kV range. Causing sparks about 3-5 cm long. Although listed as non-lethal, about 0.7% of people tased do suffer serious harm or death. And only about 260 deaths have been reported between 2001 and 2007 in the US.

Anybody know much about this device? What are some realistic safety measures? What are the actual risks associated with it?

Any contribution is much appreciated.
View user's profile View All Posts By User
hyfalcon
International Hazard
*****




Posts: 1004
Registered: 29-3-2012
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 05:35


There's is a BIG sticky at the top of this section of the forum on Birkeland-Eyde reactors. You need to read into it a little before starting a post on the subject and if you have questions post in the pertinent post already started on the subject.
View user's profile View All Posts By User
Polesch
Harmless
*




Posts: 23
Registered: 9-7-2011
Location: Norway
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 05:53


Quote: Originally posted by hyfalcon  
There's is a BIG sticky at the top of this section of the forum on Birkeland-Eyde reactors. You need to read into it a little before starting a post on the subject and if you have questions post in the pertinent post already started on the subject.


Well, I did consider writing this post on that sticky. It's not that I didn't see it or ignored it. It's that I didn't think my post had that much to do with the B-E process, but rather high-voltage devices and safety. As the purpose of the spark is irrelevant to the post.
View user's profile View All Posts By User
Morgan
International Hazard
*****




Posts: 1572
Registered: 28-12-2010
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 13:43


I found something similar on eBay once. It would make a spark 2 inches long on 6 volts. The guy who sold me a couple had some information about them saying they had an overheat shutoff and that if you ran it at 3.5 volts or something around there you could run it constantly. I ruined one of them by making the gap wider than 2 inches so now it only sparks a little over an inch. Here it's running an old 3 volt camera battery.
If you make the gap small, the device makes a faster but much more feeble spark.
I wonder how long these devices would hold up before failing? I took the one apart, removing the white tape that holds the 2 halves together. There's a tiny X-shaped spark gap on the outside of the potted material on one end inside the taped region.
http://www.youtube.com/watch?v=d33_Fhgy5Dg

[Edited on 16-11-2013 by Morgan]
View user's profile View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 16-11-2013 at 14:01


Quote: Originally posted by Polesch  
Quote: Originally posted by hyfalcon  
There's is a BIG sticky at the top of this section of the forum on Birkeland-Eyde reactors. You need to read into it a little before starting a post on the subject and if you have questions post in the pertinent post already started on the subject.


Well, I did consider writing this post on that sticky. It's not that I didn't see it or ignored it. It's that I didn't think my post had that much to do with the B-E process, but rather high-voltage devices and safety. As the purpose of the spark is irrelevant to the post.


hyfalcon does have a point though. Not so irrelevant to the purpose of your post considering you want to provide proof of concept. To do so one needs higher current. Lower currents at high voltages are better at producing Ozone than Nitrogen Oxides. The transformer you mention is not a good pick since to actually produce gasses which could yield even a small amount of acid it must run nonstop for long periods and that one would fail rapidly under those conditions. An NST would be a better choice. Your goal is impossible to obtain, i.e., creating a high voltage source you would feel (or be) safe with. Volts push Amps but it is the Amps that kills. Simply put all dealings with high voltage at currents greater than around 50 microamps can kill depending upon where the current flows. If your skin is punctured by the spark the internal resistance in your body rapidly falls to 200 ohms or less as opposed to say 50,000 ohms on dry skin. You need to be studying these factors such as this link.

http://www.physics.ohio-state.edu/~p616/safety/fatal_current...

No high voltage is safe outside of toy VanDeGraaffs. Get used to it or do not deal with it. Avoid contact obviously and especially be cognizant of possible heart paths. It can kill, given the chance it will kill. Being afraid one makes mistakes. High voltage is one place few ever get a second chance. That being said I do not see where the setup you mention is all that dangerous. The point is treat it like it is at all times. Learn safety and work safely at all times. The chart in the link above is not all that great since 10 ma across your heart kills and this chart does not really convey this. I remember a study the Navy did with far more accurate information, I will search around and see if I can find it again, to post here. One can study the over 500 Taser deaths to realize unlike a Stun Gun which makes surface contact the Taser barbs pierce flesh bring in the concept of lowered impedance yielding higher internal currents. A raw arc against the skin for all intents does provide this lower impedance, higher current path to vital organs. Something you should consider. 117 VAC has killed far more people than any other voltage yet people seem to treat the wall outlet in a more caviler way than say the overhead lines. In short learn why voltage is dangerous and learn how to avoid possible heart paths at all times when dealing with this subject.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.ht...

http://www.highvoltageconnection.com/articles/ElectricShockQ...

https://www.osha.gov/SLTC/etools/construction/electrical_inc...

http://en.wikipedia.org/wiki/Electric_shock

http://technologyinterface.nmsu.edu/3_3/3_3h.html




[Edited on 11-16-2013 by IrC]




"Science is the belief in the ignorance of the experts" Richard Feynman
View user's profile View All Posts By User
Morgan
International Hazard
*****




Posts: 1572
Registered: 28-12-2010
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 15:09


Strange but the extra wide gap doesn't seem to harm this device although from the SparkGapFun website there are some comments where the device bit the dust from stress of some sort.
It's kind of an impressive spark here. Young curious minds.
http://www.youtube.com/watch?v=f16ysxIqWJI
https://www.sparkfun.com/products/11218
View user's profile View All Posts By User
Pyrotrons
Harmless
*




Posts: 38
Registered: 13-10-2013
Member Is Offline

Mood: No Mood

[*] posted on 16-11-2013 at 17:54


Hi Polesch. That's a pretty cool little device you found there. I think I know how it works.

There is definitely a small switching power supply inside, to convert the 4.8V into something useful. The output of this power supply I think may charge a capacitor to some unknown high voltage (but still pretty low, maybe 2 or 3kv). The energy from this capacitor is then *probably* discharged into the primary winding of a high voltage pulse transformer via a small internal spark gap. In layman's terms, when this happens, a strong magnetic field basically nails the high voltage winding of the transformer and the initial 1 or 2kv is stepped up to an extremely high voltage.

I assume this is how it works, because of the rather low firing repetition rate.... it takes time to charge a high voltage capacitor with only 15 watts of power available. So you might get only 10 bangs per second. But they're pretty good bangs!

I am sure that increasing the spark gap beyond 1/2" will reduce the lifetime of the device. You may be able to push it a little, but it's clearly not rated for more than the voltage that it takes to break down 1/2" of air (very roughly 12kV).

I do seriously question the ability of this device to run continuously. Most of the applications cited on that website are non-continuous; igniters, tasers, etc.

A car ignition coil will do a GREAT job running continuously - they're made for it. The output current will be significantly lower than the aforementioned device, but I have gotten a TON of voltage (measured 8" sparks!!!) from automobile ignition coils repackaged in mineral oil ; ) They don't last long like that though, better to keep them arcing about 2".

Search for a light dimmer ignition coil driver circuit, they are powerful, simple, small, 120V input, and adjustable.

Does your chemical reaction require UV light produced from the arc to work? This may change the game, not much UV light comes from the typical low-current power supply. For UV you really need capacitor discharge, or some other means of producing very high currents in the arc (like a pulse transformer).

Edit: Added the following:

I second IrC's comments. Neon sign transformers are really great. And, all you need to do is simply hang a high voltage pulse capacitor across the output to COMPLETELY transform the arc into a painfully blue/white/ultraviolet screaming roar of intense high-current-density arcs which is what I think you may be need. I wish I knew more about the chemistry aspect.

[Edited on 17-11-2013 by Pyrotrons]




"Thus ethyl alcohol is inferior to xylene, although usable for certain applications." - Gerald Hurst
View user's profile View All Posts By User
morganism
Hazard to Others
***




Posts: 105
Registered: 8-12-2012
Location: Az.
Member Is Offline

Mood: No Mood

[*] posted on 29-11-2013 at 00:16


isn't that a sparker for an oil burner ?

may be able to find info on it thru a heating or HVAC site.


Most of the other folks playing with sparks are using flyback transformers.

here is the one i want to play with

http://www.youtube.com/watch?v=BT2JjVjmixI
View user's profile Visit user's homepage View All Posts By User
Polyolefin
Harmless
*




Posts: 5
Registered: 20-12-2013
Member Is Offline

Mood: No Mood

[*] posted on 20-12-2013 at 04:02


What you're smelling is most likely ozone. You can sometimes even smell ozone form when polyester blanket zaps static electricity on you.
View user's profile View All Posts By User
Master Triangle
Harmless
*




Posts: 13
Registered: 24-12-2013
Member Is Offline

Mood: No Mood

[*] posted on 25-12-2013 at 04:37


Since it is designed as an ignition driver and judging by the sound of it there is a capacitor on the output that causes it to discharge in one short pulse (many times a second) which makes it a little more dangerous. You can get a jolt from them and small skin burns if you leave you finger on it for a while but they pose no danger unless the current is flowing through your heart. Even then the current is probably too low but best be safe, make sure that you cannot touch it in such a way that the current would flow through the chest (hand-to-hand).

Consider that the inputs may not be isolated, try arcing either of the output leads to the input leads, if they do not then that means that the output is isolated and you do not have to worry about people touching the input side getting a shock off the output side. You should be able to hold onto one of the outputs without any effect.

The way that you have it set up is basically foolproof, you will want to secure the wires better but it is perfectly safe like that. Your production rate will be tiny but as a proof of concept you don't need much I guess?

You have probably seen this video as it's the first on google for "Birkeland-Eyde process" but the setup appears great for a hobbyist and demonstrates the process well.
http://youtu.be/2RRqIv4SoLg
View user's profile View All Posts By User

  Go To Top