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Thread: Effects of EMP on LED Lights?

  1. #1
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    Default Effects of EMP on LED Lights?

    Sorry if this is a bit of a strange question but I'm curious about something. I was chatting with my dad the other day about general preparedness as hes been getting a few things together for if the lights ever go out. He was looking at my CMG Infinity green and thinking it would be handy to have in a kit. When I told him it used circuitry to regulate the flow of power from the battery (basically what it says on CMGs website) he asked me whether that circuitry would still work after being hit by an electromagnetic pulse. The same thing generated by an nuclear explosion. He read somewhere that an electromagnetic pulse from a blast has a far greater range than the explosive effect of the bomb, so even if your not in range of the blast (say 70 miles away) you'd still get hit by the pulse which would destroy all your electronics.
    So it got me wondering, if ever a terrorist detonated a nuclear bomb or an 'E-Bomb' would all the regulated flashlights (A2's and the like) cease working?
    Cheers

  2. #2
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    Default Re: Electromagnetic pulse

    Not only would the flashlights stop working; its a good bet that the LEDs would get damaged also..

  3. #3
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    Default Re: Electromagnetic pulse

    Most damage from EMP occurs when the electronics in question are either turned on or moving during said EMP event. If they're moving, this will induce a current in the electronics as the EMP wave passes by. As long as there is no current going through the circuit, no damage can occur(remember the scene in the movie 'Broken Arrow' with John Travolta where there they are told by his character to turn everything off just before the bomb detonates). This is correct to the limit of my knowledge in this matter, however, if I'm wrong, someone please feel free to correct me.

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    Flashaholic* Orion's Avatar
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    Default Re: Electromagnetic pulse

    If they weren't on at the moment, why WOULD they be damaged? [img]/ubbthreads/images/graemlins/confused.gif[/img]

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    Default Re: Electromagnetic pulse

    LEDMOdMAn:
    You are correct,
    They most likely would not be damaged by the EMP

  6. #6
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    Default Re: Electromagnetic pulse

    All I know about EMPs are what I learned in the Army. We were told that we could protect our radios by wrapping the cords and such in a layer of....aluminum foil.

  7. #7
    Flashaholic* flownosaj's Avatar
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    Default Re: Electromagnetic pulse

    Pause for laughter.... [img]/ubbthreads/images/graemlins/yellowlaugh.gif[/img]

  8. #8
    Flashaholic* flownosaj's Avatar
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    Default Re: Electromagnetic pulse

    If you think about it...military equip is most likley shielded. Wrapping a conductive layer around the radio will act as a shield for those points of entry.

    Best way I can think of it is to seperate the conductive areas with a layer of non-conductive....instant shield.

    Wrap the infinity in electrical tape and aluminum foil...if it doesn't work then I was wrong [img]/ubbthreads/images/graemlins/tongue.gif[/img]

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    Flashaholic Abe Furburger's Avatar
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    Default Re: Electromagnetic pulse

    Hi,

    From my knowledge (35yrs in electronics), even if equipment is turned off, it can still be damaged.

    An EMP can induce a voltage in an led or ic that is much more than it can handle.

    Similar question - can a lightning strike knock out electronics even if they are switched off - of course, YES.

    Gotta go - more later.

    Abe.

  10. #10
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    Default Re: Electromagnetic pulse

    [ QUOTE ]
    Abe Furburger said:

    Similar question - can a lightning strike knock out electronics even if they are switched off - of course, YES.

    Abe.

    [/ QUOTE ]

    While this is true, isnt it usually because the high voltage arc's across an open switch? I have never heard of (altho it may be possible) of an UNPLUGGED piece of equipment being damaged by lightning unless directly hit.

  11. #11
    Flashaholic Abe Furburger's Avatar
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    Default Re: Electromagnetic pulse

    Having worked in an electronics test lab, where I performed lightning tests on the subjects (amongst other tests), I can tell you that nothing to do with high voltage/current is predictable, and that while equipment may be able to be proofed against most near lightning strikes it is no guarantee that it will pass every time.

    Now to my knowledge, the new EMP type weapons use a high amplitude pulse of microwave energy, and to shield against this is rather difficult on portable equipment, or equipment meant to use an antenna.

    About metal flashlights, - they are generally very well shielded except for the lense end.

    Now depending on the orientation of the flashlight to the incoming pulse, it may be able to survive without a problem.


    My feeling on microwave pulses is that even such things as bulb filaments in bulbs that are not even in a flashlight could be burnt out. Have you ever put slivers of metal into a microwave oven? - try it - put a dud CD into a microwave oven for 5 seconds and see what happens to it (put it on top of an empty plastic cup so it doesn't discolor the tray). Was the CD turned on? no it wasn't. It even works with 2 halves of a grape put in close proximity (about 1mm).

    All the best,

    Abe.

  12. #12
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    Default Re: Electromagnetic pulse

    Ah.. thanks for the very informative post Abe. You refer to the metal flashlights as very well shielded. But as for grounding? Will the EMP induce current into the metal flashlight? If so will any circuits inside it be fried?

  13. #13
    * The Arctic Moderator * Sigman's Avatar
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    Default Re: Electromagnetic pulse

    In the AF we used to "light up" lights/lamps with radar (and "enough said"...), never saw a bulb/lamp "blow" but "mysterious" things can be made to happen by "Jimmie & Mr. Wizard"!!

  14. #14
    Flashaholic BF Hammer's Avatar
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    Default Re: Electromagnetic pulse

    [ QUOTE ]
    Abe Furburger said:


    Similar question - can a lightning strike knock out electronics even if they are switched off - of course, YES.

    Gotta go - more later.

    Abe.

    [/ QUOTE ]

    If the energy of the lightning is high enough by the time it gets to the switch, the power can arc across the switch and damage the device. My not all devices are switched on the AC side also. Many of the photocopiers I've repaired following thunderstorms over the years had power supplies that were connected directly (through fuse or breaker) to the power mains - the main switch controlled the DC side of the power supply. I've also seen lightning energy flow into a device through the earth-ground, specifically in a garage-door openner in my parent's home when lightning struck a tree next door. I had every telephone and an answering machine get damaged in my home by a lightning strike that put current in the phone line.

    Getting to an EMP pulse, semiconductors and integrated circuits are the weak link in electrical devices in a nuclear attack. The microscopic interconections within the silicon IC can be burned out just from static electricity during handling, and are just as easily damaged by a high-energy pulse of radio-frequency across the electromagnetic spectrum. I'm certain a department of defense engineer might have the details of just how far from ground-zero you can expect an electrical device to be damaged by EMP, if it isn't classified.

    [img]/ubbthreads/images/graemlins/twak.gif[/img] - no message, I just like this graemlin!

  15. #15
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    Default Re: Electromagnetic pulse

    My (limited) understanding of nuclear weapon-generated EMP is that it requires the weapon be detonated at extremely high altitudes (ionisphere) where the subatomic particles emitted can react with the earth's magnetic field. I believe the US tested one on a rocket in the pacific in the 50's and knocked out part of the power grid in Hawaii. I don't think that low altitude/surface bursts have significant EMP effects. That's just from reading a few articles over the years.

    Larry

  16. #16
    Flashaholic Abe Furburger's Avatar
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    Default Re: Electromagnetic pulse

    [ QUOTE ]
    Nerd said:
    Ah.. thanks for the very informative post Abe. You refer to the metal flashlights as very well shielded. But as for grounding? Will the EMP induce current into the metal flashlight? If so will any circuits inside it be fried?

    [/ QUOTE ]

    Very hard to tell.

    My feeling is that you are less likely to have problems if you do not ground the device as the whole device will rise in potential as a single unit.

    But if you ground it, especially with a high rise time pulse, then you may have the possibility of a potential being generated across in the device, which may cause functionality problems.

    In closing, for storage, my best bet would be to wrap the device entirely in multiple layers of conducting foil, then a few layers of insulating material, then foil, then insulating material on the outside.

    A bit like an alfoil/gladwrap sandwich.

    Without this protection, I doubt it would survive.

    As for the comment about radar operators lighting up light bulbs etc, a microwave pulse from one of the new weapons would be orders of magnitude greater than that of a typical microwave installation.

    Regards,

    Abe.

  17. #17
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    Default Re: Electromagnetic pulse

    Just my two cents on the military applications of aluminum foil to power cords. A lot of computer cables have a shielding very similar to aluminum foil and for very similar reasons. The computer rooms are very well grounded or should be, but that is getting a little off track too. It is just EMFs and not EMPs. Close by anyways I figure. [img]/ubbthreads/images/graemlins/icon3.gif[/img]

    I guess I kind of have four cents on this one. With the atmosphere evaporating at that kind of rate would there be some sort of static charge at least. I mean go figure, bust up all of that H2O in the atmosphere and you bound to get some sort of a static charge, at least some lightening or something at least. And then again me myself and I the armchair chemists could be out to lunch again. [img]/ubbthreads/images/graemlins/icon3.gif[/img]

  18. #18
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    Default Re: Electromagnetic pulse

    Oh come on...everyone's dying to ask the one question that is burning on our minds: How do we make an EMP device? [img]/ubbthreads/images/graemlins/wink.gif[/img]

    After all, isn't this the Electronics and Other Mad Scientist Projects forum? Reminiscent of the scene in Cryptonomicon where they activate an EMP device in the back of a van...

    Oh yeah, anyone ever hear the old trick of tying a knot in a power cord to prevent damage if lightning should strike? [img]/ubbthreads/images/graemlins/smile.gif[/img]


    Mark

  19. #19
    Flashaholic* shankus's Avatar
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    Default Re: Electromagnetic pulse

    From what I understand about this subject, shielding electronic devices would do no good at all if the shield weren't carried to ground. The voltage induced by the pulse needs a path to ground. And the fact that semiconductor devices can't take very high currents just worsens matters. Aircraft with fly-by-wire flight controls are double shielded with a very thick braid specifically for this purpose. Any noise induced into the flight control computers would cause the aircraft to be unresponsive, or make uncommanded maneuvers. Shielded cables which have their shields tied together on both ends create "ground loops" in which noise induces a current that can put more noise on the conductors than if they weren't shielded, in some cases.

    EMP damage would be much more widespread if a nuke were detonated at a very high altitude. But there would be EMP in any case. Nukes are always detonated at some altitude, never on the ground, (underwater though). In fact, a first nuke would most likely be detonated at very high altitude, just for the EMP effect. It would damage a lot of electric and electronic devices, making a retaliation less severe. If you were close enough that it damaged a regulated LED light, you're screwed anyway. (Especially if you see the flash, that would eliminate your need for a flashlight altogether.)

    I worked with a guy for 4 years at my last job, that was an electronics/avionics flight test tech going way back to the SR-71 days. He worked SRs, F-117s, A-10s. He also did some instrumentation work for some underground nuke tests in Nevada. These underground nukes detonated in Nevada, had measurable EMP in California, where the instrumentation was. In fact, he said the data from the first test were unusable, because the pulse was much higher than anticipated, and the instruments were calibrated for too low a pulse.

    I have the DVD "The Atomic Bomb Movie". They covered that test from the '50s, that was mentioned above. If I remember correctly, it said that that test disrupted communications for 8 hours, and damaged circuits from Hawaii to New Zealand. I'll look at that part again, and post the altitude, yield and any other specifics.

  20. #20
    * The Arctic Moderator * Sigman's Avatar
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    Default Re: Electromagnetic pulse

    Ok - you asked - here it is:

    Build your own <font color="blue">"AFDB"</font>, complete instructions. It provides protection for various types of electro magnetic waves/pulses/scans.

    <font color="red">And don't forget to post pictures!</font>

  21. #21
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    Default Re: Electromagnetic pulse

    Once again, our buddies at Information Unlimited come through...

    http://www.amazing1.com/emp.htm

    A bit expensive for the pre-made units. But I would love to see how it works on a composite-bodied car, say a Saturn or Corvette...

  22. #22
    Flashaholic* AlphaTea's Avatar
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    Default Re: Electromagnetic pulse

    IIRC Popular Science magazine had an article last year about a "cheap" EMP weapon that almost any country could make from easily obtainable electrical/mechanical parts (non-nuclear).

    As far as your home microwave goes, dont make the mistake of putting ANY kind of recycled paper in there. Some Eco-nuts like recycled paper towels. I have seen it ignite within seconds. It seems that in the recycle process they are still not able to remove all traces of metal (i.e. aluminum foil gum wrappers etc).

    Hmmm...I wonder where recycled toilet paper comes from?

  23. #23
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    Default Re: Electromagnetic pulse

    So I wonder if those silver ESD bags we're all familiar with would protect from a device from EMP? They protect from static, why not EM? When I used to work for an electronics company, I was amazed at what kind of damage a static shock could cause to an IC. When the ones with the clear windows in them were damaged (usually these are EPROMS), you could looks at them under a microscope, and there were marks on the chip that looked like it had been through world war 3! Pieces of it blown apart!! While LEDs aren't as sensitive to static charges as some other things, a large charge can still damage them, so make sure to follow ESD procedures when you get your packages in the mail! Yes, it does feel/look stupid to be wearing a bracelet that is plugged into the ground of a wall socket, but that will pay for itself eventually.

  24. #24
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    Default Re: Electromagnetic pulse

    [ QUOTE ]
    Minjin said:
    Oh come on...everyone's dying to ask the one question that is burning on our minds: How do we make an EMP device? [img]/ubbthreads/images/graemlins/wink.gif[/img]

    After all, isn't this the Electronics and Other Mad Scientist Projects forum? Reminiscent of the scene in Cryptonomicon where they activate an EMP device in the back of a van...

    Oh yeah, anyone ever hear the old trick of tying a knot in a power cord to prevent damage if lightning should strike? [img]/ubbthreads/images/graemlins/smile.gif[/img]


    Mark

    [/ QUOTE ]
    Tying a knot in a power cord might help a bit - This will add inductance to the cord, which will increase the impedance to high-frequency spikes. Probably not enough to make a difference except in marginal situations.

    As to making an EMP device - Certain configurations of the human body and a Van De Graaf generator can result in some nice pulses going through the body. I recall once in high school physics, we did something that involved a ring of people with either one or both ends at the VDG. If the ring was interrupted (or possibly if it was closed by a person at the other end touching ground), a jolt would go through everyone that could be felt. We were told to remove any watches beforehand. One guy forgot to do so and his watch didn't survive the day!

    As to whether a light being EDCed would survive - Probably quite a bit of luck involved. Something like a MiniMag has shielding over most of its body, which would offer some protection. Wrapping it well in aluminum foil would work, so would putting it into a metal box or can (think Faraday cage) for safety. Key being that the box would have no holes/wires going in/out when closed. A "thin" solution might be a copper pipe with an endcap soldered on one end, and a threaded joint on the other so you can screw the other cap on.

    Shankus - As far as shielding needing a path to ground, this isn't true. It's a known fact in physics that electrical fields to not pass into a good conductor. Best example is a solid ball - There will be an electrical field on the surface of a charged ball, but none inside. This can be extended to a hollow ball - Same thing. Electrical field outside, none inside. Any sealed metal container has the same effect.

    Also, even nonsealed containers work well up to a given frequency (where the holes in the container are greater than the wavelength at that frequency). A cage made of window screening will block any electromagnetic energy below the high microwave region from getting in. A good example of a Faraday cage are some demonstrations people have done with huge Van De Graaf generators or Tesla coils - A person standing inside a cage getting struck by arcs of electricity from such sources will feel NOTHING. (At least not directly from the electricity - The sound of the arcs would be a different story.)

  25. #25

    Default Re: Electromagnetic pulse

    Your first concern in any weapon of mass destruction event is proximity. The most important decisions you made about surviving a massively destructive event is where you live and where you work. If you live or work in a high risk area, you and your electronics are substantially more vulnerable to EMP pulse and everything else, because you are more likely to be in close proximity to a massively destructive event.

    In instances of EMP, and every other kind of point source destructive event, the effect generally tends to follow the laws of spherical spreading loss. This is good news because the power of the destructive wave fronts are inverse cubes of the distance. There are some ground effect, transmission line, and atmospheric anomalies to be considered, but those are practically impossible for the layman to calculate due the immense number of variables involved, starting with the location and composition of the initial event. In short, however, distance from the blast is your best friend. Heading for the hills is also a good idea because terra firma stops everything but cosmic rays.

    Now back in the bad old days of the Cold War when it was not beyond the range of possibility that substantial numbers of nuclear devices would fly at any given moment, the likelihood of being caught in an EMP pulse was pretty substantial and wildly irrelevant. If you were caught by an EMP pulse, you were probably about to be in hell anyway because the infrastructure of your city just went up in smoke. Today it is much more likely that if you are caught in an EMP blast, you are going to make it because most of the barbarians and dictators striving for nuclear devices do not have the capability of delivering the repeated strikes necessary to turn your bad day into your last day. Individual nuclear weapons are not nearly as overwhelmingly powerful as movies and anti-war activists would have have you believe. Don't get me wrong, they are not something I want set off anywhere near me, but getting caught in an EMP pulse is not your death warrant.

    It is a good and worthwhile thing to create and maintain an emergency kit and plan. Keeping that kit in an old 20mm ammunition can will probably keep everything dry and EMP proof. I suspect that aluminum Mag Instruments based lights will probably hold up much better than plastic bodied flashlights. I very much hope that I never find out the hard way. I think it can be stated without contradiction that the more parts, the greater likelihood of part failure by definition.

  26. #26
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    Default Re: Electromagnetic pulse

    Sigman,
    That was a funny website. Maybe I should get some of those beanies made with earmuffs for cell phone users. [img]/ubbthreads/images/graemlins/yellowlaugh.gif[/img]

    Minjin,
    From what I have gathered magnetrons are being used now to make EMPs. I am only guessing but magnetrons may also be also in the interruption of transmitting devices used for weaponry. Some people have suggested that magnetrons have been the cause of crop circles. Something about the age of the technologies and the possible advancements and uses as a star wars type of application, kind of has me wondering if this could be true.



  27. #27
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    Default Re: Electromagnetic pulse

    Here is a couple of interesting excerpts from this document:

    “…thickness plays an important role in shielding. When skin depth is considered, however, it turns out that thickness is only critical at low frequencies. At high frequencies, even metal foils are effective shields.”

    “The amount of current flow at any depth in the shield, and the rate of decay is governed by the conductivity of the metal and its permeability. The residual current appearing on the opposite face is the one responsible for generating the field which exists on the other side.”

    Of course, what we're talking about, is NO frequency.

    http://www.chomerics.com/products/do...ory_of_emi.pdf

  28. #28
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    Default Re: Electromagnetic pulse

    Getting into the mad scientist rhythm of things here... Most of the docs I can find on the subject are about EMP bombs, single-use devices designed to take out a large area. I just want a small focused gun that will let me take out my annoying neighbor's boombox when it's keeping me awake. How much power could that possibly require... I bet the starter from my HID headlight kit could be a good first approach, and the parabolic reflector of the headlamp housing itself is probably decent for aiming purposes...

  29. #29
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    Default Re: Electromagnetic pulse

    Highlandsun...

    That's a good idea. While you're at it, put enough power in to disable a car stereo. Then it can be used for those people who are into major noise pollution. (both from the stereo &amp; engine)


  30. #30

    Default Re: Electromagnetic pulse

    www.4hv.org

    The TRUE High-Voltage maniacs. [img]/ubbthreads/images/graemlins/buttrock.gif[/img] [img]/ubbthreads/images/graemlins/bowdown.gif[/img]

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