Effects of EMP on LED Lights?

[Sable]

Well, if I'm remembering my "EMP-ology" right, you would need a weapon of around 20 megatons (quite a lot larger - on the order of a thousand times - than the Hiroshima/Nagasaki blasts) and, yes, needs to be very high indeed.

Could an electromagnetic pulse event damage quite a lot of things? Yes, yes it could - but I've never considered it to be a huge threat to my daily life. This may be because I live in Alaska, where power is an iffy thing at best anyway.

There are non-nuclear ways to induce high-intensity EM fields, most of which cannot be used (or are impractical to) to launch far-ranging events.

Furthermore, you can protect EM-sensitive equipment with a Faraday cage, proper grounding, and other techniques.

I guess my point is that a "real" EM attack would likely be a significant event - but one that would be survivable by society and a reasonably well-prepared nation. There are ways of both seeing it coming and defending against it. Moreover, on my personal heirarchy of "things to worry about," it's not very high. But your mileage may, of course, vary.

[The-David]

It's a good idea to keep plenty of tin foil around anyway. You need it to make a nice hat to keep out the government mind control rays.

HAHAH And everyone though I was nuts wareing this thing around

[NewBie]

All depends on the power in the pulse. If it's a short but powerful blast it might fry it, it might not. If the voltage across the junction goes beyond the absolute maximum in the spec spec then it is dead for sure!

I'd be more worried about the radiation introducing too many defects so your LED that was once all shiny becomes a dim glow. Of course, I'd only be worried for a day at most, after than I'd be dead.

Don't forget that CREE and Luxeon have a rather large ESD diode inside, that would greatly help to clamp that pulse from destroying the die. Usually this ESD diode is rated for 2,000 Volts. Also, the die is mounted above a "ground plane", which has capacitance, which will further help reduce the effects of the pulse.

EMP pulses are short, in the order of 100 billionths of a second, dropping to half amplitude within 200 billionths of a second, but there is low frequency energy that lasts up to 1000 seconds.

Also consider that the typical reflector opening size of an inch or so.
A wavelength at this diameter would be 1.18 GHz. Energy below this frequency would be greatly attenuated.

There are two major modes for EMP to get into equipment:
-Front Door Coupling occurs typically when power from a electromagnetic weapon is coupled into an antenna associated with radar or communications equipment. The antenna subsystem is designed to couple power in and out of the equipment, and thus provides an efficient path for the power flow from the electromagnetic weapon to enter the equipment and cause damage.

-Back Door Coupling occurs when the electromagnetic field from a weapon produces large transient currents (termed spikes, when produced by a low frequency weapon ) or electrical standing waves (when produced by a HPM weapon) on fixed electrical wiring and cables interconnecting equipment, or providing connections to mains power or the telephone network . Equipment connected to exposed cables or wiring will experience either high voltage transient spikes or standing waves which can damage power supplies and communications interfaces if these are not hardened. Moreover, should the transient penetrate into the equipment, damage can be done to other devices inside.

Notice how both modes for a significant amount of the pulse to get in, are mainly antennas and wiring.


There is one very specialized version of the EMP bomb, called a HPM, but they only have a small area of effect:

HPM weapons operating in the centimetric and millimetric bands offer an additional coupling mechanism. This is the ability to directly couple into equipment through ventilation holes, gaps between panels and poorly shielded interfaces. Under these conditions, any aperture into the equipment behaves much like a slot in a microwave cavity, allowing microwave radiation to directly excite or enter the cavity.

An example is that of a 10 GW 5 GHz HPM device illuminating a footprint of 400 to 500 metres diameter, from a distance of several hundred metres. This will result in field strengths of several kiloVolts per metre within the device footprint, in turn capable of producing voltages of hundreds of volts to kiloVolts on exposed wires or cables.

Now, how long is a flashlight like an HDS? 4 inches? So this will attenuate the voltage to 10th the voltage at 1 meter.

Anyone have the spectrum plot of what a large area EMP pulse weapon produces?

I know that in the case of a nuclear detonation, an electromagnetic pulse consists of a continuous frequency spectrum. Most of the energy is distributed throughout the lower frequencies between 3 Hz and 30 kHz. As such, most metal LED flashlights would be rather safe. There is a weaker initial spike at the first time of arrival from 1 to about 300 MHz caused by gamma radiation. Following that, there is energy from 1 to 100KHz which lasts a total of about 1 millionth of a second. Then there is a bunch of low frequency activity, that mainly threatens long power lines, data lines, and antenna cables, that goes on for up to 1000 seconds.

Also, realize the strength of the pulse drops with the distance from the detonation. For more info on this look here:
http://electromagneticpulse.quickseek.com/


In the case of a EMP bomb at altitude, typically, the field strength on the ground drops to 300 volts per meter at only 3 miles from the burst, at ground level.

Did you know that the effect of a altitude EMP burst, once you get away from "ground zero", on the ground follows a boomerang shape, and the peak field is in the V of the boomerang, which is always pointed south? And it is very weak to the North. This is due to the earth's magnetic field.

More detailed info here:
http://www.usace.army.mil/publicatio...10-3-2/c-2.pdf

[ciam]

I'm not sure exactly what fellow CPFer "etc" referred to. If it's really the ultra high intensity EM radiation burst produced by nuclear bombs or other more mundane means, I would worry more about myself than my LED flashlights, for example, mutating genes in my cells or causing havoc in my brain circuit....

If it's the gentler EM radiations you encounter in your daily life, there isn't much to worry about. Indeed, a shake LED flashlight is usually equipped with a magnetic coil. While you should be careful to keep it away from your electronic devices, the LED inside is happly sitting in the rather strong magnetic field.

[vic303]

Nice info, NewBie!
Here is some info from the Amateur Radio Relay League on EMP.

http://www.arrl.org/tis/info/pdf/88615.pdf
http://www.arrl.org/tis/info/pdf/98622.pdf
http://www.arrl.org/tis/info/pdf/108638.pdf
http://www.arrl.org/tis/info/pdf/118630.pdf


And something from another ham radio site.


http://www.qsl.net/n9zia/emp.html

[IsaacHayes]

I've heard that even pole transformers can be taken out by EMP! now that's crazy!

I don't think we have to worry much about it. There would be much worse problems if an EMP was to go off...

[AlexGT]

Is there a practical way to create big EMP without the use of nukes? Can an EMP be directed like a ray? I was thinking if we could do that maybe the police chases would end, just EMP the speeding car to make it stop since all are computer controlled.

AlexGT

[ciam]

EMP could be produced by any big explosions, not necessarily nuclear explosions. It could also be produced by a rapidly fluctuating magnetic field. But I doubt it could be deployed in the manner you described.

[NewBie]

I've heard that even pole transformers can be taken out by EMP! now that's crazy!

They have wires hooked to them that go on for miles. Makes for very efficient antennas to couple the EMP pulse into them...

[Sub_Umbra]

I'm not worried about EMP's effect on flashlights.

If the LEDs in your flashlights (with your flashlights minescule antenna length) are knocked out by EMP the blast would have to be huge. There wouldn't be any power grid left at all -- with it's antenna length billions of times the length of our lights. Anything connected to the grid would be gone forever.

Anything electronic in all cars (again, with an effective antenna length many, many times longer than any of our lights) would also be toast.

Those are pretty big ifs, IMO. This is the kind of thing that makes the news, but only on very slow news days.

I don't buy the premise. Sure, it's probably possible to generate a powerful enough EMP that could damage an LED flashlight with it's tiny effective antenna length but even then the light would have to be in very close proximity to the source of the pulse to be affected.

If the EMP takes your flashlight, build a fire -- because the power grid will be gone for years...if it ever comes back.

[wasBlinded]

Is there a practical way to create big EMP without the use of nukes? Can an EMP be directed like a ray? I was thinking if we could do that maybe the police chases would end, just EMP the speeding car to make it stop since all are computer controlled.

AlexGT

Exactly such a technology is in use by law enforcment today. It is a device laid in the road in the path of a vehicle, triggered by its passage.

[soapy]

There is a radio jammer system that does that, but I can't find a reference anywhere. I thought it was a gun device that they pointed, like a radar gun on steroids. It basically interfers with the car electronics by introducing noise into the system, causing misfires and problems. Of course, a diesel truck wouldn't notice it, and a really new car with drive-by-wire might steer off course, or even go faster as all the systems are jammed.

However, that's not EMP, since the device isn't a single power pulse that destroys things, it's more like a radio jammer in that when you turn it off the system resets to normal.

[lyyyghtmaster]

With regards to the power grid issue, and EMPs of a more modest size than some discussed here: It seems that some areas of the country would be better protected than others (think those areas hardened to protect against frequent lightning). This could create a situation of mass migration as people innundate regions comparatively protected from the EMP effects by the islanding that would (hopefully!) occur when more vulnerable sections of the grid (and/or closer to the pulse) were taken out by EMPs. Just offering another cheery thought! (But at least our lights would probably remain unaffected!)

[joema]

If you're talking about a nuclear EMP, it's easily possible many or most unshielded microprocessor-based devices within hundreds of miles could fail. The peak field strength could be 50,000 volts per meter. Diodes (inc'l LEDs) might not be damaged, but microprocessors with their vastly smaller semiconductor gates are more sensitive.

So your direct-drive LED lights might work, but anything with a microprocessor or microcontroller might not. That would include most cars, computers, radios, TVs, wrist watches, camcorders, cell phones, electronic medical equipment, etc.

It also doesn't require a deadly close nuclear EMP to cause this. A high altitude detonation that causes no harmful ionizing radiation to humans could still destroy many semiconductors. Peak field strength might be 50,000 volts per meter, over a large area: http://en.wikipedia.org/wiki/Electromagnetic_pulse

The problem isn't surviving an EMP attack or the secondary blast and radiation from the nuke that generates the EMP. High altitude nuclear bombs have already been detonated in space, and they didn't harm people beneath them: http://en.wikipedia.org/wiki/Starfish_Prime

Rather the problem is there's little rational basis for a stand-alone nuclear EMP attack. It would most likely be part of a larger attack, probably a 1st action to disrupt communication and coordination, which would be followed by a real nuclear attack.

So in a sense the people saying an EMP attack would be disastrous are correct, but not from the nuclear-pumped EMP itself. There would be no mutations or radiation-induced deaths from a high altitude nuclear EMP. We know that because several of those have already happened: http://en.wikipedia.org/wiki/High_al...lear_explosion Rather the destruction would come from the actual nuclear attack, which would would likely immediately follow the EMP strike.

[NewBie]

If you're talking about a nuclear EMP, it's easily possible many or most unshielded microprocessor-based devices within hundreds of miles could fail. The peak field strength could be 50,000 volts per meter. Diodes (inc'l LEDs) might not be damaged, but microprocessors with their vastly smaller semiconductor gates are more sensitive.

Hundreds of miles is a very small area. Keep in mind, that natural features will also help to shield against the pulse, and as I'd mentioned, there are quite a number of factors that would help a lot, in metal flashlights, to protect both the LED and the electronics.

I do know that a sample of one, an ARC4+, had no issues at all, with 300 V/m, at frequencies below 1 GHz, when I tested it. It didn't even phase it, when it was off or when it was on.


There are more details in the US Army document on the subject here:

http://www.usace.army.mil/publicatio...10-3-2/c-2.pdf

[Jedi Knife]

Do they even still make tin foil? I thought they stopped producing tin foil years ago.

[joema]

Hundreds of miles is a very small area. Keep in mind, that natural features will also help to shield against the pulse, and as I'd mentioned, there are quite a number of factors that would help a lot, in metal flashlights, to protect both the LED and the electronics...

That was a radius figure, not area. It's 50,000 volts/meter over roughly 50,000 square miles, and 37,500 volts/meter over about 1/3 the continental US -- from a single detonation.

As already stated, not sure the emitter itself would be damaged, but anything with a microcontroller or microprocessor is at more risk.

Like many flashlights, most airplane skins are solid metal with just a few apetures. However the Air Force built this gigantic facility to test how B-52s can withstand EMP: http://www.brook.edu/FP/projects/nucwcost/trestle.htm

This article discusses EMP from standpoint of energy (joules) per unit area, not volts per meter: http://www.measurement-testing.com/e...tic-pulse.html

It says 1 joule can be EMP-coupled to many systems, yet only 10^-13 joules (one 10 trillionth of that) can upset some semiconductors.

But my main point was the posters saying EMP is no problem since you'd be dead from blast/heat/gamma radiation are incorrect. There have been numerous high altitude and space nuclear detonations in the late 1950s and early 1960s. They generated plenty of EMP, and people didn't die. Unfortunately submicron gate semiconductors didn't exist then, so there's no actual empirical data from real nuclear EMP about their sensitivity.

But there's little tactical purpose of a nuclear-pumped EMP without an immediate follow on nuclear strike, so in a sense the people saying "we're doomed anyway, what's the point" may be correct.

[h_nu]

Do they even still make tin foil? I thought they stopped producing tin foil years ago.

I'm pretty sure you are right. Many Americans use the term "tin foil" when they really mean Aluminum foil. People raised in the 40's and 50's called it that and their children probably flunked chemistry.

[:)>]

I read that a single layer of tin foil, the stuff you cook your roast in is all you need to protect all your electronic equipment from an EMP blast.

regards.

John.

You can also use tin foil around your head to keep the aliens from reading your thoughts

-Goatee

[NewBie]

That was a radius figure, not area. It's 50,000 volts/meter over roughly 50,000 square miles, and 37,500 volts/meter over about 1/3 the continental US -- from a single detonation.

As already stated, not sure the emitter itself would be damaged, but anything with a microcontroller or microprocessor is at more risk.

Like many flashlights, most airplane skins are solid metal with just a few apetures. However the Air Force built this gigantic facility to test how B-52s can withstand EMP: http://www.brook.edu/FP/projects/nucwcost/trestle.htm

This article discusses EMP from standpoint of energy (joules) per unit area, not volts per meter: http://www.measurement-testing.com/e...tic-pulse.html

It says 1 joule can be EMP-coupled to many systems, yet only 10^-13 joules (one 10 trillionth of that) can upset some semiconductors.

But my main point was the posters saying EMP is no problem since you'd be dead from blast/heat/gamma radiation are incorrect. There have been numerous high altitude and space nuclear detonations in the late 1950s and early 1960s. They generated plenty of EMP, and people didn't die. Unfortunately submicron gate semiconductors didn't exist then, so there's no actual empirical data from real nuclear EMP about their sensitivity.

But there's little tactical purpose of a nuclear-pumped EMP without an immediate follow on nuclear strike, so in a sense the people saying "we're doomed anyway, what's the point" may be correct.

Actually it says:
" Nevertheless, EMP is still capable of transferring something of the order of 0.1 - 0.9 joule/m2"

As I pointed out earlier, you need something to pick up this energy. I can in fact expose an unprotected luxeon in free space, with nothing attached, to a field 36,000 V/m continously and see zero damage to the device.

Now take a look at the frequency distribution of an EMP pulse.

Lets think about something common like the HDS light. Surround a luxeon on all sides, but one, with thick aluminum. Next take a metal reflector, and essentially plug that hole with the luxeon. Go look up the frequency distribution of the EMP pulse at ground level. For a high altitude burst, that would cover CONUS, many references will say that 99% of it falls below 100MHz. You are looking at wavelengths that are roughly one meter long. Consider this again, and compare it to the reflector size, and then realize, hardly any is going to even enter the reflector at all, as it's wavelength is way too long. What magnetic field makes it thru the aluminum, remember all the wiring is quite short, and also, HDS utilizes a shielded ferrite inductor, which if was unshielded (and it is not unshielded), would be a primary point for the field to couple in at.

When folks wax and wane on, saying there were effects as far away as Hawaii, keep in mind, this was primarily coupled in by the long wires of the power grid, which serve as very nice antennas.

I've participated in equipment testing, such as indirect lighting, direct lighting, and various electromagnetic field testing. One of the hardest things to protect against is that wiring that is strung out, and how it couples into the system, serving as wonderful collectors and antennas. Seams can be overlapped as necessary, or even folded to get more effect. Consider that the HDS has a multi-fold design which is present in it's threads.

This reminds me of the time a while back, when an EA-6B Prowler accidentially jammed the flight controls of a F/A-18 aircraft. Luckily the ECMO realized what had happened, and shut down their ALQ-99 system, allowing the F/A-18 pilot to regain control of his aircraft. Even though the F/A-18 had passed all the high energy testing, including a variety of EMP pulses, the ALQ-99 jamming system had a very concentrated high power (above a kilowatt) beam of frequencies in the multiple GHz range, and they managed to easily couple into the F/A-18's flight control computer, thru the aircraft wiring. The source of entry was the seams of the aircraft skin, which nicely passed the offending source into the body of the aircraft, and on to the wiring. The fix? Just some simple low cost EMI fingers that ran around under the edge of the panels.

[Jedi Knife]

I'm pretty sure you are right. Many Americans use the term "tin foil" when they really mean Aluminum foil. People raised in the 40's and 50's called it that and their children probably flunked chemistry.

Wow. It's amazing that people simply parrot out things that they hear instead of applying some thought to what they're saying. I would have thought that inhabitants of the most advanced country in the world would know better. To think that these same people are posting advice in such a technical thread as this is hilarious.

[OCEANBEAMER]

pehaps we should all store our lights in a faraday box just in case of emp.

[ringzero]

Wow. It's amazing that people simply parrot out things that they hear instead of applying some thought to what they're saying. I would have thought that inhabitants of the most advanced country in the world would know better. To think that these same people are posting advice in such a technical thread as this is hilarious.

On the other hand, there's nothing wrong with people using slang to express themselves. CPF isn't some dry technical publication, and that is part of its charm.

"Tin foil" for aluminum foil, "Ice Box" for refrigerator, "powder" or "gunpowder" for smokeless propellant, and numerous other commonly used terms are all technically incorrect. But, anachronism is part of their appeal.

[hank]

Any of you old enough to remember when we all of a sudden changed our minds about invading Cuba the last time 'round? That's when the US and USSR found out what they could do to themselves without any surface targets being hit.

Both rattled their sabers in their sheaths to make threatening noises, and discovered it made their pants fall down. Oops.

This link was posted earlier in the thread; here's a brief excerpt:

http://en.wikipedia.org/wiki/High_al...lear_explosion

"... The Soviets detonated four high-altitude tests in 1961 and three in 1962. During the Cuban Missile Crisis in October 1962, both the US and the USSR detonated several high-altitude nuclear explosions as a form of sabre-rattling. The Soviet tests were meant to demonstrate their anti-ballistic missile defences which would supposedly protect their major cities in the event of a nuclear war. The worst effects of a Russian high altitude test occurred on 22 October 1962 (during the Cuban missile crisis), in ‘Operation K’ (ABM System A proof tests) when a 300-kt missile-warhead detonated near Dzhezkazgan at 290-km altitude. The EMP fused 570 km of overhead telephone line with a measured current of 2,500 A, started a fire that burned down the Karaganda power plant, and shut down 1,000-km of shallow-buried power cables between Aqmola and Almaty [5]. The Partial Test Ban Treaty was passed the following year, ending atmospheric and exoatmospheric nuclear tests. "

Communications gear nowadays is a bit more sensitive -- remember:

Solar flares will disrupt GPS in 2011 - tech - 29 September 2006 ...
Charged particles from solar flares also produce intense bursts of radio noise, which peak in the 1.2 and 1.6 gigahertz bands used by GPS. ...
www.newscientisttech.com/article/dn10189

[mchlwise]

This may sound like a strange question, but...

With all that's going on in the world, Iran getting close to going nuclear, terrorism, world politics, etc., something's been on my mind lately:

It seems like the U.S. and our insatiable appetite for electricity and all things electronic make us particularly vulnerable to E.M.P. and an E.M.P. attack.

(for those unfamiliar - an atomic/nuclear bomb, when detonated, produces an Electro-Magnetic Pulse. This pulse destroys anything and everything electronic in the path of the pulse. A nuclear bomb detonated at 400km over the center of the country would destroy all electronic devices (including cars) in nearly all of the country. E.M.P. can also be generated from non-atomic sources. http://en.wikipedia.org/wiki/Electromagnetic_pulse)

My question is: how vulnerable are LEDs and LED flashlights to E.M.P.?

At first it may seem like a simple question, but there are a number of factors that make it more complicated once fully examined.

For example: the best defense against E.M.P. is to enclose the electronic equipment in metal on all sides, creating in effect Faraday cage. As long as the equipment is insulated from the metal, the E.M.P. will travel around it and dissipate.

Would the aluminum body of a light like a Fenix act as a Faraday cage and protect the LED?

Would an aluminum reflector focus the E.M.P. onto the LED intensifying its effect?

Are emitters like Luxeons and Crees even vulnerable to effects of E.M.P.?

What about the electronics/circuit boards/drivers? If the emitters aren't vulnerable, and the driver is, the light would still be destroyed.



So what are everyone's thoughts?



p.s. - I've asked Gransee about the Arc AAA-P and E.M.P., and he indicated they have actually tested it and the Arc withstood and survived E.M.P. BUT, the single-mode Arc with a 5mm emitter seems to me like a whole different animal than a JetBeam or a L1dce.

[Valpo Hawkeye]

I've often wondered about this myself. My guess, and it's just that, a guess, is that lights like HDS EDC's and other circuit-driven lights would be vulnerable. Direct drive led's like an Arc AAA might be okay. But I'm not sure, so this post is pretty worthless...

[h_nu]

This comes up from time to time and thankfully we haven't had a real world test yet.

The tinfoil hat types might want to keep their lights in empty Danish butter cookie tins. Mmmmm, butter cookies.

[tebore]

It's been discussed that an EMP strong enough to damage your flashlight would be the least of your concerns. Strong EMPs are usually caused by Nukes which would turn you into red vapor.

Power LEDs like Luxeons have built in ESD protection which might help.

EMPs would kill incans as well because a surge would break the filament.

The Arc AAA is not direct drive it has a boost circuit.

Again if an EMP struck, a non working flashlight would be the least of your concerns.

[TORCH_BOY]

It depends on the Flashlight, most modern lights use a circuit or proccessor circuit
of some description, EMP would probably destroy the circuit. Thats the advantage of
direct incadescent lights

[Rubycon]

Anyone willing to put their lights in the microwave and try it out?

The EMP in the ring of a can crusher is pretty intense as well.