Effects of EMP on LED Lights?

[donn]

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

 

[INRETECH]

Re: Electromagnetic pulse

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

 

[LEDmodMan]

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.

 

[Orion]

Re: Electromagnetic pulse

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

 

[AlphaTea]

Re: Electromagnetic pulse

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

 

[flownosaj]

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.

 

[flownosaj]

Re: Electromagnetic pulse

Pause for laughter.... /ubbthreads/images/graemlins/yellowlaugh.gif

 

[flownosaj]

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 /ubbthreads/images/graemlins/tongue.gif

 

[Abe Furburger]

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.

 

[AlphaTea]

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.

 

[Abe Furburger]

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.

 

[Nerd]

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?

 

[Sigman]

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"!!

 

[BF Hammer]

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.

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

 

[tvodrd]

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

 

[Abe Furburger]

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.

 

[Wylie]

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. /ubbthreads/images/graemlins/icon3.gif

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. /ubbthreads/images/graemlins/icon3.gif

 

[Minjin]

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? /ubbthreads/images/graemlins/wink.gif

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? /ubbthreads/images/graemlins/smile.gif


Mark

 

[shankus]

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.

 

[Sigman]

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>