I'm switching my EDC lights from incandescent to LED. This sounds like a simple question, but I was wondering.

Could an EMP (I'm assuming that the explosion and radiation is far way) render LED lights non-functional. What about those new mini-flourescents that people are switching to for home use?

Thanks in advance for your thoughts!

I switched to an LED about 6 months ago because the LED was almost as bright as my minimag with a much longer battery life. During my research into EMP I found a couple of articles (I can't find them again, cause some of my searches are kinda roundabout) that said LED's were very susceptible to EMP. So I keep my minimag close by just in case.

I suspect that the voltage regulation circuit that is in most of the new LED lights would be prone to failure under EMP just as most unsheilded solid state electronics are. The LED by itself is still a diode, and certainly the the tiny circuit in there that regulates the power going to the LED could be fried.

The regulation circuit should die happily, but "would EMP kill LEDs" was an oft had debate around the lunch table when I was in college. We didn't know, the profs didn't know.

If it should happen, whatever works works, and what doesn't has the battery and other components salvaged with the rest dumped. But a big enough pulse will take out almost everything as it goes over the max wattage of the circuit in question.

Thanks to everyone for their posts. It's given me something to consider and I'll keep my incandescents around as backup. I'll keep candles in mind for a long-term solution.

The good news is that I get to buy more new gear (Hello kerosene/Coleman dual fuel lanterns)!

The great news is that I still get to tell my wife that the backyard tiki torches still have a reason to stick around.

I don't know. My current belief is that it depends on the wavelength of the pulse. EMPs are expected to have long wavelengths, so only create big currents in long wires, so LEDs are likely to be safe, especially if not connected to anything. Small, coin-cell torches may well be safer than big 2xCR123 ones because they have less of an aerial effect.

If the EMP is specifically designed to destroy integrated circuits with a high frequency pulse, then LEDs would be affected too.

Interesting topic. I'm no expert, but here are some thoughts.

It seems to me that higher-end, regulated output LED lights may be more vulnerable than cheap, unregulated ones. As suggested by others, the regulation circuitry, which may include an IC, becomes the potential weak link in this scenario. Cheap LED lights are just a diode, resistor, switch and battery pack.

I would guess that the amount of RF energy needed to generate enough current to fry, say, a Luxeon 1 in an unregulated circuit would be enormous. In a live circuit, the batteries and resistor would act as current limiters and heat dissipaters. And if you didn't have batteries in place or the switch was off, only eddy currents could be created in the wire (no circuit).

I wonder if there's an authoritative source on the amount of voltage/current generated per length of circuit wiring. This would help a lot.

I am guessing that EMP would also take out the Shake lights as well?

Would creating a simple Faraday cage made of a silver emergency blanket help?

We've had this type of discussion before, and the conclusions we reached IIRC is that if an EMP is strong enough to take out other semiconductor components, then it will take out an LED.

An EMP generates a high amplitude burst of rf energy, amplitude in this case being voltage. Semiconductors junctions are susceptible to this voltage when the amplitude is reverse to the bias of the junction. If you can understand that semiconductors work like a one way valve. They can take a fair amount of forward flow, but don't like it much when the flow reverses and the pressure gets too high. This is called peak inverse voltage, or PIV. Typically most silicon junctions have a PIV limit of between 100 and 250 volts. The junction offers a relatively high impedence to current flow up to the PIV limit, then the "barrier" is compromised, usually resulting in a temporary short circuit at the junction with high instantaneous current flow until the junction overheats and then it blows open, meaning no more current flow period. LEDs are special diodes that generate photons as the electrons migrate across the junction in forward flow. As far as I can remember, LEDS have about the same PIV as normal silicon diodes, or somewhere in the same general range.

What this means is that when an EMP occurs, the pulse may not contain a lot of energy, but it will have a high voltage, and across a great range of frequencies (I believe there is a bell curve of frequency generation depending on the EMP event). As the wave encounters the junction of semiconductors, the undulating voltage creates a high potential, low current source of electricity. When the voltage is inverse to the polarity of the junction, and the amplitude exceeds the PIV, then the junction blows, and the component is rendered useless.

Since junction blows usually occur at the weakest point in the cross setional surface of the junction, it doesn't seem to matter too much how big the device is, although there is some heat sink protection in bigger components, but it is not significant enough to be much protection at all. Surface mount and complex Integrated circuits (ICs) being built today incorporate more exotic semiconductor materials that will be even more susceptible to EMP, so the cell phones, pdas, and laptops will almost certainly croak in most any EMP environment.

Faraday screens have limits as to how much voltage they can dampen. Basically they are sinking the signal to ground, and there are so many factors to consider that simply putting your device into a grounded metal box is far too simplistic. The magnitude of the EMP and the proximity to it are perhaps the two most significant factors that will determine the effectiveness.

I believe the conclusion was that unless the device was buried in the ground a thousand or so feet deep in a highly conductive medium, the chances it would be safe from EMP are pretty slim no matter what you do. It doesn't matter if the component is in a circuit or sitting in a little baggie, they are going to get popped just as bad either way. In the movie War of the Worlds with Tom Cruise, the mechanic replaced the solid state device(s) in the car that Tom then drove off. In reality, the replacement components would be just as useless as what was already in the vehicle.

Please read from http://www.globalsecurity.org/wmd/library/report/1988/CM2.htm




I really don't understand all the fascination with all this EMP stuff on the forum. Only the major nuclear powers have the ability to deliver a large area effect EMP. The only countries that have this ability are the US and Russia and possibly China. Terrorist organisations do not. It is very difficult engineering challenge to delivery a multi megaton warhead up to altitudes higher than even the US space shuttle orbits over the CONUS. If fact most ICBMs do not have the payload capabilities to lift such large thermonuclear weapons so high. Anyway if this does happen, worrying about your flashlight or your laptop or your GPS or the nice new 42 inch LCD TV at home should be the last thing on your mind. You should start digging unless of course you have your own back yard personal nuclear bunker. You’ve got about 5 – 30 minutes before all hell breaks loose.

Some high explosive detonations can cause a localised EMP effect. There have been developments in Non-nuclear electromagnetic pulse (NNEMP) weapons that are designed to destroy localised microwave and cellular communications hubs, only because microwave communications are highly susceptible to the magnetic field vector of the electromagnetic pulse. The magnetic fields, which are induced by the pulse deflect the magnet field around the ferrite device causing the circulators in the microwave circuits to become unstable by affecting the microwave frequencies they are tuned to making them unusable. The electrical field vector of the pulse can be protected by the faraday cage effect. Mu shielding can protect most circuits in the same way for the induced magnetic field effects. Mu shielding is heavy and it expensive but does work. Faraday cages are cheap and easy to implement. You just need an aluminium box. Ones with rounded corners are even better.

Therefore to summarise, I wouldn't worry whether your flashlight would survive an EMP, chances are that it will, but you won't have enough time to appreciate that fact, chances are that you won't be able to survive the next 30 minutes. If you keep your LED flashlight in a small closed alumiunium box your flashlight will be OK. I keep a FENIX AAA cree flashlight in a BCB minimess tin only because its the container for my PSK. You don't really need to keep anything down the bottom of a mineshaft except possibly yourself. But then again EMP is not really an issue except in the realms of surviving a nuclear armageddon.