EMPShield[1] claims to make products that can protect against events such as lightning strikes and high-altitude nuclear explosions that generate EMPs. As an EE I find the design, theory, and testing[2] extremely questionable. It seems that this company has other skeptics[3]. It's infamous with mechanics who see them in cars, or are asked to install them.
They sell a small box that hooks up to your car battery, or your the mains in the breaker panel for your house. There's a few feet of cabling to a small box which they claim can clamp the energy from the EMP. If you try to search youtube for this product you can only find positive reviews from the "prepper" community, and any tear-downs seem to have been removed. The company claims to be active with the military as well.
Their testing consists of legitimate testing for EMP, however they only test the unit itself -- not hooked up to anything. I don't see any evidence that this product actually works when hooked up to a car or house. Am I going crazy here, is this a huge scam or some legitimate technology?
I've never actually looked at what an EMP does to kill electronics. I've just taken it as bad. Does it really just create an overload that fries the electronics so that a nice surge protector keeps it safe? The thing you describe basically sounds like some sort of shunt for excess to go to ground.
I don't think that works with EMPs since the pulse will induce a current in the protected circuit just as much as the path to ground, unless that path to ground is a full shield around the circuit.
> I've never actually looked at what an EMP does to kill electronics.
Ever see the school experiments where a magnet is waved by a coil of wire hooked to a volt meter which registers voltage and therefor current flow? That is how generators work - spin a big magnet in a big coil of wire and that generates lots of electricity. Moving a wire through a magnetic field induces current flow if there is a complete circuit.
Now picture your smart phone, laptop, PC, console, car, etc, anything with wires or conductors - and now wave a really really really BIG magnet next to it. That can induce currents so large that the wiring can melt, semiconductors vaporized or melted, chip bonding wires vaporized, pcb traces vaporized, etc. Basically total destruction via a massive current/voltage spike.
I read about an EMP test Russia conducted on a length of telephone wire which was placed next to a nuclear test site hooked to some instrumentation. I do not remember the exact numbers offhand but the EMP induced over 3000 amps on those little telephone wires for a few microseconds before they vaporized.
Also an EE. I struggle to see how this might be technically feasible even with space magic technology. EMPs travel at the speed of light through air. Any detection and counter pulse will lag behind by some amount. Maybe that delay could be sufficiently small and there could be enough transceivers in enough locations to be "good enough", but this seems very unlikely.
I don't really get why there is a market for this in the first place. A cheap and unpatentable solution for EMP shielding already exists: Faraday cages.
They have a market because old rich Rotary club members will spend money on black boxes to “keep them safe”.
I need to introduce these people to my special Yeti defense device. In millions of hours of testing there have been zero Teti attacks! It works perfectly!
I can see how a device could protect from an EMP surge created by a grid connection. Is that what they're selling?
But that wouldn't work to protect electronics from magnetic pulses that would induce current within an electronic device's circuits. That needs grounded shielding physically around the circuit, like a Faraday cage.
Comment #16 at that eevblog link is supposedly a direct quote from the manufacturer, and it’s pretty damning.
Most panelboard manufacturers make a device that can plug in to your main electrical panel just like a breaker and is probably much more effective due to being directly attached to the bus.
(Not necessarily against EMPs. But it should do pretty well against a conducted surge due to nearby lightning or a utility switching transient. It won’t do very well if used in a non-main-panel, because they generally lack separate neutral and ground connections — a good surge protector anywhere other than a “service entrance” will separately protect line-line, line-neutral (2x), line-ground (2x), and neutral-ground, for a total of six individual transient voltage suppression devices.)
TVS-based surge suppressors seem like wishful thinking to me, especially given MOVs' finite lifespan. Series mode surge protection is the better approach.
And regardless of the protection type, star power/ground and absolutely no wires going from any of the protected devices to other unprotected devices.
Series mode seems to mean Zero Surge or maybe one of their rather sketchy-looking competitors. If these devices were so great, I would expect to see a real standard and certification for them. And this seems a bit dubious to me:
> Unlike most surge protectors, Zero Surge products do not rely on the ground circuit for effective surge protection, so you can use them even in ungrounded outlets.
So let’s see… they apparently pass ground straight through (as they should for safety!), and they’re some sort of filter on hot and/or neutral. (I found a sketch online suggesting that they are, in fact, just an inductor on the hot wire.). So suppose a surge happens and, by some miracle, the surge is just a voltage spike on hot relative to everything else, then, into a resistive load, current and hence voltage will be limited. But the load might not he resistive! Into a switched-off MOSFET or similar, the current needed to damage something is really quite low, and the only way this seems like it will work is if there’s enough capacitance somewhere to make the filter work. If there is any filtering on neutral, though, or if ground is contaminated, then I could imagine arcing between the protected circuit and ground.
In any case, this all seems silly. If the service entrance is protected, a hot-only surge seems pretty unlikely. (Your house’s neutral and ground wiring is not that great, and surges can couple inductively from nearby lightning strikes or even result from failures inside the house.)
I’ll stick with conventional surge protectors.
(I do own a Zero Surge that I bought to test as an EMI filter. I had such bad EMI on one circuit that it made a computer buzz very audibly — this was caused by cheap LEDs dimmed by a mediocre TRIAC. The result: the Zero Surge buzzed even louder than the power supply!)
I've got a few SurgeX units that I've taken apart. It's an inductor in line with the hot, and sense circuitry that shuts off a downstream relay when the input voltage rises. I don't remember sizing up the capacitance but surely there has to be some, and presumably they've done the math so that the voltage rise downstream of the inductor is slower than the relay switching speed.
> a hot-only surge seems pretty unlikely
What do you mean? N/G should be bonded and at the same voltage with exterior surges, assuming a dedicated circuit. Across L-N/G is the only place a surge can show up - barring parasitic coupling of the equipment to ground/environment, or erroneously connecting a wire to unprotected equipment.
And compared to TVS ones that pass all the lines through, relying on their ability to shunt overvoltage/current, with the active element actually dissipating much of the surge power? The series mode of operation at least seems analytically tractable.
Yes, as I was reading their various descriptions of the device, I started to think "wait, is this just a whole-house surge protector?" ...and sure enough, they come right out and state "The EMP Shield is one of the World’s fastest whole home surge protectors" right on the main page of their site.
Call me a pawn of big business, but I'd much rather pay $200 or less for a whole house surge protector made by a respected electrical equipment manufacturer than almost $400 for one made by a company that ladles grandiose claims about nuclear weapons over their product.
I'm at a loss how they managed to convince anyone into thinking they were going to employ 1000 people, or do anything related to chip manufacturing.
Their website(https://www.empshield.com/frequently-asked-questions/) claims 500ps response time, which seems in line with MOVs(although maybe this is just a milspec test threshold so many devices will claim this response time).
I wonder if you could use an MOV or similar surge suppressor in parallel with a lightning gap to achieve useful protection?
As others have said, their device is not full EMP protection. At best, it will protect your electronics from a surge on the grid but not locally present EM fields.
Someone should call ElectroBoom and have him do a teardown.
23 comments
[ 3.0 ms ] story [ 56.3 ms ] threadThey sell a small box that hooks up to your car battery, or your the mains in the breaker panel for your house. There's a few feet of cabling to a small box which they claim can clamp the energy from the EMP. If you try to search youtube for this product you can only find positive reviews from the "prepper" community, and any tear-downs seem to have been removed. The company claims to be active with the military as well.
Their testing consists of legitimate testing for EMP, however they only test the unit itself -- not hooked up to anything. I don't see any evidence that this product actually works when hooked up to a car or house. Am I going crazy here, is this a huge scam or some legitimate technology?
[1] https://www.empshield.com/ [2] http://www.empshield.com/wp-content/uploads/2019/11/EMP_Shie... [3] https://www.eevblog.com/forum/news/emp-shield-scam/
Issues with this:
Adding a long wire to your protection device isn’t going to do much.
Signals, not power, are the biggest concern in cars.
You really need protection at the ingress of each device, and shielding of individual enclosures, to be effective.
Ever see the school experiments where a magnet is waved by a coil of wire hooked to a volt meter which registers voltage and therefor current flow? That is how generators work - spin a big magnet in a big coil of wire and that generates lots of electricity. Moving a wire through a magnetic field induces current flow if there is a complete circuit.
Now picture your smart phone, laptop, PC, console, car, etc, anything with wires or conductors - and now wave a really really really BIG magnet next to it. That can induce currents so large that the wiring can melt, semiconductors vaporized or melted, chip bonding wires vaporized, pcb traces vaporized, etc. Basically total destruction via a massive current/voltage spike.
I read about an EMP test Russia conducted on a length of telephone wire which was placed next to a nuclear test site hooked to some instrumentation. I do not remember the exact numbers offhand but the EMP induced over 3000 amps on those little telephone wires for a few microseconds before they vaporized.
I don't really get why there is a market for this in the first place. A cheap and unpatentable solution for EMP shielding already exists: Faraday cages.
I need to introduce these people to my special Yeti defense device. In millions of hours of testing there have been zero Teti attacks! It works perfectly!
Wassis?
Ignorance and salespeople.
But that wouldn't work to protect electronics from magnetic pulses that would induce current within an electronic device's circuits. That needs grounded shielding physically around the circuit, like a Faraday cage.
Most panelboard manufacturers make a device that can plug in to your main electrical panel just like a breaker and is probably much more effective due to being directly attached to the bus.
(Not necessarily against EMPs. But it should do pretty well against a conducted surge due to nearby lightning or a utility switching transient. It won’t do very well if used in a non-main-panel, because they generally lack separate neutral and ground connections — a good surge protector anywhere other than a “service entrance” will separately protect line-line, line-neutral (2x), line-ground (2x), and neutral-ground, for a total of six individual transient voltage suppression devices.)
And regardless of the protection type, star power/ground and absolutely no wires going from any of the protected devices to other unprotected devices.
> Unlike most surge protectors, Zero Surge products do not rely on the ground circuit for effective surge protection, so you can use them even in ungrounded outlets.
So let’s see… they apparently pass ground straight through (as they should for safety!), and they’re some sort of filter on hot and/or neutral. (I found a sketch online suggesting that they are, in fact, just an inductor on the hot wire.). So suppose a surge happens and, by some miracle, the surge is just a voltage spike on hot relative to everything else, then, into a resistive load, current and hence voltage will be limited. But the load might not he resistive! Into a switched-off MOSFET or similar, the current needed to damage something is really quite low, and the only way this seems like it will work is if there’s enough capacitance somewhere to make the filter work. If there is any filtering on neutral, though, or if ground is contaminated, then I could imagine arcing between the protected circuit and ground.
In any case, this all seems silly. If the service entrance is protected, a hot-only surge seems pretty unlikely. (Your house’s neutral and ground wiring is not that great, and surges can couple inductively from nearby lightning strikes or even result from failures inside the house.)
I’ll stick with conventional surge protectors.
(I do own a Zero Surge that I bought to test as an EMI filter. I had such bad EMI on one circuit that it made a computer buzz very audibly — this was caused by cheap LEDs dimmed by a mediocre TRIAC. The result: the Zero Surge buzzed even louder than the power supply!)
> a hot-only surge seems pretty unlikely
What do you mean? N/G should be bonded and at the same voltage with exterior surges, assuming a dedicated circuit. Across L-N/G is the only place a surge can show up - barring parasitic coupling of the equipment to ground/environment, or erroneously connecting a wire to unprotected equipment.
And compared to TVS ones that pass all the lines through, relying on their ability to shunt overvoltage/current, with the active element actually dissipating much of the surge power? The series mode of operation at least seems analytically tractable.
Call me a pawn of big business, but I'd much rather pay $200 or less for a whole house surge protector made by a respected electrical equipment manufacturer than almost $400 for one made by a company that ladles grandiose claims about nuclear weapons over their product.
I'm at a loss how they managed to convince anyone into thinking they were going to employ 1000 people, or do anything related to chip manufacturing.
The key quote, buried way down in the article: EMP Shield will leverage state support to apply for CHIPS Act funding to see its plans to fruition.
That’s right, this is just wishful thinking and hype. Zero dollars in government funding have been approved.
I wonder if you could use an MOV or similar surge suppressor in parallel with a lightning gap to achieve useful protection?
As others have said, their device is not full EMP protection. At best, it will protect your electronics from a surge on the grid but not locally present EM fields.
Someone should call ElectroBoom and have him do a teardown.
https://lda.senate.gov/filings/public/filing/056178b4-e8b5-4...
"Was signed." Nice use of the passive voice, there.
The tech sounds a bit dodgy, though. Could well end up in Wisconsin/Foxconn territory.
Let's hope they're legit. It's good to diversify local manufacturing and rural Kansas could use the jobs.