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Unread 07-23-2012, 09:01 AM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Ian Curtis View Post
Particularly this rocket.

On the subject of lots of electronics, take a look at this Emirates A380 getting struck. Pretty neat looking, and obviously the airplane is designed to keep these strikes from disabling any systems.
Having worked for a 'large defense contractor' who designs commercial and military aircraft engine controls, and having performing EMI, fire, and lightning testing, I can tell you the qualification requirements for just the engine controller itself are...tough. Then again, if the the engine control fails, well physics takes over in its inexorable fashion even if the rest of plane is working just fine

For an example, you can look at the MIL-STD lightning test for aircraft:
http://www.everyspec.com/MIL-STD/MIL...TD-1757A_4242/.

During this test, the 'lightning simulator' must be capable of delivering up to 1.5 MILLION volts at a peak 200,000A (average 2000A). This is applied both as an air discharge like a normal lightning bolt, as well as a direct discharge as if the item under test was part of the conduction path from a different object that was struck. Scary stuff Even crazier is the thought of a lightning strike hitting the fuel tanks of an airplane (this gets tested!)

In terms of your home protection, here's some examples of what typically protects your telephone lines: http://bourns.com/data/global/pdfs/b...duct_guide.pdf The little gray 'telephone' box found outside your house would contain those protective devices.

The protection on a circuit card is typically "secondary protection" if it exists at all, but a properly designed protection scheme on a card can protect against 1500V/100A microsecond-type surges repeatedly. Not the same class at all as a direct lightning strike, but if lightning strikes the back of your computer there isn't much that you can really do at that point
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Unread 07-25-2012, 02:57 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by joelg236 View Post
I'm wondering about lightning strikes, as to why people (At least some people who I know) are so concerned about surges and power outages damaging electrical components. ... Now, my natural instinct is to say that this is not accurate, plainly because of all the measures we have in place to prevent such things from happening (Eg. Breakers, Surge protectors in transformers, surge protectors in power bars, fuses in appliances, etc).
Nowadays, like various other posters said, the risk is miniscule, because of all the protection devices we have. However, we have the devices because, at one point, a lot of computers got damaged by electrical storms. Now, they don't. As long as a person has their computer connected to a surge protector, it will be protected against surges, and there is no reason to worry.
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Unread 07-25-2012, 05:51 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by quinxorin View Post
Nowadays, like various other posters said, the risk is miniscule, because of all the protection devices we have.
Best protection is not on the power cord. That protection is inside appliances. For example, 1970, 120 volt electronics would withstand 600 volts without damage. Today, that same number is thousands of volts.

Or view datasheets. For example, this interface semiconductor from Maxim will protect up to 15,000 volts as defined per IEC 61000-4-2:
http://datasheets.maxim-ic.com/en/ds...7E-MAX491E.pdf

Today's more robust computers routinely make a 2000 or 15,000 volt transient irrelevant. A consumer's concern is an anomaly, maybe once every seven years, that can overwhelm that protection.

Informed homeowners earth a 'whole house' protector to even make that anomaly irrelevant. Protection that costs about $1 per protected appliance so that even direct lightning strikes to incoming wires need not damage anything. Need not even damage the protector.

Those near zero adjacent protectors with obscene profit margins are not the reason. Better protection is routinely part of every appliance design.
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Unread 07-25-2012, 08:05 PM
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Re: A little off-topic - Lightning and Electrical Components

To be a little more precise, there is a difference between surge protection and lightning protection. Surge can occur during a lightning event. However, they are more often caused by electrical distribution and generator issues. Heavy loads by local users can cause brownouts and surges when the load goes off line. Even in Chicago it is not unusual to get small pulses in the 150 v(RMS) range or sustained voltage in the 90-95 range. While most international supplies are designed to handle these transients, they do as much with power supply design and surge protectors.
While a lightning strike could be clamped with one of these devices, a large spike would destroy most of these types used in consumer equipment. True lighting protection make take the form of spark gaps, motorized breakers, event detectors etc. While not usually found in consumer equipment, I have found spark gap (gas discharge) in devices I have worked on. These devices are usually installed where the power wiring enters the equipment or at the power entrance to the building. Antennas (support towers as well) will have some type of spark gap at the base with one side bonded to the grounding system or radials of the antenna. Many transmitters for tall towers, use a device that senses nearby lightning strikes and trips the transmitter to off and removes the output to prevent damage to the transmitter.
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Unread 07-25-2012, 10:55 PM
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Re: A little off-topic - Lightning and Electrical Components

I dont know if anyone mentioned this but lightning is also a natural Electo Magnetic Pulse so in theory if any electronics are outside they can be really damaged
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Unread 07-26-2012, 12:40 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Al Skierkiewicz View Post
While a lightning strike could be clamped with one of these devices, a large spike would destroy most of these types used in consumer equipment. True lighting protection make take the form of spark gaps, motorized breakers, event detectors etc. While not usually found in consumer equipment, I have found spark gap (gas discharge) in devices I have worked on. These devices are usually installed where the power wiring enters the equipment or at the power entrance to the building. Antennas (support towers as well) will have some type of spark gap at the base with one side bonded to the grounding system or radials of the antenna. Many transmitters for tall towers, use a device that senses nearby lightning strikes and trips the transmitter to off and removes the output to prevent damage to the transmitter.
The parts Al mentions here are Gas Discharge Tubes similar to the Bourns part in the link I posted, and they are part of an FCC required protection network for your telephone interface box on your home and the Central Office (telephone company). Telephone lines, particularly in rural areas where the lines are long and exposed, are routinely struck and equipment on both ends is expected to survive this. Back when there were wired telephones (or landlines at all at this point ) a user would probably be disappointed if an incoming surge continued down the wire inside your house to a handset you were holding

Quote:
Originally Posted by westom View Post
Or view datasheets. For example, this interface semiconductor from Maxim will protect up to 15,000 volts as defined per IEC 61000-4-2:
http://datasheets.maxim-ic.com/en/ds...7E-MAX491E.pdf

Today's more robust computers routinely make a 2000 or 15,000 volt transient irrelevant. A consumer's concern is an anomaly, maybe once every seven years, that can overwhelm that protection.
Those numbers represent an ESD event, NOT a lightning surge. Volts, while important, are not the whole story. Lightning and ESD are very similar in that the duration and edge rate of the voltage event are very short. The big difference is that the current delivered during the event is measured in kiloamps for lightning, and microamps for ESD, so the POWER delivered in those events is significantly different. On a dry day, a 15kV ESD event from scuffling on the carpet and hitting a doorknob can jump ~0.25", and it stings but you're alive. If you got were close enough to a 15kV transmission line to provide a convenient path to ground, where the line is capable of delivering 10s or 100s of amps, you're going to have a bad day!

Let's talk about a recent example of how robust today's electronics are. If you can recall the 2009 game Lunacy, where we routinely were generating static both on our bots and ourselves, the driver stations would often 'flake out' or the ethernet ports would die (electrically, not just mechanically, that was a different issue ) Inside the blue box there was a chip (a PHY, the physical interface to an ethernet cable) which had no external ESD protection circuitry on it. The result? If a static discharge occurred to the cable, or even nearby enough to couple onto the cable, the PHY chip could see voltages that it was incapable of withstanding, and either go into an unknown state or even burn out. Ok, so this was a small yield, custom box that was built for FIRST, but a real commercial product sold to millions of people using a common interface couldn't POSSIBLY have this type of problem, right?

Well, here's a fun story. During some ESD testing, I was zapping a T1 interface board I designed using an ESD gun set to 15kV to ensure that it would operate normally if the service technician decided that static straps were for sissies While I'm doing this, one of the engineers on the other side of the lab (~20 ft or so) says "What the heck?". The USB mouse he was using was disconnecting and reconnecting rapidly from the computer, and eventually disassociated completely until unplugged and replugged in. Keep in mind, I'm 20 feet away on a bench that is grounded and has no medium connecting my equipment to his computer or mouse except the air (and some very indirect sneak paths back through the power panel everything eventually ties to). Standard USB mouse, standard PC, doesn't work correctly during an ESD event that isn't even nearby!

Well, there goes 30 minutes of my workday, hopefully some of this was educational then I can charge this to 'Community Service'
  #22   Spotlight this post!  
Unread 07-26-2012, 01:11 PM
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Re: A little off-topic - Lightning and Electrical Components

Eric,
One of my professors was a professional witness in just such a suit. The person was using a pay phone with the armored handset and cable when the line was struck by lightning. The resultant arc to their head, took out the hearing on one side.
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Unread 07-26-2012, 02:36 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by esquared View Post
Those numbers represent an ESD event, NOT a lightning surge. Volts, while important, are not the whole story. Lightning and ESD are very similar in that the duration and edge rate of the voltage event are very short. The big difference is that the current delivered during the event is measured in kiloamps for lightning, and microamps for ESD, so the POWER delivered in those events is significantly different.
And, as a result, lighting voltages can be higher if that larger current is all but invited inside. Newer appliances have become even more robust.

A point summarized for layman - the executive summary - all appliances contain some of the best protection found inside a building. And not by using surge protectors. Best protection means a surge current gets earthed outside. Otherwise that current will hunt for destructive paths to earth via appliances.

Why is a minimally sized 'whole house' protector rated at 50,000 amps? Because it must earth even a direct 20,000 amps lightning strike. And remain fictional. If earthed, then superior protection inside all appliances is not overwhelmed.

What was a standard for 120 volt electronics appliances before 1970? Up to 600 volt spikes on AC mains without damage. Today's appliances are required to withstand even higher numbers. Some adjacent strip, rated at near zero joules, does not even claim to increase protection. Sometimes a power strip protector has even compromised protection inside the computer.

Earth a 'whole house' protector so that a rare surge - maybe once every seven years - need not damage anything. Need not overwhelm existing and now even better protection already inside appliances.
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Unread 07-26-2012, 06:00 PM
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Re: A little off-topic - Lightning and Electrical Components

BTW,
There is an interesting article in this month's National Geographic on lightning. It covers a man who is using a very high speed camera to catch a lightning bolt in action. It is really a cool camera.
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All is better now, NOS parts are working fine. Why does this year's game remind me of Violet in Willie Wonka? Hmmmm, I see blueberries!
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Unread 07-26-2012, 07:08 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Al Skierkiewicz View Post
There is an interesting article in this month's National Geographic on lightning.
Also interesting is a recent article in Scientific American. Lightning involves quantum physics - in particular electrons and positrons. Lightning is a seriuos source of x-rays and gamma rays. Accidentally discovered by a satellite while doing research on the sun.

One paragraph has me rather confused. One lightning strike to an airplane results in a human's entire lifetime exposure to gamma rays. They did not provide numbers. So I am not sure I got that right.
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Unread 07-26-2012, 08:46 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Al Skierkiewicz View Post
BTW,
There is an interesting article in this month's National Geographic on lightning. It covers a man who is using a very high speed camera to catch a lightning bolt in action. It is really a cool camera.
Al,

A coworker pointed this video out to me today and I think it may be this exact person.

http://apod.nasa.gov/apod/ap120723.html

This is a really cool video. If you watch carefully enough you can see the return stroke (bright flash) initiate from the ground and trace its way through the ionized air up to the clouds.
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Unread 07-27-2012, 11:09 AM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Deetman View Post
If you watch carefully enough you can see the return stroke (bright flash) initiate from the ground and trace its way through the ionized air up to the clouds.
Understand that you are not actually seeing the electricity flow. That riser is simply the conversion of air to plasma. The actual surge current is in microseconds. Occurs after a conductive path from cloud to earth is slowly constructed.
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Unread 07-28-2012, 09:08 PM
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Re: A little off-topic - Lightning and Electrical Components

Kevin,
The article is about a guy named Tim Samaras. His camera weighs in at 1600 lbs and shoots 1,440,000 frames per second using a three sided mirror spinning at 360,000RPM. It has 82 video processing boards and was originally designed to analyze above ground nuclear tests.
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All is better now, NOS parts are working fine. Why does this year's game remind me of Violet in Willie Wonka? Hmmmm, I see blueberries!
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Unread 08-22-2012, 01:39 PM
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Re: A little off-topic - Lightning and Electrical Components

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Originally Posted by Al Skierkiewicz View Post
Kevin,
The article is about a guy named Tim Samaras. His camera weighs in at 1600 lbs and shoots 1,440,000 frames per second using a three sided mirror spinning at 360,000RPM. It has 82 video processing boards and was originally designed to analyze above ground nuclear tests.
Can he shoot balls with that mirror? I guess it would be a little overweight for a FRC bot.
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Unread 08-22-2012, 02:47 PM
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Re: A little off-topic - Lightning and Electrical Components

It could but only at the speed of light.
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All is better now, NOS parts are working fine. Why does this year's game remind me of Violet in Willie Wonka? Hmmmm, I see blueberries!
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