Personal computing discussed
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bobboobles wrote:Don't mess with Mother Nature.
bthylafh wrote:My mailbox saved the house from a lightning strike a few years ago. Thing was masonry with a cinder-block core and chicken wire + mortar holding the two together; it must have been that chicken wire.
CasbahBoy wrote:You're completely right about the induced current. There simply isn't much you can do about a strike that close.
liquidsquid wrote:An FYI, my lightning detector consists of a 2' long antenna with a 5M ohm termination with resonant tank LC. This will "see" about 3V pk/pk signals from strikes half way across the country with NO amplification. 50' away? That is why I have a transorb on it. I saw one while I had a scope hooked up to it that was over 100V. It was 50 miles away or so.
Firestarter wrote:liquidsquid wrote:An FYI, my lightning detector consists of a 2' long antenna with a 5M ohm termination with resonant tank LC. This will "see" about 3V pk/pk signals from strikes half way across the country with NO amplification. 50' away? That is why I have a transorb on it. I saw one while I had a scope hooked up to it that was over 100V. It was 50 miles away or so.
You might want to repeat that in English, if your goal is to enlighten us poor saps with no education in these matters
notfred wrote:On his 2 foot long antenna setup, lightning 50 miles away gives about the same voltage as plugging it directly in to the wall socket!!! I'm keeping well clear of that.
Firestarter wrote:liquidsquid wrote:An FYI, my lightning detector consists of a 2' long antenna with a 5M ohm termination with resonant tank LC. This will "see" about 3V pk/pk signals from strikes half way across the country with NO amplification. 50' away? That is why I have a transorb on it. I saw one while I had a scope hooked up to it that was over 100V. It was 50 miles away or so.
You might want to repeat that in English, if your goal is to enlighten us poor saps with no education in these matters
liquidsquid wrote:On top of that, a transorb (a reverse-diode which has an abrupt breakdown voltage, like a zener diode only specialized) is placed across the center antenna conductor. Its intention is to absorb and dissipate the excess energy instead of blowing sensitive circuits. The transorb is the sacrificial component. I have no idea why there are not typically used on Ethernet cards, but they are not. Probably to sell more NICs.
liquidsquid wrote:You can easily get transorbs that only present tiny amounts of capacitive loading which would not even slightly effect signal integrity of a strong Ethernet signal (they are VERY stout), much less than you would see in a 100' twisted pair.
just brew it! wrote:liquidsquid wrote:You can easily get transorbs that only present tiny amounts of capacitive loading which would not even slightly effect signal integrity of a strong Ethernet signal (they are VERY stout), much less than you would see in a 100' twisted pair.
It isn't just the amount of loading that matters; where it is placed along the line is important too, otherwise you will get signal reflections. The capacitance does not need to be comparable to that of 100' of twisted pair to cause a problem if it is all in one spot.
Uman et al wrote:Another incident mentioned in that report but fully documented here is the freakiest for me, and not just because it involves a glider. Like most modern sailplanes, this glider's structure was entirely fiberglass, which is insulating, but contained numerous metal parts. In particular, the control linkages are mostly aluminum or steel, and in this case a positive strike apparently entered the aircraft structure through the aileron fittings and passed through the wing via the control tubes. In the process it flash-heated various components and the air inside the wing, which created enough overpressure to both blow out the canopy and delaminate the fiberglass (basically partially blowing the wing apart from the inside). The freakiest thing, though, was the damage to the control tube itself: the electromagnetic flux travelling along it was so high that it caused the tube (16mm aluminum with a 1 mm wall thickness) to collapse on itself (bottom three pictures here), becoming essentially a twisted solid rod thanks to Lorentz forces and Ampère's Law. That may have been aided by heating, but the aluminum is quite conductive and metallurgical analysis suggested the metal didn't get hotter than 200°C. Yet he investigators were completely unable to duplicate this effect with the highest (312 kA) electrical power available to them. Some things about lightning remain mysterious.The event involved a Convair aircraft, Flight 517, taking off from the Salt Lake City Airport on October 15, 1965. At the time of the event, there was some light rain in the area but apparently no lightning other than the event to be described. During takeoff, an extremely loud noise occurred. The first officer stated to the pilot that he believed they had sustained a lightning strike, subsequently confirmed by observers in the control tower, based on his observation of a blue-white glow around the nose of the aircraft at the time of the explosion. The aircraft returned to the airport. Three large holes were found in the runway which exactly matched the dimensions of the two main landing gear and the nose wheel. The largest hole, under the right main gear, was nearly 2 m in diameter and 15–20 cm deep. Pieces of asphalt as large as 0.3 m had been hurled 30–50 m down the runway. The aircraft suffered numerous burns to the wheel rims and fuselage just aft of the nose wheel-well. The rotating beacon, the grounding wire on the right main gear, and the fixed vertical stabilizer cap were burned off
ludi wrote:I remember reading about that one (or one very much like it). As I recall they had to strip all the wiring out of the house and all the appliances had to be replaced. (If it's the one I'm thinking of I recall that the strike entered through the dryer vent and the dryer, completely vaporizing that accordion-style dryer hose).Sounds like you had a (comparatively rare) positive strike, to dig up the root like that. But yes, induced potential in building wiring is quite common for nearby strikes. Could have been worse, though: about fifteen years ago, there was a strong positive strike that took out a tree near Ft. Collins, Colorado and dug up the roots in a similar fashion to what you saw, but it induced a high enough potential in the adjacent house that it blew up all of the electrical wiring. There were pictures in the paper showing ray gun blast patterns around every single light figure and coverplate in the structure.
just brew it! wrote:Wow, that's really cool. Now I want to make some of those and do a little casual "magic" with coins I borrow from others. I'm surprised they don't have any Canadian coins (the "Toonie" would be particularly interesting)The bit about the compressed aluminum tube reminded me of this site.
A Canadian "Toonie" has the center loosened at 6,500 joules, but the center is still held captive. At 14,000 joules, Rob Stephens, a friend and fellow coin shrinker from Ontario, Canada was able to separate the coin into two independent pieces. However, his blast shield failed during the shot, and he sustained considerable damage to his lab from shrapnel from the exploding work coil