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Kimmo

High voltage musings

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So the missus was coming home during a lightning storm, and she's prone to worry, and told me how she was a bit uneasy. 

But I was all, hey don't sweat it, you're safe in a Faraday cage, and she kinda knew that... But then I realised a convertible probably doesn't count as a Faraday cage. 

What do you reckon? Maybe if the roof is wet? 

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i dont know.  but even if the hole drastically diminishes the faraday cage effect her body is still surrounded by paths of less resistance.

 

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9 minutes ago, scruffy1 said:

umm, the rubber tyres are insulators

so are the dielectrics of capacitors...

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Normal hardtop car = I wouldn't much worry but still avoid metal parts.

Convertible = yeah, worry a bit.

But in the normal course of things in a built up area or country road there'd be more likely targets around most of the time.

Lightning though can reak havoc in it's journey - I do the occasional insurance reporting of tech items in the course of work.  Attended 2 or 3 recent ones which were lightning strikes nearby through phone or electrical.
Point of entry for one was likely the ADSL modem, there were exploded bits inside (likely tantalum caps), and it no longer worked at all.  The path of destruction then went right through a smart TV, internet radio, cordless headphone set and another item or 2.

Another one was slightly less damage, it fried one ethernet port on modem but the others remain fine (I'm thinking it probably uses opto-isolators) and fried the ethernet port on the TV.

In both cases, none or only partial surge protection in use.  So obviously an idea to have such sacrificial devices for not only electrical but also phone and TV antenna.
Also a valid argument for using Wifi rather than physical cabled connections if practical.

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30 minutes ago, Rybags said:

Also a valid argument for using Wifi rather than physical cabled connections if practical.

Hmm, yeah - damn straight. Wi-Fi dongles are cheap as hell. 

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But the problem remains - plenty of gear is still on "n" - get a couple of 4K streams going and it saturates the bandwidth pretty fast.

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Enough of a concern only if way out the open and the highest object around but as Scruffy says, cars are insulated from the ground to a degree but not really, steel belts and moisture etc. It is the car behaving like a Faraday cage, even a convertible, that protects the occupants in the very rare case it was actually struck in the first place.

Strikes on cars are extremely rare as in almost unheard of events.

Lightning is bloody capricious stuff though, seen tracks down computer room walls that for no obvious reason zigged around a rack to ground out on a trolley and a mate once had a bolt come through a window out of a clear sky and zap a PDP-11 right behind him - brown trouser time 🙂

Cheers

 

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2 minutes ago, chrisg said:

Lightning is bloody capricious stuff though,

Certainly seems to be. Years ago had one of our private power poles hit and it took down all the wires on the pole as well as splintering the top of the pole.

At the end of the line (about 200 metres) it didn't touch the water supply pump. In the cowshed (about 200 metres in the other direction) took out some ceramic fuses and bakelite light switches blew an electric fencer off the wall (actually snapped the plastic mounting bracket) and at my house (another hundred metres away) destroyed a router and the Telstra ISDN modem but nothing else.

The Telstra tech who came to replace the modem said he had seen strikes in town that seemed to do no damage to the nearby houses but a house a block or two away had major electronics damage. Weird alright.

Oh and cop a load of this

 

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19 minutes ago, chrisg said:

very rare

Yeah, I'd be more worried about having a stroke, I think

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6 hours ago, @~thehung said:

because its cool

Yes it is, very cool.

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On 1/30/2019 at 3:25 PM, Kimmo said:

 But then I realised a convertible probably doesn't count as a Faraday cage. 

What do you reckon? Maybe if the roof is wet? 

About as good as riding a motorbike perhaps

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