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View Full Version : Lightning, it hurts so good!! An example of why to opto-isolate



steve_b
08-04-2006, 02:00 AM
Well, we took a lightning hit at work a couple weeks ago and the radar went down.
No obvious poofs or smoke, but enough energy came down the signal lines that the electronics died.

I was just walking in to the room where the electrical conduits come in to the building from the tower.· Big flash, boom and I saw an arc flash across the 90deg elbow in the conduit.· Uh...diapers please! haha

Anyhow, some of that energy went in to the ground where we have buried cable going to a logger/wind tower.· The comms got knocked out and I just got around to looking at it.· Here's a picture of the MAX232 chip.· Big chunk blasted out....note the discolouration on pin 7 (rs232out), no doubt an arc from here across the chip...this was the main comm line pin.· I didn't have any MOV's/Tranzorbs or isolation on the line, just went with a cheapo IC that I could replace on spec.

Anyhow, no damage to anything else, but it is a pain....I'm looking in to gas arrestors (little blocks that have a chamber inside filled with some sort of ionizing gas...when the differential between your signal line and ground grows beyond it's threshold it ionizes and makes a short to ground and protects your gear).
TII is where we used to get them....I'll have to do some looking around!· These things will take multiple hits rather than one (for tranzorb/mov)....



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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

stamptrol
08-04-2006, 02:11 AM
Steve,

A little bit of epoxy to fill that hole in and the chip will be good as new!!

Tom

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Tom Sisk

http://www.siskconsult.com
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Kevin Wood
08-05-2006, 02:26 AM
Epoxy?!?!?!?

What's wrong with electrical tape?

pjv
08-05-2006, 11:07 AM
Hi Steve;

The gas tubes work, but are not very fast. A transorb switches in mere nanoseconds, and would be a good thing to put in parallel with the tubes.

Cheers,

Peter (pjv)

Loopy Byteloose
08-05-2006, 08:26 PM
Lightning is nasty stuff. Here is an odd question.

Did you smell it?

Back in July of 1994, I had just arrived in Taiwan and was wadding through a meter of water in downtown Kaohsiung while carrying my wallet and shoes in one hand and an open umbrella in the other.· This was my first big typhoon experience.

Suddenly an enormously bright flash and a thunderclap. All the autos parked nearby started their car alarms. And the hair on my arms was standing on end.

I concluded the strike was close because I could smell ozone. Also I was about 10 meters from telephone relay tower.

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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········


···················· Tropical regards,····· G. Herzog [·黃鶴 ]·in Taiwan

PJ Allen
08-06-2006, 05:52 AM
Kramer said...
wadding (sic) through a meter of water in downtown Kaohsiung while carrying my wallet and shoes in one hand and an open umbrella in the other
There's a picture.
How tall are you, anyway?·
You're practically swimming·in "flood water" (and I'm being nice, because I know all about the sanitation situation in Taiwan) and·you're afraid your shirt might get wet?· In such a situation, your saving grace was not that you'd "escaped" a lightning strike (if it had been a local strike, anywhere near, you wouldn't be posting here),·but that you'd recently had all of your shots.