USB port blew -- why?

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
> glass-encapsulated diode from his pile-o-parts, bent the
> leads about 3/4" apart and grabbed it with long-nosed pliers.
> He then shoved it into the mains outlet and sure enough it lit
> up, and quite brightly too! He did make some comment about
> his reliability problems, or some such. I just about PMP. ;-)

Well, OK. But now traffic engineers are installing LED traffic
light replacement bulbs specifically _for_ reliability?

Daisy chain a dozen or so LEDs all facing one way, and plug it in.
Face another set the other way. Parallel as many as you need for
brightness. Nicely vibration resistant.

-- Robert

 

[jad]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

reliability and power consumption,,,,,,,,,,,,,,,,
speaking of street lights I was reading yesterday that a number a US
cities are being investigated about their manipulation of the traffic
signals to burn more gas, thus creating revenue for the city, (gas
city level taxes)


"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message
news:wCa9d.1670$Lk3.801@newssvr12.news.prodigy.com...
> In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
> > glass-encapsulated diode from his pile-o-parts, bent the
> > leads about 3/4" apart and grabbed it with long-nosed pliers.
> > He then shoved it into the mains outlet and sure enough it lit
> > up, and quite brightly too! He did make some comment about
> > his reliability problems, or some such. I just about PMP. ;-)
>
> Well, OK. But now traffic engineers are installing LED traffic
> light replacement bulbs specifically _for_ reliability?
>
> Daisy chain a dozen or so LEDs all facing one way, and plug it in.
> Face another set the other way. Parallel as many as you need for
> brightness. Nicely vibration resistant.
>
> -- Robert
>
>

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"JAD" <Kapasitor@coldmail.com> top posted:

>reliability and power consumption,,,,,,,,,,,,,,,,
>speaking of street lights I was reading yesterday that a number a US
>cities are being investigated about their manipulation of the traffic
>signals to burn more gas, thus creating revenue for the city, (gas
>city level taxes)

Right. And OJ isn't guilty.

 

[jad]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

huh?


he is guilty (whatever connection there is to that) and so are the
cities involved in the lighting scam......\ or are you saying that its
impossible? very naive...but it was a side note and not meant for
debate.


"chrisv" <chrisv@nospam.invalid> wrote in message
news:2b9bm0l9b1f3sr4qs72t135rgvngcpjo1l@4ax.com...
> "JAD" <Kapasitor@coldmail.com> top posted:
>
> >reliability and power consumption,,,,,,,,,,,,,,,,
> >speaking of street lights I was reading yesterday that a number a
US
> >cities are being investigated about their manipulation of the
traffic
> >signals to burn more gas, thus creating revenue for the city, (gas
> >city level taxes)
>
> Right. And OJ isn't guilty.
>

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

Robert Redelmeier wrote:

> In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
>
>>glass-encapsulated diode from his pile-o-parts, bent the
>>leads about 3/4" apart and grabbed it with long-nosed pliers.
>>He then shoved it into the mains outlet and sure enough it lit
>>up, and quite brightly too! He did make some comment about
>>his reliability problems, or some such. I just about PMP. ;-)
>
>
> Well, OK. But now traffic engineers are installing LED traffic
> light replacement bulbs specifically _for_ reliability?

You missed the 'joke'. It wasn't an 'LED', it was a 'diode' raised to
catastrophic incandescence from being fried to hell and back. Of course,
one *could* call it a 'light emitting diode', for a few milliseconds, but
it hardly works on the same principle.

>
> Daisy chain a dozen or so LEDs all facing one way, and plug it in.
> Face another set the other way. Parallel as many as you need for
> brightness. Nicely vibration resistant.
>
> -- Robert
>
>

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Wed, 06 Oct 2004 23:50:49 -0500, David Maynard wrote:

> keith wrote:
>
>> On Wed, 06 Oct 2004 15:56:56 +1000, Lionel wrote:
>>
>>
>>>Kibo informs me that keith <krw@att.bizzzz> stated that:
>>>
>>>
>>>>On Tue, 05 Oct 2004 03:47:13 +0000, NSM wrote:
>>>>
>>>>>"keith" <krw@att.bizzzz> wrote in message
>>>>>newsan.2004.10.05.01.56.40.575135@att.bizzzz...
>>>>>
>>>>>| So do engineers when they're bringing up a system where all
>>>>>| of the tantallums were inserted backwards. You want to see fireworks!
>>>>>| (well,it was 25 years ago - I've mostly recovered and the tinninus
>>>>>| isn't so bad. <twitch>)
>>>
>>><grin> They don't smell too good either.
>>
>>
>> Hot electricity never smells good. ...ever notice that? ;-)
>>
>>
>>>>>I recall being told of a large TTL circuit board which was powered up with
>>>>>reverse polarity. This was noticed due to the considerable amount of heat
>>>>>being given off.
>>>>>
>>>>>Everyone was mystified when the correctly rewired board worked OK. I guess
>>>>>TTL is a little more tolerant than is generally believed.
>>>>
>>>>TTL protection diodes are as strong as moose!
>>>
>>>Well, the individual diodes aren't all that strong, but there's one on
>>>every single I/O pin on every chip, so on a big PCB, the load will be
>>>spread over a *lot* of diodes.
>>
>>
>> I've pumped several amps though individual ones, but you're right with
>> thousands in parallel it's tough to smoke 'em. It *can* be done, but...
>>
>>>> Unless the chips got hot
>>>>enough to let the magic smoke out, they'll likely survive, though
>>>>perhaps somewhat injured.
>>>
>>>Yup. The best I've personally seen was the time I accidentally plugged a
>>>2716 EPROM backwards into a programmer. It lit up like a xmas tree
>>>through the UV window, but worked fine when I turned it around the right
>>>way.
>>
>>
>> Oh, my! I've never done that. However...
>>
>> One time back in the '60s (when I was a mere lad playing with electronics)
>> a friend and I were talking about these new-fangled LED thingys. He said
>> they were no big deal and had them for some time. He then took a
>> small-signal glass-encapsulated diode from his pile-o-parts, bent the
>> leads about 3/4" apart and grabbed it with long-nosed pliers. He then
>> shoved it into the mains outlet and sure enough it lit up, and quite
>> brightly too! He did make some comment about his reliability problems, or
>> some such. I just about PMP. ;-)
>>
>
> A bit on the high side with power consumption too, I'll wager. hehe

Given the temperature, it was likely more efficient than the average
incandescent bulb. ;-)

--
Keith

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Thu, 07 Oct 2004 12:27:08 +0000, Robert Redelmeier wrote:

> In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
>> glass-encapsulated diode from his pile-o-parts, bent the
>> leads about 3/4" apart and grabbed it with long-nosed pliers.
>> He then shoved it into the mains outlet and sure enough it lit
>> up, and quite brightly too! He did make some comment about
>> his reliability problems, or some such. I just about PMP. ;-)
>
> Well, OK. But now traffic engineers are installing LED traffic
> light replacement bulbs specifically _for_ reliability?

They're more efficient too. LEDs are a few times more efficeint and the
monochromatic light is particularly suited for traffic lights. OTOH, in
the '60s...

Also note that some cars are using LEDs for tail lights. Headlights
are still a bit of a problem.

> Daisy chain a dozen or so LEDs all facing one way, and plug it in. Face
> another set the other way. Parallel as many as you need for brightness.
> Nicely vibration resistant.

Hmm, face another set the other way and you can plug 'em into AC. I
thought these things were a tad more specialized than that though.

--
Keith

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Thu, 07 Oct 2004 08:19:53 -0700, JAD wrote:

> reliability and power consumption,,,,,,,,,,,,,,,,
> speaking of street lights I was reading yesterday that a number a US
> cities are being investigated about their manipulation of the traffic
> signals to burn more gas, thus creating revenue for the city, (gas
> city level taxes)

I thought that was all about red-light cameras (a real scam!).

--
Keith

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Thu, 07 Oct 2004 19:39:18 -0500, David Maynard wrote:

> Robert Redelmeier wrote:
>
>> In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
>>
>>>glass-encapsulated diode from his pile-o-parts, bent the
>>>leads about 3/4" apart and grabbed it with long-nosed pliers.
>>>He then shoved it into the mains outlet and sure enough it lit
>>>up, and quite brightly too! He did make some comment about
>>>his reliability problems, or some such. I just about PMP. ;-)
>>
>>
>> Well, OK. But now traffic engineers are installing LED traffic
>> light replacement bulbs specifically _for_ reliability?
>
> You missed the 'joke'. It wasn't an 'LED', it was a 'diode' raised to
> catastrophic incandescence from being fried to hell and back. Of course,
> one *could* call it a 'light emitting diode', for a few milliseconds, but
> it hardly works on the same principle.

I'm quite sure Robert got it. He knows my silliness well (though may not
admit it

<snip>

--
Keith

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

keith <krw@att.bizzzz> wrote in
newsan.2004.10.07.02.30.33.895207@att.bizzzz:

> One time back in the '60s (when I was a mere lad playing with
> electronics) a friend and I were talking about these new-fangled LED
> thingys. He said they were no big deal and had them for some time. He
> then took a small-signal glass-encapsulated diode from his
> pile-o-parts, bent the leads about 3/4" apart and grabbed it with
> long-nosed pliers. He then shoved it into the mains outlet and sure
> enough it lit up, and quite brightly too!

I once had a bizarre failure of a USR modem immediately after a
thunderstorm. You would think it would be a typical frying of the phone
circuits etc. When I checked it out, the relay coil was open circuit. This
of course is on the control cctry and not the telecom side. I replaced the
relay and it worked perfectly. Can only assume it was a coincidence since
if it was a voltage surge it should have taken out the semis on the relay
drive.

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"Geoff C" <notinterestedin@spa.comm> wrote in message
news:yMj9d.4630$pl.67354@nasal.pacific.net.au...
> keith <krw@att.bizzzz> wrote in
> newsan.2004.10.07.02.30.33.895207@att.bizzzz:
>
> > One time back in the '60s (when I was a mere lad playing with
> > electronics) a friend and I were talking about these new-fangled LED
> > thingys. He said they were no big deal and had them for some time. He
> > then took a small-signal glass-encapsulated diode from his
> > pile-o-parts, bent the leads about 3/4" apart and grabbed it with
> > long-nosed pliers. He then shoved it into the mains outlet and sure
> > enough it lit up, and quite brightly too!
>
> I once had a bizarre failure of a USR modem immediately after a
> thunderstorm. You would think it would be a typical frying of the phone
> circuits etc. When I checked it out, the relay coil was open circuit. This
> of course is on the control cctry and not the telecom side. I replaced the
> relay and it worked perfectly. Can only assume it was a coincidence since
> if it was a voltage surge it should have taken out the semis on the relay
> drive.
>

Lightning can cause some very bizarre failures indeed. I had a USR modem
years ago that failed after a nearby lightning strike (rare here) and the
problem turned out to be a 10 ohm surface mount resistor with a crater in
it. Replaced it with a normal resistor and it worked fine until it was
retired years later.

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"James Sweet" <jamessweet@hotmail.com> wrote in message
news:jcp9d.5644$eq1.2343@trnddc08...

| Lightning can cause some very bizarre failures indeed. I had a USR modem
| years ago that failed after a nearby lightning strike (rare here) and the
| problem turned out to be a 10 ohm surface mount resistor with a crater in
| it. Replaced it with a normal resistor and it worked fine until it was
| retired years later.

What most people think is caused by lightning is really caused by induction.
A direct lightning strike will turn your computer etc. into a pile of
bubbling slag. A strike near the phone line causing induction elsewhere will
zap things in very odd ways.

N

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
> I'm quite sure Robert got it. He knows my silliness well

Entirely too well! I'm convinced you were either trying
to demonstrate prior art or "obvious to a skilled practioner
in the art" to invalidate the LED patent, and show the
general silliness of most patents.

> (though may not admit it

Why not play the straight man?

-- Robert

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Fri, 08 Oct 2004 17:13:19 +0000, Robert Redelmeier wrote:

> In comp.sys.ibm.pc.hardware.chips keith <krw@att.bizzzz> wrote:
>> I'm quite sure Robert got it. He knows my silliness well
>
> Entirely too well! I'm convinced you were either trying
> to demonstrate prior art or "obvious to a skilled practioner
> in the art" to invalidate the LED patent, and show the
> general silliness of most patents.

Naw, just busting chops. I would *never* demonstrate such! I have such
"silliness" and a few more in the pipe. It's a profitable endeavor. ;-)

>> (though may not admit it
>
> Why not play the straight man?

Ok, perhaps I will some day! ;-)

--
Keith

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:

>
> "James Sweet" <jamessweet@hotmail.com> wrote in message
> news:jcp9d.5644$eq1.2343@trnddc08...
>
> | Lightning can cause some very bizarre failures indeed. I had a USR modem
> | years ago that failed after a nearby lightning strike (rare here) and the
> | problem turned out to be a 10 ohm surface mount resistor with a crater in
> | it. Replaced it with a normal resistor and it worked fine until it was
> | retired years later.
>
> What most people think is caused by lightning is really caused by induction.
> A direct lightning strike will turn your computer etc. into a pile of
> bubbling slag. A strike near the phone line causing induction elsewhere will
> zap things in very odd ways.

Not really. Most of the lightning damage is caused by ground currents
going where you don't want them to go. A strike on a tree in the back
yard can fry all electronics in the house ifthe grounds aren't done
right. There should only be *one* ground (floating boats theory) and if
there must be more they must all be bonded together with some serious
conductors (see: floating boats).

--
Keith

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"keith" <krw@att.bizzzz> wrote in message
newsan.2004.10.09.02.13.52.928793@att.bizzzz...
| On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:
....
| > What most people think is caused by lightning is really caused by
induction.
| > A direct lightning strike will turn your computer etc. into a pile of
| > bubbling slag. A strike near the phone line causing induction elsewhere
will
| > zap things in very odd ways.
|
| Not really. Most of the lightning damage is caused by ground currents
| going where you don't want them to go. A strike on a tree in the back
| yard can fry all electronics in the house ifthe grounds aren't done
| right. There should only be *one* ground (floating boats theory) and if
| there must be more they must all be bonded together with some serious
| conductors (see: floating boats).

Yes. Induction.

N

 

[keith]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

On Sat, 09 Oct 2004 02:34:47 +0000, NSM wrote:

>
> "keith" <krw@att.bizzzz> wrote in message
> newsan.2004.10.09.02.13.52.928793@att.bizzzz...
> | On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:
> ...
> | > What most people think is caused by lightning is really caused by
> induction.
> | > A direct lightning strike will turn your computer etc. into a pile of
> | > bubbling slag. A strike near the phone line causing induction elsewhere
> will
> | > zap things in very odd ways.
> |
> | Not really. Most of the lightning damage is caused by ground currents
> | going where you don't want them to go. A strike on a tree in the back
> | yard can fry all electronics in the house ifthe grounds aren't done
> | right. There should only be *one* ground (floating boats theory) and if
> | there must be more they must all be bonded together with some serious
> | conductors (see: floating boats).
>
> Yes. Induction.

No, *NOT* induction! It's simple resistance. You simply don't want to
be in the middle. The idea is to float, like a boat.

--
Keith

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

keith wrote:

>
> No, *NOT* induction! It's simple resistance. You simply don't want to
> be in the middle. The idea is to float, like a boat.
>


Brings to mind an interesting question. Out here in well and septic
country, the code authorities make us ground the electrical system with
a UFER ground (copper wire buried in concrete, buried in the ground).
But they also make us ground our well pumps to the steel well casing.

Which gives us.... competing grounds with different ground potentials.

I wonder how much trouble that causes with lightning?

-Chuck

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"Chuck Harris" <cf-NO-SPAM-harris@erols.com> wrote in message
news:r4-dnUqY07Sz_vrcRVn-gg@rcn.net...

| Brings to mind an interesting question. Out here in well and septic
| country, the code authorities make us ground the electrical system with
| a UFER ground (copper wire buried in concrete, buried in the ground).
| But they also make us ground our well pumps to the steel well casing.
|
| Which gives us.... competing grounds with different ground potentials.
|
| I wonder how much trouble that causes with lightning?

I'd certainly want to bond the well to the UFER ground system. IME any
system with different grounds allowing potential differences is dangerous.

N

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

NSM wrote:
> "Chuck Harris" <cf-NO-SPAM-harris@erols.com> wrote in message
> news:r4-dnUqY07Sz_vrcRVn-gg@rcn.net...
>
> | Brings to mind an interesting question. Out here in well and septic
> | country, the code authorities make us ground the electrical system with
> | a UFER ground (copper wire buried in concrete, buried in the ground).
> | But they also make us ground our well pumps to the steel well casing.
> |
> | Which gives us.... competing grounds with different ground potentials.
> |
> | I wonder how much trouble that causes with lightning?
>
> I'd certainly want to bond the well to the UFER ground system. IME any
> system with different grounds allowing potential differences is dangerous.

It is bonded back at the service panel with a #10ga copper wire. The pipe
to the well is plastic.

The last time we got a direct hit by lightning, the water changed its tint
for several days. It went from grey, to yellow/orange. We lost a chunk of
terracotta flue liner on that one, and several appliances.

-Chuck

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

In comp.sys.ibm.pc.hardware.chips Chuck Harris <cf-NO-SPAM-harris@erols.com> wrote:
> It is bonded back at the service panel with a #10ga copper
> wire. The pipe to the well is plastic.

#10 is good, #00 is better~!

> The last time we got a direct hit by lightning, the water
> changed its tint for several days. It went from grey,
> to yellow/orange. We lost a chunk of terracotta flue liner
> on that one, and several appliances.

Perhaps you should install a whole-house surge protector on
the panel (~$50). You lose two-wire appiances through ground
vs power surges. Your pole transformer and it's ground is
probably a ways away.

-- Robert

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

Robert Redelmeier wrote:
> In comp.sys.ibm.pc.hardware.chips Chuck Harris <cf-NO-SPAM-harris@erols.com> wrote:
>
>>It is bonded back at the service panel with a #10ga copper
>>wire. The pipe to the well is plastic.
>
>
> #10 is good, #00 is better~!
>
>
>>The last time we got a direct hit by lightning, the water
>>changed its tint for several days. It went from grey,
>>to yellow/orange. We lost a chunk of terracotta flue liner
>>on that one, and several appliances.
>
>
> Perhaps you should install a whole-house surge protector on
> the panel (~$50). You lose two-wire appiances through ground
> vs power surges. Your pole transformer and it's ground is
> probably a ways away.
>
> -- Robert

The lightning hit the chimney cap, went down the brickwork of the
chimney, and entered the bond system by way of an outdoor flood
light that is mounted next to the chimney. The current zapped
a 3 wire treadmill (7 ft from floodlight), and flipped the breaker
on the circuit that had the flood light. No damage through the power
to any other devices. However, the induced surge in the security
wire/telephone wires that pass through the house blew two modems and
a phone answering machine. But not a cordless phone, or any other
telephones. One modem carried its surge into the RS232 line, and
toasted the drivers and uart on a Dell motherboard. I lost a
HPJetDirect card too... a failure in the 10baseT driver circuits.

Our power is buried, and the transformer is one of those steel
enclosed boxes about 70 feet from the house.

Fun!

One thing I have never been able to determine is whether we would
be safer with a lightning rod system, or without. My insurance
company is silent on this issue... you pay the same rates either
way. In our area, there have been several houses and barns that
have burned down,due to lightning strikes, and they had lightning
rod systems. Anecdotal evidence, to be sure.

-Chuck Harris

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

In comp.sys.ibm.pc.hardware.chips Chuck Harris <cf-NO-SPAM-harris@erols.com> wrote:
> The lightning hit the chimney cap, went down the brickwork of the

All bets are off in a direct strike. Common grounding only
reduces the damage from a nearby strike.

> to any other devices. However, the induced surge in the
> security wire/telephone wires that pass through the house
> blew two modems and a phone answering machine. But not a
> cordless phone, or any other telephones. One modem carried

I still doubt this was induced _unless_ 1) Phone was
run parallel to the floodlight circuit for some distance
and 2) Phone and power were on the same groundstake.

Most likely, phone was on it's own groundstake, so anything
bonded to power ground would get fried by the ground
differential between power and ground.

> Our power is buried, and the transformer is one of those
> steel enclosed boxes about 70 feet from the house.

Good!

> One thing I have never been able to determine is whether
> we would be safer with a lightning rod system, or without.

Hard to say. A lightening rod system could be dangerous
if the insulation was insufficiently heat-resistant.

-- Robert

 

[Guest]

Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

"Chuck Harris" <cf-NO-SPAM-harris@erols.com> wrote in message
news:MLKdneY2I7yE_vXcRVn-rQ@rcn.net...
.....
| One thing I have never been able to determine is whether we would
| be safer with a lightning rod system, or without. My insurance
| company is silent on this issue... you pay the same rates either
| way. In our area, there have been several houses and barns that
| have burned down,due to lightning strikes, and they had lightning
| rod systems. Anecdotal evidence, to be sure.

Lightning strikes up from the best point on the ground. IMO, the safest way
is to install a lightning rod away from the house (separately guyed) but
close enough to protect your property. Just don't stick your tongue on it
when it's stormy out!

N

 

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Archived from groups: sci.electronics.repair,alt.comp.hardware.pc-homebuilt,comp.sys.ibm.pc.hardware.chips (More info?)

Robert Redelmeier wrote:

> All bets are off in a direct strike. Common grounding only
> reduces the damage from a nearby strike.
>
....
> I still doubt this was induced _unless_ 1) Phone was
> run parallel to the floodlight circuit for some distance
> and 2) Phone and power were on the same groundstake.

When I built my house, I wanted some wiring to be available
in all rooms, so I ran loops of 25 pair CAT3 telephone cable
around the outside perimeter of each floor in the house. The
loops end at punch down (66) blocks in the basement. There
are no sections of the loops that run parallel to the power wiring
separated closer than 1 foot. There is only one area where the
loops run perpendicular to the power wiring, and that is where the
power cables drop to the service panel. At these points, the loops
are a couple of inches away from the power cables.

One of the damaged modems was connected to the loop that ran
nearest to the lightning strike. It was a zoom modem ISA bus
modem, and its protection circuitry shorted out. No damage
was done to the computer.

The other damaged modem was a $15 Centdyne. It had a chip inductor
in series with one side of the line that was completely blown away.
The MOV that was across the line was still OK. The current that entered
this modem would have had to pass through about 100 feet of
#24 gauge wire, yet it still had enough zap to burn that inductor
off of the board (and destroy the modem's chip set, and the computer's
RS232 drivers and uart)
>
> Most likely, phone was on it's own groundstake, so anything
> bonded to power ground would get fried by the ground
> differential between power and ground.

Since I did the power and telephone work, they are both grounded
to the UFER ground at the service panel, which is where they enter
the house. The nearest power pole is 600 feet away. So there is
no point in the power grid within 600 feet where lightning could
enter the system... other than my house.

>>One thing I have never been able to determine is whether
>>we would be safer with a lightning rod system, or without.
>
>
> Hard to say. A lightening rod system could be dangerous
> if the insulation was insufficiently heat-resistant.

What seems to happen, anecdotally, is the rods conduct the
bolt, and burn the roof where the ground wires run along
the ridge... even though the ground wires for the rods typically
are held 1 foot above the roof.

What I am thinking of doing is adding a lightning rod to the
masonry chimney structure. It is the highest point on the house,
and in the vicinity. I will give it a decent UFER ground
of its own, a few dozen feet from the house. My hope is this
will protect the chimney, but will not endanger the rest of
the house.

-Chuck Harris