Weather station and lightning

[mark thomas]

I'm building a weather station that connects to my computer via RS232. The
problem is I'm worried about my computer being damaged if it gets hit by
lighning, I don't want the lighning conducting through the RS232 cabling...
A few questions...

Does grounding the weather station make it more succeptible to lightning
strikes?

If I don't care about damage to the weather station and use fiber optic
cabling which doesn't conduct electricity, is there any point in grounding
the weather station?

Even if I ground the weather station, will it still get just as damaged as
if it weren't grounded when lighting hits it?

Which of these 3 scenarios should I do?

1) Ground the weather station, but keep using RS232 cabling
2) Don't ground the weather station, but use fiber optic cabling instead
3) Ground the weather station AND use fiber optic cabling

Note: I want to do the least amount of work as possible. Converting it to
fiber optic would be a pain in the ass.

 

[Jim Thompson]

I'm building a weather station that connects to my computer via RS232. The
problem is I'm worried about my computer being damaged if it gets hit by
lighning, I don't want the lighning conducting through the RS232 cabling...
A few questions...

Does grounding the weather station make it more succeptible to lightning
strikes?

If I don't care about damage to the weather station and use fiber optic
cabling which doesn't conduct electricity, is there any point in grounding
the weather station?

Even if I ground the weather station, will it still get just as damaged as
if it weren't grounded when lighting hits it?

Which of these 3 scenarios should I do?

1) Ground the weather station, but keep using RS232 cabling
2) Don't ground the weather station, but use fiber optic cabling instead
3) Ground the weather station AND use fiber optic cabling

Note: I want to do the least amount of work as possible. Converting it to
fiber optic would be a pain in the ass.

It strikes me (pardon the unintended pun) that grounding will make
your station *more* susceptible to strikes. Although lightning rods
do bleed off charge before it gets destructive.

But I would use some kind of optical isolation to keep possible static
and/or lightning from the PC.

...Jim Thompson

 

[mark thomas]

The artist formerly known as Jim Thompson wrote:

| It strikes me (pardon the unintended pun) that grounding will make
| your station *more* susceptible to strikes. Although lightning rods
| do bleed off charge before it gets destructive.
|
| But I would use some kind of optical isolation to keep possible static
| and/or lightning from the PC.

So an electrically isolated and grounded lightning rod on the roof might
discharge some of the lightning through the nearby weather station?

What about powering it... If I have a power cord going to it, is there a way
to do this safely, or do I have to use batteries?

 

[Jim Thompson]

The artist formerly known as Jim Thompson wrote:

| It strikes me (pardon the unintended pun) that grounding will make
| your station *more* susceptible to strikes. Although lightning rods
| do bleed off charge before it gets destructive.
|
| But I would use some kind of optical isolation to keep possible static
| and/or lightning from the PC.

So an electrically isolated and grounded lightning rod on the roof might
discharge some of the lightning through the nearby weather station?

What about powering it... If I have a power cord going to it, is there a way
to do this safely, or do I have to use batteries?

As soon as you use a power cord you *are* grounded.

Place a lightning rod above it and route to power entry as others have
noted.

...Jim Thompson

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

I'm building a weather station that connects to my computer via RS232. The
problem is I'm worried about my computer being damaged if it gets hit by
lighning, I don't want the lighning conducting through the RS232 cabling...
A few questions...

Does grounding the weather station make it more succeptible to lightning
strikes?

If I don't care about damage to the weather station and use fiber optic
cabling which doesn't conduct electricity, is there any point in grounding
the weather station?

Even if I ground the weather station, will it still get just as damaged as
if it weren't grounded when lighting hits it?

Which of these 3 scenarios should I do?

1) Ground the weather station, but keep using RS232 cabling
2) Don't ground the weather station, but use fiber optic cabling instead
3) Ground the weather station AND use fiber optic cabling

Note: I want to do the least amount of work as possible. Converting it to
fiber optic would be a pain in the ass.

Ground the weather station no matter what you do. You can use
optoisolators in each of the signal and control leads of the RS-232
port. If you had the old original true IBM 8-bit ISA RS-232 card, it
had built-in current loop which had the opto's already on the board.

 

[mark thomas]

The artist formerly known as Watson A.Name - "Watt Sun, the Dark Remover"
wrote:

| Ground the weather station no matter what you do. You can use
| optoisolators in each of the signal and control leads of the RS-232
| port. If you had the old original true IBM 8-bit ISA RS-232 card, it
| had built-in current loop which had the opto's already on the board.

Geeze, I'm such an idiot, I thought opto isolators had something to do with
fiber optics.

This is what I will do, thanks.

 

[Jim Thompson]

The artist formerly known as Watson A.Name - "Watt Sun, the Dark Remover"
wrote:

| Ground the weather station no matter what you do. You can use
| optoisolators in each of the signal and control leads of the RS-232
| port. If you had the old original true IBM 8-bit ISA RS-232 card, it
| had built-in current loop which had the opto's already on the board.

Geeze, I'm such an idiot, I thought opto isolators had something to do with
fiber optics.

This is what I will do, thanks.

An ordinary opto-coupler WILL NOT BLOCK LIGHTNING! Most are perhaps
good to 3000V.

You need fiber in between to ensure enough isolation.

...Jim Thompson

 

[mark thomas]

The artist formerly known as Jim Thompson wrote:

| An ordinary opto-coupler WILL NOT BLOCK LIGHTNING! Most are perhaps
| good to 3000V.
|
| You need fiber in between to ensure enough isolation.

Ah OK, good point. Plus, all the lightning would have to do is zap the
serial cable that is running across the roof through it's flimsy protective
covering anyways.

I guess if I don't get the project done in time to make it lightening-proof
with fiber, I'll just have to take my chances. Plus, there's a tall tree in
my backyard that might look more apetizing to a lightning bolt.

 

[William P.N. Smith]

3) Ground the weather station AND use fiber optic cabling

Yeah, do that one. Yes, more work, but far more safe. Lightning
striking an ungrounded/unprotected weather station will find it's own
path to ground (through the power supply, the foil insulation on your
house, the wood, the bedroom, whatever) instead of taking the
preferred one thru the ground wire to a safe ground point.

 

[w_tom]

Lets see. The telco installs wires overhead everywhere in
town and connected to their $multimillion computer. Since
they don't use opto-isolation, then clearly telephone service
must be shutdown during every thunderstorm.

So that operators don't get shocked, 911 emergency operators
remove their headsets and leave the room during every
thunderstorm.

So that expensive transmitter equipment is not destroyed, TV
and FM radio stations atop the Empire State Building (that is
struck 25 times annually) shut down commercial broadcasting
during thunderstorms.

No. They all maintain service, do not use opto-isolation or
fiber optics, and must never suffer damage or service
interruption during a direct strike. The principles are quite
sound, well proven since before WWII, and use the one
protection component that all protection systems require - a
single point earth ground. Others such as John Popelish and
Watson A.Name are saying same. Opto isolators can only
enhance existing protection. But without that essential earth
ground, then opto isolators are quickly overwhelmed - made
ineffective.

Other sources also demonstrate the principles:

http://www.erico.com/public/library/fep/technotes/tncr002.pdf
http://www.harvardrepeater.org/news/lightning.html
http://www.telematic.com/index.htm
http://scott-inc.com/html/ufer.htm
Then the benchmark in surge protection:
http://www.polyphaser.com/ppc_technical.asp .

There is one an only one component that every lightning
protection system must have - single point earth ground.
Those other devices (protector diodes, opto-isolators,
lightning rods) and peripheral devices to the main protection
device - earth ground. Notice professionals cited above all
discuss the most important protection component - earth
ground. And only a few of your responders here also posted
different protection devices always connected to the lighting
protection component - earth ground.

Nothing will stop, block, or absorb what even 3 miles of sky
could not stop. As Ben Franklin demonstrated and as John
Popelish demonstrates in both newsgroups - divert lightning to
earth before it can get to that computer. That is what the
lightning rod or overhead catenary wire does. That is also
why the RS-232 wire must make a connection to single point
earth ground before rising back up to connect to computer.
That is even required of telephone, satellite dish, and TV
cable wire before it enters your building - for same lightning
protection reasons. There is no effective protector for
cabling to computer if it does not make a short (less than 10
foot) connection to earth ground.

 

[CWatters]

I'm building a weather station that connects to my computer via RS232. The
problem is I'm worried about my computer being damaged if it gets hit by
lighning, I don't want the lighning conducting through the RS232 cabling...
A few questions...

You are right to be concerned as PC RS232 ports are quite vunerable to
static damage.

Opto-isolators are the answer.

Google found these expensive solutions. I didn't spend time looking for
cheaper ones..

http://www.rs485.com/fullphotos/iso232wbfull.html

http://www.meilhaus.com/e_me/me9100.htm

http://www.elandigitalsystems.com/interface/ic232.php

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

RS232.

You are right to be concerned as PC RS232 ports are quite vunerable to
static damage.

They're not vulnerable at all because they use regular bipolar
transistors, not CMOS. See the specs for the 1488 and 1489 chips.

Opto-isolators are the answer.

Good idea.

 

[CWatters]

The artist formerly known as Jim Thompson wrote:

| An ordinary opto-coupler WILL NOT BLOCK LIGHTNING! Most are perhaps
| good to 3000V.

Not really expecting optos to protect against a direct strive. A direct
lightening strike is unlikely and if you get one of those you will have
bigger things to worry about

A more likely problem is "nearby" strikes or simply as build up of charge
due to a passing storm. Opto provide a good solution for that. If you are
thinking of using fibre you need to work out how you are going to power the
station. A solar cell and a battery maybe the answer.

 

[Dave VanHorn]

Martin Uman's books make good reading, though he's mostly concerned with how
lightning happens in the first place.

 

[Jerry G.]

The weather system must be properly grounded to the electrical ground
of your building. This will allow for a proper discharge path for any
static buildup, as well as proper protection from any type of lightning
strike. It is the outer metal casement that has to be properly
grounded. Your computer must also be properly electricaly grounded for
safety reasons, including protecting itself.

Lightning is so powerfull, that if here was a strike within a few
hundred feet of your home, there is a chance that more than the
computer can be damaged in the way of the electrical aparatus in your
home.

One evening a few years ago, I had an air conditioner fan motor get
burned up from a lightning strike. The strike was about 500 feet from
the bedroom window where the machine was installed.

About a year ago, I had a modem that was damaged from a lightning
storm. None of the phones were effected in our building where we live.
I had to replace the modem.

Even if you put an optical isolation system of some type, the effect of
the lightning would be so strong, it would not make any difference at
all, if there was a close enough strike.

Jerry G.

 

[Jerry G.]

Another thought... Look in to doing it wireless to the computer. There
are wireless adaptors to make serial to WiFi, and WiFi back to Ethernet
or serial. It will be the most isolated you can have, and be reliable
as well.

In fact, if you were to do a wireless Ethernet from your weather
station, you would then be able to distribute if over a home network to
a number of machines, and put the results up on an updatable web page.
Jerry G.
======

 

[Stephen Tames]

We use Amplicon Rs 422 line drivers(twisted pair lines)t RS123 converters
and they have protected the computer so far but the lightning has taken oout
the line drivers

regards, Steve (reading uni met dept)

 

[Franc Zabkar]

I'm building a weather station that connects to my computer via RS232. The
problem is I'm worried about my computer being damaged if it gets hit by
lighning, I don't want the lighning conducting through the RS232 cabling...
A few questions...

Does grounding the weather station make it more succeptible to lightning
strikes?

If I don't care about damage to the weather station and use fiber optic
cabling which doesn't conduct electricity, is there any point in grounding
the weather station?

Even if I ground the weather station, will it still get just as damaged as
if it weren't grounded when lighting hits it?

Which of these 3 scenarios should I do?

1) Ground the weather station, but keep using RS232 cabling
2) Don't ground the weather station, but use fiber optic cabling instead
3) Ground the weather station AND use fiber optic cabling

Note: I want to do the least amount of work as possible. Converting it to
fiber optic would be a pain in the ass.

Have you considered wireless transmission?


- Franc Zabkar

 

[Franc Zabkar]

If you had the old original true IBM 8-bit ISA RS-232 card, it
had built-in current loop which had the opto's already on the board.

Which one was that?

The IBM AT Tech Reference manual has a circuit diagram of the
serial/parallel adapter. It used 75154 and 75150 transmitters and
receivers, but no current loop. I repaired many of these cards where
the interface chips (and some UARTs) were taken out by lightning.


- Franc Zabkar

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Which one was that?

The IBM AT Tech Reference manual has a circuit diagram of the
serial/parallel adapter. It used 75154 and 75150 transmitters and
receivers, but no current loop. I repaired many of these cards where
the interface chips (and some UARTs) were taken out by lightning.

As I said, the 8-bit ISA bus serial only card. It had the capability of
driving the weird current loop port of the displaywriter printer, which
was a noisy daisywheel type. Thing was over $4 thousand (not including
the noise reducing enclosure) and with the Displaywriter and 8 inch disk
drive 'toaster' was over $13 thousand(!)