Weather station and lightning

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

| 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

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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.

| 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

| 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.

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.

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:

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.

Noth> An ordinary opto-coupler WILL NOT BLOCK LIGHTNING! Most are

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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..

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

Good idea.

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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.

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

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.

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. ======

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

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On Sun, 12 Dec 2004 14:45:21 -0500, "mark thomas" put finger to keyboard and composed:

Have you considered wireless transmission?

- Franc Zabkar

On Sun, 12 Dec 2004 13:45:43 -0800, "Watson A.Name - \"Watt Sun, the Dark Remover\"" put finger to keyboard and composed:

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

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(!)