lightening damage prevention?

[lrgiese]

I have/had a working 1-wire sensor network using hobby board parts. RS-232 to 1wire adaptor, 6 port 1-wire hub and several temp and temp/humidity sensors(six total sensors units, one outside). Cabled with standard Cat5 cable. I then wrote my own hvac control system after extracting the data using Dan Klein's thermd program.

Last night a severe t-storm went through the area and there was alot of strong cloud to ground lightening strikes. I noticed that the A/C was off and the house was a touch on the warm side. Hmmm, after getting an alert that Thermd could not find all my sensors, I discovered the entire 1-wire network was down. I have parts on order, not sure to what extent the damage is yet as I did not have spare parts for it on hand... (silly me, once I find the issues, I will make sure I have spares)

But is there anything that can be done to mimimize lightening damage? We did not take a direct hit. We had one motion sensor light fixture go out, so I am thinking it was damage from induced voltages from the close strikes along with the strength of them.

Any thoughts or experience to share? I would rather not have this happen again.

As soon as I get my order from Hobby Boards, I can report back the extent of the damage.

Lyle

 

[apostolakisl]

Very complicated subject.

The basic idea is, everything is tied to a common ground. The ground is connected to Earth as a single unit.

What you want is for the entire house and everything in it to rise and fall with potential (volts) together. You want to avoid current and if the entire house carries the exact same charge, no current will flow. Also, you need to look at all of your utility connections or other wires/pipes exiting the house.

Saying that is one thing. Actually acomplishing that is another. Avoiding wires out in the yard is a start.

Going to the other end of extreme would be to drive grounding rounds every few feet apart around the entire perimeter of your house, tying them all together and tying your house ground into it. This makes your house into a "boat" of sorts "floating" in the sea of electric potential. When it is tied together like that, the entire house will rise and fall together nice and smooth and even rather than getting "tossed about".

The other thing of course is to consider that the surge didn't get induced directly on your house, but on a utility wire nearby and then traveled into your house. To fight that, get a whole house surge supressor on the AC and surge supressors on your telephone/cable connections.

 

[Del91574]

Common good ground connection to a single point connected to a proper ground rod would be best, with a low impedence >25 Ohms on the electrical connection. Other than the extreme of a ground ring, which I've only seen a handful of times.

a CWG is less than desirable but better than nothing in this case.

Suppression on all utilities that enter the house, bonded to the same ground as everything else.

Induced currents will also cause damage, but short of going nuts, not too much you can do. Lightning will do things you'll never expect.

 

[lrgiese]

Just to add a bit to this story...

I have a telco background and know the concepts of grounding in a telco central office. I have two racks of equipment in my basement. I ran two dedicated 20 amp circuits to Orange outlets. Because of the distance from the utility box and this rack I pulled in 8 gauge hot & neutral plus a 10 gauge ground(in conduit). All equipment in the rack is then powered from those circuts via 2 large APC UPS's(one in each rack).

Have a ground rod attached to main panel and I have opened, cleaned and put anti-oxident grease on the clamp and exposed wires. Next to the meter, I have a 15kw generator(auto-start/transfer). City inspector insisted on putting in a ground rod just for the generator, was not allowed to connect to ground rod at power meter...

The wire going to the sensors is not that long. Probably the longest is 50ft of cat 5, but not shielded nor in conduit.

Not this time around, but in the past I lost a serial port that is attached to an Adtran channel bank. I have a couple of POTS lines connected to the channel bank and then T1 to an asterisk server. I found that the Digium cards did not give me good echo control while the channel bank is perfect.

Lyle

 

[JimS]

The other responses about single point grounding, etc. are right on. That is very important and they have made some good points so I don't have much to add.

I suspect you may have picked up transients on the one wire cable itself though which is a bit different matter. I don't have any experience with one wire but it looks like others have some good information on the net. Don't mean to be flippant but...

http://lmgtfy.com/?q=1+wire+surge+protection

Lots of good DIY info.

 

[lrgiese]

Got my parts order from Hobby Board and the RS-232 adaptor DS9097U died. All is working now.

Lyle

 

[lrgiese]

The other responses about single point grounding, etc. are right on. That is very important and they have made some good points so I don't have much to add.

I suspect you may have picked up transients on the one wire cable itself though which is a bit different matter. I don't have any experience with one wire but it looks like others have some good information on the net. Don't mean to be flippant but...

http://lmgtfy.com/?q=1+wire+surge+protection

Lots of good DIY info.

More specifically:

http://gladstonefamily.net/surge-protection.html

After reading this one, now we know why...

I placed a parts order with Digikey this afternoon also.

Thanks,
Lyle

 

[BuGless]

Hobbyboards should sell something like this.

 

[BuGless]

With regard to ESD protection, a part which is both affordable and has excellent specs: 0603ESDA