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Lightning Hazards Info for newbies in "wired mode".

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  • wuhu_software
    In case there are new users who have recently set up La Crosse weather stations in wired mode (wire between the console and the remote thermo unit), I thought
    Message 1 of 1 , Feb 1, 2007
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      In case there are new users who have recently set up La Crosse
      weather stations in wired mode (wire between the console and the
      remote thermo unit), I thought it would be best to share this
      information .

      Here is a thread from the open2300/La crosse group.

      ---

      I have to agree about running wirelessly to spare your computer from
      nearby lightning strikes. Since there are probably a few new people in
      the list since Christmas, I thought I would give a bit more detail
      about the lightning situation and La Crosse units.

      Over the past couple years, there have been several reports of La
      Crosse users losing their consoles and/or PC serial ports after a
      nearby lightning strike. I am kind of surprised that the entire
      motherboard was not fried if the serial port was taken out but I
      guess that is a whole different topic.

      Because of the scheme used by La Crosse, at least one of your serial
      port lines is effectively extended all the way to the wind sensor,
      making at a nice antenna for EM energy induced by lightning.

      Last year, I had a nearby lightning strike (within 100ft I would
      guess), the serial port surge protector saved my serial port and more
      importantly my PC, but fried the console. The surge did not damage the
      serial port protector itself, and the remote thermo unit and wind
      sensor were fine. My results may not be typical, but I am glad that I
      had some minimal protection. Replacing a console is much much cheaper
      than replacing a PC.

      If you are in a region where you get a lot of lightning, and you are
      running wired mode, be prepared to switch over to wireless mode.
      Unless you plan on jumping out of bed in the middle of the night to
      switch over, you might want to consider some *minimal* form of
      protection like the protector mentioned below.

      Here is the company I purcashed mine from, type sp103 in the search
      box to find it. It is the DB-9 inline version.

      http://www.mc3llc.com/ <http://www.mc3llc.com/>

      Description: DB9 RS232 Serial DataLine Surge Protector - This DataLine
      Surge Protector protect your serial port against power surges. It has
      extremely sensitive, state of the art avalanche-diode technology. It
      has high speed throughput, automatic reset after surge, rugged &
      stylish with easy In-Line installation and negligible signal loss.


      --- In Lacrosse_weather_stations@yahoogroups.com, Ken
      <kenandmichele@...> wrote:
      >
      > In Australia, and I'd imagine the US, phone lines are not grounded
      at
      > the house, but at the exchange. It is totally verboten to connect
      the
      > phone line to anything related to ground or mains at the house.
      > Circuitry that the line goes into has to be isolated by at least
      > 3000v. Hence isolating transformers in modems etc.
      >
      > What you do get, are lightning arrestors, which will conduct phone
      > lines to ground in event of a very high voltage appearing on either
      > phone wire. But the arrestor device should normally be open circuit.
      >
      > The issue for the weatherstation setup in event of a lightning
      strike
      > is an exposed circuit outside at one end, and a PC connected to
      mains
      > ground at the other. A strike nearby will induce a current (and
      hence
      > voltage) in the connecting cable. A direct hit will apply extreme
      > voltage to the sensors. In that case, you would probably lose the
      > sensors, console and PC. Which is why a wireless setup is much safer
      > for the console and PC. A short run from wind and rain sensors to
      the
      > sender box makes sense too.
      >
      > A lightning arrestor on the WS connecting cables would still allow
      > voltages to go too high. To protect the PC, high-power zener diodes
      > on the serial lines to its ground would protect it against all but a
      > direct strike. These are/were used in repeaters in Oz along
      > telecommunication coaxial cables. Despite being underground, they
      > still had large currents induced into them. The zeners would protect
      > the first time, but self-destruct open-circuit.
      >
      > (Ex Telstra) Ken.
      >
      >
      > <snip>
      > >
      > > Does anyone know how the phone lines are grounded coming into a
      house?
      > > The cable is just a phone cord, perhaps if it is run through some
      kind
      > > of a grounding block where it enters the house...
      > >
      > > Larry
      > >
      > <snip>
      >
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