Lightning Hazards Info for newbies in "wired mode".
- 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
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.
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
> In Australia, and I'd imagine the US, phone lines are not grounded
> the house, but at the exchange. It is totally verboten to connectthe
> phone line to anything related to ground or mains at the house.strike
> 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
> is an exposed circuit outside at one end, and a PC connected tomains
> ground at the other. A strike nearby will induce a current (andhence
> voltage) in the connecting cable. A direct hit will apply extremethe
> 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
> sender box makes sense too.house?
> 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.
> > Does anyone know how the phone lines are grounded coming into a
> > The cable is just a phone cord, perhaps if it is run through somekind
> > of a grounding block where it enters the house...
> > Larry