Re: Lightning strikes TASS Cincinnati

[Tom Droege <tdroege2@earthlink.net>]

Mike,

Wow!  I am happy that you were able to get everything working after all 
that damage.  I think there is nothing to protect the Stamp input.  The 
plan would be just to replace the Stamp computer on an occasion like this.

There was a lot of care taken on the camera design.  Most of the stuff on 
the camera head printed circuit board is there to protect from 
lightning.  So I am not surprised that the cameras got by with no 
damage.  One really has to get through a lot of protection to get at the 
CCD itself.    This is one of the reasons for putting the electronics at 
the telescope.  The vulnerable parts are the two (three counting the power) 
connecting cables to the Mark IV.  The serial cable (cheap) has no 
protection.  Well, serial ports are designed with protection resistors, but 
are not very effective for lightning.  They do fine for the usual static 
discharges though.  The parallel connection has some protection, but comes 
from some cheap drivers.  Several layers of ICs have to fail before you get 
to the ADC.

All the lines that go to the camera head are protected with series 
resistance and clamps.  This will not protect from a direct strike which 
could melt the frame, but will protect from most secondary induced loops.

Happy to have you back in operation.  Hmmmm!  You mention actually taking 
data.  How about a report on what you are seeing?

Tom Droege

At 11:30 AM 7/6/02 -0400, you wrote:
>Do not fear, this story has a happy ending but lightning did indeed strike
>here.
>
>I was on vacation when it happened and nobody was at home when lightning
>struck a tree no more than 30 feet from the observatory.  Tom and I both
>have too many trees for our observatory's own good though Tom has even more
>than I do.
>
>The first symptom of the problem was when I talked to my daughter when she
>was home and I was still on vacation.  She said the ADSL connection to the
>internet was not working.  We've had problems like that before but the
>standard fixes did not work.  When I did get home I noticed that the ADSL
>modem was connecting to the phone line but not the LAN in the house.  Then
>Debby called me out back and showed me the damage to the tree.  Bark was
>blown off in two strips all the way down the tree with one strip up to a
>foot wide.  I then discovered that my whole network was non-functional.
>While I have significant surge protection on the power line, the network had
>only one surge protector and I made the mistake of unplugging it when I went
>on vacation.  What that meant is that I essentially had a 50 foot antenna
>leading from the observatory into my network.
>
>It's taken me about 5 days to restore the network.  The known damage list so
>far is:
>1 ADSL modem
>1 Router
>1 Switch
>3 Network cards
>1 Serial communications card
>
>The last one was the most worrisome since it was the communications card to
>the Mark IV Stamp and I couldn't tell if it was the serial card on the
>observatory's computer or the Mark IV itself or both.  I replaced the system
>out in the observatory with a new (used) computer yesterday and was pleased
>to see the Mark IV at least respond to commands again during the day.  Last
>night I took data and was relieved to see that all is working.  The images
>for both cameras came out fine.
>
>Many thanks to Tom who has designed a system with enough safety margins to
>make it through when so much else did not!
>
>
>Mike G.