Garage Door Opener: a bad experience

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Hanson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <huil888-at-surfside-dot-net>

I had an unfortunate experience with a garage door opener a year or so ago
while running my 6" X 32", 120ma NST powered coil at a friend's house.
 
We were running the coil on the concrete driveway, about 20 feet from the
closed, segmented-steel roll-up garage door. A relatively late-model, high-end
Stanley garage door opener controlled the door. Perhaps foolishly, I did not
disconnect the power from the opener.
 
As I increased power to the coil (~ 50" arcs to free air) the opener suddenly
actuated and proceeded to open the garage door. However, the opener DID NOT
SHUT OFF when the door was completely opened! The top end of the door was
pulled into contact with the opener housing, completely crushing the plastic
end cover and the light bulbs within, and showering a brand new Toyota Land
Cruiser with broken plastic and shattered glass. I can't believe that there was
not a mechanical limit switch in the system to prevent this type of failure. 
In the end, when we plugged the opener back in it appeared to operate normally,
but looked like it had been through a war. I didn't have an opportunity to
disassemble the opener, but I assume that it may have had a "high-tech"
solid-state optical or Hall-effect limit switch circuit that could have somehow
become latched & unresponsive due to high RF levels.  I shudder to think what
could have happened if the opener somehow pulled the door off its track & it
came crashing down on the new Land Cruiser!
 
 Scott