When I was much younger and much, much more foolish I liked to build 
multi-neon-bulb relaxation oscillator sequencers using free space wiring 
(parts just solder-tacked to each other without any board or chassis. I 
would power these creations with a direct (unisolated) half wave supply from 
the 120V line.

Knowing that the sequencing rate was related to the supply voltage I decided 
to set up an "up-and-down" full wave supply to get twice the voltage. Not 
knowing/thinking about the fact that the output capacitor in the supply 
would see peak (rather than RMS) voltage left that poor device rather 
overstressed. When it gave out, it did so in rather spectacular manner, 
blowing out the end cap and then doing a reasonable impersonation of a 
rocket engine as it dragged the whole circuit across the bench at a pretty 
good pace.

The excitement continued when the input AC line terminals then shorted out, 
resulting a very impressive spark, followed by darkness.

I stood there in the dark, inhaling the stench of the exploded capacitor and 
the result of the monster mains spark, for at least a minute, wondering if 
my heart would ever slow down to normal again.

Bob Ammerman
RAm Systems

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist