[sdiy] Let's talk AC, DC, electrocution, death, misery, and grounding.

[Horton]

Ok, allow me to play total n00b here for a moment, because I'm trying
to understand a few basic components of electricity and how
likely/unlikely I am to die while working on stuff. All of my
electronics knowledge comes from Nic Collins' excellent "Handmade
Electronic Music: the Art of Hardware Hacking," which takes you from
doing simple circuit-bending type stuff through making your own piezo
and eventually breadboarding simple CMOS stuff. Unfortunately, the
book is so anti-EVER plugging ANYTHING you make into ANYTHING
wall-powered under risk of DEATH that it's made me afraid of
electricity. I mean, he goes out of his way to mention that you should
never even plug in piezo mics you've built, or circuit-bent toys that
you've packaged and updated with a 1/4" out or you'll DIE.

I need some straight info on all of this, please.

1. I see people with home-built and circuit-bent stuff running into
huge marshall stacks frequently. Why are these guys not dying? Why is
the book so emphatic that you should NEVER EVER do this?

2. How could you get electrocuted by plugging in something that's only
spitting out an output, anyway? I mean, if I make a piezo mic, it's
only going to be outputting a signal, not taking any voltage into it.
Shouldn't I be able to plug that thing into anything from a tiny
battery-powered amp to a marshall stack without worrying?

3. I just got an Arduino, which is powered off of the USB bus. Why do
I not get electrocuted holding it?

AH