On Wed, Jan 26, 2011 at 6:56 PM, RussellMc wrote: > >>> Hook it to a laptop that is _not plugged into mains_. > > >> That's what I'm doing right now. > > Carefully note that "not plugged into the main" does NOT mean - "It > uses an isolated wall wart or waddever power supply in the lead and > feeds low voltage so I'm OK to plug it in and, urk ..." > > Carefully. > > 12 Volts applied to the chest can kill, and has. > > Many power supplies have capacitors from mains leads to ground. O/C > ISOLATED output is half mains supply. Youcan get a nasty "tickle" from > such. > > Various tables etc show fatal results for chest currents of 50 mA up. > You could argue that having even say 10kohm in each input lead would > be "safe enough" (12/10k =3D 1.2 mA). > I'd avoid arguing that. Dead is dead. > > Carried to it's illogical conclusion you could limit mains current the > same way. Get it wrong and you may never know. > I'm not taking chances. The laptop is NOT connected to ANYTHING that's touching any wall. It's on a little island table by itself, running purely off of batteries. I'm powering everything else off of 2 Li-ion or the 5 V supply from the laptop's USB port. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .