On Sat, 21 Feb 2004 07:51:26 -0800, Scott Dattalo wrote: > On Sat, 21 Feb 2004, Omega Software wrote: > >> But how can current pass from just one wire? Is it a capacitive effect? > > Assuming that you weren't touching some other conducting surface, then > yes > it is a capacitive effect. At Synaptics (where I work), we use ~10pF for > the human body free-space capacitive coupling. Our TouchPads measure the > capacitive coupling between a finger and the surface of the TouchPad > sensor. This is roughly 1pF (and our ASIC can resolve this down to 10's Assuming the distributed capacitance of a human body is around 20pF then your capacitative reactance at 50Hz is about 1.5G Ohms. This means that if you are isolated in free space around 16uA will flow at the point where you are touching the mains. This is well within safe limits, probaly too little to even feel it. However, if you are stood on ,say, a nice big ground plane with some nice high K floor tiles between you and the ground plane i am sure your capacitance to ground could be much bigger with the correspondingly larger current flow. As regards floor tiles being insulators, you really shouldn't count on it. If you want to play with sparks why not build a mans of doing it safely, check out http://www.coe.ufrj.br/~acmq/electrostatic.html if you look carefully you will one of my machines listed there. Regards Alex Rice -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads