It is VERY bad to ground the person, it involves risk of electric shock from anything not connected through a fault current breaker, including the project's power supply. As far as I know, the only place where you can ground the operator safely is in a production environment where the units are not powered.... There are chips that protect IO pins. Check MAXIM MAX336 and co. One thing ppl. keep forgetting when using PICs with external connections, is the fact that the same bulk and protection diodes that allow a PIC to be powered by its IO pins (featured elsewhere in this list), still work when there is power applied to the Vcc and GND pins as it should. Since most regulators cannot sink current, this can easily lead to a PIC being powered by its (incorrectly designed) load, which can bring the VCC RAIL TO FAR MORE THAN +5v. The cure is a zener connected between Vcc and GND after the regulator, directly at the PIC power pins (Z5V6 or such), AND the usual limiting diodes/networks at every concerned IO pin... else the limiting diodes only supply power to the PIC... I've seen many such designs in mags, and it's scary. You have this PIC running at 5 V from a 78L05, and an input or output going through a resistor to +12V or whatever. The resistor is dimensioned to limit the current into the PIC input pin. However, if the PIC sleeps then the design current flowing through the resistor raises the VCC to almost the level of the higher voltage, due to the low current drain of the part.... the regulator opposes absolutely no resistance to this. here's my 2 bits. On Mon, 15 Dec 1997, Justin Crooks wrote: > Well, how about grounding the person touching the pins? If this isn't > feasable, you could use an RC filter... > > ---------- > From: Rob Aerts > To: PICLIST@MITVMA.MIT.EDU > Subject: esd protection > Date: Thursday, December 11, 1997 3:13 PM > > hello, > > I have one question for all you guys/girls > > In a project with a PIC16C84 the inputs can be touched bij fingers, > my question : how can i protect the i/o against ESD charges ? > > Kind regards, > > Rob Aerts > Peter (plp)