Not the stress is the problem here. 240V/4.7M = 50uA, p = 0.012W
The real problem is that a "normal" 4.7M in carbon or metallic technology
are built with a spiral which allows voltage spikes between adjacent
spirals (they have too large resitance) So usualy a resistor must have
also as a parameter the maximum voltage alowed.

In this application a 500k to 1M is a very good choice, then a zenner to
protect the pic input and bingo.

top 10 wishes,
Vasile
http://surducan.netfirms.com
"Microcontrollers for all" only in romanian language.



On Tue, 16 Sep 2003, Thys wrote:

> Can you not rather use a fet to do this.(less stress on the resistor?)
>
> Thys
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@mitvma.mit.edu]On Behalf Of Jinx
> Sent: 16 September 2003 12:29
> To: PICLIST@mitvma.mit.edu
> Subject: Re: [PIC:] Why is my 12F629 resetting?
>
>
> >   240V~
> >     o-------/\/\/---+--|
> >  Neutral    4.7M
>
> Bala, make sure that 4M7 is OK to drop 230V. It would
> be better to put 3 x 1M5 or 4 x 1M2 in series
>
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