On Fri, 6 Dec 1996, peter cousens wrote:

[...]

> A .1mF cap at 50 hz has an approx resistance of  31k  at 220V gives 7mA
>   .47mF                           =              6k7                32mA
>   1mF                             =              3k1                69mA

I think you mean 'uF' (mykro-Farad = 10^-6 F) not 'mF' (milli-Farad =
10^-3 F) !

>
> At 60Hz the resistance would be lower and curent less

The resistance will be lower but this means that current increases (gets
greater, I = U / Z )

>
>
>         -------20megOhms(220V, 110V 5meg)------------ I/O pin pic
>         |
> ~ac-----O---||----------O---diode----O----7805----O-------+5V pic
>                        |             |            |
>                22v Zener diode   elec cap     elec cap
>                        |             |            |
> ~ac--------------------0-------------O------------0--------0V pic
>
> PS. The Zener does two jobs

agreed

> Peter Cousens
> email: peter@cousens.her.forthnet.gr
> snailmail: Peter Cousens, karteros, Heraklion, Crete, 75100, Greece,
> phone: + 3081 380534,    +3081 324450   voice/fax

bernhard.

Bernhard Schweighofer alias schweigi@sbox.tu-graz.ac.at
(Student at Graz University of Technology, Austria)