Mark Birks wrote:

> Hi folks,
>
> Does anyone have a general circuit for protecting PICs (and other micros)
> when used in projects for Cars ?.
>
> I guess we are talking Zener + resistor and perhaps a filter ?


A 18k goes into a parallel combination of a 5v2 Zener,
a 150k, and a 100nF to ground. Another 4k7 from the
common point into your PIC.

Just don't use a programming pin if you are going to
do ISP. The yield will not be good.

Here goes :

         18k   5V2   150k  100n     4k7
---/\/\/--o----o----o---/\/\/---- PIC
          |    |    |
                   /  \       /        ---
                     |        \        ---
                     |        /          |
                     |         |         |
--------------o-----o-----o-------------------

If you want to make the serie resistance higher,
don't be tempted into upping the 18k - the zener
will stop "zenering". Rather up the 4k7 and the150k.

--
Friendly Regards

Tjaart van der Walt
mailto:tjaart@wasp.co.za

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