Hi Jinx, thanks for answering.

    I'll quote your message:

Jinx wrote:

>Hi Rafael, have you tried putting the PIC in a grounded metal
>box and using grounded shielded wire to the sensor and PSU ?
>  
>
    Yes :-(
    Used an old ATX power supply metal box, and grounded
the sensor, my circuit and the power source to the box.
I got less noise, but still got it.

>I have a product that counts pulses from a sensor and sits next
>to a 5W radio and petrol engine. Without proper shielding it
>goes crazy. Can you also decrease the impedance of the sensor
>signal so it's not so prone to interference ? 
>
    I can try that...

>Perhaps drive the
>line with an opamp or transistor, add a couple of ferrite beads
>and bypass caps (eg small ceramics)
>  
>
    I also tried some of those ideas. Then i'll tell how wired my
problem is:
    If i disconnect ALL the wires and sensors from the board,
and let only the power supply and serial connection, the problem
persists. Yes, if i "click" the piezzoeletrical ligth firer just near the
metal box, the pic counts pulses! Without any wire connected!

    Could the problem be my board design?
    Or is the pic too sensible?

    what options more i have?

    again, thanks for your attention

[]s Rafael.


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