>I am going crazy trying to solve an interference problem and would much
>appreciate any ideas!
>
>I am using a 16C73 to control motorised entrance gates.  The PIC drives
>relays to switch motors to open and close the gates.  I am experiencing
>intermittent problems in that the PIC get frequently reset, apparently as a
>result of the motor mains switching surges.
>
>I have just added mains input filters, extra large PSU electrolytic
>capacitors and a Dallas DS1233-15 microprocessor reset controller - yet the
>problem still remains!

  Much better to drive the heavy loads with SSR's. Probably cheaper than all
  the extra filtering components you've had to add.

  Also, make sure there are no floating pins on the PIC. Set everything that's
  not used to OUTPUT. Any inputs that have a resistive pull-up or down, make
  sure the value is low, e.g. 1K. Separate ferrite beads on any lines that
  come in from the outside will often scarf up glitches.

  Reg Neale