Peter L. Peres wrote:
>
> Hello,
>
> On Wed, 23 Dec 1998, Jason Wolfson wrote:
>
> > My question is: How do I calculate the appropriate values
> > for a RC snubber network? I'm not sure of the inductance of the
> > solenoid coil.
>
> imho, for testing only, connect a standard line filter (Corcom etc)
> temporarily in series with the valve connection, and find out if it helps.
> Line filters are very good at suppressing and if it does not help, a
> snubber will help even less imho.
>
> One way that I have found to help in this case, is to place a 5V6 zener in
> parallel with the PIC Vdd/Vcc to prevent voltage rise during a spike, and
> connecting MCLR directly to Vdd (sans R). The other thing is to use a
> canned oscillator or shield the oscillator area of the PIC. I am not sure
> about the latter, it seems to have worked a few times. PICs running on RC
> oscillators seem to be less sensitive. Adding relatively high value
> (470R..10K) R's on all the connection wires emerging from the circuit also
> helps, assuming the respective attachements can work like this.
>
> In stubborn cases only opto isolators and totally separated circuits will
> help. This problem is not PIC specific, almost any CMOS and HCMOS circuit
> has it.
>
> hope this helps,
>
>         Peter

  Would a ground ring around the crystal oscillator help here, Folks?
Or would you want a complete filled-in ground plane & an above-PC Board
ground plane?  (I'm NOT a crystal expert <G>)

  I ask as I'm expecting such problems when the next big contract takes
off...  Moving 2-ton items electrically ought to generate some nice
noise.  Don't want the "Pour" circuit to trigger on same!

  Also I was planning to use a 3-terminal Vcc monitor (Panasonic etc.)
to run ~MClr, any problems with those (provided Vcc is well-decoupled
with 0.1 uF MilCer cap's) with bad noise?  Optoisolators between the
PICs and the rest of the real world, of course (Optical fibers, perhaps,
period...)

  Mark, mwillis@nwlink.com