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