I will try the shielding and then the keyboard.  Tooling charge for the =
keyboard
 is not really a problem.  I would appriciate the name of the keypad =
company=20
if you can give me.  We have keypad providers here but they do a lousy =
job=20
most of the time, and I don't think they would be up to what you =
suggested=20
here.

Could you also recommend how to make this hardware disfunction?  At the=20
customer side they complain it messes up next to a pump/motor, but when=20
I try put the unit next to the largest pump we have at the factory and =
nothing=20
happens.  In other words, how could I reproduce this problem?


-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Brian Clewer
Sent: Tuesday, July 15, 2003 11:30 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: EMI shielding, was WDT and C compiler choice ?

=D6mer,

Sounds like it's down to EMI shielding then.  You should have some sort =
of
ground plane on the PCB and put the unit in an earthed metal box.  As =
far as
the keypad goes, this could be a problem as it acts like an aerial for =
the
magnetic radiation.  I do believe you are able to get keypads made with =
a
conductive front overlay.  If you were to use such a keypad and ground =
the
front, this should make things better.  The only problem with that is =
they
cost loads.  I am about to get a keypad made with a tooling charge =
upwards
of =A3500 UKP.

Try the metal box first and see if it fixes the problem.
Don't try to fix this with software.  It just isn't going to happen.

Brian.

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