From: "Brill Pappin"
Subject: Re: Ground loops?
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Sun, 15 Sep 2002 01:23:46 GMT
NNTP-Posting-Date: Sat, 14 Sep 2002 21:23:46 EDT
> >This has got me thinking about noise as well... in my system , the boards
> >are all connected in series... I had planned to have a single ground line
> If the power grounds and the signal grounds are one and the same, then
> the last board in the string will see some of the signals from boards in
> between. It's similar to the "ground bounce" that you can get on a single
> board. Whether the extra signals will be trouble or not remains to be
> IMHO, a series connected string of boards is just asking for problems.
Yes I could see this being a problem, however the series boards are really
not much of an option for me in this design... I may be able to reduce the
number... and I may be able to put some of them into that "star" topology
mentioned in another post, but doing that will increase the length of the
So, the problem remains... and I need to think of ways to reduce noise in
the system. As I see it there are a few things I can try:
- Separate the power, digital and analog grounds into separate line (makes
for larger cables, but doable I think).
- Add filters to the power ground. (can they be added to the analog ground?,
not to digital I would expect).
- Ensure that all analog and digital grounds on a particular device contain
their own ground planes etc, and only feed to power ground once properly
filtered (Is that even right? or should it be multiple points?).
- Use buffers/inverters between boards... mostly this would not be a problem
I would welcome any suggestions anyone has on this... there will be times
when I just can't do anything about it, but when I can, I should.
- Brill Pappin