Re: gEDA-user: basic anti-EMI design q

[Karel Kulhavy <clock@xxxxxxxxxxxxx>]

On Fri, Mar 24, 2006 at 11:04:04AM +0100, Bill Sloman wrote:
> At 05:21 24-3-2006, you wrote:
> >DJ Delorie wrote:
> >
> >>It's not the drivers that mess up, it's the octal latch.
> >
> >
> >if the existing latch is in the interface with ribbon cable to the 
> >PC  - there's your problem.
> 
> Have you grounded every second wire in the ribbon cable? It sounds 
> extravagant, but if you need shielding, that's a commonly used way of 
> getting it. It also means that the residual signal wires look like 

It isn't. If it were, there would be no rule that UTP cables should be
put min. 20cm apart from power lines.

CL<

> 50R transmission lines. You can get shielded ribbon cable, but it is 
> expensive, and grounding the shielding isn't always that easy - you 
> need metal (or metallised) connector shells, and they aren't always 
> easily available.
> 
> >You could probably fix it with something gross like series R in the 
> >line and a bypass cap to ground (the ground the latch sees - the 
> >chips pin 10) right at the octal latch.
> 
> Some logic specifies minimum edge speeds on clock inputs. Too much 
> filtering can make the logic do funny things.
> 
> <snip>
> 
> Bill Sloman, Nijmegen
> 
>