[sdiy] dare I say - decoupling?

[harrybissell]

James Patchell wrote:

> Harry likes to use the analogy of "Ground == Ocean"....very important
> here...In general, you do not need a ground plane.  But when things don't
> seem to be working they way they should...well...
>

Yes... I do.   If you pour a cup of water into the North Atlantic Ocean...
does the water level rise ?   Of COURSE it does... but probably not enough to
notice or care.   Does the water level rise in England (I'm going to pour from
Boston in this case :^) ?  Yes it does... but it takes time for the change in sea
level to even out. They will notice the rise much later.

What about if I pour the cup of water into a shotglass ??? Does the water level
rise ?
Yes. Do I notice ???  Probably... unless I had been using that shotglass for hours
:^P

You think of supply rails like pipes carrying current to the circuit... well ground
is
like sewer pipes draining that current.  If any of the pipes are too small, the
water
pressure drops when you open a valve.  AND it takes time for the water to flow from

the source to where that pressure drop is.

Decoupling caps will act as local sources of 'water'... helping to hold the
pressure
steady with changing demand AND acting as a reservoir ... until the rains come
again
(from the main filter caps, through the resistance and inductance of the supply
'pipes')

This is why some "Harley Engineers" like myself and twin-separated-at-birth Jim
Patchell use LOTS of decoupling caps, probably MUCH more than we really need to.
They are not real expensive... cheap insurance.

A Harley Davidson engineer was quoted as saying "At Harley-Davidson... if we need
to make something stronger, we make it BIGGER. If that makes it ugly...we CHROME
it"

H^) harry