[rescue] Big Caps

[Dave McGuire]

On July 4, George Adkins wrote:
> What the hell would someone use a 1 farad capacitor for?
> (as in 1,000,000 microfarad).  I saw 4 of them today for $145 ea.

  If they're big (soda can sized or larger) they're used primarily by
the monster car stereo boyz.  Connecting such huge capacitors very
close to the power supply inputs of large amplifiers via low-impedance
paths improves bass response considerably by providing a reservoir of
easily accessible power to supply those large current pulses that the
amplifiers draw during the big boomy parts of Da Home Boyz music.

  Picture the car's electrical system.  A nice long run of relatively
thin wire [normally] runs from the stereo amplifier to the power
source.  That wire has a bunch of inductance...MUCH more than the
short pieces of very thick wire (or bus bars) used to connect those
big capacitors.  Inductors tend to resist changes in the current
flowing through them, so during a pulse of power through the amplifier
the current supply may thin out before the end of the period of high
demand.

  (HEY SCOTT!  Don't pick me apart here...this is intended to be a very
basic explanation. ;) )

  Smaller high-value caps (supercaps or ultracaps) are commonly used for
backup power for static RAMs and other very low-current stuff.
They're typically pretty small, about the same size & appearance as a
"regular" electrolytic capacitor.

           -Dave

-- 
Dave McGuire                  "Needing a calculator indicates that
St. Petersburg, FL              your .emacs file is incomplete." -Joshua Boyd