Re: Capacitor Applications

[John Denker <jsd@MONMOUTH.COM>]

At 06:41 PM 1/14/01 -0500, Tony Wayne wrote:
> I'm looking simple toys or appliances that utilize capacitors.
...
> small car that uses a capacitor as its energy source.

I'm not 100% sure I understand the point of the question.  Possibilities
include:
  a) Capacitors used for brute-force energy storage
  b) Capacitors in general

Also, how simple does it have to be?

Examples that spring to mind include:
 --) A photographic flash unit uses capacitors for brute-force energy
storage.  This is an attractive example, because it is something students
see in their ordinary lives.  The anticollision strobes on airplanes work
on the same principle.
 --) A spot-welding machine also uses brute-force capacitors.  It
generates a short pulse with high current at low voltage.   Such machines
are very common and important in industry.  Some but not all high-school
shops have one.
 --) Many appliances have induction motors, which depend on having
good-sized "starting" capacitors.  Examples in my house include the blower
for the forced-air heating/cooling, the clothes dryer, the grinding wheel,
and probably several others.  Any AC motor is likely to be of this type if
it is bigger than about 1/4 horsepower, is not synchronous like a clock
motor, is not variable speed, and starts under not-too-great loads.
 --) If you pull a typical card out of a computer, small capacitors will
be abundant.  I'm looking at an old "Soundblaster 32" sound card right now,
and there are more capacitors than I care to count, on the order of a
hundred.  This is pedagogically problematic, because it will be hard to
explain to the typical high-school student what all those capacitors are
for.  Some of them are just bypass capacitors on the power-supply lines,
others are precision capacitors for signal-processing filters, oscillators,
.......
 --) The power supply for any piece of electronics (such as a stereo
amplifier) will have capacitors in it.  A unit that is more than about 20
years old will have quite hefty capacitors in it.  (Afterward people got
smart about switch-mode power supplies and the capacitors got smaller.)
 --) The ignition-spark system for a car has an important capacitor in it.