Re: U.S. Pat 6,366,028 LED Flashlight Circuit

"Robert Monsen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
: "Bill Garber" <[EMAIL PROTECTED]> wrote in message
: news:[EMAIL PROTECTED]
: [nip]
: > Are there certain types of device that produce
: > inductance? Sorry if I am asking so many questions,
: > I've only ever done repairs to electronic devices
: > by advisement of technical personnel.
:
: No problem.
:
: Yes, they are called inductors. You can buy inductors (chokes,
coils, they
: have lots of names) at radioshack, or various other electronics
suppliers.
:
: You can also make them by making a coil of wire. The idea is to
reinforce
: the magnetic field that gets generated when current flows
through a wire.
: Inductors basically build up a magnetic field, the value of
which is related
: to the current flowing through the coil.
:
: The 'formula' for making them depends on their radius, length,
number of
: turns, and 'core material'.
:
:  L = mu(r) * (N^2 * A / l) * 1.26e-6
:
: where mu(r) is the relative permeability of the core material,
which is
: simply 1 for air; N is the number of turns of the coil; A is
the area of a
: loop of the coil in sq meters; and, l is the length of the coil
in meters.
: (The 1.26e-6 term is the permeability of air in SI units,
called mu nought.
: Its a fudge factor for using SI units. The real formula is
permeability of
: the core times turns squared times area over length.)
:
: So, to get 33uH on an air coil, you need about 82 turns of wire
on a 1cm
: diameter coil of 2cm length. If you use an iron or steel core,
you'll need
: considerably fewer turns.
:
: Regards,
:  Bob Monsen

Thank you Bob. I did discover that they were chokes/coils,
as I had suspected, but your explanation of their construction
and how they are formulated made it very clear. I now know
what to call them and how to find out what their ratings are
when I reverse-engineer a circuit. Incidentally, is there an easy
method for taking a reading on them to find out their value?

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - [EMAIL PROTECTED]
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