At 09:01 AM 8/28/2008 -0400, you wrote:
><echristley@nc.rr.com>
>
>Brantel wrote:
>>That being said, what if any advantages would the kitplanes article
>>driver have over one of these off the shelf drivers and would the noise
>>problem still exist with that driver as well?
>>
>Education.
Jim's choice of silicon for an LED driver is curious. Perhaps
he likes the part's package . . . it's a dual-inline-plastic
which is easier for the neophyte to work with. There are
some more modern, constant current LED driver devices that
are electrically more suited to the task. An exemplar device
is shown here:
http://www.national.com/ds/LM/LM3404.pdf
This is one of a host of similar one to multi-channel dimmer
controllers. The 3404 delivers up to of constant current
to it's companion loads.
It's a switcher. It hums at 1 to 2 Mhz with a butt-ugly
wave-form rich in harmonics. This device needs to be
a very compact layout (small antenna aperture) and be fitted
with conduction filters on the input/output wires. It
MIGHT be okay in a plastic enclosure . . . but a metal
one never hurts.
If folks are interested in an LED driver tested for
radiated and conducted emissions, I might be able to
add that to our catalog in the not too distant future.
My consulting work is going to require me to spend a
lot more time in an RFI lab. I can probably piggy-back
some of my 'government jobs' on top of a paying task.
I used to do this years ago by letting my little gizmo
run in parallel with test articles in the chamber. As
long as we were both cool, I could get two sets of test
data with one scan. If we had an out-lying data point,
I'd turn off my gizmo to see who was responsible
for busting the limits. I think I'll be able to do
this again pretty soon. I'm working three paying jobs
that need to get into the lab soon.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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