To Jim Weir

Stealth Pilot wrote:
On Fri, 08 Jan 2010 16:54:14 -0800, Bug Dout
wrote:

Stealth Pilot writes:

charlie, assuming that you are using a 12 volt bus, all you need to do
to use an LED is put a 680ohm resistor in series with it.

Huh? You can't generalize about LEDs like that! There are many different
LEDs with different electrical characteristics. Given the OP's post,
you can't even state that a simple resistor is what he wants; he may
want variable lighting, in which case a potentiometer is what's needed.


I can state what I like. it is a free society.
what I wrote works for me.
ymmv
Stealth Pilot


Quite so. Moreover, the idea of providing an individual series resistor
to pass about 20 mA works for a good variety of LEDs.
Focussing on the desire to dim a LED, there is no reason (that I know)
not to reduce the current. This has the great advantage over pulse width
modulation that it does not kick up radio interference. There are LED
drive chips on offer now that might suit....

Brian W

brian whatcott wrote:


Quite so. Moreover, the idea of providing an individual series resistor
to pass about 20 mA works for a good variety of LEDs.
Focussing on the desire to dim a LED, there is no reason (that I know)
not to reduce the current. This has the great advantage over pulse width
modulation that it does not kick up radio interference. There are LED
drive chips on offer now that might suit....

Brian W

Maybe this will help the builder. A current source (rather than a
voltage source) will make the LED brightness varaiable. A typical (red)
LED runs at about 20 mA for full brightness, while dropping about 1.7V
across the LED. Lowering this current dims the LED. The shown circuit
can be set to supply up to about 400 mA, enough for about 20 LEDs. Of
course, he will want to use red LEDs in place of the white ones drawn in
the circuit...

http://radiolocation.tripod.com/LEDd...ampDimmer.html

Scott

Scott wrote:
brian whatcott wrote:


Quite so. Moreover, the idea of providing an individual series
resistor to pass about 20 mA works for a good variety of LEDs.
Focussing on the desire to dim a LED, there is no reason (that I
know) not to reduce the current. This has the great advantage over
pulse width modulation that it does not kick up radio interference.
There are LED drive chips on offer now that might suit....

Brian W

Maybe this will help the builder. A current source (rather than a
voltage source) will make the LED brightness varaiable. A typical (red)
LED runs at about 20 mA for full brightness, while dropping about 1.7V
across the LED. Lowering this current dims the LED. The shown circuit
can be set to supply up to about 400 mA, enough for about 20 LEDs. Of
course, he will want to use red LEDs in place of the white ones drawn in
the circuit...

http://radiolocation.tripod.com/LEDd...ampDimmer.html

Scott


Didn't Weir do an article in "Kit Planes" awhile back on this subject?

Dan, U.S. Air Force, retired

Scott wrote:
brian whatcott wrote:


Quite so. Moreover, the idea of providing an individual series
resistor to pass about 20 mA works for a good variety of LEDs.
Focussing on the desire to dim a LED, there is no reason (that I
know) not to reduce the current. This has the great advantage over
pulse width modulation that it does not kick up radio interference.
There are LED drive chips on offer now that might suit....

Brian W

Maybe this will help the builder. A current source (rather than a
voltage source) will make the LED brightness varaiable. A typical (red)
LED runs at about 20 mA for full brightness, while dropping about 1.7V
across the LED. Lowering this current dims the LED. The shown circuit
can be set to supply up to about 400 mA, enough for about 20 LEDs. Of
course, he will want to use red LEDs in place of the white ones drawn in
the circuit...

http://radiolocation.tripod.com/LEDd...ampDimmer.html

Scott


Yep.

Here's another idea that sticks with the non pulsed approach.

It uses a variable voltage reg in constant current form - allowing a
string of several LEDS as is:
http://www.instructables.com/id/Circuits-for-using-High-Power-LED_s/step11/an-even-simpler-current-source/

...or in TinyURL format:
http://tinyurl.com/yb9kyyr


....this could be massaged to provide the drive for 24 LEDs at rather low
cost and component count.

Brian W

Scott wrote:


Maybe this will help the builder. A current source (rather than a
voltage source) will make the LED brightness varaiable. A typical
(red) LED runs at about 20 mA for full brightness, while dropping
about 1.7V across the LED. Lowering this current dims the LED. The
shown circuit can be set to supply up to about 400 mA, enough for
about 20 LEDs. Of course, he will want to use red LEDs in place of
the white ones drawn in the circuit...

http://radiolocation.tripod.com/LEDd...ampDimmer.html

Scott


Didn't Weir do an article in "Kit Planes" awhile back on this subject?

Dan, U.S. Air Force, retired

Dunno. Haven't gotten the rag in a couple years. Price stayed the same
but page count went down, didn't find it cost effective, with all the
magazines I was gettin'. That said, I wouldn't doubt it was covered at
one time or another...

Hello, Charlie ...

The main reason I post on this newsgroup is so that my answers are
vetted by the group and we don't cut holes in the airplane when
something obviously isn't going to work.

Tell you what, and with a couple of options:

1. Post on these newsgroups in alt.binaries.scientific.electronics
and attach the schematic with a request to look it over and I (as well
as a dozen other folks whose opinion I value) can massage it for you.

2. Join the newsgroup Pilots Of America and post the schematic in
Maintenance Bay. Again, there are folks in there who will certainly
not let me give you bum information.

Jim




On Thu, 07 Jan 2010 15:39:13 -0500, Charlie Smith
wrote:

Jim,

From info I have located on the internet, I have cobbled together a
circuit diagram for illuminating my instrument panel using LED's. I was
wondering if I emailed you a copy, would you would be kind enough to
take a peek at the circuit and see if I missed anything? Electronics
isn't my expertise but I enjoy it all the same.

Thanks in advance,
Charlie Smith

Make that

alt.binaries.schematics.electronic


Jim


On Thu, 07 Jan 2010 15:39:13 -0500, Charlie Smith
wrote:

Jim,

From info I have located on the internet, I have cobbled together a
circuit diagram for illuminating my instrument panel using LED's. I was
wondering if I emailed you a copy, would you would be kind enough to
take a peek at the circuit and see if I missed anything? Electronics
isn't my expertise but I enjoy it all the same.

Thanks in advance,
Charlie Smith

RST Engineering wrote:
Hello, Charlie ...

The main reason I post on this newsgroup is so that my answers are
vetted by the group and we don't cut holes in the airplane when
something obviously isn't going to work.

Tell you what, and with a couple of options:

1. Post on these newsgroups in alt.binaries.scientific.electronics
and attach the schematic with a request to look it over and I (as well
as a dozen other folks whose opinion I value) can massage it for you.

2. Join the newsgroup Pilots Of America and post the schematic in
Maintenance Bay. Again, there are folks in there who will certainly
not let me give you bum information.

Jim




On Thu, 07 Jan 2010 15:39:13 -0500, Charlie Smith
wrote:

Jim,

From info I have located on the internet, I have cobbled together a
circuit diagram for illuminating my instrument panel using LED's. I was
wondering if I emailed you a copy, would you would be kind enough to
take a peek at the circuit and see if I missed anything? Electronics
isn't my expertise but I enjoy it all the same.

Thanks in advance,
Charlie Smith


Thanks Jim.

I knew of Matronics but not these other places. This all I really need;
some good, trustworthy advice.

Thanks again.


Charlie

RST Engineering wrote:
Make that

alt.binaries.schematics.electronic


Jim


On Thu, 07 Jan 2010 15:39:13 -0500, Charlie Smith
wrote:

Jim,

From info I have located on the internet, I have cobbled together a
circuit diagram for illuminating my instrument panel using LED's. I was
wondering if I emailed you a copy, would you would be kind enough to
take a peek at the circuit and see if I missed anything? Electronics
isn't my expertise but I enjoy it all the same.

Thanks in advance,
Charlie Smith




Good grief!
I thought rec.crafts.metalworking had a lot of noise...



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http://www.home.earthlink.net/~cavelamb/


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