On Tue, 19 Jan 2010 10:54:09 -0500, Spehro Pefhany
wrote:

On Tue, 19 Jan 2010 07:32:10 -0500, "Charlie Smith"
wrote:


"RST Engineering" wrote in message
. ..
Why is EMI bad news in an airplane as opposed to anywhere else?

Jim


Hi Jim.

I will be building the PWM board and will simply test it. As you have often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

It's so cold the Democrats have their hands in their own pockets.

On Tue, 19 Jan 2010 07:32:10 -0500, "Charlie Smith"
wrote:


"RST Engineering" wrote in message
.. .
Why is EMI bad news in an airplane as opposed to anywhere else?

Jim


Hi Jim.

I will be building the PWM board and will simply test it. As you have often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?

On Mon, 18 Jan 2010 23:28:49 -0800, RST Engineering
wrote:

On Fri, 15 Jan 2010 20:01:25 -0800, John Larkin
wrote:

Did you really need to quote 40+ lines for a one line response?

Jim

Get rid of the 555 PWM thing! It accomplishes nothing.

John

Are you incapable of using the bottom-posting convention?

John

I will be building the PWM board and will simply test it. As you have
often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)

...Jim Thompson


Don't be so tough Jim. Ignorance is not a bad word. Its an entirely
curable condition. Stupid. Now that's incurable. And experimental doesn't
mean making an airplane the way the A-Team would; with a canvas, a couple
bamboo poles and duct tape. All it really means anymore is that the
airplane can be more modern than 1950's technology and you don't have to
auction off your first born. In the larger scheme of things, I don't see
instrument panel lights in the same arena as wing bolts. Let's try and keep
some perspective. Most of the suggestions made here would work just fine.
Just fuse the lights conservatively from the main buss and the very worst
that would happen is you would find yourself getting the flashlight from the
flight bag. And that happens more often than you might think.


Charlie

On Tue, 19 Jan 2010 12:10:28 -0500, "Charlie Smith"
wrote:

I will be building the PWM board and will simply test it. As you have
often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)

...Jim Thompson


Don't be so tough Jim. Ignorance is not a bad word. Its an entirely
curable condition. Stupid. Now that's incurable. And experimental doesn't
mean making an airplane the way the A-Team would; with a canvas, a couple
bamboo poles and duct tape. All it really means anymore is that the
airplane can be more modern than 1950's technology and you don't have to
auction off your first born. In the larger scheme of things, I don't see
instrument panel lights in the same arena as wing bolts. Let's try and keep
some perspective. Most of the suggestions made here would work just fine.
Just fuse the lights conservatively from the main buss and the very worst
that would happen is you would find yourself getting the flashlight from the
flight bag. And that happens more often than you might think.


Charlie


How many times have you been told that PWM'ing (without an inductor)
DOES NOT use any less power than the linear regulators that John
Fields and I have presented?

And PWM'ing creates EMI.


Ignorance simply means "without knowledge"... not bad in itself... but
if you adhere to doing it your way when you've been told by experts
that there is no advantage, you graduate to stupid ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

It's so cold the Democrats have their hands in their own pockets.

How many times have you been told that PWM'ing (without an inductor)
DOES NOT use any less power than the linear regulators that John
Fields and I have presented?

And PWM'ing creates EMI.


Ignorance simply means "without knowledge"... not bad in itself... but
if you adhere to doing it your way when you've been told by experts
that there is no advantage, you graduate to stupid ;-)

...Jim Thompson

Tell you what Jim, we've been over these issues too often. I've tried to be
as courteous as I can since I do appreciate the feedback and it has helped
make a more robust design. But wink or not, this thread is ended when you
resort to that kind of insinuation. You can go back to your regulars here
for that kind of conversation. I refuse to participate.

The shipment from Newark will arrive tomorrow and I may pop back in and let
you know how it worked out. And experts? The one expert in this forum
who's opinion I respect didn't have an issue with EMI. So I won't either.

End of debate.

Jim Thompson wrote:

On Tue, 19 Jan 2010 10:54:09 -0500, Spehro Pefhany
wrote:

On Tue, 19 Jan 2010 07:32:10 -0500, "Charlie Smith"
wrote:


"RST Engineering" wrote in message
. ..
Why is EMI bad news in an airplane as opposed to anywhere else?

Jim


Hi Jim.

I will be building the PWM board and will simply test it. As you have often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)



That may be but Bliss was stupid, and dangerous!


--
Greed is the root of all eBay.

John Larkin wrote:

On Mon, 18 Jan 2010 23:28:49 -0800, RST Engineering
wrote:

On Fri, 15 Jan 2010 20:01:25 -0800, John Larkin
wrote:

Did you really need to quote 40+ lines for a one line response?

Jim

Get rid of the 555 PWM thing! It accomplishes nothing.

John

Are you incapable of using the bottom-posting convention?


That requires the ability to think.


--
Greed is the root of all eBay.

On Tue, 19 Jan 2010 12:49:27 -0500, "Charlie Smith"
wrote:




How many times have you been told that PWM'ing (without an inductor)
DOES NOT use any less power than the linear regulators that John
Fields and I have presented?

And PWM'ing creates EMI.


Ignorance simply means "without knowledge"... not bad in itself... but
if you adhere to doing it your way when you've been told by experts
that there is no advantage, you graduate to stupid ;-)

...Jim Thompson

Tell you what Jim, we've been over these issues too often. I've tried to be
as courteous as I can since I do appreciate the feedback and it has helped
make a more robust design. But wink or not, this thread is ended when you
resort to that kind of insinuation. You can go back to your regulars here
for that kind of conversation. I refuse to participate.

The shipment from Newark will arrive tomorrow and I may pop back in and let
you know how it worked out.

It'll dim, but it'll also produce current pulses in your wiring.

And experts? The one expert in this forum
who's opinion I respect didn't have an issue with EMI.

What "expert" would that be?

So I won't either.

End of debate.


A shame! Another obstinate dummy is born :-(

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Tue, 19 Jan 2010 08:52:40 -0700, Jim Thompson
/Snicker wrote:

On Tue, 19 Jan 2010 10:54:09 -0500, Spehro Pefhany
wrote:

On Tue, 19 Jan 2010 07:32:10 -0500, "Charlie Smith"
wrote:


"RST Engineering" wrote in message
...
Why is EMI bad news in an airplane as opposed to anywhere else?

Jim


Hi Jim.

I will be building the PWM board and will simply test it. As you have often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)

...Jim Thompson


People that spew this comment like they are quoting something from the
past are stupid because they (YOU) got it wrong.

It goes: "If ignorance is bliss, then knowledge must be folly."

Which is the modern resolve of the original:

"If ignorance is bliss, 'tis folly to be wise."

BIG difference between that and your 'phrase'. Nice admittance of the
facts about yourself though. It was not a surprise, however, as
associating you with severe tunnel vision doesn't even require mention.

On Tue, 19 Jan 2010 12:10:28 -0500, "Charlie Smith"
wrote:



Stupid. Now that's incurable.


With an attitude like that... you are the proof.

On Tue, 19 Jan 2010 11:05:41 -0700, Jim Thompson
/Snicker wrote:



A shame! Another obstinate dummy is born :-(

...Jim Thompson


Here is where the remark "Can it." is ****ing doubly appropriate.

On Fri, 15 Jan 2010 21:02:27 -0500, Charlie Smith wrote:

Group,

Many thanks for all the innovative and informative posts on the LED
lighting scheme. Many of you have been quite generous with your time
and knowledge and I am most appreciative.

Certainly there are many different ways to put this together and each
has a particular strength. I would prefer to stay with PWM techniques
for dimming versus voltage changes. With 20 (and perhaps more) LEDs in
the circuit, some are certain to begin to shut off before others when Vf
starts falling too low. I have taken as many of your suggestions as I
could understand
(Sorry JosephKK, but for me, yours was grad school.
Beta sounds like a coefficient of some sort. Perhaps you could post a
primer for me.)

No problem. Simply stated beta is the ratio between base current and collector
current. So 10 mA base current yields about 500 mA through the collector (with
something like 2 V collector to emitter. With R3 = 1K your base current will be
about 10 to 12 mA. A bit stronger drive by reducing R3 to 500 ohms will give you
better consistency for the LED drive because the 3055 will be fully switching.
Do make sure that your 555 can source at least 50 mA for this to be reliable.

and put them into a modified design. I have de-rated
the LEDs somewhat and switched to a low noise regulator that uses a trim
pot to adjust Vout. This way, should I need to go to two or even three
LEDs in series, I can accommodate this in the design.

Here I have calculated the total power consumption of the circuit at
4.56W with the LEDs consuming 1.23W (27% efficient). At 14V, it should
require 0.33A to run. The most critical part is the junction temp of
the regulator. It seemed to me to run too hot as is so I put in a
series resistor (12 ohms, 7W) to absorb some (3.075W) of the power. I
now estimate Tj to be 31.5°C hotter than ambient with an allowable Tmax
of 125°C on the chip. Safe even in the desert.

I also fixed a couple errors on the original schematic. As always, I
would appreciate some experienced eyes looking at this and letting me
know if I have seriously screwed something up somewhere. I'm not at all
familiar with linear low-noise regulators.

Thanks,
Charlie

On Sun, 17 Jan 2010 10:23:00 -0800, John Larkin wrote:

On 17 Jan 2010 16:54:58 GMT, mick wrote:

On Sun, 17 Jan 2010 08:35:12 -0800, John Larkin wrote:

On 17 Jan 2010 16:01:35 GMT, mick wrote:

On Fri, 15 Jan 2010 23:02:08 -0800, John Larkin wrote:

snip

There's a pot on the linear regulator; it's in plain sight. And that's
all this thing needs. The PWM accomplishes nothing.



PWM dimming is more efficient than linear dimming - by a long way. It
all depends on how much heat the OP is willing to let the dimmer
dissipate.

PWM is no more efficient than resistive dimming the way he did it. There
are no inductors in his circuit. All this sort of PWM can do is move the
heat around.



I couldn't see his circuit on my server, but I assumed that he was
varying the mark/space ratio. In that case power dissipation in the
output device is always low, depending on Vsat.

That just moves the heat into the series resistors. Overall efficiency
is always the same for a dissipative (inductor-free) regulator.

I don't believe you. Foe a given diode plus resistor at the same supply
voltage load the power dissipation varies closely with % on time.
Lower % on time = less power.

You could always LTspice it to see what it says, or you could build an
example circuit and measure it. Or you could blow me off.

With a linear regulator and properly chosen series resistors, you can
balance the regulator heat distribution versus dimming level.
Regulator power dissipation versus output voltage is sort of
parabolic... low at low illumination, low at max illumination, peaking
somewhere between.

It's easier to heatsink a voltage regulator than a lot of small
resistors.

Another advantage of a voltage regulator is that it regulates.

John

On Tue, 19 Jan 2010 10:28:56 -0700, Jim Thompson /Snicker wrote:

On Tue, 19 Jan 2010 12:10:28 -0500, "Charlie Smith"
wrote:

I will be building the PWM board and will simply test it. As you have
often
said, there is a reason why we put that one word promanently in our
aircraft.

"Experimental"?


Ignorance is bliss ?:-)

...Jim Thompson


Don't be so tough Jim. Ignorance is not a bad word. Its an entirely
curable condition. Stupid. Now that's incurable. And experimental doesn't
mean making an airplane the way the A-Team would; with a canvas, a couple
bamboo poles and duct tape. All it really means anymore is that the
airplane can be more modern than 1950's technology and you don't have to
auction off your first born. In the larger scheme of things, I don't see
instrument panel lights in the same arena as wing bolts. Let's try and keep
some perspective. Most of the suggestions made here would work just fine.
Just fuse the lights conservatively from the main buss and the very worst
that would happen is you would find yourself getting the flashlight from the
flight bag. And that happens more often than you might think.


Charlie


How many times have you been told that PWM'ing (without an inductor)
DOES NOT use any less power than the linear regulators that John
Fields and I have presented?

Really? Care to back that up with a LTspice simulation? Use Charlie Smith's
circuit or a near variant, steps of say 5% from 5% to 95% on time.

And PWM'ing creates EMI.
Yep.


Ignorance simply means "without knowledge"... not bad in itself... but
if you adhere to doing it your way when you've been told by experts
that there is no advantage, you graduate to stupid ;-)

...Jim Thompson

On Tue, 19 Jan 2010 11:05:41 -0700, Jim Thompson /Snicker wrote:

On Tue, 19 Jan 2010 12:49:27 -0500, "Charlie Smith"
wrote:




How many times have you been told that PWM'ing (without an inductor)
DOES NOT use any less power than the linear regulators that John
Fields and I have presented?

And PWM'ing creates EMI.


Ignorance simply means "without knowledge"... not bad in itself... but
if you adhere to doing it your way when you've been told by experts
that there is no advantage, you graduate to stupid ;-)

...Jim Thompson

Tell you what Jim, we've been over these issues too often. I've tried to be
as courteous as I can since I do appreciate the feedback and it has helped
make a more robust design. But wink or not, this thread is ended when you
resort to that kind of insinuation. You can go back to your regulars here
for that kind of conversation. I refuse to participate.

The shipment from Newark will arrive tomorrow and I may pop back in and let
you know how it worked out.

It'll dim, but it'll also produce current pulses in your wiring.

And experts? The one expert in this forum
who's opinion I respect didn't have an issue with EMI.

What "expert" would that be?

Good question. I have issues with the EMI but may not have brought it up.

So I won't either.

End of debate.


A shame! Another obstinate dummy is born :-(

...Jim Thompson

On Fri, 29 Jan 2010 17:37:28 -0800,
wrote:

On Sun, 17 Jan 2010 10:23:00 -0800, John Larkin wrote:

On 17 Jan 2010 16:54:58 GMT, mick wrote:

On Sun, 17 Jan 2010 08:35:12 -0800, John Larkin wrote:

On 17 Jan 2010 16:01:35 GMT, mick wrote:

On Fri, 15 Jan 2010 23:02:08 -0800, John Larkin wrote:

snip

There's a pot on the linear regulator; it's in plain sight. And that's
all this thing needs. The PWM accomplishes nothing.



PWM dimming is more efficient than linear dimming - by a long way. It
all depends on how much heat the OP is willing to let the dimmer
dissipate.

PWM is no more efficient than resistive dimming the way he did it. There
are no inductors in his circuit. All this sort of PWM can do is move the
heat around.



I couldn't see his circuit on my server, but I assumed that he was
varying the mark/space ratio. In that case power dissipation in the
output device is always low, depending on Vsat.

That just moves the heat into the series resistors. Overall efficiency
is always the same for a dissipative (inductor-free) regulator.

I don't believe you. Foe a given diode plus resistor at the same supply
voltage load the power dissipation varies closely with % on time.
Lower % on time = less power.

Sure. And lower linear regulator output current pulls less supply
power, too.


You could always LTspice it to see what it says, or you could build an
example circuit and measure it. Or you could blow me off.

Without inductors, using PWM to adjust LED brightness is just as
efficient as using a variable linear regulator. Or just a series
rheostat.

You could get higher efficiency using a rather complex inductorless
charge pump, but that wouldn't be worth the effort.

A linear regulator driving multiple paralleled LED strings, each a
resistor and two or maybe three LEDs, is clearly the easiest way to do
this.

John