"Perfect" LED current limiting challenge

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jimandy
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Re: "Perfect" LED current limiting challenge

Post by jimandy » Sat Jan 14, 2006 6:43 pm

Well, you see, cadstarsucks, you would have to read the entire thread which would probably take an infinitely long time to realize that (usurping a line from a popular song)...

"everything new is old again"
"if it's not another it's one thing."

jimandy
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Re: "Perfect" LED current limiting challenge

Post by jimandy » Sat Jan 14, 2006 6:44 pm

(duplicate post, sorry)

<small>[ January 14, 2006, 06:45 PM: Message edited by: jimandy ]</small>
"if it's not another it's one thing."

Mike6158
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Re: "Perfect" LED current limiting challenge

Post by Mike6158 » Sat Jan 14, 2006 6:45 pm

Yep

Yep

:D
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Sat Jan 14, 2006 6:55 pm

On the contrary,...Im on topic as I pointed out all the flaws in your original post.

You pretend you were on topic, as you revised time after time and then made claim it was everyone else’s mistake, and not yours.

Yes you revise, so what if you do this well with out admitting to your original mistake.

Why should we take you serious now?

Some one will solve that problem only to be confronted by you again with yet one more “change in plans”, and then what, they made a mistake? [where is your part in all of this?]

NO, SNL or other wise, the only fool here is you for playing others.

Fool us once, shame on you, fool us twice, shame on us.

How many time did you change or revise?

I Dare you to answer that one and If you cant, I will!

NO, you cant be taken serious and Im on track and your adrift in a sea of revision.

NO IAN, your the myopic fool who cant even keep track of your own words and post.

Verbatim, argue away?


posted December 02, 2005 04:59 AM
--------------------------------------------------------------------------------
Here's a challenge for you hacks.........
I need a battery operated very efficient(bordering on perfect) circuit for diving a LED but it has to be safe. Right now I'm using a PIC to control the a DC to DC converter voltage to a LED, but the LED "on" state is still controlled by a 2n3904 transistor. I intend to use a large enough resistor into the base of the transistor so that the current through the LED can only be a maximum of 30mA, then control the LED with PWM.
The transistor only creates a voltage drop of .1V allowing the DC to DC controller to be efficient. I need an average of 20mA through the LED but if the micro goes haywire I can't have the LED burning out so I need a max 30mA through the LED in a worst case scenario.
My concern is that the hfe of a 2n3904 transistor may vary so much that a design resistor producing a nominal 30mA may yield less than 20mA or more than 40mA depending on the hfe variance. Is that true? Are there transistors with "set" hfe's? Is there a better way to limit the current to 30 or so mA without creating a large voltage drop?


"Beauty is transitory" Spock

[ December 02, 2005, 05:04 AM: Message edited by: ian ]

jimandy
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Re: "Perfect" LED current limiting challenge

Post by jimandy » Sat Jan 14, 2006 7:22 pm

Fool us once, shame on you, fool us twice, shame on us
And fool us a million times and you're talking real confusion!
"if it's not another it's one thing."

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Sat Jan 14, 2006 7:25 pm

Confuse you or fool you.

Often mistaken with out a the proper education.

ian
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Re: "Perfect" LED current limiting challenge

Post by ian » Sat Jan 14, 2006 8:45 pm

Chris, do us all a favour and NEVER work on the shuttle, or nukes, or anything like that ok?
And Will, I'm glad you're on Chris' side, you're in Damn good company.

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Sat Jan 14, 2006 10:44 pm

IAN,....Is that an admission that you got it wrong, cant admit it, and must dodge the bullet at all cost?

Well, we accept your mistakes, your revision, and your elusive B.S. for the purpose of showing us what Canadians can also be like.

And we love Canadians.

From your posts we can in fact tell that Canadians can also be like half of the voters in this country, especially the ones that chose the current Resident.

Not too bright and definitely not able to handle the truth of their own decisions or words, with revision in heavily sunk in their resume.

Keep on Flipping.

And that’s is the nice response.

Much easier to own up to your words, than to deny them.

ian
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Re: "Perfect" LED current limiting challenge

Post by ian » Sun Jan 15, 2006 12:13 am

"I need a battery operated very efficient(bordering on perfect) circuit for diving a LED"

You're calling THAT off topic?????

You and Will need reading lessons.

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Sun Jan 15, 2006 9:37 pm

Ian

When you start a post off poorly, don’t blame it on others? And dont take chastizing for it as a victory.

When you don’t define your goals, don’t pretend others have failed you.

When others meet your original goals perfectly, mainly because you failed to define them, don’t change the playing field or rules. Start over.

You screwed up by not stating the parameters you actually needed to meet up front, then when many here met your simple rules and paramaters, you said "oops, did I forget to mention" and then keept adding in or changing everything.

Things like my suggestion that yes, indeed you can change any bigger battery pack for several smaller ones was met with, no I cant?

If you have the room, yes you can.

Things like higher percentages than you requested were also met, but again you came up with excuses, not reasons, and rule changes, that were never stated in the original post.

Another of YOUR failures to mention.

So with out whining, concede you have no skills in the asking of technical questions and parameters, and start over, reading all YOUR mistakes before the next post,.....and WE, with a full set of parameters will happily solve the problem.

However if you change the equations mid stream we can only conclude your either a big amature or you don’t seriously want the problem solved?

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MrAl
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Re: "Perfect" LED current limiting challenge

Post by MrAl » Tue Jan 17, 2006 12:34 pm

Hello again,

So...

Has anyone met the challenge yet? hee hee

Take care,
Al
LEDs vs Bulbs, LEDs are winning.

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Tue Jan 17, 2006 7:28 pm

The Shifting sands you mean?

Jarhead
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Re: "Perfect" LED current limiting challenge

Post by Jarhead » Wed Jan 18, 2006 7:34 am

Chris,

I tried your high current rapid pulse, in an attempt to validate your claim that LEDs miraculously get more efficient with fast high current pulses.

They don't.

The actual pulse, under loaded conditions across the LED:

<img src="http://www.molalla.net/~leeper/luxpulse.jpg" alt=" - " />


It actually ended much less efficient, but the LED does put out a pulse for 12nS (12 billionths of a second). Though the intensity of the pulse is remarkable. I am getting 10 Amps through the LED.

I tried a wide range of duty factors, 0.0000294 to 1 as well as many above and below that.

There is no magic mode.

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philba
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Re: "Perfect" LED current limiting challenge

Post by philba » Wed Jan 18, 2006 11:57 am

Thank you for doing this - there is nothing so concrete as actual results. Everything else is just hot air.

What was the perceived intensity at a duty cycle (or what ever, lets not go there) of, say, .2% (20mA avg)? I think you were saying that it wasn't higher than the steady state 20 mA situation.

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Chris Smith
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Re: "Perfect" LED current limiting challenge

Post by Chris Smith » Wed Jan 18, 2006 2:52 pm

"Though the intensity of the pulse is remarkable."

As in brighter?

Mine was brighter than a modern 10,000 mcd led
[a increase in brightness of about 400 x] and it was a lowely little green led.

"I am getting 10 Amps through the LED."

10 amps is the claim.[as per diagram]

"LEDs miraculously get more efficient with fast high current pulses"???

I never made that statment, what I claim is they get brighter with more current and less time, and they do.

You get more light out when you have larger pulses and shorter times.

Yet the over all amperage consumption drops.

So if you call this more efficient [light], then yes, its more efficient.

In my case it put out 400 time or more the brightness, something impossible to achieve through straight DC.

But because we cant compare one with the other, because one is impossible and the other is achievable, the term efficient is hard to appreciate.

However a ten amp pulse that has a duty cycle and duty factor equal over all to 20 milliamps does indeed produce more light for the same given [amps], and thus this too is more efficient.

I also stated that the over all current is less, and there fore they dont get as hot. Also true.

I also stated that they can run at these amperages with out simply burning out, also true.

I stated that the manufacture suggestions are just that, just a suggestion. Also true.

I stated that if you lower your over all on time with larger pulse amps you consume less over all current, also true.

Perhaps like Philba, we have a reading problem here where some wish I said something else?

I would like you to review my actual words, [they are still there] and If I mistated something Id be happy to deal with it.

So whats is the real problem?

Sounds like you did an excellent job, now try increasing the voltages and shortening up the pulse width, and see if you can achieve higher currents, perhaps even as high as 100 amps?

<small>[ January 18, 2006, 09:53 PM: Message edited by: Chris Smith ]</small>

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