Re: 12 LED resistance circuit help

On Tue, 26 Apr 2005 01:46:16 GMT, "Anthony Fremont"
<spam@xxxxxxxxxxxx> wrote:


>The point had nothing to do with whether it worked or not. The point
>was your mistake, or "trypo" as you like to call them.

---
I think I already admitted that but, just in case you missed it, here
ya go: I made a typographical error. Happy now?
---

>
>> ---
>>
>> >Just like the fact that it wouldn't have worked anyway.
>>
>> ---
>> You say that now like you knew it then, but the _fact_ is had Fred not
>> found it you'd still be just as in the dark now as you were then.
>
>I never bothered to look that close. Obviously Fred is well aware that
>you often post non-working circuits.

---
Well, since this _is_ an electronics group, I post circuits. Some
have technical errors in them, some don't. They usually get fixed.
The point is, _I_ post circuits. You, OTOH, critique typos when
someone catches you in a technical error.
---

>It might be different if I was actually looking for errors in the
>schematic, but I simply wasn't. I just noticed the glaring "trypo" in
>the text.

---
More's the pity.
---


>> >LMAO I'm not the one
>> >touting myself as a "professional circuit designer".

---
Perhaps that's because you aren't.

It's what I do for a living, so that makes it my profession. So I put
what I do in my .sig, what's wrong with that?

Interestingly, the fact that I do seems to thoroughly irk you since
you've mentioned it in a derogatory way more than once. Perhaps it's
because I choose to include "Professional" and you think that I should
be more humble and merely post "Circuit designer"? Perhaps you need
to get over yourself and come to the realization that not everyone is
going to accede to your whims as to what does and what doesn't
constitute proper behavior.
---

>Do you think that I have no other skills, or is circuit design all that
>is important?

---
What skills you may have, other than in electronics, are of very
little interest to me since, in these groups, what's important is
electronics and the ability to communicate. In seb, it's also
important to be able to render technical criticism
non-confrontationally in order to not scare off the newbies.
---

>> >I'm in it for the hobby and I've never pretended any different.
>>
>> ---
>> Good move on your part since the pretense would easily be found out.
>
>Kinda like the pretense where you come off as a civil human being?

---
I generally respond to civility with civility and to non-civility with
non-civility, and I very seldom make a non-preemptive strike.
---

>> >Perhaps you should have
>> >told the OP that your circuit was untested and unsimulated, because
>even
>> >I made the mistake of figuring that you actually posted stuff that
>you
>> >knew would work.
>>
>> ---
>> "Even" you? My, my, you _are_ a pretentious little prick, arent you?
>
>Actually, I meant that in a gullable sort of way. I've got your number
>now though.

---
Did you know that 'gullable' isn't in the dictionary?
---

>> You, on the other hand, seem to be interested in little more than
>> assuaging the effects that "current hogging" incident had your ego.
>
>Actually, I've been getting a kick out of watching you blow your top.
>:-)

---
Just a ruse to get you to bite, and now that the hook is set I own
you!
---


>I seriously doubt that I'll be reporting back much of anything about any
>of your circuits.

---
As do I. After all, it takes a modicum of acumen to do much more than
discover a typo in a technical article.
---

>I do suspect that I will be hearing from you more often in the future though.

---
Perhaps.

I will say one thing now, though, and that is that after having
checked your posting history last night I found that you do seem to
know what you're talking about, technically, most of the time, so I
apologize for any inaccurate broad-brush slurs I may have made
earlier.

However, as far as the PIC VS "discrete" logic thing goes, you're
still all wet. :-)
---




>> Well, duhhh...
>>
>> If you can't write properly, how can you expect people not to
>> misunderstand you?
>
>My comments in the original post were rhetorical, haven't you figured
>that out yet?

---
Nope. Would you mind going back and dredging up those comments and
explaining what made them rhetorical?
---


>> ---
>> So, when you can't defend yourself technically you slip into sarcasm?
>
>What's to defend, I admitted my little faux pa.

---
Then what was the reason for the sarcasm? Surely you realized it
would lead to no good.
---


>> >At any rate, you are the one setting the precident around here of
^^^^^^^^^
precedent

>> >jumping down someones throat when you don't like the accuracy of
^^^^^^^^
someone's
>their posts.


>> ---
>> If you want to find out how really stupid that statement is I suggest
>> you go to Google groups and read through my last 10,000 posts then,
>> once you're done, report back here with what you've learned.
>
>I didn't have to read 10,000 of them to figure out that you often go off
>like this. Four letter words, invectives and ad-hominem attacks seem to
>be a part of your regular forte.

---
Ahhh, you only read the juicy stuff. Try the tech, you might enjoy
it.
---


>> ---
>> That's because you had nothing to do any "cussing out" about and
>> because you're a ***.
>
>Really? Do ya think so?

---
Wellll... yeah.

After all, you say "WTF" so you can pretend that that's not saying
"What The ***", which is a *** trait because pussies dont like the
"F" word, and you say that you don't use "cuss words" when the
acronym embodies the 'cuss words' you know the reader will expand
mentally to yield the 'cuss words' you want to wield, but can't.
So, your saying that you don't use 'cuss words' is a lie and lying is
another *** trait.
---


>> If you can't see that as making a scene, then saying that you didn't
>> feel the need to, then you're even stupider than I thought.
>
>As I said before, I didn't see a need to make a scene when I first saw
>your mistake in SED. After that, when you posted your little trick
>setup question in SEB, I felt a bit different. And then after Watson's
>snide little remark about attrocious advice, I posted my little
^^^^^^^^^^
atrocious
>sarcastic rant. And now here we are. Is that timeline really so hard
>to grasp?

---
Certainly not, but it's not about a timeline, it's about changing
streams in mid-horse. What you said earlier, unconditionally, was that
you didn't feel it was necessary to make a scene, while what you're
saying now is that you're now attaching conditions which made it OK to
make a scene. Can't you see that that's an ex post facto violation of
the first statement by the second?

"Please, Mommy, Oh, pleeeease make him give me back my marbles...
---


>> So, you admit your reply was confrontational, and yet you said that
>> you didn't feel a need to make a scene. You just can't keep your
>> facts straight, can you?
>
>See above.

---
See reply, above, to "See above"
---



>> And, in view of the fact that you've proven yourself to be a liar, and
>> a stupid one at that, I maintain that you actually meant 'current
>> hogging' and decided that 'power hogging' would be a nice little
>> phrase to switch to to get you out of a jam.
>
>As I originally posted in reply to your little trick query:
>
><quote>
>Perhaps "dissipate more power" would have been more appropriate than
>"hog more current".
></quote>
>
>So as we can all plainly see, 'current hogging' is your own little
>fabrication of terminology that I never used.

---
Not at all, just a substitution used to tighten up of the sloppy
construct, which included my substitution of 'power hogging' for your
"dissipate more power".
---

>> ---
>> Yup, I thought so. You're the stereotypical petulant little puke who,
>> when she starts running out of ammunition starts whining about how I
>> should run _my_ business and how I should run _my_ life.
>
>If you think I'm running low on ammo, just keep posting. ;-) I could
>care less how you run your business _or_ your life. That is until you
>wish to horn into my life with your petulent, pedantic crap.
^^^^^^^^ ^
petulant cuss word

---
I don't consider B-Bs much of a threat, but I _am_ tiring of your
uninspired banter, so unless you can pick up the pace I'm outta here.
---


>> You were plain enough, the bobbing and weaving part was about the
>> transfer to the "power hogging" ploy, the intent of which was to make
>> it seem like you knew what you were talking about, but merely used the
>> wrong choice of words to describe what you meant. What I'm saying is
>
>Do you think that you've somehow proved that I didn't know the
>difference?

---
No. _You_ proved it with:

"Since there are two LEDs in series, one may hog more current than the
other resulting in its demise."

I merely asked a question designed to determine whether you did, in
fact, know the difference, but you took affrontery and refused to
answer it directly.
---

>> that I think you were being intellectually dishonest in that there is
>> no use of "power hogging" in the context into which you cast it.
>> "Power hogging, in all the cases I've been able to find refers to one
>> device, alone or in parallel with others connected to a common power
>> supply, which draws what seems to be an inordinate amount of power
>> from the supply.
>
>Again, like as stated earlier. I was originally going to say "juice"
>not current and not power. Again, I wish that I had just so I could see
>how you could have twisted that around.

---
Perhaps that's what you should have done. "Juice" is vague enough to
have covered all your bases and is a cutesy colloquialism, so I
probably would have just ignored it.
---

>Is juice power, or is it current or maybe even energy?
>Again, my original intent was not to use the word power either,
>even though it would have been the "most correct" term.
>Hard to believe that set you onto a personal crusade to prove me
>a liar.

---
You've supplied the proof, I merely pointed out the incidents.
---


>> Again, the context of your "prompt" was goading and your attitude was
>> clearly confrontational, yielding a richly deserved insulting reply.
>
>What type of reply do you think you deserve at this point in our
>relationship?
>

>> >I think I can still tell the difference between current, power and
>> >energy.
>>
>> ---
>> Really? Then be my guest and tell us all about it...
>
>Why do I think that no matter what I posted you would ridicule it?

---
That's not ridicule. I really don't think you know the difference and
I'm challenging you to provide proof that you do.
---

>> I can't imagine what makes you think you're important enough that I
>> should give a *** about your past errors.
>
>As you have so aptly demonstrated, you would leave no stone unturned in
>order to crucify me.

---
Oh, Gawd... Now you're casting yourself in the role of Christ and I'm
pounding in the nails. Get over yourself.
---

>> I know nothing about you which precedes your "current hogging" faux
>> pas, and I'm _certainly_ not interested in the genealogy of the huge
>> family of errors I'm sure you've procreated over the years.
>
>Too funny.

---
Thanks. :-)
---


>> ---
>> Awww... poor baby's playing the passive-aggressive "If you're smarter
>> than me then why pick on me?" card.
>
>I never said that I thought you were smarter than me. Only that you
>knew more about electronics. Don't flatter yourself, there is a
>difference.

---
Not so far.
---

>> I don't feel a need to dominate the NG, sweetie, but what I do like to
>> do is bring down self-important little bull*** artists like you, just
>
>Self important bull*** artist? That's got to be the most serious case
>of projection I've ever seen. Do you see me waving my credentials
>around? Do I have a sig line making bodacious claims?

---
Nope, but then, you've got nothing to make bodacious claims about.
---

>> for fun. And as far as being an expert goes, I could be a complete
>> moron and you'd still have to consider me an expert.
>
>That's not far from how I see things right now.

---
Ah, a double entendre; how delicious! Intended?
---

>> BTW, what happened with running those numbers to see whether the power
>> dissipation spec of an LED with Vf max in series with an LED with Vf
>> min and If running through _both_ of them would be exceeded?
>
>I don't know, what happened? How about you pick your own experiments,
>and I'll pick mine.

---
Awww... baby demurs. And here I thought I was going to get to see
some good stuff.

OK, _I'll_ do it.

Here's the circuit:


E1
|
[R1]
|
+---->E2
|
[DS1]
|
+---->E3
|
[DS2]
|
GND

Unfortunately, the data *** at the link you provided:

http://www.epitex.com/Catalog_PDF/08_Point_source_LED/L590CE-34F.PDF

doesn't show Vf min, and I couldn't find any Vf min for white LEDs so,
since you said that Vf can vary 2:1, looking at a Vf max of 4.0V for a
"typical" white LED at 20mA yields a Vf min of 2.0V. Also, 100mW
seems to be a pretty typical max dissipation, so if we redraw the
circuit with that in mind, and with LEDs with equal low Vf's we'll
get:


9.0V-+---->E1
|
[R1]
|
4.0V-+---->E2
|
[DS1]
|
2.0V-+---->E3
|
[DS2]
|
GND


The choice of 9V for E1 is based on the assumption that E1 will be
regulated and will give 1V of headroom if DS1 and DS2 are both at Vf
max.

Now, since the current in a series circuit is everywhere the same,
solving for R1 with 20mA of LED current yields:

(E1-E2) 5V
R1 = --------- = ------- = 250 ohms
It 0.02A


and the LEDs will each be dissipating:


P = IE = 0.02A * 2V = 0.04W


so everything will be fine.


Now, though, let's select a high Vf LED for DS1 and see what happens.


Here's the circuit now:

9.0V-+---->E1
|
[250]
|
6.0V-+---->E2
|
[DS1]
|
2.0V-+---->E3
|
[DS2]
|
GND


Since we now have a 3V drop across R1 the current will fall to:


E 3V
I = --- = ------ = 0.012A
R 250R


and the power being dissipated by DS1 will be:


P = 0.012A * 4V = 0.048W

So, if the LED is rated for 100mW max, it will be dissipating 48mW
and everything will still be fine, except the light output will
suffer.

If we have two Vf max LEDs in the circuit it'll look like this:


9.0V-+---->E1
|
[250]
|
8.0V-+---->E2
|
[DS1]
|
4.0V-+---->E3
|
[DS2]
|
GND


and the current in the circuit will fall to:

1V
I = ------ = 0.004A
250R

So, while everything will still be fine from a power dissipation
viewpoint, the light output from the LEDs will be greatly degraded.

Although it would be possible to fiddle with supply voltages and
series resistances in order to come up with a solution which would
allow a greater light output without overdriving the LEDs regardless
of the Vf spread, It would be more practical, IMO, to drive them with
a constant current.
---


>> If you'd pull that narcissistic little head out of your ass you might
>> come to the realization that you're not the arbiter of who's deserving
>> of what, and you might find that I am, in fact, civil. That doesn't
>
>Really, and I'm supposed to be convinced by that statement? ROTFL I
>think I'll continue to decide for myself who I respect.

---
Spoken like a true narcissist. It's 'whom', BTW.
---

>> mean that when a disingenuous little twat like you wanders in here and
>> starts playing games that she's not going to be called on it.
>
>Yeah, you're real civil.

---
We've already covered that.

--
John Fields
Professional Circuit Designer
.