LEDs in parallel

[Adam Funk]

I understand the points about calculating the series resistance for an
LED and the battery voltage, and about using a small resistor just to
be safe even if the battery voltage is "about right" for the LED.

The general advice "do not connect LEDs in parallel" refers to this
sort of circuit:

D1
R1 /---|<---\
ground------\/\/\/\/--| |-----+V
\---|<---/
D2

where even if D1 and D2 are the same model, slight variations could
cause one to burn out.


Of course, the following circuit is OK, provided R1 is correct for V
and D1, and R2 is correct for V and D2. And it can be extended for
additional Rs and Ds.

R1 D1
/----\/\/\/\/-----|<----\
ground-----| |-----+V
\----\/\/\/\/-----|<----/
R2 D2



What about the following variation on the first circuit? Both LEDs
are the same model, R1 + R2 is calculated for V and D1 and R2 is quite
small.

R2 D1
R1 /----\/\/\/-----|<----\
ground---\/\/\/--| |-----+V
\----\/\/\/-----|<----/
R2 D1



--
"Gonzo, is that the contract from the devil?"
"No, Kermit, it's worse than that. This is the bill from special
effects."

[Tom Biasi]

On Tue, 24 Jan 2012 13:08:48 +0000, Adam Funk <a24...@ducksburg.com>
wrote:

R1 will limit the current in both branches. Besides not being
necessary in your circuit what is your point?

Tom

[fungus]

On Jan 24, 2:08 pm, Adam Funk <a24...@ducksburg.com> wrote:
>                               R2       D1
>                 R1     /----\/\/\/-----|<----\
>      ground---\/\/\/--|                       |-----+V
>                        \----\/\/\/-----|<----/
>                               R2       D1
>

So you took a working circuit and added
an extra resistor? What does that achieve?

[Chiron]

This circuit is more complicated than the others, without offering any
benefit. You've already got two R2's to limit the current through the
diodes. R1 serves no additional purpose. If you want to lower the
current through the whole circuit, simply raise the values of the R2
resistors.

So you should ask yourself what advantage this circuit offers over the
other. How is it better, or what can it do that the others can't?

In this case you seem to believe that having low values for R2 is an
advantage. Why would it be? You need to limit the current through the
diodes, and because of the way that semiconductors work, a resistor in
parallel would not reliably do this. The reason for this is that a diode
that heats up begins to offer lower resistance, which allows more current
to flow through it, which causes it to heat up. You can wind up with
thermal runaway.

With diodes in parallel, you can wind up with most of the current flowing
through one diode. Since the resistor is valued for twice the desired
current per diode (since it's in parallel), the diode can easily be
stressed into failure.

With individual resistors, the current is limited for each diode,
avoiding this problem. Adding yet another resistor in parallel would
offer no advantage that I can see.


--
I'm always looking for a new idea that will be more productive than its
cost.
-- David Rockefeller

[Adam Funk]

On 2012-01-24, Chiron wrote:

> On Tue, 24 Jan 2012 13:08:48 +0000, Adam Funk wrote:

>> What about the following variation on the first circuit? Both LEDs are
>> the same model, R1 + R2 is calculated for V and D1 and R2 is quite
>> small.
>>
>> R2 D1
>> R1 /----\/\/\/-----|<----\
>> ground---\/\/\/--| |-----+V
>> \----\/\/\/-----|<----/
>> R2 D1
>
>
> This circuit is more complicated than the others, without offering any
> benefit. You've already got two R2's to limit the current through the
> diodes. R1 serves no additional purpose. If you want to lower the
> current through the whole circuit, simply raise the values of the R2
> resistors.
>
> So you should ask yourself what advantage this circuit offers over the
> other. How is it better, or what can it do that the others can't?

That's what I thought after I posted it. I guess the only advantage
is if you're short of higher valued resistors!


--
Bob just used 'canonical' in the canonical way. [Guy Steele]

[Jamie]

the last two will work.. and the problem is not some much burn out, it
is uneven forward current. One will dominate the other, which ever one
has the lowest forward voltage.

LED's work with current, not voltage, and have a forward starting
point of voltage before they even start to exert current, which is the
reason for the R, a simple way to get sufficient voltage but limiting
the current.

Trying to regulate the voltage with out over doing the current rating
on the LED is very hard to do, unless you have a current source that is
regulated or simply linearly limited like an R.

Jamie

[Kaz Kylheku]

On 2012-01-24, Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:
> LED's work with current, not voltage, and have a forward starting
> point of voltage before they even start to exert current, which is the
> reason for the R, a simple way to get sufficient voltage but limiting
> the current.

LEDs "don't work with voltage" but have a "starting point of voltage".

Brilliantly worded! :)

[petrus bitbyter]

"Adam Funk" <a24...@ducksburg.com> schreef in bericht
news:04n2v8x...@news.ducksburg.com...

LEDs are current drive devices so you will always need to limit the current
somehow. You will sometimes meet LEDs driven directly from a battery but
then the internal resistance of that battery accounts for the current
limiting. Sometimes you see LEDs directly in parallel which may do for LEDs
from the same batch as long as they are not driven to their limits. It is
nevertheless considered bad practice.

Usually you will not use three resistors if you can do with two of them. If
the LEDs differ widely they may also influence each other. Nevertheless
there may be some use for this circuit. For instance you may want to spread
the dissipated heat.

petrus bitbyter

[Jamie]

Yes it was, and right to the point.


Jamie

[Bill Bowden]

On Jan 24, 3:29 pm, "petrus bitbyter" <petrus.bitby...@hotmail.com>
wrote:
> "Adam Funk" <a24...@ducksburg.com> schreef in berichtnews:04n2v8x...@news.ducksburg.com...

I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
parallel across two AA batteries.

-Bill

[Tom Biasi]

On Tue, 24 Jan 2012 21:02:16 +0000, Adam Funk <a24...@ducksburg.com>
wrote:

>

>That's what I thought after I posted it. I guess the only advantage
>is if you're short of higher valued resistors!

That would come under "Making what you need with what you have."
Stay in there Adam, electronics is fun and never be afraid to ask for
help.

Tom

[Tom Biasi]

On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden

>
>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>parallel across two AA batteries.
>
>-Bill

They rely heavily on the battery's internal resistance and luck.

[John Larkin]

On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
wrote:

LEDs have a current:voltage slope that's not a brick wall. They can be
run at constant voltage, and often are.

The dynamic impedance of a flashlight-type LED is a lot higher than
the impedance of an AA battery.

John

[fungus]

On Jan 25, 2:13 am, Tom Biasi <tombi...@optonline.net> wrote:
>
> >That's what I thought after I posted it.  I guess the only advantage
> >is if you're short of higher valued resistors!
>
> That would come under "Making what you need with what you have."
> Stay in there Adam, electronics is fun and never be afraid to ask for
> help.
>

Yep, not all of us have an extensive parts bin
or single-click access to all those goodies in
the electronics catalogs.

Wouldn't be the first time I've twisted two or
three higher value resistors together to get
a lower value...

[fungus]

On Jan 25, 12:56 am, Bill Bowden <bper...@bowdenshobbycircuits.info>
wrote:

>
> I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
> parallel across two AA batteries.
>

Doesn't mean it's a good design that should be emulated...

The problem with LEDs is that their resistance isn't constant,
it varies with voltage.

There's a point where the resistance of a LED drops off
a cliff, allowing enough current through to burn them out.
That voltage needed for that is usually very very close to
their 'optimum' voltage. If you try to run them anywhere
near that voltage without current limiting you're living
dangerously.

[default]

On Tue, 24 Jan 2012 17:02:49 GMT, Chiron <chir...@gmail.com> wrote:

>This circuit is more complicated than the others, without offering any
>benefit. You've already got two R2's to limit the current through the
>diodes. R1 serves no additional purpose. If you want to lower the
>current through the whole circuit, simply raise the values of the R2
>resistors.

You are 100% correct but...

I've run into places where I'm switching on and off tri color leds
from the same supply with a common anode (in my case) then a limiting
resistor in the supply as well as the cathodes may come in handy to
balance light output among different colors.

[Tom Biasi]

True, but the slope drops off sharply. Not good design.

[John Larkin]

On Wed, 25 Jan 2012 02:07:02 -0800 (PST), fungus <to...@artlum.com>
wrote:

>On Jan 25, 12:56 am, Bill Bowden <bper...@bowdenshobbycircuits.info>
>wrote:
>>
>> I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>> parallel across two AA batteries.
>>
>
>Doesn't mean it's a good design that should be emulated...
>
>The problem with LEDs is that their resistance isn't constant,
>it varies with voltage.
>
>There's a point where the resistance of a LED drops off
>a cliff,

The typical small (like, 20 to 50 mA rated) LED has the classic
exponential current:voltage curve at lower currents, and gets ohmic at
higher currents. Actually, almost all diodes do this. Check the data
sheets on specific parts.

allowing enough current through to burn them out.
>That voltage needed for that is usually very very close to
>their 'optimum' voltage.

Not usually true. Again, check the curves on a specific part.

Constant-current drive is better of course, but CV can be usable.

John

[fungus]

On Jan 25, 5:54 pm, John Larkin

<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> Constant-current drive is better of course, but CV can be usable.
>

In the context of the thread:

Using CV to run LEDs in parallel near their
optimum current is risky (the first circuit in
the thread).

If you're using CV then at least make sure
each LED has its own resistor. If you're
really paranoid then design for a couple
of mA less then spec.

[Adam Funk]

Doesn't that flashlight design cause inconsistent behavior when you
switch between alkaline & rechargeable batteries?


--
It is probable that television drama of high caliber and produced by
first-rate artists will materially raise the level of dramatic taste
of the nation. (David Sarnoff, CEO of RCA, 1939; in Stoll 1995)

[John Fields]

On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
>wrote:
>
>>On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
>>>
>>>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>>>parallel across two AA batteries.
>>>
>>>-Bill
>>
>>They rely heavily on the battery's internal resistance and luck.
>
>LEDs have a current:voltage slope that's not a brick wall.

---
Pretty close, though, once you get past the knee.
---

>They can be
>run at constant voltage, and often are.

---
Inadvisedly so, unless the source voltage can never rise high enough
to over-current the LED.
---

>The dynamic impedance of a flashlight-type LED is a lot higher than
>the impedance of an AA battery.

---
All that says is that if the voltage from the constant-voltage low
impedance source is high enough to over-current the LED, then the
source's impedance won't stop the destruction of, or enhance the
limited life of, the LED.

--
JF

[John Larkin]

On Wed, 25 Jan 2012 19:26:26 -0600, John Fields
<jfi...@austininstruments.com> wrote:

>On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
>>wrote:
>>
>>>On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
>>>>
>>>>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>>>>parallel across two AA batteries.
>>>>
>>>>-Bill
>>>
>>>They rely heavily on the battery's internal resistance and luck.
>>
>>LEDs have a current:voltage slope that's not a brick wall.
>
>---
>Pretty close, though, once you get past the knee.

It's usually the other way around: exponential at low currents, ohmic
at higher currents.

John

[k...@att.bizzzzzzzzzzzz]

On Wed, 25 Jan 2012 18:44:44 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Wed, 25 Jan 2012 19:26:26 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
>>>wrote:
>>>
>>>>On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
>>>>>
>>>>>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>>>>>parallel across two AA batteries.
>>>>>
>>>>>-Bill
>>>>
>>>>They rely heavily on the battery's internal resistance and luck.
>>>
>>>LEDs have a current:voltage slope that's not a brick wall.
>>
>>---
>>Pretty close, though, once you get past the knee.
>
>
>It's usually the other way around: exponential at low currents, ohmic
>at higher currents.

Some people still think an exponential has a "knee".

[Adam Funk]

Ha ha, thanks!

[John Fields]

On Wed, 25 Jan 2012 18:44:44 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Wed, 25 Jan 2012 19:26:26 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
>>>wrote:
>>>
>>>>On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
>>>>>
>>>>>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>>>>>parallel across two AA batteries.
>>>>>
>>>>>-Bill
>>>>
>>>>They rely heavily on the battery's internal resistance and luck.
>>>
>>>LEDs have a current:voltage slope that's not a brick wall.
>>
>>---
>>Pretty close, though, once you get past the knee.
>
>
>It's usually the other way around: exponential at low currents, ohmic
>at higher currents.

---
It never really gets ohmic unless you drive the junction hard enough
to short it, and once you get past the knee - where a relatively large
voltage change results in a small current change - the slope changes
so that for a relatively small increase in voltage you get a large
increase in current.

--
JF

[Adam Funk]

On 2012-01-24, Jamie wrote:

> the last two will work.. and the problem is not some much burn out, it
> is uneven forward current. One will dominate the other, which ever one
> has the lowest forward voltage.
>
> LED's work with current, not voltage, and have a forward starting
> point of voltage before they even start to exert current, which is the
> reason for the R, a simple way to get sufficient voltage but limiting
> the current.
>
> Trying to regulate the voltage with out over doing the current rating
> on the LED is very hard to do, unless you have a current source that is
> regulated or simply linearly limited like an R.

Thanks.

[John Fields]

On Thu, 26 Jan 2012 17:50:24 -0600, John Fields

---
news:86g8i7pot46vjj41o...@4ax.com


--
JF

[John Larkin]

On Thu, 26 Jan 2012 17:50:24 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Wed, 25 Jan 2012 18:44:44 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Wed, 25 Jan 2012 19:26:26 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>>
>>>On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tomb...@optonline.net>
>>>>wrote:
>>>>
>>>>>On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
>>>>>>
>>>>>>I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
>>>>>>parallel across two AA batteries.
>>>>>>
>>>>>>-Bill
>>>>>
>>>>>They rely heavily on the battery's internal resistance and luck.
>>>>
>>>>LEDs have a current:voltage slope that's not a brick wall.
>>>
>>>---
>>>Pretty close, though, once you get past the knee.
>>
>>
>>It's usually the other way around: exponential at low currents, ohmic
>>at higher currents.
>
>---
>It never really gets ohmic unless you drive the junction hard enough
>to short it,

Nonsense, unless you plan to quibble about the word "really."

> and once you get past the knee -

As noted, diodes don't have a "knee" unless you arbitrarily define
one.

where a relatively large
>voltage change results in a small current change - the slope changes
>so that for a relatively small increase in voltage you get a large
>increase in current.

No, that's backwards. Diodes, and LEDs, have current exponential on
voltage at low currents. At higher currents, the contact and bulk
resistivity start to dominate, and the voltage:current curve gets
nearly linear.

Just look at the curves on real led data sheets. The smaller parts
start to get ohmic at low currents, just a few mA. Bigger junctions
will stay exponential at higher currents, because they have less bulk
resistance.

This is a really tiny junction, so the v/i curve is a straight line at
operating currents:

http://vcclite.com/wp-content/files/VAOL-S8GT4-LED-0805-green.pdf

Bigger parts start to go ohmic at higher currents:

http://www.vishay.com/docs/81345/vlmp232.pdf

http://catalog.osram-os.com/jsp/download.jsp?rootPath=/media/&name=LA_LO_LY_E67F_Pb_free.pdf&docPath=Graphics/00057343_0.pdf&url=/media//_en/Graphics/00057343_0.pdf


Ordinary diodes do this, too. That's why diodes have some current
where their v:i curve has a zero temperature coefficient; the
exponential part has a negative TC but the bulk resistance TC is
positive. For small schottky diodes, that can be in the 10 mA
ballpark, so that can be useful.


--

John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[John Larkin]

On Wed, 25 Jan 2012 11:58:29 -0800 (PST), fungus <to...@artlum.com>
wrote:

>On Jan 25, 5:54 pm, John Larkin
><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>> Constant-current drive is better of course, but CV can be usable.
>>
>
>In the context of the thread:
>
>Using CV to run LEDs in parallel near their
>optimum current is risky (the first circuit in
>the thread).
>

Well, lots of people do it and get away with it.

John

[Bill Bowden]

On Jan 28, 11:59 am, John Larkin

<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Wed, 25 Jan 2012 11:58:29 -0800 (PST), fungus <to...@artlum.com>
> wrote:
>
> >On Jan 25, 5:54 pm, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >> Constant-current drive is better of course, but CV can be usable.
>
> >In the context of the thread:
>
> >Using CV to run LEDs in parallel near their
> >optimum current is risky (the first circuit in
> >the thread).
>
> Well, lots of people do it and get away with it.
>
> John
>

I executed a red LED to see what it would withstand. The LED just
starts to glow at about 1.47 volts and drops 2 volts at 160mA. At 2.7
volts the current is 200mA and brightness is fairly constant over the
range of 20Ma to 200mA. At 230mA the voltage rises to almost 5 volts
and the brightness falls off. The LED dies a little above that, but it
lived a happy life.

-Bill

> --
>
> John Larkin, President       Highland Technology Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

[John Fields]

On Sat, 28 Jan 2012 11:58:15 -0800, John Larkin

---
There's no quibbling about the word "really", the quibble is about
your assertion that a diode junction is ohmic at vaguely described
qualitative "higher currents".
---

>> and once you get past the knee -
>
>As noted, diodes don't have a "knee" unless you arbitrarily define
>one.

---
"As noted"???

I don't really think an "arbitrary" definition is necessary, since the
location of the knee has been with us for decades.
---

>where a relatively large
>>voltage change results in a small current change - the slope changes
>>so that for a relatively small increase in voltage you get a large
>>increase in current.
>
>No, that's backwards. Diodes, and LEDs, have current exponential on
>voltage at low currents. At higher currents, the contact and bulk
>resistivity start to dominate, and the voltage:current curve gets
>nearly linear.

---
True enough, but "nearly linear" isn't quite the same as "ohmic", is
it?

And, it's just plain silly talk since it has very little to do with
what we're talking about, which is running LEDs from a voltage source.
Look at the V:I curve for a vanilla silicon diode at from zero volts
to where it lets, say, 1mA through the diode and you'll see that the
voltage across the diode, at that point, will be about 0.7V, mas o
menos.

Now run the voltage up to about 1.4V.

Will the current through the diode stop at 2mA?
---

>Just look at the curves on real led data sheets. The smaller parts
>start to get ohmic at low currents, just a few mA. Bigger junctions
>will stay exponential at higher currents, because they have less bulk
>resistance.
>
>This is a really tiny junction, so the v/i curve is a straight line at
>operating currents:
>
>http://vcclite.com/wp-content/files/VAOL-S8GT4-LED-0805-green.pdf

---
Surely you can't be serious.

If you examine the Forward Current vs Forward Voltage curve with some
care, you'll find that with 10mA through the LED it drops about 1.9
volts, and with 20mA through it drops about 2 volts.

Simply using Ohm's law in both cases - in order to determine the
resistance of the LED in each case - yields for the first case:

E 1.9V
R = --- = ------- = 190 ohms
I 1e-2A

and for the second:


E 2.0V
R = --- = ------- = 100 ohms
I 2e-2A


then, since an ohmic load's resistance must be constant as the current
through it varies, that LED is clearly _not_ an ohmic load.
---

>Bigger parts start to go ohmic at higher currents:
>
>http://www.vishay.com/docs/81345/vlmp232.pdf
>
>http://catalog.osram-os.com/jsp/download.jsp?rootPath=/media/&name=LA_LO_LY_E67F_Pb_free.pdf&docPath=Graphics/00057343_0.pdf&url=/media//_en/Graphics/00057343_0.pdf
>
>
>Ordinary diodes do this, too. That's why diodes have some current
>where their v:i curve has a zero temperature coefficient; the
>exponential part has a negative TC but the bulk resistance TC is
>positive. For small schottky diodes, that can be in the 10 mA
>ballpark, so that can be useful.

---
Grasping at straws?

--
JF

[k...@att.bizzzzzzzzzzzz]

On Sat, 28 Jan 2012 18:43:09 -0600, John Fields

John, I told you there are people who believe there is a "knee" in an
exponential function. ;-)

>---
>
>>where a relatively large
>>>voltage change results in a small current change - the slope changes
>>>so that for a relatively small increase in voltage you get a large
>>>increase in current.
>>
>>No, that's backwards. Diodes, and LEDs, have current exponential on
>>voltage at low currents. At higher currents, the contact and bulk
>>resistivity start to dominate, and the voltage:current curve gets
>>nearly linear.
>
>---
>True enough, but "nearly linear" isn't quite the same as "ohmic", is
>it?

What do you think constant dI/DV means?

<...>

[k...@att.bizzzzzzzzzzzz]

On Sat, 28 Jan 2012 16:31:37 -0800 (PST), Bill Bowden
<bpe...@bowdenshobbycircuits.info> wrote:

>On Jan 28, 11:59 am, John Larkin
><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>> On Wed, 25 Jan 2012 11:58:29 -0800 (PST), fungus <to...@artlum.com>
>> wrote:
>>
>> >On Jan 25, 5:54 pm, John Larkin
>> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>> >> Constant-current drive is better of course, but CV can be usable.
>>
>> >In the context of the thread:
>>
>> >Using CV to run LEDs in parallel near their
>> >optimum current is risky (the first circuit in
>> >the thread).
>>
>> Well, lots of people do it and get away with it.
>>
>> John
>>
>
>I executed a red LED to see what it would withstand. The LED just
>starts to glow at about 1.47 volts and drops 2 volts at 160mA. At 2.7
>volts the current is 200mA and brightness is fairly constant over the
>range of 20Ma to 200mA. At 230mA the voltage rises to almost 5 volts
>and the brightness falls off. The LED dies a little above that, but it
>lived a happy life.

Your eye is "fairly constant" over that range. Measure it with a light meter.

[Jim Thompson]

On Sat, 28 Jan 2012 18:43:09 -0600, John Fields

\
Let it go Fields. It's Larkin. Did you notice the new narcissistic
SIG ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
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I love to cook with wine. Sometimes I even put it in the food.

[John Larkin]

And there are people who think that the only kind of resistance is
E/I.

Some famous person once said "When all you know is Ohm's Law,
everything looks like a resistor."

Well, that was me, actually.

[John Larkin]

On Sat, 28 Jan 2012 18:43:09 -0600, John Fields

Lots of consumer products do exactly that.

>Look at the V:I curve for a vanilla silicon diode at from zero volts
>to where it lets, say, 1mA through the diode and you'll see that the
>voltage across the diode, at that point, will be about 0.7V, mas o
>menos.

0.7 volts at 1 mA? Where can I get some of those cool silicon LEDs?

What color are they?

John

[John Larkin]

On Sat, 28 Jan 2012 16:31:37 -0800 (PST), Bill Bowden
<bpe...@bowdenshobbycircuits.info> wrote:

>On Jan 28, 11:59 am, John Larkin
><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>> On Wed, 25 Jan 2012 11:58:29 -0800 (PST), fungus <to...@artlum.com>
>> wrote:
>>
>> >On Jan 25, 5:54 pm, John Larkin
>> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>> >> Constant-current drive is better of course, but CV can be usable.
>>
>> >In the context of the thread:
>>
>> >Using CV to run LEDs in parallel near their
>> >optimum current is risky (the first circuit in
>> >the thread).
>>
>> Well, lots of people do it and get away with it.
>>
>> John
>>
>
>I executed a red LED to see what it would withstand. The LED just
>starts to glow at about 1.47 volts and drops 2 volts at 160mA. At 2.7
>volts the current is 200mA and brightness is fairly constant over the
>range of 20Ma to 200mA.

Yeah, efficiency drops at high currents, partially due to heating.

At 230mA the voltage rises to almost 5 volts
>and the brightness falls off. The LED dies a little above that, but it
>lived a happy life.

Something small like this

http://www.kingbrightusa.com/images/catalog/SPEC/APTD1608QBC-D.pdf

could be reasonably run from a couple of alkaline cells.

--

John Larkin, President Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

[John Larkin]

If you have anything intelligent to say on topic, give it a try.

[John Fields]

On Sat, 28 Jan 2012 17:51:38 -0800, John Larkin

---
Sure, and if they're designed properly, the resistance of the LED and
the internal resistance of the battery will limit the current through
the LED to safe levels.

If not, LED life will be reduced; sometimes drastically.
---

>>Look at the V:I curve for a vanilla silicon diode at from zero volts
>>to where it lets, say, 1mA through the diode and you'll see that the
>>voltage across the diode, at that point, will be about 0.7V, mas o
>>menos.
>>

>>Now run the voltage up to about 1.4V.
>>Will the current through the diode stop at 2mA?
>
>

>0.7 volts at 1 mA? Where can I get some of those cool silicon LEDs?
>What color are they?

---
More silliness, since since when is a "vanilla silicon diode" an LED?

I've got a vanilla 1N4148 on the bench with 1.0000 mA through it and
0.618 V across it, so what do you think will happen if I double the
voltage across it?

--
JF

[John Larkin]

On Sun, 29 Jan 2012 10:44:58 -0600, John Fields

Something like 350 mA. But there's a lot of variation between
different manufacturers' parts.

If it's on a PC board, with a bit of pad+trace to heatsink the leads,
it should survive.

At that voltage, it will be well into its ohmic range, namely the
current:voltage line will be straight, not exponential. That should be
close to the zero TC point too.

Without the series resistance component, pure exponential, increasing
the diode voltage from 0.6 to 1.2 would increase the current by a
factor of about 10^10.

If you paralleled a bunch of 1N4148s from the same reel, and ran them
at, say, 100 mA or so, I'd expect pretty good current sharing.

[John Fields]

On Sun, 29 Jan 2012 10:18:28 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sun, 29 Jan 2012 10:44:58 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>
>>I've got a vanilla 1N4148 on the bench with 1.0000 mA through it and
>>0.618 V across it, so what do you think will happen if I double the
>>voltage across it?
>
>Something like 350 mA. But there's a lot of variation between
>different manufacturers' parts.

---
Snipped irrelevant pontificating.

--
JF

[John Larkin]

On Sun, 29 Jan 2012 13:53:22 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Sun, 29 Jan 2012 10:18:28 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Sun, 29 Jan 2012 10:44:58 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>>
>>>
>>>I've got a vanilla 1N4148 on the bench with 1.0000 mA through it and
>>>0.618 V across it, so what do you think will happen if I double the
>>>voltage across it?
>>
>>Something like 350 mA. But there's a lot of variation between
>>different manufacturers' parts.

What did you measure?

>
>---
>Snipped irrelevant pontificating.

Electronics is irrelevant to you?

The LT Spice model for the 1N4148 has an Rs value of 0.568 ohms, which
looks a tad low to me.

[John Fields]

On Sun, 29 Jan 2012 12:18:40 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sun, 29 Jan 2012 13:53:22 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Sun, 29 Jan 2012 10:18:28 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Sun, 29 Jan 2012 10:44:58 -0600, John Fields
>>><jfi...@austininstruments.com> wrote:
>>>
>>>>
>>>>I've got a vanilla 1N4148 on the bench with 1.0000 mA through it and
>>>>0.618 V across it, so what do you think will happen if I double the
>>>>voltage across it?
>>>
>>>Something like 350 mA. But there's a lot of variation between
>>>different manufacturers' parts.
>
>What did you measure?

---

712mA.
---

>>---
>>Snipped irrelevant pontificating.
>
>Electronics is irrelevant to you?

---
No, irrelevant pontificating about it is.
---

>The LT Spice model for the 1N4148 has an Rs value of 0.568 ohms, which
>looks a tad low to me.

---
Assuming 750mA puts it into the linear region, then Rs = Vf/If ~ 1.7
ohms, so I agree.

How's that for a first? ;)

--
JF

[John Larkin]

On Sun, 29 Jan 2012 15:33:40 -0600, John Fields

That's the static resistance. A more useful value is dV/dI, the slope
of the curve in the linear region. That's the Spice 0.568 value. The
value from several 1N4148 data sheets is more like 0.7 ohms.

>
>How's that for a first? ;)

LT Spice shows 0.64 amps at 1.236 volts. Most diode data sheets show
about half that current.

[John Fields]

On Sun, 29 Jan 2012 14:27:45 -0800, John Larkin

---
Since there will always be a disparity between minority and majority
carriers in the mix, and charge will be shared between them, there can
never be a linear region.

Except, perhaps, for the fleeting moment when the TC across the
junction equals zero.
---

>That's the Spice 0.568 value. The
>value from several 1N4148 data sheets is more like 0.7 ohms.

---
Maximum, at If(nom) or, perhaps, at If(max).

Do you have some real data to support your position or are you just
looking to blame LTspice for your failings?
---

>>How's that for a first? ;)
>
>LT Spice shows 0.64 amps at 1.236 volts. Most diode data sheets show
>about half that current.

---
Most 1N4148 data sheets show the drop across the diode with up to a
couple of hundred milliamps through it, so what are you talking about?
--
JF

[John Larkin]

On Thu, 02 Feb 2012 19:38:06 -0600, John Fields

You don't actually care about diodes, you just want something to whine
about.

[AllInTheChi]

On Thu, 02 Feb 2012 19:49:41 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>
>You don't actually care about diodes, you just want something to whine
>about.

And you guys call *me* a troll?

I have PCBs with 30 LEDs and limit resistors on it. Powered by a 12V
6W dongle.

I posted a hi res pic of them on flickr.

[josephkk]

On Sat, 28 Jan 2012 17:42:27 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>
>>>I don't really think an "arbitrary" definition is necessary, since the
>>>location of the knee has been with us for decades.
>>
>>John, I told you there are people who believe there is a "knee" in an
>>exponential function. ;-)
>
>And there are people who think that the only kind of resistance is
>E/I.
>
>Some famous person once said "When all you know is Ohm's Law,
>everything looks like a resistor."
>
>Well, that was me, actually.
>

Switch famous to infamous and the description of yourself is all too apt.

?-)

[John Larkin]

After almost a week of brooding, that's all you can come up with?

[John Larkin]

You connected LEDs and resistors?

[Jim Thompson]

On Thu, 02 Feb 2012 20:28:15 -0800, josephkk <joseph_...@sbcglobal.net>
wrote:

Arguing with Larkin is like arguing with a liberal, they're all mouth and no
math.

...Jim Thompson
--
[On the Road, in New York]

[AllInTheChi]

On Thu, 02 Feb 2012 21:10:07 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 02 Feb 2012 20:16:11 -0800, AllInTheChi
><Hos...@magicregion.org> wrote:
>
>>On Thu, 02 Feb 2012 19:49:41 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>
>>>You don't actually care about diodes, you just want something to whine
>>>about.
>>
>> And you guys call *me* a troll?
>>
>> I have PCBs with 30 LEDs and limit resistors on it. Powered by a 12V
>>6W dongle.
>>
>> I posted a hi res pic of them on flickr.
>
>You connected LEDs and resistors?

36 LEDs and 12 resistors.

12 sets at one dongle per set of two sticks. That's only 3 Watts each
stick. Unless the dongles lie or are being overtaxed.

I am quite sure I could put more than two sticks on a single dongle,
but I didn't want to sit down and configure an LVDC distribution panel.
They work fine in pairs, and the power strip is a 'panel' for the
dongles. Same juice ends up getting used either way, though there are
likely a bit more losses on the many dongles method. Making fewer dongle
fight harder is probably a slight bit more efficient. (splitting it on
the DC side).

[John Larkin]

On Fri, 03 Feb 2012 05:24:52 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Thu, 02 Feb 2012 20:28:15 -0800, josephkk <joseph_...@sbcglobal.net>
>wrote:
>
>>On Sat, 28 Jan 2012 17:42:27 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>
>>>>>I don't really think an "arbitrary" definition is necessary, since the
>>>>>location of the knee has been with us for decades.
>>>>
>>>>John, I told you there are people who believe there is a "knee" in an
>>>>exponential function. ;-)
>>>
>>>And there are people who think that the only kind of resistance is
>>>E/I.
>>>
>>>Some famous person once said "When all you know is Ohm's Law,
>>>everything looks like a resistor."
>>>
>>>Well, that was me, actually.
>>>
>>
>>Switch famous to infamous and the description of yourself is all too apt.
>>
>>?-)
>
>Arguing with Larkin is like arguing with a liberal, they're all mouth and no
>math.
>
> ...Jim Thompson

How come you never post anything with content?


**********************************

John Larkin, President
Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser controllers

Photonics and fiberoptic TTL data links

VME thermocouple, LVDT, synchro acquisition and simulation

[Jim Thompson]

On Fri, 03 Feb 2012 10:39:57 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>On Fri, 03 Feb 2012 05:24:52 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Thu, 02 Feb 2012 20:28:15 -0800, josephkk <joseph_...@sbcglobal.net>
>>wrote:
>>
>>>On Sat, 28 Jan 2012 17:42:27 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>
>>>>>>I don't really think an "arbitrary" definition is necessary, since the
>>>>>>location of the knee has been with us for decades.
>>>>>
>>>>>John, I told you there are people who believe there is a "knee" in an
>>>>>exponential function. ;-)
>>>>
>>>>And there are people who think that the only kind of resistance is
>>>>E/I.
>>>>
>>>>Some famous person once said "When all you know is Ohm's Law,
>>>>everything looks like a resistor."
>>>>
>>>>Well, that was me, actually.
>>>>
>>>
>>>Switch famous to infamous and the description of yourself is all too apt.
>>>
>>>?-)
>>
>>Arguing with Larkin is like arguing with a liberal, they're all mouth and no
>>math.
>>
>> ...Jim Thompson
>
>
>How come you never post anything with content?
>

I knew you were going to say that ;-) However, when I _do_ publish technical
content, it is complete, and _works_ >:-}

Didn't anyone ever teach you about separating the message body from your
signature with dash-dash-space ??

See... http://linux.sgms-centre.com/misc/netiquette.php

>
>**********************************
>
>John Larkin, President
>Highland Technology, Inc
>
>jlarkin at highlandtechnology dot com
>http://www.highlandtechnology.com
>
>Precision electronic instrumentation
>Picosecond-resolution Digital Delay and Pulse generators
>Custom laser controllers
>Photonics and fiberoptic TTL data links
>VME thermocouple, LVDT, synchro acquisition and simulation

[John Fields]

On Fri, 03 Feb 2012 10:39:57 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>On Fri, 03 Feb 2012 05:24:52 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Thu, 02 Feb 2012 20:28:15 -0800, josephkk <joseph_...@sbcglobal.net>
>>wrote:
>>
>>>On Sat, 28 Jan 2012 17:42:27 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>
>>>>>>I don't really think an "arbitrary" definition is necessary, since the
>>>>>>location of the knee has been with us for decades.
>>>>>
>>>>>John, I told you there are people who believe there is a "knee" in an
>>>>>exponential function. ;-)
>>>>
>>>>And there are people who think that the only kind of resistance is
>>>>E/I.
>>>>
>>>>Some famous person once said "When all you know is Ohm's Law,
>>>>everything looks like a resistor."
>>>>
>>>>Well, that was me, actually.
>>>>
>>>
>>>Switch famous to infamous and the description of yourself is all too apt.
>>>
>>>?-)
>>
>>Arguing with Larkin is like arguing with a liberal, they're all mouth and no
>>math.
>>
>> ...Jim Thompson
>
>
>How come you never post anything with content?

---
He often does, whether or not you're capable of understanding the
content.

--
JF

[John Larkin]

Well, that was a great technical contribution too.

[John Fields]

On Thu, 02 Feb 2012 19:49:41 -0800, John Larkin

---
Nonsense.

Whenever I checkmate you, and you realize you've lost, you sidestep,
pretending you have moves left which you don't, in order to prolong
the knell of your death bell and hope for a miracle to save you.

--
JF

[John Fields]

On Fri, 03 Feb 2012 16:09:58 -0800, John Larkin

---
Sorry you misunderstood, but that was a non-technical comment directed
at your reticence to admit to error.

--
JF

[John Larkin]

On Fri, 03 Feb 2012 18:59:44 -0600, John Fields

Checkmate? Save me? How pathetic.

You are raving again, in really corny stilted prose, and it's not
about diodes.


To 500 mA:

http://www.nxp.com/documents/data_sheet/1N4148_1N4448.pdf


To 800 mA:

http://www.fairchildsemi.com/ds/1N/1N4148.pdf


~~800 mA:

http://www.vishay.com/docs/81857/1n4148.pdf


which you could have found yourself in a couple of minutes if you were
interested in diodes. But you'd rather whine and strut and cluck.

**********************************

John Larkin, President
Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser controllers

Photonics and fiberoptic TTL data links

[DarkMatter]

On Fri, 03 Feb 2012 10:39:57 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>

>How come you never post anything with content?

Is that what you call the crap you post?

[Numer0 Un0]

On Fri, 03 Feb 2012 16:09:58 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>Well, that was a great technical contribution too.

Hey, idiot. YOU are UNqualified to make a valid assessment about
anyone else.

You got that, boy?

[k...@att.bizzzzzzzzzzzz]

On Thu, 02 Feb 2012 21:09:10 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 02 Feb 2012 20:28:15 -0800, josephkk
><joseph_...@sbcglobal.net> wrote:
>
>>On Sat, 28 Jan 2012 17:42:27 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>
>>>>>I don't really think an "arbitrary" definition is necessary, since the
>>>>>location of the knee has been with us for decades.
>>>>
>>>>John, I told you there are people who believe there is a "knee" in an
>>>>exponential function. ;-)
>>>
>>>And there are people who think that the only kind of resistance is
>>>E/I.
>>>
>>>Some famous person once said "When all you know is Ohm's Law,
>>>everything looks like a resistor."
>>>
>>>Well, that was me, actually.
>>>
>>
>>Switch famous to infamous and the description of yourself is all too apt.
>>
>>?-)
>
>After almost a week of brooding, that's all you can come up with?

Week? He's been on the rag for years.

[John Larkin]

Your new nym: NumeroZero.


--

[Hattori Hanzo]

On Fri, 03 Feb 2012 17:32:24 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>Checkmate? Save me? How pathetic.

No different than you with "word salad", you fucking total retard, AND
total PATHETIC hypocrite!

In fact, his usage is quite common. Just not so much among brainless
bloodlines in their little rat races. You are a member of one such
bloodline.

[John Larkin]

On Fri, 03 Feb 2012 18:06:55 -0800, Hattori Hanzo
<Outint...@billsbackyard.org> wrote:

>On Fri, 03 Feb 2012 17:32:24 -0800, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>>Checkmate? Save me? How pathetic.
>
> No different than you with "word salad", you fucking total retard, AND
>total PATHETIC hypocrite!
>
> In fact, his usage is quite common.

Way, way too common.


--

[Hattori Hanzo]

On Fri, 03 Feb 2012 18:12:17 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>Way, way too common.

You are way too uncommonly stupid for the position you claim to be in.

[John Larkin]

On Fri, 03 Feb 2012 11:50:09 -0700, Jim Thompson

The alternator switcher thing that you posted was neither.


--

John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[John Larkin]

I was talking about diode series resistance, part of the issue of
paralleling LEDs, and JF got into his usual clucking and whining mode.

Do you own any LED flashlights? Open one up and see if there are any
resistors.


--

John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[Hattori Hanzo]

On Fri, 03 Feb 2012 19:17:51 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>
>Do you own any LED flashlights? Open one up and see if there are any
>resistors.
>

Mine are not the dumb versions. The switch, and control circuit is in
the tail. That means that it takes the 4.5 volts in and correctly
controls the feed to a single, super-bright LED with 3 distinct modes.

It is so well designed that when your batteries begin to avalanche,
the second mode no longer functions precisely as designed, signaling
the operator to use the first mode or third mode, but to also prepare to
replace or recharge your cells. The 'nose' end of the battery pack gets
applied directly to the LED. The circuit and equivalent limit resistance
presented to the virtual series circuit and LED and power source resides
in the tail of the lamp and is electronic. Bike riders use similar LED
drivers units in headlights that flash (tail lights too).

I know more about LED flashlights and bike lights than a "see if there
are any resistors" dope like you ever will.

[John Larkin]

Cool. How does it actually work?

[Hattori Hanzo]

On Sat, 04 Feb 2012 10:37:19 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 04 Feb 2012 03:23:03 -0800, Hattori Hanzo
><Outint...@billsbackyard.org> wrote:
>
>>On Fri, 03 Feb 2012 19:17:51 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>
>>>Do you own any LED flashlights? Open one up and see if there are any
>>>resistors.
>>>
>>
>> Mine are not the dumb versions. The switch, and control circuit is in
>>the tail. That means that it takes the 4.5 volts in and correctly
>>controls the feed to a single, super-bright LED with 3 distinct modes.
>>
>> It is so well designed that when your batteries begin to avalanche,
>>the second mode no longer functions precisely as designed, signaling
>>the operator to use the first mode or third mode, but to also prepare to
>>replace or recharge your cells. The 'nose' end of the battery pack gets
>>applied directly to the LED. The circuit and equivalent limit resistance
>>presented to the virtual series circuit and LED and power source resides
>>in the tail of the lamp and is electronic. Bike riders use similar LED
>>drivers units in headlights that flash (tail lights too).
>>
>> I know more about LED flashlights and bike lights than a "see if there
>>are any resistors" dope like you ever will.
>
>Cool. How does it actually work?

It is beyond your grasp, resistor boy.

Go read your degreaser manual.

[John Larkin]

On Sat, 04 Feb 2012 10:54:57 -0800, Hattori Hanzo

<Outint...@billsbackyard.org> wrote:

>On Sat, 04 Feb 2012 10:37:19 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Sat, 04 Feb 2012 03:23:03 -0800, Hattori Hanzo
>><Outint...@billsbackyard.org> wrote:
>>
>>>On Fri, 03 Feb 2012 19:17:51 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>
>>>>Do you own any LED flashlights? Open one up and see if there are any
>>>>resistors.
>>>>
>>>
>>> Mine are not the dumb versions. The switch, and control circuit is in
>>>the tail. That means that it takes the 4.5 volts in and correctly
>>>controls the feed to a single, super-bright LED with 3 distinct modes.
>>>
>>> It is so well designed that when your batteries begin to avalanche,
>>>the second mode no longer functions precisely as designed, signaling
>>>the operator to use the first mode or third mode, but to also prepare to
>>>replace or recharge your cells. The 'nose' end of the battery pack gets
>>>applied directly to the LED. The circuit and equivalent limit resistance
>>>presented to the virtual series circuit and LED and power source resides
>>>in the tail of the lamp and is electronic. Bike riders use similar LED
>>>drivers units in headlights that flash (tail lights too).
>>>
>>> I know more about LED flashlights and bike lights than a "see if there
>>>are any resistors" dope like you ever will.
>>
>>Cool. How does it actually work?
>
> It is beyond your grasp, resistor boy.

I think all you know about that flashlight is how to push the button
on the end.

[John S]

You give him way too much credit, John.

[Hattori Hanzo]

On Sat, 04 Feb 2012 11:16:56 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>I think all you know about that

degreaser is that your employees use it, not you. The reason is because
even that simple device is beyond your understanding.

So you are not going to understand the drive circuit in my LED lamp.

Hell, it took you nearly a decade to figure out how to add a pathetic,
self aggrandizing sig to your pathetic, abusive posts.

[Michael A. Terrell]

John Larkin wrote:
>
> I think all you know about that flashlight is how to push the button
> on the end.

He knows how to push your buttons. :(


--
You can't have a sense of humor, if you have no sense.

[Jamie]

In other words, you don't know?

Jamie

[John Fields]

---
Actually, I did peruse two of those sites and found that with the
voltage drop across the diode, at the currents you mentioned, both
cases resulted in real-world power dissipation in excess of the limits
allowed.

In addition, the Fairchild site which, in figure 5, clearly plots the
ordinate in millivolts, is wrong.

Apparently not having noticed that, I suspect you'll now make excuses
and bitch on forever about how unimportant accuracy is.

--
JF

[John Larkin]

On Sat, 04 Feb 2012 19:03:59 -0600, John Fields

Now you are weaseling.

>
>In addition, the Fairchild site which, in figure 5, clearly plots the
>ordinate in millivolts, is wrong.
>
>Apparently not having noticed that, I suspect you'll now make excuses
>and bitch on forever about how unimportant accuracy is.

It's not a matter of "accuracy", it's an obvious typo. The axis is
obviously volts.

--

John Larkin, President Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[John Fields]

On Sat, 04 Feb 2012 18:08:32 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 04 Feb 2012 19:03:59 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>


>>Actually, I did peruse two of those sites and found that with the
>>voltage drop across the diode, at the currents you mentioned, both
>>cases resulted in real-world power dissipation in excess of the limits
>>allowed.
>
>Now you are weaseling.

---
Nope, just stating a fact.
---

>>In addition, the Fairchild site which, in figure 5, clearly plots the
>>ordinate in millivolts, is wrong.
>>
>>Apparently not having noticed that, I suspect you'll now make excuses
>>and bitch on forever about how unimportant accuracy is.
>
>It's not a matter of "accuracy", it's an obvious typo. The axis is
>obviously volts.

---
If the axis was correctly annotated, would that not be more accurate
than if it were annotated incorrectly?

--
JF

[John Larkin]

On Sun, 05 Feb 2012 10:24:56 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Sat, 04 Feb 2012 18:08:32 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Sat, 04 Feb 2012 19:03:59 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>>
>
>
>>>Actually, I did peruse two of those sites and found that with the
>>>voltage drop across the diode, at the currents you mentioned, both
>>>cases resulted in real-world power dissipation in excess of the limits
>>>allowed.
>>
>>Now you are weaseling.
>
>---
>Nope, just stating a fact.
>---
>
>>>In addition, the Fairchild site which, in figure 5, clearly plots the
>>>ordinate in millivolts, is wrong.
>>>
>>>Apparently not having noticed that, I suspect you'll now make excuses
>>>and bitch on forever about how unimportant accuracy is.
>>
>>It's not a matter of "accuracy", it's an obvious typo. The axis is
>>obviously volts.
>
>---
>If the axis was correctly annotated, would that not be more accurate
>than if it were annotated incorrectly?

The y-axis on that fig 5 graph is obviously volts, and the "m" is
obviously a typo. Given that, there's no accuracy problem. My job is
to design stuff, not freeze in my tracks at the slightest excuse.

If you look at a smattering of 1N4148 data sheets, there's a huge
spread of I-V curves. So I certainly wouldn't design a circuit that
depends on the high-current I-V curve without making sure we'd
purchase only one vendors's parts, and even then it would be risky. I
wouldn't depend on their capacitance or reverse leakage behavior,
either. 1N4148 is a very sloppy part.

All of which is aside from the issue of paralleling LEDs, which lots
of people seem to do.

[John Larkin]

On Sat, 04 Feb 2012 11:46:35 -0800, Hattori Hanzo
<Outint...@billsbackyard.org> wrote:

>On Sat, 04 Feb 2012 11:16:56 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>I think all you know about that
>
>degreaser is that your employees use it, not you. The reason is because
>even that simple device is beyond your understanding.
>
> So you are not going to understand the drive circuit in my LED lamp.
>

Cool, let's talk about that:


OK, you have your super multimode Wal-Mart LED flashlight, maybe with
optional laser pointer. The question is, how does it regulate the LED
current? Inductive boost? Capacitive charge pump? Resistor? Linear or
PWM current-regulator IC? Raw battery connected to LEDs?

You could take it apart and see what's inside. Or you could search the
web for controller ICs. Or, more fun, you could learn some things
about the issue without opening the flashlight at all.

Any ideas how?

[John Larkin]

I don't know either. He should tell us how his flashlight regulates
current. Or, if he doesn't know (which he doesn't) he could do a
little work to find out, and tell us. Which he won't.

[Bart!]

On Sun, 05 Feb 2012 09:44:44 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>
>
>OK, you have your super multimode Wal-Mart LED flashlight,

What is this another attempt at a social insult?

Fuck off and DIE, John Larkin. You are a sad excuse for a civil,
intelligent man. That may well mean that you qualify for none of the
three titles. Likely even. You are worse, in fact, than Ross Perot could
have ever been. And his remarks were not racist. It was just a poor
choice of words. You actually were trying to be insulting. Big
difference.

It means that a real, intelligent man like Ross has more honor and
character than an insulting, pathetic, self aggrandizing piece of shit
like you ever will.

[k...@att.bizzzzzzzzzzzz]

On Sun, 05 Feb 2012 10:43:46 -0800, Bart! <B@rt_The_Sheriff_Is_A_Nig***!.org>
wrote:

>On Sun, 05 Feb 2012 09:44:44 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>
>>
>>OK, you have your super multimode Wal-Mart LED flashlight,
>
> What is this another attempt at a social insult?

Interesting that you would take a slight of a *flashlight* as such a personal
insult....

> Fuck off and DIE, John Larkin. You are a sad excuse for a civil,
>intelligent man. That may well mean that you qualify for none of the
>three titles. Likely even. You are worse, in fact, than Ross Perot could
>have ever been. And his remarks were not racist. It was just a poor
>choice of words. You actually were trying to be insulting. Big
>difference.
>
> It means that a real, intelligent man like Ross has more honor and
>character than an insulting, pathetic, self aggrandizing piece of shit
>like you ever will.

...it's like he was insulting your manhood. You certainly respond as such. I
wonder what Freud would have to say?

[Bart!]

On Sun, 05 Feb 2012 09:44:44 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>The question is, how does it regulate the LED
>current?

A simple ditz like you wouldn't know.

> Inductive boost? Capacitive charge pump? Resistor? Linear or
>PWM current-regulator IC? Raw battery connected to LEDs?

Think about cost, idiot.

>You could take it apart and see what's inside.

Here we go with retarded primer boy, on his retarded primer boy soap
box... again.

> Or you could search the
>web for controller ICs. Or, more fun, you could learn some things
>about the issue without opening the flashlight at all.
>
>Any ideas how?

It's a 555 timer circuit, you fucking retard. Even when it appears to
be "full on",it is really being pulsed. It is detectable at night.

A fucking retarded punk like you deserves no further information.

[Bart!]

On Sun, 05 Feb 2012 09:47:40 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>I don't know either.

The first time you have spoken the truth in this group in quite some
time.

> He should tell us how his flashlight regulates
>current.

I would, but only if it is MY desire, you pathetic, cringing little
milksop.

> Or, if he doesn't know (which he doesn't)

Back to the lying horseshit behavior already, I see. There was a time
when a man would simply drop you where you stand for pathetic, uncivil
behavior like that. That is where the Colt motto came from.

> he could do a
>little work to find out,

You are an idiot.

> and tell us. Which he won't.

For all you know, utilization of LEDs is what will make me rich.

Fact is, you don't know a goddamned thing, you pathetic, characterless,
honorless piece of shit.

[Bart!]

On Sun, 05 Feb 2012 13:49:11 -0500, "k...@att.bizzzzzzzzzzzz"
<k...@att.bizzzzzzzzzzzz> wrote:

>Interesting that you would take a slight of a *flashlight* as such a personal
>insult....

You are too retarded to know what I was referring to as being an
insult, much less an insult to whom, which is obvious since you didn't
catch the remainder of the reference.

Essentially, you are almost as big an idiot as he is, except yours is a
senility thing. Before that, it was a stupid fucktard thing. His is a
sub-human thing.

[Jamie]

Bart! wrote:

> On Sun, 05 Feb 2012 09:47:40 -0800, John Larkin
> <jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>
>>I don't know either.
>
>
>
> The first time you have spoken the truth in this group in quite some
> time.

You mean it is the first time you have understood comments made from
JL in a long time?

>
>>He should tell us how his flashlight regulates
>>current.
>
>
> I would, but only if it is MY desire, you pathetic, cringing little
> milksop.

I am sure it would be your desire to do so, if you only knew, and then
most likely would be a case where we wouldn't be able to shut you up!

>
>>Or, if he doesn't know (which he doesn't)
>
>
>
> Back to the lying horseshit behavior already, I see. There was a time
> when a man would simply drop you where you stand for pathetic, uncivil
> behavior like that. That is where the Colt motto came from.
>

And there were and still is, times where the pen is mightier than the sword.

>>he could do a
>>little work to find out,
>
>
> You are an idiot.

Yes, how shameful of him to make such rude remarks about you doing work!

>
>>and tell us. Which he won't.
>
>
>
> For all you know, utilization of LEDs is what will make me rich.

Well, there is a sucker born in every crowd. I am sure with your
skills you'll be able to find some. Most people tend to hang with their
own kind.

> Fact is, you don't know a goddamned thing, you pathetic, characterless,
> honorless piece of shit.

He may appear to you to be character less in your eyes, but I believe
that would be due to lack of time on his part, wasting such traits to
pamper the likes of you.


Have a good day, I am sure i'll be next on the list.

Jamie

[Jamie]

It's truly amazing what woman are pushing out these days.

Jamie

[Bart!]

On Sun, 05 Feb 2012 14:22:16 -0500, Jamie
<jamie_ka1lpa_not_v...@charter.net> wrote:

> I am sure it would be your desire to do so, if you only knew, and then
>most likely would be a case where we wouldn't be able to shut you up!

You're an idiot. Go away, little boy.

[Bart!]

On Sun, 05 Feb 2012 14:22:16 -0500, Jamie
<jamie_ka1lpa_not_v...@charter.net> wrote:

> Well, there is a sucker born in every crowd. I am sure with your
>skills you'll be able to find some. Most people tend to hang with their
>own kind.

Which is why we see you "hanging with" John, particularly in the midst
of his dishonorable moments, which is nearly always.

You are pathetic. A coattail hanging twit, if there ever was one.

[John Larkin]

On Sun, 05 Feb 2012 10:43:46 -0800, Bart!
<B@rt_The_Sheriff_Is_A_Nig***!.org> wrote:

>On Sun, 05 Feb 2012 09:44:44 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>
>>
>>OK, you have your super multimode Wal-Mart LED flashlight,
>
> What is this another attempt at a social insult?

Hey, I like Wal-Mart. Too bad there are none nearby. We go to the ones
in Sacramanto or Reno when we're in the neighborhood.

>
> Fuck off and DIE, John Larkin. You are a sad excuse for a civil,
>intelligent man. That may well mean that you qualify for none of the
>three titles. Likely even. You are worse, in fact, than Ross Perot could
>have ever been. And his remarks were not racist. It was just a poor
>choice of words. You actually were trying to be insulting. Big
>difference.
>
> It means that a real, intelligent man like Ross has more honor and
>character than an insulting, pathetic, self aggrandizing piece of shit
>like you ever will.

Which means that you don't know how your flashlight works, and you're
not interested anyhow.

[John Larkin]

That still doesn't say how the current is controlled. Or what stores
the multiple operating states.

[John Larkin]

On Sun, 05 Feb 2012 10:57:00 -0800, Bart!
<B@rt_The_Sheriff_Is_A_Nig***!.org> wrote:

>On Sun, 05 Feb 2012 09:47:40 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>I don't know either.
>
>
> The first time you have spoken the truth in this group in quite some
>time.
>
>> He should tell us how his flashlight regulates
>>current.
>
> I would, but only if it is MY desire, you pathetic, cringing little
>milksop.
>
>> Or, if he doesn't know (which he doesn't)
>
>
> Back to the lying horseshit behavior already, I see. There was a time
>when a man would simply drop you where you stand for pathetic, uncivil
>behavior like that. That is where the Colt motto came from.
>
>> he could do a
>>little work to find out,
>
> You are an idiot.
>
>> and tell us. Which he won't.
>
>
> For all you know, utilization of LEDs is what will make me rich.

Then start by understanding how they work. How does your high-end
flashlight regulate LED current?

[Jim Thompson]

On Sun, 05 Feb 2012 09:38:32 -0800, John Larkin

It must be hell to be manic depressive.

...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 | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I do not suffer from stress, but I am a carrier.

[Phil Hobbs]

Nah, some of my favourite transistors are bipolar.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[k...@att.bizzzzzzzzzzzz]

On Sun, 05 Feb 2012 14:22:16 -0500, Jamie
<jamie_ka1lpa_not_v...@charter.net> wrote:

>Bart! wrote:
>
>> On Sun, 05 Feb 2012 09:47:40 -0800, John Larkin
>> <jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>
>>>I don't know either.
>>
>>
>>
>> The first time you have spoken the truth in this group in quite some
>> time.
>
> You mean it is the first time you have understood comments made from
>JL in a long time?

DimBulb didn't this time, either.

>>>He should tell us how his flashlight regulates
>>>current.
>>
>>
>> I would, but only if it is MY desire, you pathetic, cringing little
>> milksop.
>
> I am sure it would be your desire to do so, if you only knew, and then
>most likely would be a case where we wouldn't be able to shut you up!

When has knowledge ever had anything to do with AlwaysWrong's screeching on?

>>>Or, if he doesn't know (which he doesn't)
>>
>>
>>
>> Back to the lying horseshit behavior already, I see. There was a time
>> when a man would simply drop you where you stand for pathetic, uncivil
>> behavior like that. That is where the Colt motto came from.
>>
>
>
>And there were and still is, times where the pen is mightier than the sword.

Certainly mightier than Nymbecile's limp-wristed threats.

>>>he could do a
>>>little work to find out,
>>
>>
>> You are an idiot.
>
>Yes, how shameful of him to make such rude remarks about you doing work!

But not unexpected. It's the thought of a little knowledge that's really got
his back hair in a bun.

>>>and tell us. Which he won't.
>>
>>
>>
>> For all you know, utilization of LEDs is what will make me rich.
>
> Well, there is a sucker born in every crowd. I am sure with your
>skills you'll be able to find some. Most people tend to hang with their
>own kind.

Come on. Dimbulb couldn't calculate the resistance of an LED's ballast
resistor. He's called DimBulb for a reason.

>> Fact is, you don't know a goddamned thing, you pathetic, characterless,
>> honorless piece of shit.
>
> He may appear to you to be character less in your eyes, but I believe
>that would be due to lack of time on his part, wasting such traits to
>pamper the likes of you.
>
>
> Have a good day, I am sure i'll be next on the list.
>

Back of the line. Back of the line.

[Jamie]

You're correct to assume so, I hang with the best!

At least you got something correct, for a change.

Jamie

[Jim Thompson]

Mine, too >:-}

...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 | |
| Voice:(480)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.

[Jamie]

:)