LED car lights flicker - no need!

[Major Scott]

On Wed, 24 Apr 2013 00:09:36 +0100, Dave Plowman <dave@davesound.co.uk> wrote:

In article <op.wvz5n4px2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
Take for example the brake/tail lights. These are often pulsed for
tail and on for brake. So what you said doesn't make sense.
Anything less than full voltage on (as for brake) will be lower heat.

LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven.

Why would you have a 'series resistor' if they are pulse driven?

But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't they use it in domestic LED bulbs?

--
"One dies in Istanbul suicide attack"

 

[Daniel47@teranews.com]

Major Scott wrote:

On Tue, 23 Apr 2013 16:58:35 +0100, Dave Plowman <dave@davesound.co.uk
wrote:

In article <op.wvzz3ywg2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
Pulsing an LED is a way of getting a higher light output from it
without overheating. Overheating an LED kills it in short order.

Take for example the brake/tail lights. These are often pulsed for tail
and on for brake. So what you said doesn't make sense. Anything less
than full voltage on (as for brake) will be lower heat.

LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven. Anyway electronics to lower the current can be made without
pulsing.

No, the series resistor merely determines the maximum current that could
flow through the LED.

Daniel

 

[Ian Jackson]

In message <53411d7de7dave@davenoise.co.uk>, Dave Plowman
<dave@davesound.co.uk> writes

In article <op.wvz5n4px2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
Take for example the brake/tail lights. These are often pulsed for
tail and on for brake. So what you said doesn't make sense.
Anything less than full voltage on (as for brake) will be lower heat.

LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven.

Why would you have a 'series resistor' if they are pulse driven?

But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

Nothing is really only 'current driven'. It's more correct to say that

LEDs need to be driven from a power source which provides a fairly
well-defined current. Even when you drive them with pulsed current, the
amplitude of the pulses will be determined by the voltage producing the
pulses. At any instant, the power dissipated in the LED is simply the
product of the voltage across it (typically 2V, depending on the colour)
and the current flowing through it. When pulsed, the average power is
also determined by the mark-space ratio of the pulses.
--
Ian

 

[Dave Plowman]

In article <op.wv0oip1h2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:

But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

No idea. They are crap and I wouldn't have one in the house.

--
*I don't suffer from insanity -- I'm a carrier

Dave Plowman dave@davesound.co.uk London SW 12

 

[Dave Plowman]

In article <3sN4ACCMs4dRFwS6@g3ohx.demon.co.uk>,
Ian Jackson <ianREMOVETHISjackson@g3ohx.demon.co.uk> wrote:

Nothing is really only 'current driven'. It's more correct to say that
LEDs need to be driven from a power source which provides a fairly
well-defined current.

Very well defined if you're driving them hard. The source voltage is
irrelevant. Provided it is more than the forward voltage drop of the LED
or LED chain.

Even when you drive them with pulsed current, the
amplitude of the pulses will be determined by the voltage producing the
pulses. At any instant, the power dissipated in the LED is simply the
product of the voltage across it (typically 2V, depending on the colour)
and the current flowing through it. When pulsed, the average power is
also determined by the mark-space ratio of the pulses.

As I said, it's the current flow through the LED that you design for.

--
*Why do overlook and oversee mean opposite things?

Dave Plowman dave@davesound.co.uk London SW 12

 

[DavidR]

"Major Scott" <no@spam.com> wrote

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

Because a large number of morons in and around the motor industry have
become attached to the idea that if some lighting is good, brighter lights
must be better.

Thy don't seem to recognise that the the current standard of lighting is
making the roads more dangerous.

 

[Ian Jackson]

In message
<2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.or
g>, Steve Firth <%steve%@malloc.co.uk> writes

Dave Plowman <dave@davesound.co.uk> wrote:
In article <op.wv0oip1h2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use 1/10th
the electricity of equivalent halogen bulbs and can be bought as flood or
spotlight versions.

I was under the impression that they did use a pulsed supply in domestic

lighting.
--
Ian

 

[Dave Plowman]

In article
<2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:

No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use 1/10th
the electricity of equivalent halogen bulbs and can be bought as flood or
spotlight versions.

They may well use less electricity. But if that's the only criterion for
domestic lighting a fluorescent tube will do the job rather better and for
less cost.

--
*IS THERE ANOTHER WORD FOR SYNONYM?

Dave Plowman dave@davesound.co.uk London SW 12

 

[Steve Firth]

Dave Plowman <dave@davesound.co.uk> wrote:

In article <op.wv0oip1h2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use 1/10th
the electricity of equivalent halogen bulbs and can be bought as flood or
spotlight versions.

--
<•DarWin><|
_/ _/

 

[Dave Plowman]

In article
<1453041046388492124.730151%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:

Dave Plowman <dave@davesound.co.uk> wrote:
In article
2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:
No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use
1/10th the electricity of equivalent halogen bulbs and can be bought
as flood or spotlight versions.

They may well use less electricity. But if that's the only criterion
for domestic lighting a fluorescent tube will do the job rather better
and for less cost.

Where did I say it was the only criterion?

It's the first thing you mentioned about them?

The major objection from
SWMBO is that they are "too bright".

Typically yes - when you look at them. Sadly the actual usable light from
them is anything but.

Way better than CFL and, as I mentioned, equivalent to halogen, in fact
a 3W LED with SMD elements providers better illumination than a 35W
halogen.

Define better. That usually means the latest thing to impress the gullible.

There are no LEDs on the domestic market that come even close to matching
the quality of light from halogen. Of course that doesn't much matter to
many.

--
*I want it all and I want it delivered

Dave Plowman dave@davesound.co.uk London SW 12

 

[Steve Firth]

Dave Plowman <dave@davesound.co.uk> wrote:

In article
2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:
No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use 1/10th
the electricity of equivalent halogen bulbs and can be bought as flood or
spotlight versions.

They may well use less electricity. But if that's the only criterion for
domestic lighting a fluorescent tube will do the job rather better and for
less cost.

Where did I say it was the only criterion? The major objection from SWMBO
is that they are "too bright".

Way better than CFL and, as I mentioned, equivalent to halogen, in fact a
3W LED with SMD elements providers better illumination than a 35W halogen.

--
<•DarWin><|
_/ _/

 

On Wed, 24 Apr 2013 09:59:22 +0100
Dave Plowman <dave@davesound.co.uk> wrote:

As I said, it's the current flow through the LED that you design for.

Look what article appeared on Slashdot today:

http://tech.slashdot.org/story/13/04/23/2332245/cause-of-led-efficiency-droop-fi
nally-revealed

NJR

 

[Dave Plowman]

In article
<1375092268388505952.292767%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:

There are no LEDs on the domestic market that come even close to
matching the quality of light from halogen. Of course that doesn't
much matter to many.

I love the way your opinion masquerades as fact.

Then publish some plots of their spectrum that proves me wrong. I'll not
hold my breath.

--
*i souport publik edekashun.

Dave Plowman dave@davesound.co.uk London SW 12

 

[Steve Firth]

Dave Plowman <dave@davesound.co.uk> wrote:

In article
1453041046388492124.730151%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:
Dave Plowman <dave@davesound.co.uk> wrote:
In article
2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.org>,
Steve Firth <%steve%@malloc.co.uk> wrote:
No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use
1/10th the electricity of equivalent halogen bulbs and can be bought
as flood or spotlight versions.

They may well use less electricity. But if that's the only criterion
for domestic lighting a fluorescent tube will do the job rather better
and for less cost.

Where did I say it was the only criterion?

It's the first thing you mentioned about them?

The major objection from
SWMBO is that they are "too bright".

Typically yes - when you look at them. Sadly the actual usable light from
them is anything but.

Way better than CFL and, as I mentioned, equivalent to halogen, in fact
a 3W LED with SMD elements providers better illumination than a 35W
halogen.

Define better. That usually means the latest thing to impress the gullible.

There are no LEDs on the domestic market that come even close to matching
the quality of light from halogen. Of course that doesn't much matter to
many.

I love the way your opinion masquerades as fact.

--
<•DarWin><|
_/ _/

 

[Major Scott]

On Wed, 24 Apr 2013 08:33:48 +0100, Daniel47@teranews.com <dxmm@albury.nospam.net.au> wrote:

Major Scott wrote:
On Tue, 23 Apr 2013 16:58:35 +0100, Dave Plowman <dave@davesound.co.uk
wrote:

In article <op.wvzz3ywg2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
Pulsing an LED is a way of getting a higher light output from it
without overheating. Overheating an LED kills it in short order.

Take for example the brake/tail lights. These are often pulsed for tail
and on for brake. So what you said doesn't make sense. Anything less
than full voltage on (as for brake) will be lower heat.

LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven. Anyway electronics to lower the current can be made without
pulsing.

No, the series resistor merely determines the maximum current that could
flow through the LED.

Take for example a 6 volt DC supply connected to an LED in series with a 200 ohm resistor.
2V 20mA at the LED, 4V 20mA in the resistor.

Now change the supply to 4V.
2V 10mA at the LED, 2V 10mA in the resistor.

Lowering voltage will dim the LED.

--
Did you hear about the new instant lottery game in India?
You scratch the ticket and if the dot matches the one on your forehead, you win a convenience store in the US.

 

[Major Scott]

On Wed, 24 Apr 2013 10:05:18 +0100, DavidR <dr6092@gmail.com> wrote:

"Major Scott" <no@spam.com> wrote

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

Because a large number of morons in and around the motor industry have
become attached to the idea that if some lighting is good, brighter lights
must be better.

Thy don't seem to recognise that the the current standard of lighting is
making the roads more dangerous.

Some xenon headlights, yes. But LED brakelights are not too bright. They're just too flickery. They appear the same brightness as a standard 21W brakelight bulb to me.

So why can't this pretend brightness be applied to domestic lighting? An LED lamp which currently equates to a 50W incandescent could give out what looks like 100W. If it's not done because people are more likely to notice the flicker at home, then why not have a higher pulse frequency?

--
If it's zero degrees outside today and it's supposed to be twice as cold tomorrow, how cold is it going to be?

 

[Major Scott]

On Wed, 24 Apr 2013 09:54:44 +0100, Dave Plowman <dave@davesound.co.uk> wrote:

In article <op.wv0oip1h2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

No idea. They are crap and I wouldn't have one in the house.

Have you ever seen a CREE LED? I've got a load of GU10 CREE LED spots and they're better than the 50W halogens they replaced. 6W in, 50W out, and to my eyesight they look more like 75W out, and a whiter light too. And they don't keep tripping the circuit breaker when they go, or making the fitting to hot to touch which is worrying next to a wood panelled ceiling.

--
I went to San Francisco. I found someone's heart.

 

[bm]

"Major Scott" <no@spam.com> wrote in message
newsp.wv17zex82eh2io@red.lan...

On Wed, 24 Apr 2013 08:33:48 +0100, Daniel47@teranews.com
dxmm@albury.nospam.net.au> wrote:

Major Scott wrote:
On Tue, 23 Apr 2013 16:58:35 +0100, Dave Plowman <dave@davesound.co.uk
wrote:

In article <op.wvzz3ywg2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
Pulsing an LED is a way of getting a higher light output from it
without overheating. Overheating an LED kills it in short order.

Take for example the brake/tail lights. These are often pulsed for
tail
and on for brake. So what you said doesn't make sense. Anything less
than full voltage on (as for brake) will be lower heat.

LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven. Anyway electronics to lower the current can be made without
pulsing.

No, the series resistor merely determines the maximum current that could
flow through the LED.

Take for example a 6 volt DC supply connected to an LED in series with a
200 ohm resistor.
2V 20mA at the LED, 4V 20mA in the resistor.

Now change the supply to 4V.
2V 10mA at the LED, 2V 10mA in the resistor.

Fuck a duck, they DID teach you something.

 

[Major Scott]

On Wed, 24 Apr 2013 11:06:50 +0100, Ian Jackson <ianREMOVETHISjackson@g3ohx.demon.co.uk> wrote:

In message
2082196069388490010.841939%steve%-malloc.co.uk@news.eternal-september.or
g>, Steve Firth <%steve%@malloc.co.uk> writes
Dave Plowman <dave@davesound.co.uk> wrote:
In article <op.wv0oip1h2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:
But in any case it is irrelevant. It's the current they are driven with
that matters - not the voltage.

If this pulsing can make them appear brighter than they are, why don't
they use it in domestic LED bulbs?

No idea. They are crap and I wouldn't have one in the house.

The LED bulbs I have used have been anything but "crap". They use 1/10th
the electricity of equivalent halogen bulbs and can be bought as flood or
spotlight versions.

I was under the impression that they did use a pulsed supply in domestic
lighting.

If they do then it's a much higher frequency. Some old cheap ones I've got have a definite flicker, but that's mains flicker (I looked inside one I accidentally dropped from the loft through the hatch onto wood flooring and smashed it and found simply a bridge rectifier, a capacitor, and a couple of resistors, with 50 tiny LEDs in series).

The decent CREE ones I've got have zero flicker. Here's one that expired and I opened to show Ian Field the circuit a month or three ago if you want to try to work out what it does:
http://petersphotos.com/temp/cree%20circuit.jpg I don't have it anymore it's gone in the bin.

--
Interesting fact number 476:
80% of millionaires drive used cars.

 

[Major Scott]

On Wed, 24 Apr 2013 20:36:32 +0100, bm <a@b.com> wrote:

"Major Scott" <no@spam.com> wrote in message
newsp.wv17zex82eh2io@red.lan...
On Wed, 24 Apr 2013 08:33:48 +0100, Daniel47@teranews.com
dxmm@albury.nospam.net.au> wrote:

Major Scott wrote:
On Tue, 23 Apr 2013 16:58:35 +0100, Dave Plowman <dave@davesound.co.uk
wrote:

In article <op.wvzz3ywg2eh2io@red.lan>,
Major Scott <no@spam.com> wrote:




LEDs are current, not voltage, driven.

When there's a series resistor, then you can think of them as voltage
driven. Anyway electronics to lower the current can be made without
pulsing.

No, the series resistor merely determines the maximum current that could
flow through the LED.

Take for example a 6 volt DC supply connected to an LED in series with a
200 ohm resistor.
2V 20mA at the LED, 4V 20mA in the resistor.

Now change the supply to 4V.
2V 10mA at the LED, 2V 10mA in the resistor.

Fuck a duck, they DID teach you something.

I have a fucking degree in it (not that it gets you a job).

--
Basketball analyst: "He dribbles a lot and the opposition doesn't like it. In fact you can see it all over their faces."