LED car lights flicker - no need!

[Major Scott]

On Wed, 24 Apr 2013 22:06:00 +0100, Adrian <toomany2cvs@gmail.com> wrote:

On Wed, 24 Apr 2013 21:43:32 +0100, Major Scott wrote:

It lies in the fact that the sort of job I apply for attracts up to
180 applicants.

So apply for several hundred jobs.

I'm applying for about 2 a week at the moment.

Which, on the law of averages, means you won't find a job for nearly two
years.

It's been just over 1, so not long to go.

--
I got invited to a Muslim party the other night.
It was the fastest game of pass the parcel I've even seen!

 

[bm]

"Major Scott" <no@spam.com> wrote in message
newsp.wv4dogd02eh2io@red.lan...

On Wed, 24 Apr 2013 22:06:00 +0100, Adrian <toomany2cvs@gmail.com> wrote:

On Wed, 24 Apr 2013 21:43:32 +0100, Major Scott wrote:

It lies in the fact that the sort of job I apply for attracts up to
180 applicants.

So apply for several hundred jobs.

I'm applying for about 2 a week at the moment.

Which, on the law of averages, means you won't find a job for nearly two
years.

It's been just over 1, so not long to go.

The problem is, these companies need people with a clue.

 

[Major Scott]

On Fri, 26 Apr 2013 00:48:57 +0100, bm <a@b.com> wrote:

"Major Scott" <no@spam.com> wrote in message
newsp.wv4dogd02eh2io@red.lan...
On Wed, 24 Apr 2013 22:06:00 +0100, Adrian <toomany2cvs@gmail.com> wrote:

On Wed, 24 Apr 2013 21:43:32 +0100, Major Scott wrote:



So apply for several hundred jobs.

I'm applying for about 2 a week at the moment.

Which, on the law of averages, means you won't find a job for nearly two
years.

It's been just over 1, so not long to go.

The problem is, these companies need people with a clue.

Actually both jobs I've been in congratulated me for getting things done instead of arseing around with paperwork like others do.

--
How many potheads does it take to change a light bulb?
Two. One to hold the bulb against the socket, and the other to smoke up until the room starts spinning.

 

[Major Scott]

On Thu, 25 Apr 2013 15:30:03 +0100, Mr Pounder <MrPounder@rationalthought.com> wrote:

"Major Scott" <no@spam.com> wrote in message
newsp.wv2buus82eh2io@red.lan...
On Wed, 24 Apr 2013 21:35:56 +0100, Adrian <toomany2cvs@gmail.com> wrote:

On Wed, 24 Apr 2013 21:26:17 +0100, Major Scott wrote:



I rather suspect your problem in finding gainful employment lies in
your personality, not your qualifications.

It lies in the fact that the sort of job I apply for attracts up to 180
applicants.

So apply for several hundred jobs.

I'm applying for about 2 a week at the moment. They seem to come like
London Buses.

Except that, even if you were the only applicant, any sane employer would
rather continue searching than have to deal with you for eight hours a
day, five days a week.

You've never met me. I can be extremely polite and diplomatic when
required.

{Falls off chair}

You've never met me either because you were scared to.

--
Love conquers all, except in tennis.

 

[Major Scott]

On Tue, 23 Apr 2013 11:10:27 +0100, Dave Plowman <dave@davesound.co.uk> wrote:

In article <kl5ibr$qiu$1@speranza.aioe.org>,
neil@the.shed> wrote:
On Mon, 22 Apr 2013 19:44:38 +0100
"Major Scott" <no@spam.com> wrote:
Surely they can design LED lights on cars to have a higher frequency
PWM= ? Even =A3100K cars flicker dramatically, especially when filmed.
It m= akes them look really cheap. All it would take is a higher
frequency PW= M, or a smoothing capacitor?

They flicker for a reason. If they smoothed the current they might just
as well use DC direct from the battery. I don't know the technical
reasons why but apparently using the equivalent DC voltage required to
get the same brightness as you can get by strobing them would burn them
out. I'm sure some electronics guru on here can explain more. But it
does lead to interesting effects on video as you say )

Pulsing an LED is a way of getting a higher light output from it without
overheating. Overheating an LED kills it in short order. Seeing a flicker
from them on a video is the same effect as wagon wheels appearing to turn
backwards on old cowboy and indian films - stroboscopic effect.

The front LED running lights don't even flicker on camera. And I don't think brakes do either. So why make the tails any different? They're made up of many LEDs, so just power up less of them (which I've seen buses doing) for tail and all of them for brake.

--
Peter is listening to "Eagles - Hotel California"

 

[Ian Field]

<neil@the.shed> wrote in message news:kl5o0j$9t9$1@speranza.aioe.org...

On Tue, 23 Apr 2013 11:10:27 +0100
Dave Plowman <dave@davesound.co.uk> 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. Seeing a flicker

Its odd though isn't it. The way they're constructed must mean the amount
of
heat generated for a given voltage or current must slowly tail off so
although
they'd heat up too much at constant voltage X you can pulse them at for
arguments sake X*2 producing the same or even more total light but without
a
doubling of the heat generated so allowing for cooling down to safe levels
during the OFF periods of the pulse. Or something like that.

LEDs can be pulsed close to the limit for the bond wires - but only for very
low duty cycle, a short time on and (relatively) long time off allows
cooling between pulses.

being pulsed very rapidly, you're not aware of the interruptions
(persistence of vision) so the perceived brightness is much brighter than
you'd get for the equivalent average current.

 

[Ian Field]

"Dave Plowman" <dave@davesound.co.uk> wrote in message
news:5340f60899dave@davenoise.co.uk...

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.

I'm sort of wondering how that holds up with the typical example of a
current controlled buck converter.

Certainly you have the series current sense resistor fed to the fb input of
the controller - but there's usually the catch diode behind the inductor,
which as in any buck routes the collapsing field energy through the LED.

 

[Ian Field]

"Major Scott" <no@spam.com> wrote in message
newsp.wv199bfr2eh2io@red.lan...

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.

There doesn't look enough components for it to be a half bridge, a flyback
is most likely.

Switching frequency is probably somewhere between 20kHz & 50kHz.

 

[Major Scott]

On Sat, 27 Apr 2013 21:43:25 +0100, Ian Field <gangprobing.alien@ntlworld.com> wrote:

"Major Scott" <no@spam.com> wrote in message
newsp.wv199bfr2eh2io@red.lan...
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:




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.

There doesn't look enough components for it to be a half bridge, a flyback
is most likely.

Switching frequency is probably somewhere between 20kHz & 50kHz.

Somebody oughta tell BMW.

--
Sex is one of the most wholesome, beautiful and natural experiences that money can buy.

 

[Ian Field]

"Dave Plowman" <dave@davesound.co.uk> wrote in message
news:534159e0bedave@davenoise.co.uk...

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.

Last time I saw LED bulbs in the supermarket, they were about 3x the price
and about 1/3 the lumen/W.

Too dim to use for anything - and too expensive to buy for technical
interest.

A local supermarket had such a deal once on CFLs - I bought a few just for
the diac inside!

 

[Ian Field]

"bm" <a@b.com> wrote in message
news:51786c95$0$45284$c3e8da3$40cb80c2@news.astraweb.com...

"Dave Plowman" <dave@davesound.co.uk> wrote in message
news:5341a2d2d9dave@davenoise.co.uk...
In article <51786764$0$3690$c3e8da3$40cb80c2@news.astraweb.com>,
bm <a@b.com> wrote:

"Dave Plowman" <dave@davesound.co.uk> wrote in message
news:53419fdcd1dave@davenoise.co.uk...
In article <51783438$0$49048$c3e8da3$40cb80c2@news.astraweb.com>, bm
a@b.com> wrote:
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.

That makes two of you who failed GCE electronics.

Sorry, Dave, but I think you'll find that his 'sums' are pretty much
correct, amazingly.

I must be from a different generation. 'Sums' are either correct or not.
Anything else is a guess.

How correct do you wanna be? 10mA/11mA 20mA/21mA?
You have to admit he's in the right ballpark or thereabouts.
I'm still recovering.
PHucker with a clue? Blimey.

He's astonishingly dim at everything else!

 

[Dave Plowman]

In article <jRWet.135280$Pj4.98527@fx14.fr7>,
Ian Field <gangprobing.alien@ntlworld.com> wrote:

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.

Last time I saw LED bulbs in the supermarket, they were about 3x the
price and about 1/3 the lumen/W.

Too dim to use for anything - and too expensive to buy for technical
interest.

A local supermarket had such a deal once on CFLs - I bought a few just
for the diac inside!

My main complaint with LEDs is the spectrum is non continuous. And as that
improves, the efficiency drops. Their life is also rather variable.

Of course I do realise many won't care if colour rendering is poor under
LED lighting.

--
*If I throw a stick, will you leave?

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

 

[Steve Firth]

Ian Field <gangprobing.alien@ntlworld.com> wrote:

Last time I saw LED bulbs in the supermarket, they were about 3x the price
and about 1/3 the lumen/W.

One third of the lumens per W compared to what?

Tungsten halogen lamps max out at 24 lm/W;
CFLs are quoted as 46-75 lm/W[1];
LEDs range from 29 - 100 lm/W for the bulbs sold in supermarkets.

Note that the LEDs are available in the same packages as the halogen
bulbs and are a direct replacement for them. There are no equivalent
CFLs in the same packages, so changing to CFL often requires a brand new
light fitting.

Also unlike CFLs LEDs provide good light from the moment they are turned
on, CFLs take forever to warm up and even then provide a sickly dim
glow. I replaced four 25W E14 R50 bulbs in downlighters with 4x14W CFLs
(280 lm; 20 lm/W according to the info sheet). The light output was
appaling and resulted in needing to use two standard lamps and a table
lamp in that room as well as the CFLs just to see what one was doing.
These were changed for 4x3.5W LED units (315 lm; 90 lm/W) and the
improvement in illumination was drastic. Although supposedly the same
output as the CFLs, these provide more light than the tungsten E14s,
much more than the CFLs and unlike the CFLs the bulbs are an exact fit
for the downlighter. The CFLs protruded from the fitting by about five
CM and were ugly as sin.

Also the CFLs weren't cheap, costing Ł5 each, the LEDs were Ł6 each but
worth the extra for the light output and efficiency.

So what are you comparing LEDs to?

BTW, unlike Dave P, I don't spend time in my living/dining room
comparing Pantone colour charts with print samples produced on a range
of professional lithograph machines, so small variations in spectrum are
irrelevant. The CFLs were also pants in that regard, since everything
was coloured a sickly greenish tinge. The LEDs are "warm" white which
gives a good even illumination that looks to me like daylight around
noon.

[1] But never seem to achieve it.

--
Burn Hollywood burn, burn down to the ground

 

[Steve Firth]

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

Of course I do realise many won't care if colour rendering is poor under
LED lighting.

Yes it must be terrible for you having to run multiple Heidelberg
presses in your living room. No doubt you only use Apple computers so
that you can get exact pre-press matching that is impossible on your BBC
computer, spectrum being so terribly important to you.

--
Burn Hollywood burn, burn down to the ground

 

[Dave Plowman]

In article <1l21h6j.ukplawjmf82dN%%steve%@malloc.co.uk>,
Steve Firth <%steve%@malloc.co.uk> wrote:

BTW, unlike Dave P, I don't spend time in my living/dining room
comparing Pantone colour charts with print samples produced on a range
of professional lithograph machines, so small variations in spectrum are
irrelevant. The CFLs were also pants in that regard, since everything
was coloured a sickly greenish tinge. The LEDs are "warm" white which
gives a good even illumination that looks to me like daylight around
noon.

Not warm white then. Warm white is more akin to evening light.

I'm glad your happy with poor light quality to save a few pennies.

--
*If God dropped acid, would he see people?

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

 

[Dave Plowman]

In article <1l21i8z.1wdiefwm3fh2N%%steve%@malloc.co.uk>,
Steve Firth <%steve%@malloc.co.uk> wrote:

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

Of course I do realise many won't care if colour rendering is poor
under LED lighting.

Yes it must be terrible for you having to run multiple Heidelberg
presses in your living room. No doubt you only use Apple computers so
that you can get exact pre-press matching that is impossible on your BBC
computer, spectrum being so terribly important to you.

Strange how you are picky about so many things, but are more keen to save
pennies on electricity than have decent quality light.

--
*Hang in there, retirement is only thirty years away! *

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

 

[Clive George]

On 28/04/2013 13:48, Steve Firth wrote:

Also the CFLs weren't cheap, costing Ł5 each, the LEDs were Ł6 each but
worth the extra for the light output and efficiency.

Got a brand/supplier for the LEDs?

 

[Nick Finnigan]

On 28/04/2013 13:48, Steve Firth wrote:

;

glow. I replaced four 25W E14 R50 bulbs in downlighters with 4x14W CFLs
(280 lm; 20 lm/W according to the info sheet). The light output was
appaLling and resulted in needing to use two standard lamps and a table
lamp in that room as well as the CFLs just to see what one was doing.

Well, yes, 1000 lumens isn't enough. But why were they so low?

 

[Steve Firth]

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

In article <1l21h6j.ukplawjmf82dN%%steve%@malloc.co.uk>,
Steve Firth <%steve%@malloc.co.uk> wrote:
BTW, unlike Dave P, I don't spend time in my living/dining room
comparing Pantone colour charts with print samples produced on a range
of professional lithograph machines, so small variations in spectrum are
irrelevant. The CFLs were also pants in that regard, since everything
was coloured a sickly greenish tinge. The LEDs are "warm" white which
gives a good even illumination that looks to me like daylight around
noon.

Not warm white then. Warm white is more akin to evening light.

What LED manufacturers call "warm white" 3200K, is what CFL
manufacturers would term "blazing actinic light", if their claims about
daylight white (guttering candle colour) are anything to go by.

I'm glad your happy with poor light quality to save a few pennies.

I'm glad that you don't know what you are talking about.

--
Burn Hollywood burn, burn down to the ground

 

[Steve Firth]

Clive George <clive@xxxx-x.fsnet.co.uk> wrote:

On 28/04/2013 13:48, Steve Firth wrote:

Also the CFLs weren't cheap, costing Ł5 each, the LEDs were Ł6 each but
worth the extra for the light output and efficiency.

Got a brand/supplier for the LEDs?

The brand is Peritus. The supplier was the usual "some guy on eBay"
which I suspect is a front for Peritus, charging less than their prices
on Amazon.

I had a bit of trouble finding them again since they didn't leave
feedback after I bought the bulbs. They have an eBay shop:

http://stores.ebay.co.uk/Ivys-shop

They charged about Ł6.50/bulb if bought individually and Ł60(ish) for
ten or more with free postage. I bought a mix of MR16 and E14 R50 from
them a year ago, so far I'm pleased with the bulbs.

The ones I chose were the 21xSMD units which put the SMD elements
directly behind the front glass of the bulb. This gives even
illumination over a wide area. They also have units with a number of 1W
packages in each bulb which I avoided because it seemed to me that these
would produce spot lighting.

These seem to have fallen in price and are now about Ł5.30 per bulb
bought in bulk.

http://www.ebay.co.uk/itm/10x-E14-SES-R50-21-SMD-BULB-WARM-WHITE-UK-SELLER-/160590003951

And the MR16 has fallen to about Ł1.90/bulb which seems good VFM to me
compared to the price that Ikea charge for CFLs that don't illuminate
worth a damn.

http://www.ebay.co.uk/itm/10x-MR16-21-LEDs-BULB-WARM-WHITE-UK-SELLER-/150606814415

I haven't changed the transformers used for the halogen lighting tracks
(yet). If I use all LED bulbs there's unacceptable flickering - the
bulbs don't draw enough current for the transformers to provide stable
output. A mix of three LED to 2 halogen bulbs keeps things stable. It's
noticeable that the 35W halogens have lower light output than the 3.5W
LEDs.

--
Burn Hollywood burn, burn down to the ground