LED Lightbulbs

[Huge]

Naah. It's because a vary large proportion of drivers are knobheads. I once got out of my car in a traffic jam and asked the k*****ad in front to turn off his rear fogs (it wasn't foggy. At all.) He replied that his car wasn't fitted with rear fogs. I pointed at the illuminated switch on his dashboard, he prodded it and it (and the fogs) went out. "I wondered what that did", he said. Then I shot him in the head with a .44 Magnum and burned his car. I may have lied about that last bit.

Can't remember what my D2 did. Other than leak rain onto my head.

BTFOOM. Almost certainly fogs, since the thing has BFO Xenon headlamps that light up half the county. I'd probably hardly ever use them, except you have to have them on to get the rear fogs on. :o(

[Mike Clarke]

states that it's mandatory to have (at least) one rear fog lamp but 2 lamps are optional. In the event of only one lamp then it must be on the centre-line or offside of the vehicle but there are no restrictions if

2 lamps are fitted.

[Andy Burns]

So you could be stupid and have two on the nearside, so close together that they're barely distinguishable, it only mentions separation between stop and fog lamps ...

[dennis]

What makes you think LEDs need a baffle to throw half the light away?

Obviously not.

I wonder how many things started out by someone showing a drawing, or a slide show to someone else before it became something real.. lets think a few seconds.. that would be almost everything in the last decade or three.

[Dave Plowman (News)]

What makes you think there's another way of doing it? Not a knowledge of optics, obviously.

[dennis]

So do you know the difference between a filament and a silicon junction?

[Adam Aglionby]

[e-mail]...

few since, self levelling are very common via tilt servo.

Advantage here is probabkly very efficient optics getting most of light from LED in collimated beam and then using multiple beams to cover the area.

Works well in a car becasue area needing lit is relatively narrow.

Cheers Adam

[David]

Seriously?

you do realise that you just modulate the drive current to turn a LED on/off.

No mechanical parts required.

cheers

David

[Huge]

And that directs the light in a particular direction how, exactly?

[Andrew Gabriel]

An LED-based headlamp is likely to be multi-LED source. With LEDs being tiny sources anyway, it's relatively easy to build optics around them to very accurately direct each LED source to a specific part of the output beam. This means you can do beam dipping simply by switching off those LEDs which give the high beam. As I eluded in another post, you could have beams which are much more dynamically adjustable than just main/dip. Could also vary intensity of parts of the beam, and unlike either filament or HID, colour shift would be minimal if you did this.

[David]

by having multiple LEDs that you simple switch on/off

this is not a smooth transition but rather a discrete group of settings - a digital rather than analogue directional control if you like.

[Dave Plowman (News)]

LEDs don't need optics, then?

[Dave Plowman (News)]

Which discussion do you think you're reading?

[dennis]

Stop wriggling.

[Dave Plowman (News)]

Ok Dennis. Explain how you get a sharp cutoff on an LED without using optics. My breath is bated.

Hint: Just how the light is produced - filament or discharge etc make little difference. The more of a point source it is just makes the optics easier.

[Steve Firth]

Dennis seems to be hitting new depths. Power LEDs generally have one or two reflectors (sometimes the manufacturer has a reflector in the LED ) and usually two lenses, one incorporated in the package and a second lens and reflector for the array. Blathering away than a lens is not required is, errm total bollocks, again.

[Dave Plowman (News)]

Indeed - I've never even looked at a car headlight LED, but laws of physics don't change regardless of what Dennis wants.

But having at least some of the optics as part of the 'bulb' is nothing new - some tungsten Lucas ones had a built in flag in the '50s.

[Andrew Gabriel]

Um, read what I wrote above again...

The difference from other light sources is the size - they're tiny - much smaller than a filament, or the arc in a HID. What this enables you to do is to build optics which concentrate the light in very specific directions. The ideal light source for this is a point which you can use to generate images with sharp boundaries. As that light source grows in size, you can think of it as an out-of-focus point, and it will generate correspondingly out-of-focus boundaries. An LED is nearer to a point source than existing technologies.

'Flag' is too loosely defined in this case. You may have a set of LED with optics which give you the dip beam pattern, and another set which give you the (main beam) - (dip beam) pattern. No 'flag' is required to block anything, it's simply that the optics only direct the light where it's wanted.

[Dave Plowman (News)]

To provide a very sharp cutoff, you'd need rather a large number of LEDs. ;-)

The size of the source (within reason) only make a difference to the size and complexity of the optics. If this weren't the case cinema projectors etc could never have been made to work well.

[dennis]

Well there you are, that is exactly what I said in the first place and what you have been arguing about since. I knew you would hang yourself if I let you.