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[H]ard|On
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Quote:
Originally Posted by shmoblar View Post
This is stuff i got from the people at candlepowerforums. The spikes and drops are all fractions of a second long. You would need an oscilloscope to see these kinds of things; no normal voltmeter has that sort of refresh rate.

If you have a working regulator none of this should happen. I can't imagine how an alternator could dish out that sort of voltage anyway, at any RPM in any condition.

I have to call BS until I can see some kind of case study - sounds like batteries on concrete to me.

If the delicate ICs inside an ECU can live through these nanosecond magical energy spikes so can a fat-ass LED. In other words don't let this stop you from trying - it hasn't stopped several manufacturers, and furthermore I wouldn't make a point out of telling this to a lot of people without substantial proof.

Besides a surge protector and a fuse cn go a long way even if there is some truth to this - although I've never heard of voltages spiking more than 17-18v (which will already cause a lot of issues just with the equipment your car has as it is)
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Old 05-03-2011, 06:56 PM [H]ard|On is offline  
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You can't believe everything you read on Candlepowerforums.
Old 05-03-2011, 08:14 PM Stereodude is offline  
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The biggest issue with car led lighting is making a filter for the dirty dc power a car alternator/battery produces. Even though the voltage is normally 11-14.8v you can have dips down to 5v and pikes up to 100v. This can fry an unprotected led instantly. Pretty much you need a bank of different size capacitors and some zerner diodes.
Having designed plenty of automotive electronics, it's a non-issue.

Most stuff that touches an automotive 12V bus is designed to handle a 25V momentary surge - meaning that the thing will function properly at 25V, but it will likely overheat if it's a prolonged short. Short spikes are taken care of with passive filtering, and in "important" modules (ECU, ABS computer, etc) there's usually a resettable PTC fuse and a crowbar circuit to save the module if there's a big surge.

A bulletproof, constant current driver for running automotive LEDs is actually pretty easy to make. There are development platforms from a few different chip companies that are specifically designed for driving LED headlamps for cars.

The main reason that LED headlamps haven't taken off in cars is:

(1) cost - a simple halogen bulb costs far less than LED, heatsinking, ballast, etc.
(2) optics - halogens and HID lamps emit light from a relatively small point, so building housings that project light in a defined pattern is straightforward. LED lamps of equivalent light output tend to be in the form of large "panels" which are harder to project.
(3) thermals - LEDs have to be kept cool in order to maintain decent efficiency. Which requires elaborate thermal design... not an easy thing to do when the back side of the LEDs faces an engine compartment. You can't count on airflow from the car moving to keep the LEDs cool, adding cooling fans/peltiers/etc reduces reliability and efficiency, etc. Meanwhile halogens and HID lamps will work at basically any temperature.
(4) efficiency - LEDs aren't significantly more efficient than HID lamps, which makes the added cost/complexity of a LED solution not really worthwhile.
Old 05-04-2011, 07:14 AM gee is offline  
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A bulletproof, constant current driver for running automotive LEDs is actually pretty easy to make. There are development platforms from a few different chip companies that are specifically designed for driving LED headlamps for cars.

Just hard to find ones that can do a 9+ amps and be a reasonable size.
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Old 05-05-2011, 03:30 AM Selfsucker is offline  
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Just hard to find ones that can do a 9+ amps and be a reasonable size.
Simple. Give me a day to design the thing, and I'll give you a MAX16821C based design that's the size of a postage stamp and drives a SST-90 from automotive 12V bus.

Electronics part of it is easy. The biggest problem with LED headlamps is that LED efficiency goes to shit at high temperatures; when LEDs start keeping their full efficiency at junction temperatures above 100C, the difficult heatsinking issues go away and you'll probably see them take over automotive headlamps..
Old 05-05-2011, 05:25 AM gee is offline  
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Simple. Give me a day to design the thing, and I'll give you a MAX16821C based design that's the size of a postage stamp and drives a SST-90 from automotive 12V bus.

Electronics part of it is easy. The biggest problem with LED headlamps is that LED efficiency goes to shit at high temperatures; when LEDs start keeping their full efficiency at junction temperatures above 100C, the difficult heatsinking issues go away and you'll probably see them take over automotive headlamps..

Well If this is for stand alone offroad lights, cooling is easy. Airflow wouldnt be a problem. Otherwise auto power has one advantage; there is alot of it. You can get a hell of a 12 volt fan that is small and can push a lot of air past a heatsink. Honestly a 10min visit to newegg would get you a pretty powerful blower. Hell watter cool it :P
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Old 05-06-2011, 03:43 AM Selfsucker is offline  
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Just hard to find ones that can do a 9+ amps and be a reasonable size.

What's a "reasonable size"? You can get regulator circuits that are a fraction of the size of a HID ballast. We're literally an inch away from mainstream LED headlights. Once this happens production cost should plummit. An LED headlight system, by design, is far simpler than HID [I'll put an IMO on this], and should last longer. No bulky ballast, no AC s, no glass, longlivety etc.
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Old 05-06-2011, 03:45 AM pepperochini is offline  
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Quote:
Originally Posted by shmoblar View Post
Well If this is for stand alone offroad lights, cooling is easy. Airflow wouldnt be a problem. Otherwise auto power has one advantage; there is alot of it. You can get a hell of a 12 volt fan that is small and can push a lot of air past a heatsink. Honestly a 10min visit to newegg would get you a pretty powerful blower. Hell watter cool it :P
Where's your fan/blower going to get its air from - the engine compartment (too hot), outside air (dust/debris get sucked in)? Also remember that a good brushless fan has a lifetime of about 5 years, and that's in a static location (eg, a computer server) and not in a car where it's being bounced around.

And watercooling just means you've moved the heat you have to dissipate to a separately located radiator, which then needs cooling - plus you need a circulation pump. And you're not going to cool a LED with the same ~100C water used to cool the engine.
Old 05-06-2011, 09:45 AM gee is offline  
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Where's your fan/blower going to get its air from - the engine compartment (too hot), outside air (dust/debris get sucked in)? Also remember that a good brushless fan has a lifetime of about 5 years, and that's in a static location (eg, a computer server) and not in a car where it's being bounced around.

And watercooling just means you've moved the heat you have to dissipate to a separately located radiator, which then needs cooling - plus you need a circulation pump. And you're not going to cool a LED with the same ~100C water used to cool the engine.

No way engine water. A small rad in front of the main radiator would do. (Side thought, blinker fluid could finally be a reality)

I'd guess that car lights are used 95% in motion and not much at all sitting around for prolonged periods of time. So if you make a heavy, well designed copper heat sink (maybe half a pound) Between the airflow and the point that it does take a good amount of time to saturate that much metal with heat, something could be worked out.

Im not arguing that it would be difficult, im saying that with some thought its definitely possible especially since the led's like this are intended for stationary indoore lighting. Just might have to spend some time doing heat flow analysis. Also a high temp kill circuit can be done.
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Last edited by shmoblar; 05-06-2011 at 03:53 PM..
Old 05-06-2011, 03:39 PM Selfsucker is offline  
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No way engine water. A small rad in front of the main radiator would do. (Side thought, blinker fluid could finally be a reality)



I don't think it's going to be quite as bad as everyone's thinking. Look at the new consumer-level LEDs coming out: they've got decent-sized heat sinks, and no falns whatsoever--and those designed for can lights (R30s and R40s) will always have a worse problem with airflow and heat, and a can environment isn't any better than that in a car body.

Speaking of, just saw a new product, an LED motion-sensor security light, where the entire backside of the light head is heat sink--and far more than what one could reasonably expect a pack of 6 LEDs would need.

Most headlights aren't used during the day, meaning the worst of the heat problems go away, even in warmer climates where nighttime temps can be in the 80's.
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Old 05-06-2011, 04:26 PM Tex Arcana is offline  
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i have one of those LED Maglite flashlights

how hard would it be to retrofit one of these bad boys into it?
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Old 05-06-2011, 04:35 PM Colicious is offline  
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i have one of those LED Maglite flashlights

how hard would it be to retrofit one of these bad boys into it?

www.candlepowerforums.com thats a place where people get off to putting these in maglites. Also, if you know what you are doing, not too hard.
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Old 05-06-2011, 10:43 PM Selfsucker is offline  
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I don't think it's going to be quite as bad as everyone's thinking. Look at the new consumer-level LEDs coming out: they've got decent-sized heat sinks, and no falns whatsoever--and those designed for can lights (R30s and R40s) will always have a worse problem with airflow and heat, and a can environment isn't any better than that in a car body.

Speaking of, just saw a new product, an LED motion-sensor security light, where the entire backside of the light head is heat sink--and far more than what one could reasonably expect a pack of 6 LEDs would need.

Most headlights aren't used during the day, meaning the worst of the heat problems go away, even in warmer climates where nighttime temps can be in the 80's.

Those LEDs are 3 - 5w. This is a 35w; there is a tad bit bigger heat issue. But still, this led is designed to sit in a light fixture with little to no forced convection passed its heatsink so a setup which has forced convection on its side is definably doable.
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Old 05-06-2011, 10:48 PM Selfsucker is offline  
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www.candlepowerforums.com thats a place where people get off to putting these in maglites. Also, if you know what you are doing, not too hard.
No too hard, but also not too cheap. Expect to put at least $100 dollars into the project, and that's assuming you skimp on pretty much everything.
Old 05-07-2011, 06:32 AM Stereodude is offline  
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Wow, nice build. I'm working on a custom build as well, but what I'm doing is far smaller (Optek Optimal XIV 600+ lumen LED, Shark driver, 2x 16850 power in a slender-body light about 9" long) and I'm not a machinist by any stretch of the imagination so mine isn't gonna be nearly as formidable-looking. That thing you made is a beast...

BTW, get a sapphire watch crystal to use as a lens for that beast if you haven't already - it'll cost a ton compared to glass but it's heat-conductive (so you trap less in the head) and scratch-resistant (second only to diamond) so it can take actual use.
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