Um...Me123 Posted November 26, 2009 Report Share Posted November 26, 2009 What has everyone found for the brightest LEDs out there?For white I know PhlatLight has one pushing 6000lm and LedEngin will have a 40 watt RGB approaching 2000lm. Anyone know of brighter ones? Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 3, 2009 Report Share Posted December 3, 2009 You can buy extremely bright LEDs on E-Bay.The Chinese discovered that a dim old LED chip is extremely bright when its case focusses the light in a very small angle. But then it cannot be seen if it is not pointing directly at you.Light bulbs shine all around. Good LEDs shine almost all around. Some Good LEDs are fairly bright. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 6, 2009 Author Report Share Posted December 6, 2009 I did notice that Phlatlight had a RGBW (perfect for my app) that is brighter than the 40W but its $200. yaouchMy idea is to use these on my car as fog lights. Already have regular halogen ones so it would replace the bulb only, using the stock reflector. I would be able to precisely color match my HIDs and have a bazillion other options to fit whatever situation. My only worry is cooling. The brightest led I've worked with is a 1watt so I'm not sure how to approach it. All application notes have all these equations and junk but I need to see practical examples. My space and availability to mount and secure a giant heat sink is limited so I was thinking of using a peltier and maybe a small fan on the hot sink but I have zero experience with those as well. Tinkering is out of the question because of part cost so planning is vital. Has anyone ever worked with these super leds? If anyone knows of links to projects (videos/pictures/instructs) using 15+ watt leds that shows the cooling process that would be great. I'm still in the "is this possible?" stage of this one. Thanks Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 6, 2009 Report Share Posted December 6, 2009 In my opinion a Peltier cooler is not an option due to the excessive power required.Rather than a fan, is it possible to rely on the fact that the car is moving through the aire anyway?I imagine that using the car's chassis as a heatsink is probably the best option. You could probably dump quite a lot of heat into the chassis and hardly get any temperature rise at all.How are you gong to power the LED?I wouldn't recommend a resistor due to the excessive power dissipation. High power LEDs also often have quite a high voltage drop because they're actually composed of many smaller LEDs connected in series and parallel. For both reasons you really need a switched mode constant current power supply.As far as monitoring the temperature is concerned, I've noticed that the forward voltage drops with temperature which might in itself help guard against overheating if a constant current supply is used, if not you could cut the power if the voltage drop is too low.Usable lamp life is something you need to consider because LEDs get dimmer with age. I'd recommend underrating the LED slightly because not only does it make LEDs last longer, they're also more efficient at lower currents: running at 80% of the current rating does not normally reduce the brightness to 80% of the full rating, it's normally closer to 90%, see the datasheet to be sure. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 9, 2009 Author Report Share Posted December 9, 2009 Some very good things to think about on the last posts. Thanks My reasoning for the peltier is because I don't think a fan would be reliable enough because of dust/rain and I know peltier use a ton of power but I don't see too much of a problem there as long as the car is running, right? Some of the leds have a thermistor built right in so that would help and I could PWM the peltiers accordingly to save power as well. I just have no general idea of how big the heat sink needs to be so my vision is that heat sink only is out of the question. The fogs are mounted in what would be better called the bumper cover so there isn't much to work with except plastic but it's been a few months since I had it apart.Found something very helpful: "http://www.luminus.com/stuff/contentmgr/files/0/0179ad38a075ca3c31f708ed19392fa3/miscdocs/960031_rev_a_dk_414n_and_dk314n_development_kit_manual.pdfUser manual for the dev kit for the RGBW led...it can approach 120W!!! $850 though :(Sink = 82 mm x 65 mm x 38mm plus fan Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 9, 2009 Report Share Posted December 9, 2009 Without seeing the fitting it's difficult to say.If one of the reasons for using LEDs is for the efficiency then you're defeating it with a Peltier cooler.CPUs normally use around 100W so a CPU heatsink plus a decent fan should do the job, even then you could use a thermostatic control so the fan doesn't need to run continuously.I think you should do some experiments before you decide for sure. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 10, 2009 Author Report Share Posted December 10, 2009 Does anyone know of white leds at 8000k or are they all <6500k? Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 11, 2009 Report Share Posted December 11, 2009 It depends on the viewing angle. Cheap Chinese LEDs have a high brightness number because the case focusses the beam into a very narrow angle. Good LEDs are very bright over a wide angle. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 11, 2009 Report Share Posted December 11, 2009 Does anyone know of white leds at 8000k or are they all <6500k?Why do you want 8000k? That's blue.If you get a RGB LED you can alter the current to each LED to get any colour you desire. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 12, 2009 Author Report Share Posted December 12, 2009 My HIDs are 8000k. So the idea was that if I decided on not doing the RGBs for financial and flux reasons then I want something to match. Do color temps differ between types of light sources?--> would 8000k on a LED be more blue than a 8000k xeon arc? My HIDs are blue-white...mostly white. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 12, 2009 Report Share Posted December 12, 2009 My compact fluorescent bulbs have 3000k colour temperature and are pure white.2700k is warm-white (yellowish-orange like incandescent) and 3500k is cool-white (bluish).Very blue ones are called "daylight" but I don't know their colour temperature because I hate them.Corrected colour temperatures are in red. Quote Link to comment Share on other sites More sharing options...
Alex Tsekenis Posted December 12, 2009 Report Share Posted December 12, 2009 Daylight bulbs are amazing, a pure bliss to the eye in an electronics lab. The only issue is that the eye is not so sensitive to that light so maybe you need a few more tubes. If I have daylight tubes on and then change to warm white my eyes hurt. I think they are great, you should try them maybe on a bigger scale. I even convinced Intel Corp. to change the ones in my area. :D Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 12, 2009 Report Share Posted December 12, 2009 Colour temperature is the equivalent to the light emitted by a black body at that temperature. The filament of a typical incandescent bulb is around about 2700K, a halogen filament is hotter about 3000K.It's a matter of opinion, I hate daylight bulbs, they don't emit daylight but a horrible bluish grey coloured light, give me 2700K any day. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 18, 2009 Author Report Share Posted December 18, 2009 I know this is getting a little off topic but while I have you all here...An led I'm considering is the Luminus Devices CST-90. It seems to be the best balance between $s and lumens. $45@2700lm with a perk of having a thermistor. Question: It runs at 3.2-3.7V @ 1-13AWith a car as the source what is the best method of power supply which has the following qualities: cheap, easy, full dimming, and doesn't destroy led in 2 days? Quote Link to comment Share on other sites More sharing options...
Alex Tsekenis Posted December 18, 2009 Report Share Posted December 18, 2009 You could use a normal constant current source which will be quite inefficient, you could use a hysteretic driver much more efficient or you could use very specialised ICs based on hysteresis again like the new LT3743 or the MAX16818. These are in order of increased complexity.But I am sure there must be a ready product that meets these specs. That is where I would start. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 18, 2009 Report Share Posted December 18, 2009 An SMPs can be made using fairly common components.The first shows how it can be done using diecrete components and the second shows a comparator. If a comparator with a push-pull output is used Q1, D1 R4 and R5 can be eliminated. Quote Link to comment Share on other sites More sharing options...
Um...Me123 Posted December 22, 2009 Author Report Share Posted December 22, 2009 I'm new to SMPs but see that is definitely my way to go. For benefit of learning, what would be wrong with just PWMing a mosfet and putting a cap across the output? I can see that there could be fluctuations in output when the input changes but besides that is there any reason one couldn't do such a thing?Thanks,A Quote Link to comment Share on other sites More sharing options...
Alex Tsekenis Posted December 22, 2009 Report Share Posted December 22, 2009 No, no reason why you couldn't do that. But do you want to do that?Once the transistor is ON, your output will shoot to 12 V (assume car battery) and there is nothing you can do about it by changing the duty cycle. When the transistor is OFF your output volatge will fall depending on component values. You can't regulate this system.Anyway, constant voltage drive is not suitable for power LEDs. You need constant current drive (see suggestions below).Attached is a waveform of the output voltage of your proposed system to illustrate my point.Also, see what I came across:http://www.amazon.co.uk/gp/product/0750683414/ref=sib_rdr_dpProb. an overkill. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 22, 2009 Report Share Posted December 22, 2009 I'm new to SMPs but see that is definitely my way to go. For benefit of learning, what would be wrong with just PWMing a mosfet and putting a cap across the output? I can see that there could be fluctuations in output when the input changes but besides that is there any reason one couldn't do such a thing?Thanks,AYou're half way there.You need an inductor, not a capacitor if you're going to do that. The value will depend on the switching frequency, input voltage, LED voltage, current and maximum acceptable current ripple.It's true that the current will vary depending on the input voltage but that might not be a problem. This circuit is the switch mode equivalent of just using a resistor but it's well worth it as it's much more efficient. Quote Link to comment Share on other sites More sharing options...
Alex Tsekenis Posted December 22, 2009 Report Share Posted December 22, 2009 And just to expand on Hero's post below, this is the topology of the ICs suggested earlier in this topic. You can google hysteretic LED driver for more info, Elektor Electronics (the magazine) published an article this year too.By adding a resistor in the LED's path you can sense it's current and modily your duty cycle. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted December 22, 2009 Report Share Posted December 22, 2009 The unregulated circuit in my previous post is based on the same topology as the circuits in the post before it.The two regulated circuits I posted both work on the same principle: the output transistor turns on, as the current in the coil builds the voltage across the sense resistor exceeds a certain threshold, set by either a comparator or the conduction voltage of a base-emitter transistor junction, the output transistor turns off for a time determined by an RC time constant and the cycle repeats.Here's an article which describes how the comparator circuit I posted works, see page 38.http://ww1.microchip.com/downloads/en/DeviceDoc/41215C.pdfYou could use a discrete comparator if you like but it needs to be push-pull, if it's not i.e. it's LM311, LM393, use the circuit with a comparator above.Note that the circuit contains an error: the +/- inputs are the wrong way round. Quote Link to comment Share on other sites More sharing options...
The Master Posted March 16, 2011 Report Share Posted March 16, 2011 Hi Folks, hope this info is useful to someone.I was searching for a similar item when I came across this LED unit. It looks quite impressive however, it shows the LED's output in Candle power. I'm contemplating adding two of these babys as driving lights..... low current high power, as used on various aircraft as landing lights. Cool eh........ or what?https://www.aircraftspruce.com/catalog/elpages/teledynelandinglight.php * Lamp Type: TIR Lens * Bulb: PAR36 * Product Technology: LED * Wattage: 30w * Voltage: 10.5V - 30V DC * Rated Life: 5000hrs * Max Beam Candlepower (MBCP): 165,000 * Maximum Overall Length (MOL): 2.75 inches * Bulb Diameter: 4.5 inches * Case Operating Temperature: 65 Quote Link to comment Share on other sites More sharing options...
mbalegria Posted May 2, 2011 Report Share Posted May 2, 2011 What brightest LED should i put in my Headlight motor?Dashquidfatlossprofessional.co.ukfatlossprofessionalmobilehelpersecuretripwhichpetcovergoogleabcfacebookcraigslist Quote Link to comment Share on other sites More sharing options...
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