Newbe with some LED questions (yet another tail light thread)

[cadstarsucks]

I will be using the luxeon Rebel LEDs that JUSTDIY gave me this link to
http://www.luxeonstar.com/luxeon-rebel-led-redorange-50-lumens-350ma-p-153.php?id=5161&zenid=12rh7d6ujv5262gamncavrvnq7

Although I may go with the pure reds that put out 80Lm

Do I still need the stars for these, or can I go strait to the aluminum housing as the heat sink?

The rebels are excellent LEDs but are a bit tricky to handle.  I would recommend buying stars to mount them to if you can not buy them mounted as that company does not advertise them mounted other than the whites.  I know they will sell them separate but I do not know if they will sell red stars.

[justDIY]

yes, sourcing the unpopulated stars is a bit of a challenge ... they show up on ebay from time to time, and I think dealextreme had them at one point.   I ordered a bunch directly from a factory in Germany; a 30mm star that holds three rebels.  They also make 20 and 16mm stars which holds three rebels or a single rebel.  I'll have to look through my records to find their contact info if you're interested in going that route. (there's a substantial minimum purchase involved)

http://forums.linear1.org/index.php/topic,1447.0.html

here's the sample kit they sent me of their entire rebel product line:

http://projects.dimension-x.net/pictures/rebel/stars.jpg

[cadstarsucks]

I thought I saw them there as well...

They have red CREEs now: http://www.dealextreme.com/details.dx/sku.1776

And they have the bare CREE boards... Of course those boards above are all premounted so you can screw them to your heatsink with a proper interface material after soldering the wires to them.

[majorboost]

It looks like the red CREEs are under 40Lm @ 350ma - that should be around 80-90Lm @700 right? I noticed the angle on them is 90*, that's about the only tech difference I noticed from the Rebels.  Any other input on the CREEs?

It looks like the CREE stars have a different pattern to them for the Anode and Cathode, along with the heat transfer. I don't think the Rebels would work on the CREE stars?

Why would they not sell all of the Rebels as a star version? I am starting to feel a dog chasing my tail. I was all gun ho on the Rebels.

Can the star portion of the assembly be painted black after assembly (naturally after taping off the LED portion)?

[cadstarsucks]

It looks like the red CREEs are under 40Lm @ 350ma - that should be around 80-90Lm @700 right? I noticed the angle on them is 90*, that's about the only tech difference I noticed from the Rebels.  Any other input on the CREEs?

It looks like the CREE stars have a different pattern to them for the Anode and Cathode, along with the heat transfer. I don't think the Rebels would work on the CREE stars?

Why would they not sell all of the Rebels as a star version? I am starting to feel a dog chasing my tail. I was all gun ho on the Rebels.

Can the star portion of the assembly be painted black after assembly (naturally after taping off the LED portion)?

In reverse order:

Of course you can paint the rest of the star, and some are black to begin with. 

They do not bother selling the rebels as stars directly since rebels can be handled with normal surface mount equipment.  Others require a $20K machine to epoxy down the thermal pad and resistance weld/solder the leads.  Because of this the suppliers put them on stars so normal manufacturers could handle them.  I do not know off hand if the crees can survive infrared reflow, I know for a fact that the older luxeons and probably none of besthongkongs can.

As to using rebels on cree stars, the land pattern is very different.  There are some rebel star makers out there but they seem to be popular and not in need of advertising.

The red cree data sheet, from memory, implies that it would put out about 80Lm.  Looking closer you find a big difference: the rebel is rated at 25°C pad and the cree is rated at 25°C die with 8°C/W.  That means with a perfect heat sink at 3W the rebel will perform as specified and the cree will be about 15% down in lumen output.

[minimum]

I do not know off hand if the crees can survive infrared reflow

Yes, reflow soldering compatible, according to datasheet.

The red cree data sheet, from memory, implies that it would put out about 80Lm.

Unfortunately, red/orange are available only in XR-C package, not the XR-E
The highest bin XRCRED-L1-0000-00M01 is 39,8lm@350mA and 51,7lm@700mA (the @700 was taken from binning&labeling document, as the datasheet didn't present this info.)

Highest bin Rebel LXML-PD01-0040 is 40lm@350mA and 85lm@700mA

Looking closer you find a big difference: the rebel is rated at 25°C pad and the cree is rated at 25°C die with 8°C/W.

The red/orange XR-C are rated at 15°C/W.

That means with a perfect heat sink at 3W the rebel will perform as specified and the cree will be about 15% down in lumen output.

For red XR-C, the +15°C would give about -10% , for orange however, the drop would be a bit more than -20%

[cadstarsucks]

That means with a perfect heat sink at 3W the rebel will perform as specified and the cree will be about 15% down in lumen output.

For red XR-C, the +15°C would give about -10% , for orange however, the drop would be a bit more than -20%

You obviously have the specs in hand, I was shooting from a day or two old memory.  At any rate, the original reason for the stars was really marketing, if your customers can not mount it, you can not sell it.

Even now, the smaller customers are in lighting companies with no SMT equipment.  My company does not generally use them, although it looks like I will be getting rebels actually in house for production within the year.

[majorboost]

Due to how readily available they are, I am just going to go with the Prolight 3W red high power led. All of the other suggestions you guys made are great............ But I either don't have the ability to mount the LEDs to the stars, or I can't find suppliers for them. I will still be using a Buckpuck with dim ability. This is what I came up with array wise.


                   >-->-->-->-->
Pos----------                      ------------ Neg
                   >-->-->-->-->

This will give me 11.0 volts needed @ 2.2 average fv
These are 700ma high powers

Due to the parallel array the lights will want 1400 ma

Buck Pucks are rated at 350ma, 700ma, and 1000 ma

I am assuming that I should go with the 1000ma unit due to the current sharing? This would mean that the lights will be slightly dimmer than rated right? But in theory it will help with the heat output of the units correct?

Then back to a diode...................
I will need to run a diode to keep my voltage from back feeding to the front lights of the system on my tail circuit. Any diode suggestions?

Thanks again guys! Without you, I would be in the dark! Literally LOL

[justDIY]

I'd go with the red cree star instead of the prolight - the difference in brightness will be very dramatic.

I'm not sure that you need a diode for anything ... as it stands right now, your front lights don't come on when you apply the brakes right?  so how will that be changed when you replace the hotwire bulb with a buck puck + leds

Edit:

Here's an alternative... the K2 star:

http://ledsupply.com/05027-ph12.php

75 lm at 700ma ... the K2 is advertised as being very heat tolerate as well, claiming an operational junction temperature of 185C.   tolerance to high temps might be worth considering for an automotive application.

[majorboost]

I'd go with the red cree star instead of the prolight - the difference in brightness will be very dramatic.

I'm not sure that you need a diode for anything ... as it stands right now, your front lights don't come on when you apply the brakes right?  so how will that be changed when you replace the hotwire bulb with a buck puck + leds

Edit:

Here's an alternative... the K2 star:

http://ledsupply.com/05027-ph12.php

75 lm at 700ma ... the K2 is advertised as being very heat tolerate as well, claiming an operational junction temperature of 185C.   tolerance to high temps might be worth considering for an automotive application.

The CREE's on the link that was given to me give no info on what series  they are (KR or KR-C), nor any type of specs. So I don't trust what I will actually receive. And I have had a heck of a time finding other sources to purchase the KR-C's from.

Right now my filament bulbs are dual elements, meaning there is a seperate circuit for the tails vs. the turns/brake. When I go to the Buckpuck, I will need both the tail circuit and the turn/ brake circuit powering up the Buck puck. That way it can get voltage from one OR the other. So I will need a diode on the Tail light wire so I don't back feed voltage when the Brake lights are illuminated.

I like the K2's (it seems that everyone is against the Prolights) so I will go that route.
Do either of these arrays look like they would work? They are rated @ 2.95 fv, I am running 14.0


                 >---->---->
Pos--------                  --------Neg
                 >---->---->


Or should I go


                >---->---->---->
Pos--------                       ---------- Neg
                >---->---->---->
Again with a series circuit like this they would want 1400ma for full Lm. Would I then run the 1000 ma Buckpack to try and get close to the full amperage handling capabilities?

[justDIY]

the 1a buckpuck can be tweaked to pump out about 1300ma, which will be close enough for your 2x700ma requirement.

ok, you're right, you'll actually want three diodes I think... one from the driving light / headlight circuit, one from the brake light circuit and one from the turn indicators.  all these diodes would be on the +12v side of the buckpuck (vin).  I recommend 3-5amp schottky diodes, because of their low voltage drop (figure on 0.3v)

figuring out the logic for combining braking and turning lights is boggling my mind for some reason.  I'm sure it's possible, but I'm at a loss on the simplest way to achieve it in the analog world. 

If it were up to me, I'd run the +12v feeds for the three lights into a microcontroller's inputs via some 100k resistors, and leave the buck puck wired up to +12v all the time.  the microcontroller could then output an appropriate pwm signal to the buckpuck as needed for the desired effect, driving, braking, turning, etc.

[cadstarsucks]

the 1a buckpuck can be tweaked to pump out about 1300ma, which will be close enough for your 2x700ma requirement.

ok, you're right, you'll actually want three diodes I think... one from the driving light / headlight circuit, one from the brake light circuit and one from the turn indicators.  all these diodes would be on the +12v side of the buckpuck (vin).  I recommend 3-5amp schottky diodes, because of their low voltage drop (figure on 0.3v)

Actually even most schottkys are 0.5V at their rated current.  At 1/3 rating they go down to 0.4V unless you are specifying a low Vf version like the B340LA in which case it will be down at 0.3V at 1/3 rating.

figuring out the logic for combining braking and turning lights is boggling my mind for some reason.  I'm sure it's possible, but I'm at a loss on the simplest way to achieve it in the analog world. 

If it were up to me, I'd run the +12v feeds for the three lights into a microcontroller's inputs via some 100k resistors, and leave the buck puck wired up to +12v all the time.  the microcontroller could then output an appropriate pwm signal to the buckpuck as needed for the desired effect, driving, braking, turning, etc.

Since you only need bright and normal it is pretty easy to put a simple PWM oscillator in there and just override it for braking, etc.  Generally the turn signals are amber and not red, so they would be on a separate circuit.

[majorboost]

the 1a buckpuck can be tweaked to pump out about 1300ma, which will be close enough for your 2x700ma requirement.

ok, you're right, you'll actually want three diodes I think... one from the driving light / headlight circuit, one from the brake light circuit and one from the turn indicators.  all these diodes would be on the +12v side of the buckpuck (vin).  I recommend 3-5amp schottky diodes, because of their low voltage drop (figure on 0.3v)

figuring out the logic for combining braking and turning lights is boggling my mind for some reason.  I'm sure it's possible, but I'm at a loss on the simplest way to achieve it in the analog world. 

If it were up to me, I'd run the +12v feeds for the three lights into a microcontroller's inputs via some 100k resistors, and leave the buck puck wired up to +12v all the time.  the microcontroller could then output an appropriate pwm signal to the buckpuck as needed for the desired effect, driving, braking, turning, etc.

Perfect, thank you.

I will order up 12 X2's and 2 1000ma Buckpucks tonight then.

This is what I came up with relay wise to control dim function. Please excuse the messiness I did this before I ran to work this morning.


By majorboost at 2008-07-09

When Relay #1 is at rest it is supplying the Buckpuck with it's own 5volt cut down voltage. When it is energized by the brake pedal, it goes open circuit to the Buckpucks reference making 0volts and allowing full Lm.


Micro controller..................... That MAY be a little over my head to build, but if it looks better than what I have I can give it a shot.

[majorboost]

the 1a buckpuck can be tweaked to pump out about 1300ma, which will be close enough for your 2x700ma requirement.

ok, you're right, you'll actually want three diodes I think... one from the driving light / headlight circuit, one from the brake light circuit and one from the turn indicators.  all these diodes would be on the +12v side of the buckpuck (vin).  I recommend 3-5amp schottky diodes, because of their low voltage drop (figure on 0.3v)

Actually even most schottkys are 0.5V at their rated current.  At 1/3 rating they go down to 0.4V unless you are specifying a low Vf version like the B340LA in which case it will be down at 0.3V at 1/3 rating.

figuring out the logic for combining braking and turning lights is boggling my mind for some reason.  I'm sure it's possible, but I'm at a loss on the simplest way to achieve it in the analog world. 

If it were up to me, I'd run the +12v feeds for the three lights into a microcontroller's inputs via some 100k resistors, and leave the buck puck wired up to +12v all the time.  the microcontroller could then output an appropriate pwm signal to the buckpuck as needed for the desired effect, driving, braking, turning, etc.

Since you only need bright and normal it is pretty easy to put a simple PWM oscillator in there and just override it for braking, etc.  Generally the turn signals are amber and not red, so they would be on a separate circuit.

I don't doubt the ease of PWM at all, I'm just not familiar with building or timing of the unit. I figure I am starting to annoy you guys enough with all of the questions I have already asked too, so I don't want to push it =). I deal with PWM on automotive module systems all of the time, but never building it from scratch. like I stated before, I am used to programming ECM's and BCM's, not building them. If it is simple enough to build, I will give anything a shot though. The worst that can happen is it won't work because of builder error LOL.

THANK YOU AGAIN TO THE BOTH OF YOU FOR ALL OF YOUR HELP!!!!

[cadstarsucks]

I don't doubt the ease of PWM at all, I'm just not familiar with building or timing of the unit. I figure I am starting to annoy you guys enough with all of the questions I have already asked too, so I don't want to push it =). I deal with PWM on automotive module systems all of the time, but never building it from scratch. like I stated before, I am used to programming ECM's and BCM's, not building them. If it is simple enough to build, I will give anything a shot though. The worst that can happen is it won't work because of builder error LOL.

THANK YOU AGAIN TO THE BOTH OF YOU FOR ALL OF YOUR HELP!!!!

Not a bother at all.  A lot of us here enjoy helping people. 

Actually I was thinking you would turn on the puk with the main power and driving it's modulation input with an oscillator running off of it's 5V reference.  The brake/turn switch just has to disable the oscillator to turn on full intensity.