Project off-road lightbar featuring SST-90's

[Diman]

oh no, i think you misunderstand, all my passive cooling stuff will still be in place, massive u-channel and heatsinks along the backside.
But I hear you Diw!
Let's say then a 12mm air tube originating from inside the car, for the inlet.
then a fan blowing out air, but not into another tube that runs back inside, but into some kind of one way outlet of appropriate diameter.

Regarding water, I was considering that, but it's far more complex solution. But it wold be nice. Whole project must have been designed with water cooling in mind from the beginning for it to work properly.

And yeah !! I'm very exited! I want it to be complete now now now !!!.

[Hoop]

I agree with hellokitty's water cooling suggestion. PC water cooling pumps are 12 volt so it would be easy to power off of your battery. A triple 120mm or 140mm pc radiator setup would certainly dissipate 400 watts, or you could possibly use a car heater core rad. You would want to run antifreeze through the loop. You don't want to mix copper and aluminum in the same loop or oxidation will occur, but they make square copper tubing, which you could probably mount the SST-90's directly onto, and run the coolant straight through it. I would use 1/2 tubing and a Swiftech MCP655 (cheapest from newegg) pump. Running water through a tube will do the job, whereas running air through a tube wont.

[DKlaser]

I decided to push through with my project but only at half scale for now. I decided to modify an already existing pair of light housings with 9, xml emitters each to see how that goes before I dive into the BIG project of the light bar. I still have the material for it I will just keep it in storage for now. I will let you know how it is going.

[Diman]

good to hear :-) Half the fun is in the building :-)
I have now received a test piece of u-chanell from (another) cnc guy
the reason for that is to lower u-channels "wings" a bit so that reflectors sitting on the front plate are at the appropriate distance on top of the leds.
I will test fitment tomorrow, see if I can produce a photo...

[DIWdiver]

You could also (thermal) epoxy square copper tube to the heatsink to cool it, instead of to the LED directly. It might be easier.

[viper37]

I'll be following this with great interest. I spend a lot of time off road and I would love to supplement my 6 HID's with some close range LED light.

[DKlaser]

Here is maybe an option to safeguard against overheating...

http://search.digikey.com/us/en/prod...518-ND/2195532

You can thank the driver guy for that.

[Hoop]

Here is a watercooling solution similar to what I was suggesting. I only saw the thread just now, so it seems it's an intuitive enough solution that several people have though of it: http://www.candlepowerforums.com/vb/...archlight-quot

[DKlaser]

Anything new going on here?

[Diman]

Hi there
The project is not abandoned, just need more time.
I've been too busy rebuilding some stuff on my Jeep in time for a big meet, so this project had to wait a bit.
I plan to pick this up in about a month or so.
The idea is still the same, but I think I will add one or two fans to create a steady air flow inside the bar.
Water cooling is not an option for now...

[DKlaser]

I know what you mean. I am just now getting to the end of one of my 2 windshield mounted lights. If all goes well I will be getting on the other in short order.

[Diman]

It takes more time than you think
the light bar project will probably be completed just in time for a three-day autumn meet and will certainly prove itself useful during night trails
So now I have a deadline *hehe*

[Apprentice]

I am interesting in building a similar light set up. I was wondering how well your set up worked, maybe it has been posted and I overlooked it. Did it give you the desired distance that you were looking for? is it comparable to other off road lights? If not, is there any alterations that could be made to give better distance or a more comparable light output to that of more common off road lights?

[DKlaser]

It's not done yet. And after my recent experience with sst-90 emitters his light bar is going to be stupid bright.

[Apprentice]

I guess my next question is how do I go about getting one of those drivers? I think DIWdiver made them. I am wanting to make only a 3 LED light bar to start just to test it out. I think i will prob move forward to making one that has 12 or 15 LEDs sometime later if I like the set up. Here are my list of questions as I am not very familiar with some of this:
1. How do I get a driver?
2. This driver I believe is for 3 LEDs in series but does it have to be for 3. If I make a light bar with more LEDs, can there be one driver to power them all or is it better to have one driver per 3 LEDs?
3. When wiring this to the vehicle; does there need to be anything else wired in the loop besides the driver and the 3 LEDs? Such as a relay or something of that nature.
4. I believe that the driver mentioned has a tendency to overheat and may require a heat sink. Is this always going to be a problem with an LED light bar powered by a ~12 V DC power source? Or could the driver be designed differently so that it would be less likely to over heat?

I greatly appreciate any feed back and advice one might have to offer.

Thanks

[Hoop]

1. How do I get a driver?
Drivers are available from several sources. Taskled's drivers are highly recommended. DW's drivers are also popular. Be sure and see DIW's linear 10A driver too.
Illumination supply sells various drivers and so does the sandwich shoppe. There are various European retailers as well such as Cutter and LED-Tech. DW is in Europe as well but ships worldwide.
DX and KD have various import drivers and they are inexpensive but usually provide a bit less power than they are rated for, typically have no documentation, and it takes a long time (several weeks) to get your items because they ship from china.

This thread may also be of interest.

2. This driver I believe is for 3 LEDs in series but does it have to be for 3. If I make a light bar with more LEDs, can there be one driver to power them all or is it better to have one driver per 3 LEDs?
If are referring to the DW 9A driver: you can power 1-5 SST/CST-90's with it. You need 2 volts higher input voltage than output voltage to stay in regulation, and the maximum input voltage is 22 volts, although it can handle 24 volts ok. A Battery's voltage changes with its charge state though, so for practical purposes you wouldnt want to have more than 3 LEDS in a string... Five 4.2 volt lithium batteries powering the string would cause the driver to fall out of regulation when the batteries hit 2.8 volts. If you had a constant voltage power source of 22 to 24 volts, you could theoretically power 5 CST/SST-90's @ 9 amps and stay in regulation.

With a car battery you are going to have between 12 and 13.5 volts or so at any given time. You probably can only power 2 SST/CST-90's and stay in regulation at all times with the DW driver. You might be able to get away with 3 in series per driver, but the leds would probably be out of regulation at first, (dim) and then as they heat up and their Vf drops, they may go into regulation. This would be a bit of a balancing act and it would depend on how low an SST/CST-90's Vf drops to at a given Tj temperature and also how cold it is outside. This might work in the summer time... but I don't know about in winter. This would not be practical, I am merely brainstorming.

You shouldn't use more than 2 LEDs in series because the car voltage can drop below the minimum voltage needed for 3 LEDs.

The DIW 10A driver, being a linear driver, is probably best suited to this application if you want 3 CST/SST-90's in series per driver. You would have to ask DIWdiver about the version which will accept up to 16v input, as the standard version only handles 12v max input. Since the cars battery voltage is pretty close to the LED string voltage it should be fairly efficient, which means the driver wont get overly hot if heatsinked properly. This driver offers modes and dimming.

The cheapest/simplest option is going to be to direct drive the CST/SST-90's in strings of 3, with each 3s string being wired to the battery in parallel. You will not have dimming capability or modes, but if you just want BRIGHT, then this is an option. Keep in mind that as the LED's warm up they need less voltage to reach the same amperage draw, which is to say as they warm up they will be drawing more amps, so when you are using a constant voltage power source you have to be careful as this can lead to "thermal runaway" if there is not adequate heatsinking. SST-90's are pretty robust however and people have run 13 and even 15 amps through them. Since CST-90's are rated for 13.5 amps and are mounted to a copper board, they will probably be well suited to direct drive in an automobile environment. Make sure that on a warm, calm night, and when the vehicle is parked, (less airflow) the current draw doesn't exceed like 15 amps or so by too much, if you are using CST-90's. For SST-90, you probably don't want to exceed 13 amps... I don't know exactly when either goes , but I have seen other people run at these values.

3. When wiring this to the vehicle; does there need to be anything else wired in the loop besides the driver and the 3 LEDs? Such as a relay or something of that nature.
You're going to want to use fuses. In direct drive this would prevent you from killing your LEDS in a thermal runaway situation. Maybe a 13A for SST-90 and 15A fuse for CST-90. One fuse per string. A kill switch would be a good idea too. The LED driver itself will probably need a switch wired to it and possibly a potentiometer if it has dimming capability. If you are going to go direct drive, you will want a switch capable of handling the current you will be running. You could use multiple switches too if you want to be able to turn your LED strings on one at a time... This would almost be like giving you low/med/high but in practice you might not be able to see much of a difference between 6/9 leds at a time, so maybe just a switch for a single string and another switch for all the rest of the strings. 1 string "Low mode" should still out-throw your cars headlights by far tho...

4. I believe that the driver mentioned has a tendency to overheat and may require a heat sink. Is this always going to be a problem with an LED light bar powered by a ~12 V DC power source? Or could the driver be designed differently so that it would be less likely to over heat?
You need to heatsink high power drivers. They are not 100% efficient so there is some waste heat which needs to be dissipated. Sometimes flashlights are compact and aren't adequately heatsinked, but in an automobile environment you'll have plenty of space for adequate heatsinking. You typically either use potting compound or thermal tape and attach the driver to a heatsink. This is normal procedure. If you don't heatsink a high power driver it will burn up.

[cmacclel]

I made a back-up light for my Jeep using 4 SST-50 LED's in series and when running they where seeing around 3 amps. I highly doubt you could run 3, SST-90's direct drive from a automobile as when the car is running your seeing over 14v which means each LED would be seeing almost 5v each.

Mac

[DIWdiver]

Excellent response, Hoop.

I'm not sure I'd agree that direct drive is viable, though. That's a lot of excess voltage when the vehicle is running. With short fat wires, it would be easy to exceed 15A on the emitters.

With the vehicle running and 3 SST-90 or CST-90 emitters in series, I'd expect the efficiency of my IS1006 to be 80-85%. When the vehicle is off, the efficiency would be over 90%. 80% efficiency translates to around 27 watts of heat in the driver. That's pretty much the worst case, and it's very similar to the amount of heat generated in the emitters, so similar heatsinking is required, though it's a little more difficult on the IS1006 because electrical isolation is usually required.

I'm working on a new driver very similar to the IS1006, but designed from the ground up for automotive use. I thought I'd have samples by now, but Hong Kong Post is not known for reliability, and my PCBs have not arrived yet. The IS1011 has several advantages over the IS1006 for automotive use, and if you aren't in a hurry, it will be a better choice, if I ever get my boards. Specs are the same or better than the IS1006.

I won't disagree that the IS1006 has a 'tendency to overheat', but this is dependent on the design and construction and is therefore under control of the builder. For some designs it would be a great choice, for others it would be a terrible choice.

[Hoop]

Good point Mac. I was assuming the battery would be at something like 13.5 volts and there will be some voltage drop over the several meters of wire, switches, and fuses. Could some resistors be used to remedy a slightly too high voltage?

Edit: Thanks DIWdiver. Say, when does your 10 amp linear driver fall out of regulation? can it work as low as .5 or 1 volt over nominal?

[Apprentice]

DIWdiver, what is the time line of having the automotive driver available? I have no problem waiting; however, I don't want to wait to long. If it is going to be more than a month I might go ahead with the IS1006. Is there a specific heat sink that is recommendable? Please keep in mind that I am trying to keep my size down if possible. It could be narrow and long and fit what I am trying to do. Is an air cooled heat sink sufficient or would it need a closed system liquid cooling system similar to what is on an Xbox 360?

Thanks for all of the feed back. Greatly appreciated.

[DIWdiver]

Good point Mac. I was assuming the battery would be at something like 13.5 volts and there will be some voltage drop over the several meters of wire, switches, and fuses. Could some resistors be used to remedy a slightly too high voltage?

Edit: Thanks DIWdiver. Say, when does your 10 amp linear driver fall out of regulation? can it work as low as .5 or 1 volt over nominal?

Yes, a resistor could be used. It's pretty crude and not a very good regulator, because it allows the current to change when the voltage changes. There's a pretty substantial change when you start or turn off the engine. There is resistance in all the various parts, and possibly enough to protect the emitters. but there are too many unknowns for me to recommend it to someone who isn't well versed in such things.

The IS1006 driver needs 0.25-0.3V of overhead to maintain regulation.

[DIWdiver]

DIWdiver, what is the time line of having the automotive driver available? I have no problem waiting; however, I don't want to wait to long. If it is going to be more than a month I might go ahead with the IS1006. Is there a specific heat sink that is recommendable? Please keep in mind that I am trying to keep my size down if possible. It could be narrow and long and fit what I am trying to do. Is an air cooled heat sink sufficient or would it need a closed system liquid cooling system similar to what is on an Xbox 360?

Thanks for all of the feed back. Greatly appreciated.

I just got my hands on the boards, so I should know in a week or so if the first rev is good enough to sell. If so I'll put up a sales thread.

There isnt a particular heatsink that's recommended, because everyone's application is different. I know that a half-brick size heatsink (it's a standard module size, about 2.4" square) with 1.25" fins is adequate with a high-speed fan blowing directly on it. In still air you'd need 5-10 times that.

[ThirstyTurtle]

any updates?! I'm salivating reading this...

[alpg88]

You don't want to mix copper and aluminum in the same loop or oxidation will occur,.

it only occurs if those 2 metals touch each other, there are planty of cars that use copper radiators\intercoolers, with aluminium heads\fittings.

[Diman]

any updates?! I'm salivating reading this...

Unfortunally this project is on ice for now, I got involved in a couple of other projects so there's simply no time for this right know. This is sad, because i really really want to finish this and I WILL return to this as soon as I have more free time.

The configuration is still unchanged, although I am leaning towards CST-90s mainly because of it's much lower thermal resistance and an on-board thermistor
However, I haven't found any appropriate driver to power a CST-90 yet.

[ThirstyTurtle]

Unfortunally this project is on ice for now, I got involved in a couple of other projects so there's simply no time for this right know. This is sad, because i really really want to finish this and I WILL return to this as soon as I have more free time.

The configuration is still unchanged, although I am leaning towards CST-90s mainly because of it's much lower thermal resistance and an on-board thermistor
However, I haven't found any appropriate driver to power a CST-90 yet.

What about using XM-L's instead? There's dozens of drivers for them...

Either way, PLEASE post updates whenever you do get working again, i'm still subscribed and can't WAIT to see what this bad boy will do when it's finally done.

[DKlaser]

I used XML's on my build. The thread is somewhere in this forum if you are interested. I know how easy it is to put these projects on the back burner I did it for a long time myself and am still not done with both lights yet. Problem is I want to keep changing the design every time I turn around.

[Diman]

I used XML's on my build. The thread is somewhere in this forum if you are interested. I know how easy it is to put these projects on the back burner I did it for a long time myself and am still not done with both lights yet. Problem is I want to keep changing the design every time I turn around.

I know, it's a pain Every time I'm in my shop and working on something else, and i see the parts lying in a corner and waiting, I feel bad ....

Anyway... I totally intent to return to this.. and XMLs are not an option It just wouldn't be the same ... an SST/CST -90 that's what I want!

[TEEJ]

There's some new LED options that can handle higher amps too now a days...

Like:

http://www.cree.com/led-components-a...onal/xlamp-mkr


or


Luminus SBT-70, etc...

[DIWdiver]

There's some new LED options that can handle higher amps too now a days...

Like:

http://www.cree.com/led-components-a...onal/xlamp-mkr


or


Luminus SBT-70, etc...

Neither of which is capable of the light output that the '90 can do, or anywhere near the current.