Project off-road lightbar featuring SST-90's

[Diman]

Some numbers:

DX-refllector is 7.3cm (73mm) diameter.
With 1mm space inbetween, 15 reflectors add up to 1111 mm
That's a maximum width I can put on my Jeep without worrying about stickout.

As previously stated, using DIWDivers drivers I'll be able to run them in groups of three. = 5 driver boards. (Diw - say otherwise if not true)
15 LEDs.
Assuming 9A drive at 13V (well 13.8V but to be on the safe side let's say 13V)
1 LED = Vf 3.87V, If 9A
1 Group - 3.87V * 3 = 11.61V, 9A
5 groups = 9A * 5 = 45A
45A at 13V = 585W, round up to 600W
Cable length - roof to distribution center = 3 meters
Cable area - 3 meters, 600W, 13V, 0.0018 Ohm/mm2/meter = 16 mm2 (gauge 5 I believe)


Feel free to jump right in if you see that I've missed something or thinking wrong...

 

[TheExpert]

This is very cool, please keep us updated on this. I thought about doing something like this but I just don't feel like I have enough knowledge to do so.

 

[Diman]

received two drivers today

I really want to test them now, but I have to either wait for SSRs that I will order in a couple of days, or attempt a reflow soldering of my sst-90 dies onto comex boards.

I've seen some videos of that being done using a stove and a frying pan. Doesn't seem too complicated - but the lesson is learned (buy pre-soldered stars!!! )

 

[DIWdiver]

Some numbers:
As previously stated, using DIWDivers drivers I'll be able to run them in groups of three. = 5 driver boards. (Diw - say otherwise if not true)
15 LEDs.

Cable area - 3 meters, 600W, 13V, 0.0018 Ohm/mm2/meter = 16 mm2 (gauge 5 I believe)

Feel free to jump right in if you see that I've missed something or thinking wrong...

Yes, 3 leds per driver should work. I've never tried this, but it should work.

5 ga seems like overkill. Let's see what the numbers say...

I think it's safe to assume you will have 13.8V while the motor is running, probably higher. I would plan on the LEDs dropping 4.0V each, as my limited experience is that they are a little worse than rated. You need 0.3V for the driver, so a total of 4.0*3 + 0.3 = 12.3V. That means you can lose 1.5V in the wires. You don't say whether 3m is battery to LEDs or battery to LEDs and back, making the total wire length 6m.

I'll assume it's 6m total. You have a max resistance of 1.5V/45A = 0.0333 ohms. Divide that by the length, and you have .0333/6 = .0056 ohms/m. 12 ga is 0.0052 ohms/ft, so it should be okay for the voltage drop. 12 ga wire is 3.31 mm^2. But I wouldn't put 45A in a 12 ga wire, in the US we'd use 8 ga for this. 8 ga wire is 8.37 mm^2, and that should be plenty. Basically, any wire that's safe for 45A is okay for the voltage drop.

 

[HB021]

Tjenare! Nice project you've got going here, I'm also interested in making a similar project. But man 15x SST-90 that's insane! I'd love to see a first person view 34000(?) lumen led power! This is going to be interesting...

 

[Diman]

Cool, another Swed here! Thanks I love that "insane" thing! Och tack förresten!

Now for some updates:
Soldering LEDs on stars seem to have worked - but I never want to do that again, I was actually nervous *hahaha*
Ruining €37 LED is not my idea of fun...

Running 3A testing - damn that thing is bright... I guess the photo cannot really tell the brightness

DX reflectors (3 out of 15 ) arrived a couple days ago

Very nice finish, all aluminum, and dimension are exactly what dx-site says.
The opening at the bottom fits around led die and the hole edges sit on top of that little frame flap u-shaped corner thingys.. :thumbsup: not touching the green board.
I tried to take a picture, but it kept getting all blurry because of the reflector.





I'm in process of modelling the front frame, tried Sketchup first, but apparently it's impossible to export a model in any format suitable for CNC.
So I have to remodell the whole thing in some other software - which means learning curve .
The idea is that 7.3 cm holes are machined 2mm down into the frame, then contracted to 7.1cm so an 1mm edge forms on which reflectors will seat. These will then be secured in place by
polycarbonate front window. It's all in my head now, but I'll post a picture as soon as I have one

 

[ExtremeX]

:thumbsup:

Cant wait to see the finish results! Keep us posted!

 

[HB021]

Why do you need that big reflectors, do you want a lot of throw? With 34k(yes truly insane) lumen in addition to your other lights wouldn't it be better with smaller reflectors for less space and more flood? This is for off road in the woods right? I think 34k lumen flood light will go very very far anyway! You could also make the hole light bar a lot smaller then. I just built a 4x Cree XM-L using 18mm(diameter) x 12mm(height) and I love the beampattern. So I'm going to buy 16 more for my car hehe!
Anyway I'll keep looking a close eye to your project and see how things turn out, keep the work up!

 

[Diman]

well, I see you point.
When I started thinking about making this bar, I did some research. Leds, drivers, combinations of both, and finally optics and reflectors.
SST-90 was an easy decision, being the badass it is
I remember asking a question on a Swedish electronics forum about what I could use to drive 40 SSC-P7 Leds
I got mugged down by HID-folks and how impractical that would be.. heat, power waste etc. etc. (Still want to make that one tho... maybe next project will be 40 P7s )
Not that HIDs are not good, they are fantastic, I have nothing against HID, but it's a different technology. I want to do LEDs, and it requires knowing the limitations.

Anyway... got little ot here (it's early in the morning here)
There're optics and reflectors (and maybe both, but I don't see the point.), right? I've read almost all threads here at cpf (and other places) about optics vs reflectors and
decided to go with reflectors on this one.
There're no smaller reflectors for SST-90 (off the shelf)
There are smaller aluminum reflectors that can be modded to fit over an SST-90, but they require work. As I understand with reflector of this size I get both throw and usable spill.
Spill combined from 15 LEDs will probably be more than enough for immediate surroundings, say up to ten meters in front of the car, and the beams will then light up everything else.

regarding bar size, it's actually a pro - large bar = more surface = better heatsinking.
It's an uncharted territory here, you see.. I'm actually not sure of anything right now. But we will see, right ?

 

[HB021]

Yes we will hehe, I have 200w HID which I like but LED is the poop now! They're just jealous maybe? Why P7 and not XML? XML is like 20% more effective and smaller. About the reflector yes the spill combined from 15 SST-90 + 75mm reflector will probably give a good wide view anyway but have you tried one LED with the reflector and looked at the beam pattern? Trustfire X6 uses a setup like that and it looks very "throwy".

 

[idleprocess]

I am mulling something similar to this for my truck for off road use, but will likely base it on some triple XP-G's using triple optics.

With some ingenuity, I imagine that I could make the setup removable and also use them as bicycle lights (with much lower drive current).

 

[hoppy_bounce]

Your project is looking very promising. Can't wait to see more photo's.
I am curious, and thinking of experimenting with a smaller scale sst 90 4wd configuration, how do the drivers you mention handle the DC supply from an alternator? Does the alternator supply a consistent current and or voltage that won't burn the drivers? It would be a shame to find out the hard way, and I can imagine it would add significantly to the cost to fit some sort of pre-driver regulator.

 

[Diman]

I've not been able to try the drivers and LEDs on my Jeep yet. I've just finished another project (it's a build that never finishes ), and now will turn my full attention to this one.
I have another batch of SST-90s arriving (hopefully) today and I am planning to test DIWDivers drivers and three LEDs in series this weekend.
Had only two leds, so I've been waiting.
This time I've ordered SSR stars, from Mouser, so I won't have to solder them myself

 

[DIWdiver]

Your project is looking very promising. Can't wait to see more photo's.
I am curious, and thinking of experimenting with a smaller scale sst 90 4wd configuration, how do the drivers you mention handle the DC supply from an alternator? Does the alternator supply a consistent current and or voltage that won't burn the drivers? It would be a shame to find out the hard way, and I can imagine it would add significantly to the cost to fit some sort of pre-driver regulator.

The DC supply in a vehicle is a very nasty environment for electronics. The voltage is not very well regulated, and under certain conditions, noise, spikes, and surges occur which can damage electronics that aren't designed to handle them.

Fortunately the pre-regulator costs only a few cents (shipping costs me more than the parts). I also changed a few parts on Diman's driver to allow it to handle higher voltages (like a 100V FET). You have to be careful wiring it, but I have every expectation that it will handle the automotive environment. It should handle 100V surges and 30V for extended times. I've sold a couple modified for use in vehicles, and haven't heard any complaints. I'd love to hear some feedback on this.

The thing you have to watch out for is power dissipation. I won't go into it here, but if the battery voltage is more than a few volts higher than the LED voltage, you will have serious heat problems at 8-10A. Fortunately most of the voltage fluctuations don't last long enough to cause heating issues, and you are only left to deal with the heating issues of the average voltage.

Don

 

[LEDobsession]

Wow, this looks awesome! You've caught my attention. I did a project similar a few years back, but I used 8 SSC-P7's. I also machined all of mine, including the reflectors. I really had no idea what I was doing, I just had access to all the machines I needed to use to make it. I really learned a lot though. Wow. Anyways, this should be a lot of fun. I'll keep my eye on it. You may have seen my thread, if not, take a look here (http://www.candlepowerforums.com/vb/showthread.php?213704-HELP!-10-SSC-P7-LEDs-in-offroad-racing-light). You may find some ideas or something that could possibly help. Feel free to ask me any questions too.
Good luck!:thumbsup:

 

[HB021]

Keep the good work up, post some pictures along the way please! I've ordered 4x 4XM-L lights for a similar project now

 

[Diman]

pics


tested LEDs and driver today.
mounted them on a heatsink of the type described in my first post.

driver too... it turned out it gets really hot!

I used arctic sivler 5 thermal compound between leds and driver and heatsink

Mounted at a distance approximate to that when reflectors will be added.

2A low mode

2A

8A

Jeep is running, and the alternator output was actually 14.4 V

the heatsink got really hot within maybe two minutes and I shut everything off. Driver was really hot too.
I needed to know what is generating that heat so I moved the driver to another heatsink, and ran another test. Three sst-90s warm up that heatsink pretty much.
I don't have a IR-thermometer, but after three minutes I couldn't hold the heatsink in my hand anymore.
I will do more precise measurements

The bar - made from solid u-channel and with these heatsinks thermo-glued to the back should provide enough temp-drop (I hope!!! )

 

[HB021]

Nice pics! Hehe 3minutes isn't a long time but too hot for hand is about 45 celsius isn't it? An IR-meter is very good for these kind of situations, yes
That's what I used to test my fan cooled quad XM-L.

 

[DIWdiver]

An IR meter probably will not get a good reading off bare alumimum. Try taking a reading on a piece of black electrical tape that's on the aluminum. It might read quite a bit higher, and would be closer to actual temperature.

 

[Diman]

thanks for the tip I will do that.
I've ordered an IR-meter off ebay, shouldn't take more than a couple of days to arrive.
After doing some more reading on heat, heat dissipation and different ways of cooling techniques, I am replacing the heatsink type in my first post with this one:

The main difference is that this one has vertical fins. (when mounted horizontally of course ) Heated air between fins travels upwards and with horizontal fins (as in the first heatsink model) it will move poorly and it will not be able to absorb more heat the higher it travels.
Second difference is that this one is anodized black. Because of that some heat will be dissipated through radiation. Not much probably, but better than nothing really

I've ordered one of these, will probably arrive at the same time as the IR-thermometer.