# Help me design a 25K lumens searchlight



## HugeOne (Jun 23, 2010)

I want to make compact ultra powefull light.
My idea is 12 SST-90 in a 3x4 config measuring 40mm x 33mm (All leds touch each others)

The array will be liquid cooled, by soldering the led to 5mm square copper pipes.

My problem still, is to find 10mm optics that will give me 30 degrees FWHM or less for those 12 leds

Any idea?


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## deadrx7conv (Jun 23, 2010)

Make a bigger light to fight the optics available for the large size of the SST90.


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## rayman (Jun 23, 2010)

I would leave a little space between the emitters: 1. because even with liquid cooling the heat will be very intense and 2. because as deadrx7conv said you need some space for optics/reflectors.

PhotonFanatic sells optics and holders for SST-90 in his thread over at the MP.

rayman


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## John_Galt (Jun 23, 2010)

With the die size of the SST LED's, you're not going to find small optics that give you anywhere near that beam width... 

What do you mean by "liquid cooled?" You say something about liquid filled copper tubing, and, while that's good for moving heat to another area, but if you don't significantly increase surface area to dissipate that heat in another area, then your liquid filled copper tubing is not a heat-sink, in the sense that it will help dissipate heat elsewhere, but instead a thermal mass, which will heat up quickly when the light is lit up.


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## alpg88 (Jun 23, 2010)

HugeOne said:


> I want to make compact ultra powefull light.
> My idea is 12 SST-90 in a 3x4 config measuring 40mm x 33mm (All leds touch each others)
> 
> The array will be liquid cooled, by soldering the led to 5mm square copper pipes.
> ...


 12 sst 90 in a space smaller than maglite head??????? lol.
soldering leds to a heatpipe???? 
your problem is a lot more than just optics.
good luck.


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## HugeOne (Jun 23, 2010)

> 12 sst 90 in a space smaller than maglite head??????? lol.
> soldering leds to a heatpipe????
> your problem is a lot more than just optics.
> good luck.


 
Sorry for not giving more infos,

Soldering to a heatpipe must be quite a challenge 
I mean to solder the led along a square copper pipe in which fresh 60-70degree water will constantly circulate.

Indeed such a small optic for such a large die is probably beyound the laws of physic.

Using the ledil "lily" reflector should make the light 68mm by 91mm, bit large for my use, but possible.


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## alpg88 (Jun 23, 2010)

HugeOne said:


> Sorry for not giving more infos,
> 
> Soldering to a heatpipe must be quite a challenge
> I mean to solder the led along a square copper pipe in which fresh 60-70degree water will constantly circulate.
> ...


it is not optics, 
sst90 mags can't run full power for long, even massive heatsink for 1 led isn't enough, there was a thread here iirc someone turned halogen spotlight into sst 90 spotlight, heatsink was a lot bigger than for maglite, it also had a fan, yet still it was not capable of sustaining heatransfer at full power.
and you want to fit 12 sst90 (110amps at full power) into a base the size of even 68 by 91????? lol you'll melt your optics and leds along with it.
my advice search all sst90 mods on this forum, you will have lots of answers to questions you have not thought of yet.

heat pipes aren't cooling devices, they transfer heat, once i took apart a small comp that had a cpu on a aluminium base not bigger than cpu itself, 1 heatpipe about 3\16 and 6 in long was screwed into a heatsink 4 times the size, and with all fins pbly 100 surface area, that was for only 1 cpu. the reason for pipe was small size and arrangement, it is always better to have as short heat path as possible, heatpipes do exact opposite, they are necessary evil


also afaik spotlights are made for throw, i assume you want it as well , but tiny reflectors will not give you much throw, you'll have wall of light (before you melt everything) but not much throw, diametre and depth of reflector produce throw. that is why all spotlights have big reflector.
i have 3xp7 mag it is a wall of light, but xp-g with 2x as big reflector throws a lot farther.

if you want tiny size spotlight, get a white laser, and defuse the beam


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## joe1512 (Jun 23, 2010)

Is there any way you can use XP-Gs instead? I would think that would be a heck of a lot more efficient and thus produce much less heat. Yeah I realize that is a crapload of emitters, but 12 SST-90s seems about as crazy.


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## HugeOne (Jun 23, 2010)

> heat pipes aren't cooling devices, they transfer heat, once i took apart a small comp that had a cpu on a aluminium base not bigger than cpu itself, 1 heatpipe about 3\16 and 6 in long was screwed into a heatsink 4 times the size, and with all fins pbly 100 surface area, that was for only 1 cpu. the reason for pipe was small size and arrangement, it is always better to have as short heat path as possible, heatpipes do exact opposite, they are necessary evil



I don't want to use a heat pipe, heat pipe rely on a heat sink, which have a finite heatsinking capability.

I'm talking about water cooling, leds gonna be soldered on the side of a four faced copper tube. In that tube a endless supply of cool water is then feed.

Heating 1 L\min by 10F take about 390W of power.


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## alpg88 (Jun 23, 2010)

HugeOne said:


> I don't want to use a heat pipe, heat pipe rely on a heat sink, which have a finite heatsinking capability.
> 
> I'm talking about water cooling, leds gonna be soldered on the side of a four faced copper tube. In that tube a endless supply of cool water is then feed.
> 
> Heating 1 L\min by 10F take about 390W of power.


 
you mean radiator, fan, and water pump liquid cooling???
sounds like you building overcomplicated light, it would be a lot easier to go with hid, for now 25k lm reliably is hid territory, but hey, i guess you like challenges, good luck, keep us posted.


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## deadrx7conv (Jun 23, 2010)

Water, pump, radiator/fan..... and you're worried about the size of the light? 

What about the generator you'll have to lug around to power it? 

Are you trying to retrofit an existing housing? 

And, what will this searchlight be used with? heli? boat? ATV?


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## SmurfTacular (Jun 23, 2010)

12 SST-90's!!!??? 

What the hell do you plan on using that for?

400th Post!


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## spencer (Jun 23, 2010)

This is in the transportation forum so my guess is that he has a hole to mount it in with lots of space behind it to do all the cooling. I think you guys are overthinking it. 

Good luck with this and keep us updated.


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## SmurfTacular (Jun 23, 2010)

Have you thought about using several computer CPU heatsinks? They can dissipate alot of heat.


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## spencer (Jun 24, 2010)

Damn! I wanna know what you are putting on that thing.


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## HugeOne (Jun 29, 2010)

www.micropumps.co.uk

Found the pump for the cooling, 650ml/min only 12g
Believe it or not, this is going on a rc helicopter.

8Ah li-po pack should yield 12min rum time.


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## John_Galt (Jun 29, 2010)

What about something to radiate that heat... Sure, the pump will work, it'll definitely circulate the water, but even still, once that water is fully heated it is pointless to pump anymore... And with 12 SST's that won't take long at all.

Do you have a radiator that is capable of dissipating anywhere near that amount of heat? I realize this will have lots of air flow, but still.

Also, most Li-ion chemistries, even IMR, will not safely handle enough current draw for this to be anywhere near 25k lumens. You're going to need to take a look at Lithium polymer for that, or your flying searchlight will be more of a flying explosive event.

How big is this heli, anyway? You're talking a great deal of weight and size, not to mention the power requirements.


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## HugeOne (Jun 29, 2010)

Yes, 8Ah li-polymer (120A capable)

The heli is a 90size (4ft 10" rotor diameter) can lift 5lb without a sweat.

The rad I'm looking right now is a 150mm 120mm unit made for PC water cooling. Placed over the boom directly under the prop wash.


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## HugeOne (Jun 29, 2010)

And the rad:

http://www.performance-pcs.com/cata...oduct_info&cPath=59_457_336&products_id=22275

200g, not bad at all

Look like the weight of the whole thing will be little over one kilo.


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## John_Galt (Jun 29, 2010)

Are you including the mass of the amount of water it will require?


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## HugeOne (Jun 29, 2010)

550g for the battery
12g for the pump
200g of H2O
250g for the light
100g of tubing

1112g or 2.5lb


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## Walterk (Jul 15, 2010)

When it is in turbulent air anyhow, using CPU heatpipes would save you a lot of work and bulky mechanics. And 200ml water isnt that much capacitating unless you have again an intercooler to cool the liquid, TMHO.

I plan on using this for a single SSR90 @ 10Amp:







I used Dremel-like to get me the 5mm heatpipes from a laptop heatsink. Bending it back straight was easy, done by hand. Glued with arctic silver.
It was originally force ventilated and used for a Pentium 3, so I guess it would be rated at something like 70 Watt. With natural ventilation in open air I hope to get 30 Watt. (The copper is much oversized, and the aluminium is for aligning and mounting only. )
Have to test it yet.


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## MikeAusC (Jul 17, 2010)

Aircraft engines also need to have a lot of heat removed - but have you ever heard of a water-cooled aircraft engine ?

Getting rid of the heat using large volumes of high velocity air will be a much better way to make use of the weight.


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## AnAppleSnail (Jul 17, 2010)

HugeOne said:


> I want to make compact ultra powefull light.
> My idea is 12 SST-90 in a 3x4 config measuring 40mm x 33mm (All leds touch each others)
> 
> The array will be liquid cooled, by soldering the led to 5mm square copper pipes.
> ...




Saying it's impossible is no fun. I'll run through the numbers, but I have a summary and a question with some suggestions at the end. You can almost do it with a computer heat pipe, not even a pump. Read the following, it'll answer why the pump alone won't do it (unless you boil water off!)

A 9-amp SST90 gives about 2250 lumens, or 27000 lumens. This will drop with heat. At 100 C Junction temperature (always hotter than your heatsink), you lose 15% of your output from heat.

This sounds like a fun project - I saw someone's recently that was a helicopter with several XP-Gs mounted on a camera turret for seeing in the dark. If you've got an 8 amp-hour battery you'll be able to run 12 SST90s flat-out (9 amps per) depends on us knowing the voltage of it. Can you tell me more about this battery? Let's say that it's one 3.9v cell - that's the forward voltage of the SST90 at 9 amps. You're pulling 108 amps from this battery, which is close to its limit - but it'll live. That'll run for .074 hours, or 4.4 minutes. Really it'll trail off in current draw and output towards the end, but this is starting to look doable. If you don't mind such short runtimes (Do RC helicopters have alternators? LOL!)

Amps = 12 LEDs times 9 amps per LED
108 Amps

8 Amp-hours / 108 amps = .074 hours = 4.4 minutes
4.4 minutes

So we're running 108 amps for 4 and a half minutes. If we pretend that the SST90s are 0% efficient - that is, that ALL of the power going into them has to be dealt with in heat, then we'll be getting 108 amps at 3.9v, which is 421.2 watts of heat. The real number will be about 15% less than this - some power leaves as light - but it's a good planning figure. So 421 watts of heat for 4 anda half minutes.

Watts = volts*amps = 3.9v * 108 amps
421 watts for 4.4 minutes

421 watts is 421 joules per second - and 4.187 Joules is 1 calorie. A calorie raises 1 gram of water by 1 degree C. We have (421/4.187) calories per second, or 100.6 calories per second. These are thermal (small) calories. Handily, you have 200g of water. Ignoring the mass of your heat pipe and other stuff, you are going to be putting 100 calories per second into 200g of water. This is enough to raise 200g of water by 1 centigrade in 2 seconds, or 9/5ths degree F per two seconds. Ignoring boiling, the water will have increased by (4.4 minutes * 60 sec per minute) / 2 = 132 degrees, in 4.4 minutes. This assuming no cooling, that is.

This next step until the ASCII sword assumes no heat sinking power.


421 watts per second = 100.6 calories per second.
This will raise the temperature of 100g of water by 1 C each second.
That's the same as heating 200g of water by 1 deg C or 9/5 deg F every other second.
The total temperature rise, ignoring cooling and pipe mass, will be 132 degrees C or 237 deg F. The SST90 is rated for 150 degrees C. Near the end of the flight you'll start boiling water.

The pump will keep the SST90's water supply below 100 degrees C, ASSUMING THAT IT CAN FIGHT STEAM FORMATION. You'd have to talk to a radiator man, but I think that steam formation at the back of the SST90 mounting point would make back pressure - and if water doesn't flush by quickly, the LED temperature will skyrocket.

A PROBLEM is that heat pipes almost completely stop working at the freezing and boiling points of their liquid. Once the water inside the heat pipe reaches the boiling point, it cannot condense and recirculate - now the heat pipe will carry the equivalent heat that its copper walls would. If we add a little bit more heat capacity or radiation then this will barely work.
(0XXX{===============>

Ok, now we consider the heatsink and radiator. Let's say that you make a heatsink that can dispose of some reasonable amount of heat - I dunno, twice as many calories as there are degrees between its temperature and the air temperature. There's now a good chance that the water would stay below its boiling point and work. You're just within what's possible, although you'll need either a heatsink for the water to dump heat into, or more water (depending on the weight). Heat pumps would probably work, although I can't remember if they depend on orientation - my laptop doesn't overheat in any particular position though.

This is not a movement-based system, so you could actually try this with one SST90 and 17 grams of water, at 9 amps, for 4.4 minutes, to see what happens. Your plans really are at the limit of what is feasible.

Optics! There aren't any, really. And you'd lose another 10% to 15% output here.


The 10mm optics for the XP-G are pretty good, and you can get around 400 lumens out of an XP-G driven at spec - and they can be slightly overdriven (for not much gain though). That'd take 60 XP-Gs for the same output, which is a heck of a lot of light. But that's a loooooooooooot of soldering. Even the Cree MC-E only gives you about 800 lumens at spec, so you'd only need 30 of them for that lumen value. How did you pick that number?

I regret not weighing the ballast of the Stanley HID while I had it out. The ones for cars are about 200g, and won't take much heatsinking. For about $80 you can get a pretty decent searchlight out of a HID, and the 50w ones for cars are hellishly bright. Also, a 50W one would want 12v, but that's still less power than the SST90s.

So in summary:
The SST90 setup is almost feasible as you've designed. But you'll boil your cooling water, which might make steam pockets and cook the LEDs, or break your pump.

The XP-G is similar, but you'll be running at 90 amps instead, and at 3.5Vf instead - so you get 320 or fewer joules of heat. You probably wouldn't boil the water if you started it quite chilled.

HID is the way to go here, honestly - unless you absolutely cannot spare a comparable reflector, which wouldn't be big for the performance you asked.

And how did you pick 25k lumens? That's a LOT of light.


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## AnAppleSnail (Jul 18, 2010)

I feel like I hit a perfectly good thread with a hammer and killed it.


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## Therrin (Jul 18, 2010)

Well, I think you made an great effort at touching on several of the salient points. =) I'm still absorbing some of that, and I'm sure I'll have to re-read it, but it sounds like you've got it all figured out; so other people should be able to as well.

Perhaps you could use anti-freeze-like liquid to change up some of those levels you mentioned to allow for a wider range of operational temperatures.


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## RusDyr (Jul 19, 2010)

Looks like he wants to search life on the Mars from the Earth 

I think that using SST is a bad idea.
Use XP-G or HID lights, really.


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