Kitchen Sink CFL to LED Project

[GSX-1300R]

I'm thinking really hard about starting a project to replace my 23w CFL (6500K/Daylight) that is currently over my kitchen sink. The wait time for the CFL to get up to full intensity is lenghty. For a couple of minutes it like this: :candle:

I'm proposing this... One Bridgelux array (2000 lumen) with a heatsink placed in a custom made box (mounted to the ceiling of course). For extra cooling I'm thinking of putting two fans in the sides of the enclosure. One to push cooler air in and the other to pull the hotter air out.

Bridgelux info:
operating current
1750 mA
forward voltage
16.6v
max current
2500 mA
thermal resistance
0.5°C/W

Comments?

I've also been looking for a driver for that one LED. I didn't want to buy something that was overkill or not enough. Any suggestions?

 

[blasterman]

If you really insist on using the big, 2000 lumen monster Bridgelux you can note that Xitanium makes a 1750mA AC/DC driver.That's the only name brand driver I can find at the moment that will push that beast.

If I may suggest though perhaps using 3-4 smaller Bridgelux because this will provide more even lighting and potentially easier driving (and also less likely to burn holes in the back of your skull when directly viewed ).

This is my approach with my current Bridgelux project because when I added up the extra cost of an exotic high current driver I was break even with using a horde of Cree P4s.

If you use the smaller, 800mA Bridgelux arrays you could get away with a more common 700mA driver and just under-drive them a bit. You also might be able to use 700mA bucks on each of the smaller Bridgelux and just feed them 12volt / high current from a spare computer PSU or something.

 

[GSX-1300R]

Thanks blasterman.

If I go down with a setup of say 4 800 lumen arrays it would give me better light dispersion and an easier way to power them, correct?

Forgive me a little since I am a little noobish when it comes to the electrical side of LEDs. Will a MagTech 25w driver do the job for four arrays with a Forward Current of: 900mA; and Forward Voltage: 13V or will a Microdriver 9 Small Case better suit the application

Is there a place on CPF that I can learn how to do the electrical calculations for myself when dealing with simple things like this?

Thanks for your help,
Jason

 

[blasterman]

it would give me better light dispersion

Oh yes.

and an easier way to power them,

Possibly. All depends on the math.

While I'm a bit of a noob myself at electronics, best thing to do here I found is to simply ask. :twothumbs Basic LED power calculations seem daunting at first, but once you understand a couple simple basic rules it gets real easy to design LED arrays. Unless you want to start designing your own drivers the learning curve is pretty flat - IMHO.

One basic rule that's helped me with electronics over the decades is that current tends to be cumulative in parallel, while voltage is cumulative in series. This also seems to work with powering LEDs.

So, lets say you want to power four smaller neutral white Bridgelux that have spec of 800mA at a forward voltage of 9.7. If you wired them in series, you'd need a driver that was 800mA, but had to provide almost 40volts (9.7 x 4)of power when driven that hard. If you wired them in parallel, you'd need a whopping 3200mA (4 x 800mA) but only 9.7 volts. You could always go 2x2, which would then require 1600mA at around 20 volts.

(anybody feel free to check my math or explanation please do so)

You can always fudge current a bit with power LEDs because they are designed to handle large current swings (which why they are called power LEDs). If the normal spec current of the LED is 800mA and you have it heatsinked adequatley, then over driving them at 900mA or under-driving them at 700mA won't do much other that adjust light output a bit. Obviously you can under-drive an LED all you want. Since we aren't designing street lamps with exacting lumen specifications I'm assuming we have some fudge room here, correct?

So, at least in regards to current, you've got some wiggle room when it comes to figuring out how to drive them with stock power supplies. However, voltage is another matter and should be taken at pretty much face value. Just realize that if that 9.7 volt Bridgelux I referenced above is driven higher than 800mA than obviously it will need more than 9.7 volts, but not much.

So, when you take the above into account, you'll seee it's a lot easier to power the smaller Bridgelux than the bigger ones with common LED drivers. This doesn't mean you can't drive the bigger ones though since you can buy the big Xitanium for example. It's just that 700mA LED drivers are far more common, and this puts you in the ballpark for driving the 600mA and 800mA Bridgelux. However, that LED Driver will have to supply enough total voltage, and that's the kicker.

Just a word of caution on the Bridgelux. While they are tough as hell and clearly tolerate as much abuse as an industrial LED is required to take (mine have injured me more than me them) they put out absurd amounts of heat. My 400 lumen versions will easily heat up a Pentium 4 class heat-sink pretty good.

 

[purduephotog]

I'm thinking really hard about starting a project to replace my 23w CFL (6500K/Daylight) that is currently over my kitchen sink. The wait time for the CFL to get up to full intensity is lenghty. For a couple of minutes it like this: :candle:

I'm proposing this... One Bridgelux array (2000 lumen) with a heatsink placed in a custom made box (mounted to the ceiling of course). For extra cooling I'm thinking of putting two fans in the sides of the enclosure. One to push cooler air in and the other to pull the hotter air out.

Bridgelux info:
operating current
1750 mA
forward voltage
16.6v
max current
2500 mA
thermal resistance
0.5°C/W

Comments?

I've also been looking for a driver for that one LED. I didn't want to buy something that was overkill or not enough. Any suggestions?

Don't forget: You can get a reflector for the 400lumen device
http://www.ledil.fi/datasheets/DataSheet_Bridget.pdf

The 40W xitanium drivers would do 4 of those in a 2x2 setup, or there is a cheap 6W (slight underdrive) unit from DealExtreme that can do a single.

 

[GSX-1300R]

I was thinking of using this type of a heatsink plus fans. Heat shouldn't be an issue, I would think.

http://www.heatsinkusa.com/asfdas.html

 

[blasterman]

5.117 lbs?

Must not be aluminum.

Heatsinking problems have also put a snag on my project. I need a vertical heatsink with the Bridgelux on top, and that type of animal doesn't seem to exist.

 

[GSX-1300R]

Guess there's a little more too these LED projects lol. My HID on my motorcycle was simplistic compared to this :laughing:

Yeah it was a fat lady lol at 5+ lbs. So Aluminum is a poor choice for heat sinking. What material is the best suited for this :thinking:

 

[purduephotog]

5.117 lbs?

Must not be aluminum.

Heatsinking problems have also put a snag on my project. I need a vertical heatsink with the Bridgelux on top, and that type of animal doesn't seem to exist.

That's aluminum. It's 8.5" wide with 1" high fins and 12" long. That's a pretty big chunk of aluminum.

I don't understand what sort of heat sink you're looking for- you need a round cylindrical sink? Those exist. You can also get heat pipes that are vertical and bend 90 degrees if you need.

Can you draw me a photo?

Yeah it was a fat lady lol at 5+ lbs. So Aluminum is a poor choice for heat sinking. What material is the best suited for this :thinking:

Nope aluminum is still a great choice. Copper too. Either metal will do well- one is cheaper than the other.

Rule of thumb is 10 sq inch / watt. So with that sink you quoted you have in each 1" segment (12" to that foot) you have 22 fins (44 sq inches) plus the bottom (8.5"x1"= 8.5") plus the top segments (call it 6") so nearly 50 sq"- so you could handle 5 watts on only 1 inch of that sink. Spray it with black BBQ grill paint (krylon hi temp) and you've got a very efficient emitter.

 

[GSX-1300R]

You can always fudge current a bit with power LEDs because they are designed to handle large current swings (which why they are called power LEDs). If the normal spec current of the LED is 800mA and you have it heatsinked adequatley, then over driving them at 900mA or under-driving them at 700mA won't do much other that adjust light output a bit.

With the bolden text about heatsinking I was thinking LARGE HEATSINK.

My 400 lumen versions will easily heat up a Pentium 4 class heat-sink pretty good.

A P4 heatsink isn't that small the last time got to see one, while blasterman was only running 400lm emitter(s) on it, it again made me think LARGE HEATSINK because I was going to run a set of 4 800lm emitters.

With the larger heatsink it gives more area to work with as far as placement goes... I would think.

Again please forgive my noobishness I think I developed ADHD while thinking about LEDS. Too many ideas going through my head, complicatinng things lol. I want to thank you guys for giving me some insight.

 

[purduephotog]

With the bolden text about heatsinking I was thinking LARGE HEATSINK.


A P4 heatsink isn't that small the last time got to see one, while blasterman was only running 400lm emitter(s) on it, it again made me think LARGE HEATSINK because I was going to run a set of 4 800lm emitters.

With the larger heatsink it gives more area to work with as far as placement goes... I would think.

Again please forgive my noobishness I think I developed ADHD while thinking about LEDS. Too many ideas going through my head, complicatinng things lol. I want to thank you guys for giving me some insight.

The heat sink you posted is just your standard extruded ones. There are other types that offer more surface area per sq-in in order to help achieve those cooling affects.

Heat sinks operate best in the vertical orientation or when they can have constant air across them- as you can imagine a horizontal heat sink is effectively 'starved' for cool air in the middle - so the inside heats up faster than the outsides. Those fins also do not permit air intrusion (hence you'll see some that are cross-cut so they can work in both orientations)

Anyway- if you look at my thread on heat sink vendors you'll see there are TONS of profiles- but only if you buy 200$ worth a pop. You can see that you can get as exotic as you want to as simple as you want- the flat extrude you've got is pretty simple. More complex shapes are designed to 'soak' the heat into a central region and quickly radiate it off tens of barbs as rapidly as possible.

http://www.mmmetals.com/

I don't think you'd go wrong with what you've got- it's cheap, it's available, and it should work... but just watch the temp and especially watch it if you're going to enclose it.

 

[blasterman]

It's 8.5" wide with 1" high fins and 12" long. That's a pretty big chunk of aluminum.

I'm still guessing the base on this mother must be really thick to explain the weight.

Also, in terms of surface area, if a 8.5x12 heatsink has 1" high fins running lengthwise, then wouldn't each fin contribute 24^inches? This would mean his heatsink has several hundred square inches of radiating area, which we then multiply by it's orientation coefficient (assuming it's passively cooled).

Bridgelux advises 60^inches of radiating area for the 400lumen coolwhite, which means GSX is in the right ballpark with that big heatsink and three small Bridgelux then.

As I recall, heatsinks with more/denser fins that are closer together are optimized for active cooling. Fins further apart and lower profile are better for passive cooling because of the limits of natural convection. I saw some thermo modeling a few years ago on the topic and found it facinating as hell.

I also noticed that the Bridgelux rapidly scale down in terms of heat out-put as current drops, so their specs are obviously rated when run at full advertised current load.

I don't understand what sort of heat sink you're looking for- you need a round cylindrical sink?

My LEDs must be on top of a long column, and the column would ideally be the heatsink. The heatsink cannot extend above the LEDs by more than 1/2 inch and the column cannot be very wide, but can be quite tall. This pretty much eliminates heatpipes and clam shells. Standard CPU heatsinks have typically wide profiles and don't work well at all upside down. Ideally, a star/finned column a foot tall would be perfect, but custom machine costs would be absurd.

 

[purduephotog]

I'm still guessing the base on this mother must be really thick to explain the weight.

My LEDs must be on top of a long column, and the column would ideally be the heatsink. The heatsink cannot extend above the LEDs by more than 1/2 inch and the column cannot be very wide, but can be quite tall. This pretty much eliminates heatpipes and clam shells. Standard CPU heatsinks have typically wide profiles and don't work well at all upside down. Ideally, a star/finned column a foot tall would be perfect, but custom machine costs would be absurd.

I'd be tempted to say the heat sink material is this:
http://www.mmmetals.com/extrusions/drawings/MM11945.JPG

Anyways- back to your heat sink issues-

You need LEDs to face upwards, thus be mounted upwards. I keep seeing your original square light- is this different? Can you 'cheat' the light by making a flat plate of heat sink material, put LED's facing up and put a few lower power ones facing down?

Can you use some of the innovative reflectors at Ledil to help cover the areas?

You're right- tube based heat sinks are not going to be effective and almost all heat pipes need to be gravity fed to return the liquids. Now if you were to have a triangular operation you *could* do something unique like place all the radiating components in the center of the light path so that they were not directly shadowing out and then put 90 degree bends to allow radiation upwards.

But I just can't envision what you're trying to do- sorry about that- so my suggestions are going to be a little weak. That and I've lost my thermo modeling licensed software

 

[Garibaldi]

5.117 lbs?

Must not be aluminum.

Heatsinking problems have also put a snag on my project. I need a vertical heat sink with the Bridgelux on top, and that type of animal doesn't seem to exist.

Search Mouser (for some reason, I can't get to half the links in my favorites today or I'd give you a direct link) for "Ledengin" and look at the heatsinks from Cooler Master. Click on the data sheet link to take you to the Cooler Master web page (I can't find them from the home page). They have some long thin ones that might be what you're looking for.

My internet connection is working again, here's the direct link for [lazy] lurkers http://ecd.coolermaster.com/english/products/products.php?_ledlist.

I've used the 50x15mm versions with LEDEngin's 5W chips and they barely get warm. I've tried the 50x34mm heat sink with one of the 800 lm Bridgelux chips and it got too hot to touch after about five minutes. The 200mm ones would probably work in their intended orientation where the heat pipe would function, but I don't know about upside-down...

 

[blasterman]

Ah, found it. Cooler Master has a Cylindrical shaped heatsink designed for 10watt applications that might work. I'd like something bigger (taller), but it's the right format at least.

 

[blasterman]

The Coolermaster mentioned above has a power rating of 10watts. Cross referencing on Bridgelux's site shows a thermal resistance double what is needed, so that should work. Wait (tired)...it's the other way around. Lower Thermal Resistance means better heat handling. So, the Cooler master isn't nearly efficient enough to handle the Bridgelux after I go through the fine print.

Now that I think about it, Thermaltake had a line of CPU 'ORB' coolers that were radial/cylindrical in design, and they were very cool looking. As I recall, they sucked as active coolers but using them passive with a Bridgelux on top should be ideal.

You know, I think I used to have an Orb with a broken fan I found in a tech junk pile, but gave it away (smacks head with fist).

 

[purduephotog]

The Coolermaster mentioned above has a power rating of 10watts. Cross referencing on Bridgelux's site shows a thermal resistance double what is needed, so that should work. Wait (tired)...it's the other way around. Lower Thermal Resistance means better heat handling. So, the Cooler master isn't nearly efficient enough to handle the Bridgelux after I go through the fine print.

Now that I think about it, Thermaltake had a line of CPU 'ORB' coolers that were radial/cylindrical in design, and they were very cool looking. As I recall, they sucked as active coolers but using them passive with a Bridgelux on top should be ideal.

You know, I think I used to have an Orb with a broken fan I found in a tech junk pile, but gave it away (smacks head with fist).

I would confirm this independently, but I was just told that the Coolermaster sinks have an integrated heat pipe in them- so if you're going to try and operate them vertically with the LED on top you'll be SOL.

 

[bshanahan14rulz]

heatpipes usually work in any orientation, but fins on the sink should probably either be vertical or have forced air through them.

 

[purduephotog]

heatpipes usually work in any orientation, but fins on the sink should probably either be vertical or have forced air through them.

I stand corrected- a properly engineered heat pipe with a damp wick will work in any orientation due to both high pressure and capillary action.

I was thinking of thermosiphons for some reason.

 

[blasterman]

In regards to orientation, the manufacturer usually dictates which way the heat pipe can be orientated to work. Some work better vertically while some work better horizontally. Haven't see any that are recommended to work upside down.

The longer, cylinder shaped Coolermaster heatsinks at Mouser have adequate Thermal Coefficients, but I need to find out from Coolermaster if they'll work upside down.

Funny, but looking at various 'high performance' heat pipe based CPU heatsinks and their reviews I can see why there are discrepencies in terms of performance. Most use high density, closely stacked layers of thin fins which is *lousy* when it comes to passive radiation. Plus, if those stacks are horizontal it will seriously impede the performance of the radiator unless you have a fan on it. At least the Coolermasters don't follow this trend and are smart enough to use a good fin structure for passive cooling.

If I were using down firing LEDs I would certainly use the same beast GSX found.