# [work in progress] 16 Luxeon Rebels RGBW array - PWM controlled by Arduino board



## marco1988 (Aug 7, 2009)

Hi!

This is my first post, and also my first experience with high power leds.
I want to share my work in progress with you.

My idea is to make an RGBW array controlled by a cheap C programmable microcontroller called Arduino (very popular here in Italy).

I purchased the Arduino board (and already programmed it with test code and inexpensive 5mm leds), and then I ordered 16x luxeon rebels from www.led-tech.de (I was unable to find a cheap and well “equipped” online reseller here in Italy.. please suggest me some alternatives here in EU, if you know something!).
Leds are 180lm cool white (6x), 145lm green (3x), 495mw royal blue (3x) and 85lm red (4x).
I put 4 reds because of their lower light emission.
Rebels are reflow-mounted (from led-tech) on 1cm square aluminium boards, which I hope provide good thermal conductivity.
I decided to mix colors in different positions to maximize color blending and minimize colored shadows.
Reds are mounted at corners because of lower maximum allowed junction temperature and greater light degradation at high temperature condition.







This RGBW array is a sort of small-scale test, and if everything goes well I will light the main room of my house with some of these lamps.

The main problem is represented by thermal dissipation.
Leds are sticked to heatsink through a VERY thin layer of cpu (not adhesive) thermal compound (I pressed down hard to make compound strate as thin as possible) and epoxied all-around.
Although the result may seem a bit messy in the following photos, it’s actually very very solid and of good appearance.
I hate math but I’ve done a little research and it ended up that I need a heatsink of at least 2C/W.
For this test array I decided not to go fanless, because it would have required a huge and bluky heatsink (at least 15x15x5cm).
So I “stole” a pentium4 full-copper heavy heasink from my father’s office 

Now, without doing math: a p4 has a TDP of 50-100w.. my array (driven in pwm at 700ma per channel) has a heat dissipation, in the worst case (rgbw channels all at 100% duty cycle), of about 35w (correct me if I’m wrong!).
The fan is very noisy, but driven at 5volts it’s unnoticeable. I’ll do some tests to check whether the cooling is sufficient or not (I hope and I believe so!).
Tomorrow I’m going to power up the array and check light output (with sunglasses ) and COOLING.
The heatsink may seem too small to the naked eye, but provided that heat dissipation performance GREATLY increases using forced air, I hope it’s going to be adequate.
My future plan is to connect the Arduino board to ethernet and develop an iphone client to change colors and turn on-off the array wirelessly.

Please post your comments/suggestions, THANK YOU.

(now pics-time!)

Arduino with test board connected:




Heatsink hand-lapping:




Led pcbs without thermal compound:




Led pcbs with thermal compound:




Led pcbs with expoy thermal-resistant glue:




Heatsink with fan:


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## snarfer (Aug 8, 2009)

Why don't you also put a thermal sensor on the heatsink, and then PWM the fan, so that it stabilizes the temperature? You would definitely reduce the fan noise, or be able to eliminate it just by dimming down the light. Something like MCP9700 would just require one ADC port.


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## Ny0ng1 (Aug 9, 2009)

:welcome:

looks very nice and adventurous. thanks for sharing it with us. cpf needs more people like you  

hope it works flawlessly, cant wait for the beamshot. i'm slightly worried that the light may have some 'colourful' corona at the edges of the main flood.


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## marco1988 (Aug 9, 2009)

hi! thank you for your replies.

About the temp sensor and pwm fan control, I totally agree, it's on my future plans! I'm just worried that not placing the sensor in the centre of the heatsink may cause incorrect temp readings (I mean.. side temp not linearly proportional to the temperature in the center of it)

I just tried the array and I'm totally satisfied with colored light output ( they're just 3 blues /greens and 4 reds.. but they make A LOT of light!).. but not with the whites.

I drove them at 800ma (even reds, but for 10secs max) and I thought that 1000+ lumens would have been more.. bright!

One question: is it safe to drive whites at 1A? I'm a bit worried about junction temp.. I hope-think that my array provides great thermal dissipation-transfer, but does the slight output increase justify the risk of damaging dies (if there's actually the risk)?

Thank you so much, later today I'll post some shots.

Thank you.


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## gswitter (Aug 9, 2009)

Interesting. I thought about trying something similar with an Arduino, but have never gotten beyond the what-if stage.

Can you drive high-power LEDs with the Arduino output pins? I thought the current was limited to something like 20mA?


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## marco1988 (Aug 9, 2009)

gswitter said:


> Interesting. I thought about trying something similar with an Arduino, but have never gotten beyond the what-if stage.
> 
> Can you drive high-power LEDs with the Arduino output pins? I thought the current was limited to something like 20mA?



40mA per pin.. just useful for testing with 5mm rgb leds.

With bigger loads you have to use mosfets.


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## snarfer (Aug 9, 2009)

I wouldn't worry about the location of the temp sensor on that heatsink. Just put it wherever you have space and then figure out what the relation is between the reading you get from the sensor and the actual temperature you want to measure. Chances are it will be pretty linear. Anyway with that all copper heatsink the temperature probably doesn't vary much more than a few degrees.


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## jeffosborne (Aug 10, 2009)

Nice project!

I've not seen a copper heatsink for a P4 before.

I know copper is an excellent heatsink, better than aluminum, but the fins on your unit are very short, compared to other P4 heatsinks I've seen.
Perhaps not enough heat is being carried away by your underpowered fan.
By the way it is okay to power the white LED's at 1.0 amp, but not the red ones - up to 700ma only.
Thanks for sharing your work!

Jeff O.


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## bshanahan14rulz (Aug 10, 2009)

I'm drooling over the heatsink, how nerdy is that?! 

I think it will be fine, since it is copper fins, big chunk of copper, and there is a fan, but it's all in the testing.


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## lolzertank (Aug 10, 2009)

This array is uh... AWESOME. I can't think of any word that's more appropriate.



bshanahan14rulz said:


> I'm drooling over the heatsink, how nerdy is that?!
> 
> I think it will be fine, since it is copper fins, big chunk of copper, and there is a fan, but it's all in the testing.



Drool over these: http://www.frostytech.com/top5heatsinks.cfm :naughty:


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## marco1988 (Aug 10, 2009)

hi!

heatsink temp with 6 whites @800mA is 45-50°C / 113-118°F with fan powered at 4volts. absolutely NO noise at all.

a little math:

room temp 25c
difference between room and heatsink = about 23c

now, let's suppose that ALL the input energy generates heat:

3.2v * 800ma * 6 = 15watts

so I suppose the heatsink, with fan revving @ 4volts, being about 1.5 c/w (am I right?)


if we apply full load (I can't test now, I have to build 4 current regulators<--tomorrow):

3.2v * 1a * 12 = 38.5watts (GBW)
3.4v * 700ma * 4 = 9.5watts (reds)

Tot= 48watts * 1.5 + 25c (room temp) = 97c (<-- heatsink temperature)
Considering a thermal resistance of 15c/w (junction->pad->pcb->thermal paste), led junctions temps would be under 135c (datasheet limit, excluding reds).
So, powering the fan at 6-7 volts would solve all the heat issues. (also considering that in a real scenario whites and all colors will never be at 100% all together!)

I don’t want to pwm the fan because I googled and found out that pwm switching frequency is too high and does not work well with brushless motors. And even if I decide to pwm it, now what I want is to find how power dissipation varies, in correlation with changes in fan speed.
Tomorrow I’ll try and let you know.

Sorry for my english, here in Italy it’s very late and I’m writing/sleeping at the same time


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## marco1988 (Aug 10, 2009)

jeffosborne said:


> Nice project!
> 
> I've not seen a copper heatsink for a P4 before.
> 
> ...



these are industrial heat sinks for industrial systems where space is a problem, but fan noise is not (small fan-->high noise)

this is for p4 2.2ghz max --> max tdp 50-55w



bshanahan14rulz said:


> I'm drooling over the heatsink, how nerdy is that?!
> 
> I think it will be fine, since it is copper fins, big chunk of copper, and there is a fan, but it's all in the testing.



drool over this:

all copper, very, very, very, VERY heavy. the center is a giant cylinder of copper 
(again.. from my father's office )






I think I'll stick a p7 on it


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## snarfer (Aug 12, 2009)

I din't think about the PWM frequency problem. Maybe you could try using a very slow PWM. I mean not using the built in PWM generator, but just a timer interrupt that increments a counter. I know when you have just one of the units running it will be pretty quiet, but once you get a whole bunch of them in one room, well the noise of the fans might start to get annoying.

Also, are you generating your constant current for the LEDs with some sort of buck converters? There are some Arduino projects out there on the web that did some things that are pretty much MOSFET destruction machines.


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## marco1988 (Aug 12, 2009)

snarfer said:


> I din't think about the PWM frequency problem. Maybe you could try using a very slow PWM. I mean not using the built in PWM generator, but just a timer interrupt that increments a counter. I know when you have just one of the units running it will be pretty quiet, but once you get a whole bunch of them in one room, well the noise of the fans might start to get annoying.
> 
> Also, are you generating your constant current for the LEDs with some sort of buck converters? There are some Arduino projects out there on the web that did some things that are pretty much MOSFET destruction machines.


please tell me more about these projects..

now i'm using lm317 to limit the current, and a small circuit that generates analog 450hz pwm, and this setup works flawlessly (but it's not so energy-efficient)

With arduino I think it would be ok to use an irf530 and lm317 as current limiter.. (or it's not ok?)

thank you very much.


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## marco1988 (Aug 24, 2009)

UPDATE:

beamshot with W, B, G @1A and R @ 700mA

astonishing!











color rendering is VERY VERY GOOD. (even better if I shut down Blues - not in these pics).











but.. heat dissipation is not sufficient, even with the fan at full speed. (it's a disaster!!!)

I'll cut out all the fins and use this heatsink as a copper plate to attach to a bigger hs.


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## John_Galt (Aug 24, 2009)

Looks like that has excellent color clarity. Even on the red's, which i've noticed tend to be lacking with most white LED's. Excellent idea! I hope you figure out your heatsinking problems. Good luck~​


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## snarfer (Aug 24, 2009)

Also you need to check out the heat dissipation on your PCB. You are using a linear dimming technique so the FETs will have to dissipate a lot of heat. Linear dimming is not recommended for power LEDs. Also check the temperature of the heatsink. What feels hot to you may actually be within tolerance.


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## uplite (Aug 24, 2009)

WOW, marco, _awesome_ project! :bow: 

I have a friend who lit his entire home theater with LED RGB clusters, DMX controlled, ~2 years ago...but they are _much_ lower power lights. Probably less than 100 lumens per cluster. I think he used about 20 of them. Color only. Halogens for white light.

You could light an entire room, color _and_ white, with just ONE of your arrays. 

I have a few comments/suggestions, plus some questions if you don't mind :

*1)* Your Rebel LEDs, do they have copper thermal pads? Can you _solder_ those pads to the heatsink? That would give much better heat transfer. :thumbsup: Thermal compound is actually a poor thermal conductor. It's OK for filling the air pockets between a CPU and heatsink, but that's about it.

*2)* The Rebel datasheet says that it can handle 1000mA max current, *but* _"Maximum Ratings limits are specified when applied singularly and for device operation not to exceed 60 seconds"_. So you probably don't want to drive it at 1A continuous... 

*3)* I am really curious about the driver circuitry. Can you post any photos or schematics of your driver, with the mosfets? What are you using for a power supply? :thinking:

*4)* I am also curious about your UI. Are you thinking hardware, or software? If you implement a DMX interface, you can use commercial lighting controllers and software. Very expensive though. Another approach is to control everything through a PC over wifi (so you can use, say, an iphone to control your color mix). 

*5)* Did you see the announcement for the new Cree MC-E RGBW LEDs? Each package has red, green, blue, and white LED dies. Here is *the datasheet*. I think I might get a bunch of these to do home accent lighting...maybe 4 packages per light. I also program Arduino for hobby microcontroller stuff. Will you share your source code? Feel free to PM me if you want to collaborate. I don't work for anyone. This is just my hobby. 

Ciao!

-Jeff


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## IMSabbel (Aug 25, 2009)

If i take it correctly, than the rebels are put on the heatsink with thermal compound, and then fixed with epoxy. 

That alone is already a very bad situation, as without pressure a far to thick compount layer will be betweem the pcb and the heatsink.

2nd, i cannot really imagine that HSF ever working for a P4. The fins are very short, and the aspect ratio wastes at least 80% of the fans possible airflow. 50W being too much for it seems entirely reasonable.

I have a similar power on one example design (was 4*P7 at 2.8A). Well. Exactly the same design power. I used a big-*** thermal pipe heasink mounted on the back of a 1cm lapped aluminium headspreader and screwed the stars on this heatspreader (until almost all thermal grease was squeezed out). Even though its a HUGE heatsink, and amoung the best rated ones on review sites, it still got pretty hot without a fan. To hot to touch, actually.


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## Oznog (Aug 25, 2009)

The thermal epoxy here is unlikely to be a significant thermal impedance, unless it's crappy epoxy.
The MCPCB is the BIG thermal impedance. Depends on the board, but it's typically quite significant. Unfortunately, soldering directly to the sink is not very practical. A decent thermal via board- with a LOT of vias per device- will greatly outperform MCPCB.

The Rebel Reds should not be run over 350mA. They have both a worse thermal impedance AND a higher derating at elevated die temps. I measured it and found that the output at 700mA is nowhere _near_ twice as high as at 350mA. It only increased a little, actually, and it's hard to get long life at 700mA continuous. Wasn't worth it.


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## Oznog (Aug 25, 2009)

Wait were the Rebels soldered onto the MCPCB, or glued on with thermal epoxy or simply floated with thermal compound?

Yeah, that would be all kinds of wrong. Rebels should be reflowed onto the MCPCB, for sure.


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## bshanahan14rulz (Aug 25, 2009)

Don't knock him for the way he mounted the LEDs. If you had 16 rebels, would you sand the backs of the emitters, scrape off the silicon on the topside, heat the entire heatsink, reflow all 16 LEDs onto it in exact position within 10 seconds, and then cool the heatsink? 

I think the way he mounted them is fine. 
He has rebels soldered onto mcpcb (ok, so fr4 w/ filled vias is supposedly better, but who has those?)
He has mcpcb pushed down onto a LAPPED heatsink with thermal compound
the stars are held in place with epoxy
the epoxy is heat resistant, so it should not loosten with time

I WILL say, though, that if you took the time to lap the sink flat, you could have mounted the emitters directly to the sink, provided you keep them from shorting out, but you probably bought the emitters already on boards.


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## marco1988 (Aug 25, 2009)

hi!

thank you all for your replies and for your attention and suggestions. 


-the way I mounted the leds is actually fine, because almost all the heat is transferred to the heatsink.
I'm not using thermal epoxy between mcpcb pads and heatsink, glue is only used to laterally fix the pads. pads are attached to heatsink through a very thin (and squeezed) layer of high performance thermal grease.

the thing that F***** me is that the datasheet of the heatsink says it is able to dissipate 50 watts.. and I don't understand why it isn't able to cool down my array which is outputting 30-40 watts (even with the fan at full speed).

The problem here is not thermal resistance between pads and heatsink.. it's the heatsink itself.

today I cutted all the fins on the heatsink, now my leds are attached to a beautiful shiny copper plate.. now it's time to find another heatsink (and do some math to prevent other wrong choices).

BRB to answer the questions some of you asked me some days ago.


ciao!


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## Illum (Aug 25, 2009)

forced cooling capabilities also has to do with the ambient air temperature as well, if its 80F in your room it won't add up to the cooling charts [Tj = 25C]

Also, you could try a box fan with the same size lengthwise to replace the existing fan, they usually run quieter on 12V and create more airflow than the slim style ones

If that still doesn't work, you could epoxy smaller finned heatsinks to the sides of your copper one and add a couple blowfans, just make sure your power supply is capable of at least one amp if your considering multiple blow fans as some draw more current than their flat brothers


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## marco1988 (Aug 25, 2009)

uplite said:


> WOW, marco, _awesome_ project! :bow:
> 
> I have a friend who lit his entire home theater with LED RGB clusters, DMX controlled, ~2 years ago...but they are _much_ lower power lights. Probably less than 100 lumens per cluster. I think he used about 20 of them. Color only. Halogens for white light.
> 
> ...



Hi Jeff!
1.Rebels are reflowed onto a 1x1cm mcpcb (AL) It seems to transfer heat very well. Pads are attached to hs the way described in the previous post.


2.the newest rebel white cri enhanced datasheet says they can be overdriven at 1A only for 60 secs, but the old general purpose white/color leds datasheet does not mention that thing. It says you only have to maintain junction temperature below 135c.


3.at the moment I drive them with a simple and inefficient lm317 (it’s a voltage-current regulator), but it wastes a lot of energy (heat). 
24v indistrial switching power supply, 6A max.
Lm3404 is the way to go.. inexpensive , very efficient and small. (look at the datasheet.. it has a very wide range of input voltage - it’s a step down).


4.At the moment the UI is hardware.. I wrote a simple sketch and uploaded on the arduino to try some ways to debounce buttons. I ended up with a very simple way to debounce using a system timer to compare the time of the last two actions on the same button.
At the time the sketch is very simple, there is no rgb automatic fading cycle, it only adjusts colors brightness when buttons are pressed (one button per color, first push UP, second push down, third push up, …). I also wrote a function to drive a piezo and emit different tones to indicate that the brightness is at MAX, MIN, ascending, descending.

BUT..

I just ordered the arduino ethernet shield. When installed (and libraries loaded), the arduino becomes a small ethernet server (or client.. if you want). Loading OSC libraries and adjusting the sketch allows me to control my lamp with an iPhone (with an app called TouchOSC). A PC is not required, the iphone communicates dircetly with the arduino board.

THIS is the way I plan to drive my lamp  (and in the near future, the led lamps illuminating the main room of my house).
Of course a minimal hardware UI is always required.

5.Cree RGBW, in my opinion, are not the way to go, because to achieve the right rgb color balance, you have to use 4 reds, 3 blues and 2 greens. It’s cool to have separate whites because you can put a lot of them (in cool white flavour) and adjust color temperature with reds and greens (but not in 1:1 ratio.. so having the same exact amount of red, blue, green and white leds does not help you).


6.I will share my code with CPF, but only once it’s finished (or at least a bit useful!).. now it is completely useless because iphone control is not implemented yet and it also lacks of some basic functions (automatic rgb cycle, switch between manual control and automatic cycles, random color, store the chosen rgb setting and restore it after a power-down, etc..).

If you have any other question feel free to ask me.
CIAO!
marco




IMSabbel said:


> If i take it correctly, than the rebels are put on the heatsink with thermal compound, and then fixed with epoxy.
> 
> That alone is already a very bad situation, as without pressure a far to thick compount layer will be betweem the pcb and the heatsink.
> 
> ...



Hi! thank you for your reply.

I tried to squeeze as hard as possible to make the compound layer very thin.. hope it worked.. led mcpcbs seem not to be hotter than the heatsink, and checking with a multimeter, during heatsink heat-up, led Forward voltage does not change much (0.2-0.3v, and very slowly --> I think this means heat transfer is good).

one more thing.. can you post some photos of your heatsink/array? I'm very curious.. I don't want to use a passive heatsink because my main goal is to make a wall washer (or table lamp, with a diffuser over it, removable) as small as possible.. so a quiet fan and the right heatsink is the best choice (I think..)


Thank you very much.


Ciao!

Marco


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## IMSabbel (Aug 25, 2009)

Was the HS shipped with exactly that fun, too?

Because the only application i have seen such a profile the last 5 years or so was for 1HE servers, which have their airflow horizontally...


I am 100% sure the people who sold that HS are lying *******s.

take a look how a heatsink looks like that was made cheaply for cpus using about 50W maximum power nearly 10 years ago:
http://geizhals.eu/a288668.html

The fact that the one from OP is copper doesnt really make any difference, because such short fins are not thermal conductivity limited anyways...


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## bshanahan14rulz (Aug 25, 2009)

Amazing! you do know that this has got some killer potential! home lighting that can be controlled by your iphone? :twothumbs Nice work


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## marco1988 (Aug 25, 2009)

IMSabbel said:


> Was the HS shipped with exactly that fun, too?
> 
> Because the only application i have seen such a profile the last 5 years or so was for 1HE servers, which have their airflow horizontally...
> 
> ...



the problem is.. this heatsink was ACTUALLY used to cool down 2+ ghz p4 in many products (industrial automation computers) of my father's company.. and it worked well.
Maybe I'm using the wrong fan..

bah.. this is no more an issue: that heatsink now is a beautiful shiny copper plate


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## uplite (Aug 25, 2009)

marco, thanks for the detailed reply! :thumbsup:

I have a few more comments if you want... 



> 1.Rebels are reflowed onto a 1x1cm mcpcb (AL) It seems to transfer heat very well. Pads are attached to hs the way described in the previous post.


Ah sorry, I did not read your original post closely enough.  My only other suggestion is to drill small holes in the Al boards and screw them tightly to the heat sink. But I understand this is not a problem right now.



> 2.the newest rebel white cri enhanced datasheet says they can be overdriven at 1A only for 60 secs, but the old general purpose white/color leds datasheet does not mention that thing. It says you only have to maintain junction temperature below 135c.


I would reduce the current anyway. Obviously heat management is a problem. Running at 1A is inefficient. Vf is higher, relative lumens are lower, heat is much higher...and the heat reduces the lumens even more, especially for the red LEDs. 

Maybe use the manufacturer's test current, 350mA? If you need more lumens, you can always add more LEDs/cluster...or more clusters around the room. That would also spread the lighting nicely. At 1A this cluster is an _extremely_ concentrated light source for a typical room. It seems more appropriate for outdoor or theater spot lighting.



> 4. ...I just ordered the arduino ethernet shield. When installed (and libraries loaded), the arduino becomes a small ethernet server (or client.. if you want). Loading OSC libraries and adjusting the sketch allows me to control my lamp with an iPhone (with an app called TouchOSC). A PC is not required, the iphone communicates dircetly with the arduino board.


Nice. 

If you plan to do multiple lights, you might still consider a PC for centralized control & coordination. A very old, very small laptop would do the job.

One reason to do this is to go wireless. Use XBee radio modules and you only have to wire the power to your lights. No Cat5/6 cable for ethernet. 

Another reason is that PC software is _much_ easier to program and customize. TouchOSC looks cool, but I don't know how much you can customize it. Say you want to select from a photoshop-style color picker instead of dials and sliders. Or if you want to coordinate multiple lights in a single action. A PC bridge gives you a lot of flexibility. You could also run a web server and expose the lighting commands on a web page. Then you could get to it from any computer, or any handheld device with a web browser.

I think your ethernet-iphone-touchosc setup sounds great. These are just some other ideas. 



> 5.Cree RGBW, in my opinion, are not the way to go, because to achieve the right rgb color balance, you have to use 4 reds, 3 blues and 2 greens. It’s cool to have separate whites because you can put a lot of them (in cool white flavour) and adjust color temperature with reds and greens (but not in 1:1 ratio.. so having the same exact amount of red, blue, green and white leds does not help you).


Gotcha. I guess it depends on the range of hues that you want to generate at full luminance. You could always generate more hues by dropping the total luminance.

I am attracted to the simplicity of fewer packages per cluster with the MCE RGBW...but I guess that's about it. I suppose it might be _worse_ for thermal management, and for optical diffusion, since the dies are so close together... :thinking:


Anyway...great project! :bow: Please keep posting as it develops!

-Jeff


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## marco1988 (Aug 25, 2009)

uplite said:


> marco, thanks for the detailed reply! :thumbsup:
> 
> I have a few more comments if you want...
> 
> ...




In this project efficiency is not my main target, so I think i'll keep with my 1A configuration, because in real usage only one-two colors will be powered at the same time, so the heat generated will be a lot less (I want to squeeze out all the lumens!) and will not be a limiting issue.

Lifetime is not a target, too (This light is only a prototype)


If everything goes well, I will pay more attention about lifetime and efficiency in my next project (room wall lights).

Touch OSC is easy to start with, because I already have all the required libraries to include in my C sketch.. and I don't have to learn Cocoa to program on iPhone.
Making a small webserver out of an Arduino is also possible.. I absolutely want to eliminate the need of a pc, I want something portable!



ciao!


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## uplite (Aug 26, 2009)

marco1988 said:


> I want something portable!


Efficiency is a good friend of portability... 

Speaking of portability...a wifi-ethernet bridge is a big chunk of hardware. Have you seen the *WiShield wifi shield*? 1Mbps/2Mbps, adhoc or infrastructure, TCP/IP, UDP, WPA/WPA2...and it runs on a 168! There's *a big thread* about it on the Arduino forum.

Thanks for pointing out Touch OSC...it is wicked cool!  I love the minimal interface...and the screen editor!! :twothumbs

Do you use recotana's OSCClass for Arduino? Or some other OSC library? Thanks.

ciao!
-Jeff


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## marco1988 (Aug 26, 2009)

uplite said:


> Efficiency is a good friend of portability...
> 
> Speaking of portability...a wifi-ethernet bridge is a big chunk of hardware. Have you seen the *WiShield wifi shield*? 1Mbps/2Mbps, adhoc or infrastructure, TCP/IP, UDP, WPA/WPA2...and it runs on a 168! There's *a big thread* about it on the Arduino forum.
> 
> ...



doh! wishield is awesome!!!!!!!!!!! (but it uses a lot of arduino pins..)

yes i'm using recotana's libraries.

ciao!


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## uplite (Aug 27, 2009)

marco1988 said:


> wishield is awesome!!!!!!!!!!! (but it uses a lot of arduino pins..)


Same as the ethernet shield...four pins for SPI (10-13), plus one pin for interrupt (2 or 8). 

I don't know if WiShield has interfaces that are compatible with the simple ethernet library. But OSCClass is very small, so it should be easy to convert. Assuming you _really_ want to parse OSC messages on your arduino. 

I wish I had a project that needs wifi, so I could try it!

-Jeff


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## bretti_kivi (Sep 2, 2009)

Ok, so your thoughts basically extend to "no blue"... which makes sense if you want a warm light. 

The idea of having either XBee or Wifi for light control is extremely attractive. I've had an Arduino here for too long doing nothing.. will have to look into making it do something 

There's no way I'd mount that many rebels onto a heatsink "that small"; remember that the TDP of a 3.0GHz P4 is up to 90W, but that's running those fans at full power and with a defined airflow. Probably running two fans, one at either end, one pushing and one pulling air, would work well.

Bret


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## HarryN (Sep 2, 2009)

Hi - very nice project and build.

I know some engineers at Lumileds, and we have various discussions about LEDs. The Rebels are a great product, but they strongly recommended to stay down around 700 ma instead of 1 amp. Keep in mind, they are the ultimate of conservative, but if you really want to drive at 1 amp +, that is what the K2 is intended for.

If you are interested in higher color quality, then one approach is to use even more LED colors. I know that in theory, RGB can cover the range, but you can do better if interested.

Something like
- 1 deep blue
- 1 cyan
- 1 green
- 1 amber
- 1 red orange
- 1 red

Doubling up on green is also good.

Fun project.

HarryN


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## bretti_kivi (Sep 3, 2009)

this PDF - http://www.crcc.cnrs.fr/IMG/pdf/DiodesElectroLuminescentes_AIC2005_Vienot-Mahler-Ezrati_en.pdf - also appears to point out massive gaps in the spectrum. I think maybe a quick check of the various wavelengths is in order....

Bret


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## rizky_p (Sep 3, 2009)

how much that driver cost you? intereseting


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