RGB LED controller/dimmer

[Someone Electro]

A heatsinked luxeon can pass up to 1500mA.You would need hell lot of 10mm to achive that kind of power.And yes you wouldnt need a heatsink becuse the surcae area of the plastic cases and the coper wires would be so big to act as a heatsink.

But the Luxeons dosent realy need a all that huge heatsink.meaby if you run them on some old CPU heatsinks whithout the fan.

 

[Tarsil]

I agree that is a lot of power. Those LED's disipate 1W or so. Don't believe every thing told by the manufacturer. 1.5A at 2.8V+ .....come on. Works if u have a very good cooling sistem and a duty cicle of what...5%?
Read this https://www.electro-tech-online.com/custompdfs/2006/11/AB11PDF.pdf
And this https://www.electro-tech-online.com/custompdfs/2006/11/AB05.pdf
They are optimistic.
At 105C the leds wont last for long
The luxeon are simply great things (don't get me wrong) but have their limits.

 

[Someone Electro]

Well the K2 can.They produce 100 Lumens of light.

 

[Blueteeth]

Hi,

Someone electro, and Tarsil, good to see you guys discussing this..'power' is really out of my field, I'm more of a 'control freak' I guess its a careful balance of efficiency, reliability, cost, and size (who wants to use 700 5mm led's?).

As for 'viewing angle', I wouldn't worry, I doubt very much that any 'commercial' devices would use the LED's 'as is', they would probably put them in a diffuse enclosure, or at least behind some frosted acrylic to mix the colours better and scatter light. The luxeons seem like a good idea, although, as tarsil pointed out...they do disipate a lot of power as heat. Maybe I'm missing the point here, but I always though that the reason some LED's can take more current (and therefore, be 'brighter') than others was purely down to how much current they could take and for how long....and this would be down to heatsinking. The luxeons are designed specifically to disipate heat in a certain way, and from the app notes i've read, careful PCB design should be used for non-heatsinked ones. And they often quote 'peak power', not continuous. I mean, if you pulse a standard 5mm LED with a massive amount of current (within its limits), and give it time to cool..it can be used as a flash for a camera, now THATS bright.

I ismply don't have the money right now to buy up some 'super LED's' and test em. I do'nt know if anyone has seen these 'strips' of LED's, enclosed in a translucent tube, they seem to do the job quite nicely:

**broken link removed**

Of course, you could design your own control circuitry/power driver, And I'm not sure if they are what you are after, but I've got a few of the LED's used there and they are BRIGHT. Not luxeons, but for size, they do the job nicely.

Anyway, as I said, I'm a bit out of my depth when it comes to working out the right 'lumens' needed, because you can't really compare LED's to incadesant lighting, with light scattering, efficiency, plus the fact that our eyes have different sensitivity to different wavelengths, so blue and red won't appear as bright as yellow/green.

Keep it up!

Blueteeth.

 

[Tarsil]

Good point Blueteeth. I was just pointing that 1 luxeon can give as much light as 5-6 10mm (10mm!!!!!!! ) LEDs. I can buy those at @.20$ or less/piece at higher qt (25+ or so). Also I can PWM drive those at 50-55mA and 50% Duty Cicle whithout any problem ..any!!!!!. A luxeon K2 can be driven at 1,5A for a v short period with good heat sinking (the 5mm LED flash is a good example). U can cont use the luxeon at 300-350mA tops with a bit too much heat.
The link given by Blueteeth is a perf example about puting togheder lots of leds. Those 5-6 10mm LEDs will be cheaper, more reliable, less hot!! and whithout any heatsinking will ocupy same space.
Of course Philips wil point out peak values (duuhhh) like any company...is a psichological impact (1,5A for a LED!!...Damn ..is cooooool ). The 1.5A isn't a lie ..technicaly speaking .
BTW.....I got the 'control freak' virus too :LOL

 

[Someone Electro]

No 1500mA is continues curent.Luxeons dont realy like high curent pulsing but pusling wont help when you need to light a room.Also you will only be pulsing it lower then the max continues curent becuse you are not pulsing it in PWM for the purpuse ot gte more curent trough but for the purpuse to lower the power output.

Shure you will light up a bathroom whith 10mm LEDs but you will need afuly a lot to make enugh output to properly light the bathroom.So in the end it would be way biger than when using luxeons.Also if you jam lots of small LEDs togeter you evetuly also get a heating problem.

Its just not posible whith todays technology to make a compact non heatsinked and powerful enugh LED light.You would need to use rediculusly a lot of small LEDs that would have to be placed a part a bit to prevent heat build up.

You will even need multiple luxeons to properly light the place up.I think 2 RGB blocks would do it.

 

[audioguru]

You can't light a bathroom with LEDs.
I use LEDs in flashlights (torches to the brits) and mood lights.
I use 60W of compact fluorescent light bulbs in my bathrooms. I used to use 240W of incandescent light bulbs.
Light bulbs are bright and shine all around. LEDs shine brightly in a single direction but are very dim if they are behind a diffuser.

 

[Blueteeth]

Hi,

Well, as I said, I'm steering clear of the 'power' issue. I'm sure you could light a bathroom with led's.....of course you can. As for whether it can compete with other forms of lighting, or just how many LED's it would take (ammount, cost etc..) I just don't know. I could work with lumens and plug in the numbers but I think it might be beneficial to use 'standard' lighting >as well< as the RGB unit, to give colour, but also illumination, just change the 'tint' of that illumination.

Blueteeth.

 

[Someone Electro]

I think 2 packs per Red Green and Blue should do.The best luxexons are 5W so that 30W of power.We light our bathroom whith a 20W compact flurescent bulb.

 

[Bronx68]

BlueTeeth,
I believe there is a relationship between the dimming and color level. Several Engineers believe it is color level x dimming level = total number of bits required. Is this your observation? What have you seen to substantiate this?

 

[audioguru]

LEDs are not suitable for lighting a room.
They are tiny extremely bright dots. You don't want the glare shining in your eyes.
Some LEDs are very directional so only the top of things will be lighted.
Thousands of dimmed, diffused LEDs would be needed.

My bathroom uses four 13W compact fluorescent bulbs. They are behind a diffuser. Some light comes through the diffuser and most light reflects from two walls and the ceiling. They do not produce glare.
Try to make 52W worth with LEDs then start counting them all.

 

[TrevorP]

Yeah audioguru raises a really good point. Most bright LED's have a very thin projection cone. So lighting a room would actually be pretty awkward. Now you could probably use them to light a hot tub or something...that could be kind of cool.

 

[Hero999]

Also fluroscents are more efficient than LEDs when a diffuse light source is required.

LEDs are only good for direct light sources or for when your desire a certain colour.

 

[Blueteeth]

Hi again,

Good to see this topic rearing its colourful head again...

I still say one could light a bathroom, competing with flouresant lighting..it is simply a question of whether its worth it or not, and how long one wishes to solder up LED's. As for LED's being 'direcitonal', As far as I'm aware, aside from certain specific power LED packages (with relfective cones), it is only the shape of the epoxy case that determines the viewing angle.

When I have used LED's to make pretty flashy things, lighting , as opssed to panel indicators etc.. I have always epoxied them into a lightguide. Be it sideways, or direct with a diffuser. That usually bumps up the angle to a good 120 degree minimum, and ensures a thinner panel with even lighting. Note: for RGB led's, or RGB arrays this is a must...as to get colours to mix properly 'within' a fitting is tough.

I looked at my last post, and for once I made a half-decent point If one was to light an entire room purely with LED's (colour changing) then with pure Red Green, or Blue it would look quite offensive to the eye. Using standard white lighting WITH an RGB LED array would allow you to change the tint, without going 'pure green'. Still colour changing, and all 'radical' but it would simplify construction, keep some form of practicality to the scenario...as in you could just use the standard lighting when you're not feeling all *wacky* but still keep most of the control.

Bronx, sorry for the late reply. I am not sure I fully understand your question about PWM dimming. I *think* what you are refering to is the way in which RGB controllers control 'colour' and 'brightness' seperately. That is, 'colour' is determined purely by the ratio of the PWM duty cycles between R,G and B. Where-as 'brightness' affects all the led's at the same time, by equal amount.

So, say for example we want 8-bit colour (255 colours)..with a 16 level dim. You can multiply the dimming value by the PWM value of each LED. Therefore, dimming the array without changing the colour. I have done this myself, both with binary multiplication and PWMing a PWM signal ...2Khz for colour, gating another PWM of 50Khz. Although depsite all that, I would use a controlled current source to dim the array. (don't use it with white LED's as they change their colour over current).

Blueteeth