SparkFun Forums

[apullin]

OK, so, I've just been thinking about this a little bit, and I'm not a hot-shot EE, so I thought I'd ask for some feedback from you folks.
I see that Sparkfun sells some nice, powerful LED's, such as:
http://www.sparkfun.com/commerce/produc ... cts_id=603

And they have them in Red, Green, and Blue. I happen to have a light fixture at the top of my room with a big white diffuser with plenty of space inside it. My idea is to make a board with 3 each of R, G, and B LED's, and a small power supply, so the whole thing can plug into the socket directly. Will that be bright enough? (3W of LED's for any given color, that is).

As for control, I plan to just do PWM with some transistors via an olimex board, or possibly one of these Tmote Sky motes I have. PWM driving will work at that low a voltage, yeah?

[bigglez]

My idea is to make a board with 3 each of R, G, and B LED's, and a small power supply, so the whole thing can plug into the socket directly. Will that be bright enough? (3W of LED's for any given color, that is).

Greetings (No Name Supplied),

Bright enough for what? If the fixture has a type A bulb, 60W
120V for example then the LEDs will obviously not be as bright.
If you plan to turn the fixture into an art piece then the LEDs
are probably bright enough to be noticed but you may not get
the diffusion you expect with only three LEDs of each colour
inside the fixture.

As for control, I plan to just do PWM with some transistors via an olimex board, or possibly one of these Tmote Sky motes I have. PWM driving will work at that low a voltage, yeah?

That should work if you are seeking wireless control. The
fixture will require power all the time, which may not be the
case if it has a regular wall switch.

Comments Welcome!

[apullin]

Well, I'd actually like to run the normal lightbulb and the LED's in the same fixture, with a solid state relay or something to switch the light on and off. Yes, there is a wall-switch, so I'll just have it default to the standard bulb on a reset.

I'd like the setup to cast a signifigant colored light into the room when the main lightbulb is off. So, in the dark, to do this, I guess I don't need >that< much; but I'd still like it to be bright. Would the best solution be going to 5 or 7 or so (expensive!) of each color LED? Or maybe I'd be better off getting a huge bunch of super cheap LED's from a bulk supplier?


Failing wireless, I think I'd just run a couple of thin wires down the wall for rs232 TX,RX.

-Andrew

[bigglez]

Or maybe I'd be better off getting a huge bunch of super cheap LED's from a bulk supplier?


Failing wireless, I think I'd just run a couple of thin wires down the wall for rs232 TX,RX.

Greetings Andrew,

I'd opt for the large array of cheapie LEDs. You might
consider SMT types that you could put on homebrew
'breakout boards' that are in turn positioned in the
existing globe.

I did one recently with 64 LEDs in a 50mm x 50mm
array. Check it out!


Wireless comms would be slick.... Be careful if you mix logic
or comms wiring with AC house current in the same project.

Comments Welcome!

Peter

[apullin]

Hrm, your LED array is quite neat, but I am really just looking for sheer power. Looking on ebay, bags of blue LED's and such can be had, but 50 at 45 mcd each is going to add up slowly!

I think I might just design the board to use, say, 5 of each color of the Luxeon I LED's, but just start out with 1 of each, and see how it does in-situ.

Is there any special voodoo to LED power supply design? I guess it'd be different if I an using 1 or 5... because if I was using 5 then I could put the string (of each color) in series and not need such a high ratio transformer.