I'm looking to control LEDs for room lighting with my Arduino, both white and RGB. Since they will be used in ceiling fixtures, I'd want something that won't have problems lighting a 12'x12' room and also won't burn out after a few hours. What are recommendations for something this bright, and a PWM chip to power them. I've managed to get a low power RGB working, but now I'm ready to move up. I do additionally have a power supply for the LEDs as I imagine they might pull a few amps.
You can find 3W & 10W LEDs. Most of the high-power RGB LEDs I've seen are 3W, most of the 10W LEDs I've seen are white.
10W might be enough, but look at the lumens and compare to an incandescent bulb. IIRC, a 100W incandescent bulb is more than 1000 lumens. If the LED is rated in mcd, you'll need to find the conversion factor.
I'm guessing you'll need more than one LED. The LED bulbs you buy at the hardware store to replace light bulbs normally have multiple LEDs inside.
I do additionally have a power supply for the LEDs as I imagine they might pull a few amps.
In general, you need a special [u]Constant Current LED Power Supply[/u]. Dimmable LED power supplies are usually dimmed by a 0-10V DC control voltage, or 10V PWM.
These constant-current power supplies use a switching design, and they are nearly 100% efficient. You can build or buy one, but switching power supplies aren't that simple to build. A series current-limiting resistor like you use with a standard LED or a linear (non-switching) transistor/MOSFET regulator is usually less than 50% efficient, with more power being consumed by the series resistor (or transistor/MOSFET) than is consumed by the LED.
If you want to control each color independently, you'll need 3 power supplies. You can connect white LEDs in series and they can all share a constant current power supply. RGB LEDs can't be connected in series, since all 3 LEDs in the package share a common anode or cathode (4 wires for 3 LEDs). So, using multiple RGB LEDs might require multiple power supplies, and this could get complicated and expensive.
and also won't burn out after a few hours.
High power LEDs need to be heatsinked, but as long as they don't heat, and as long as they are not over-powered (with too much current or voltage), they should last a long-long-long time!
P.S.
Another possibility is a "stage" or "DJ" light ([u]example[/u]). These things are AC powered and [u]DMX[/u] controlled. You can build a DMX controller around the Arduino (or you can buy one).
DVDdoug:
In general, you need a special [u]Constant Current LED Power Supply[/u]. Dimmable LED power supplies are usually dimmed by a 0-10V DC control voltage, or 10V PWM.These constant-current power supplies use a switching design, and they are nearly 100% efficient. You can build or buy one, but switching power supplies aren't that simple to build. A series current-limiting resistor like you use with a standard LED or a linear (non-switching) transistor/MOSFET regulator is usually less than 50% efficient, with more power being consumed by the series resistor (or transistor/MOSFET) than is consumed by the LED.
This is to avoid wasted power from inefficient components?
FuzzyWombatSoup:
This is to avoid wasted power from inefficient components?
Indeed. And wasted power also represents undesirable heat dissipation.
Note something that not infrequently tricks novices. If you want to dim LEDs using a constant current power supply, you must use a power supply that has the dimming circuit built in with a separate control input.
You absolutely cannot dim a constant current (switchmode) power supply using PWM and indeed, you should not switch them on the output side in any case.