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Topic: Another LED dimmer project (Read 4315 times) previous topic - next topic

ks

I have bought a few of these LED strips:
http://www.dealextreme.com/details.dx/sku.41016

12V/1.8W - each strip has 12 blue 5050 LEDs

I want to use these in an aquarium as a moonlight. To get even lighting, I may use 2 or even 4 strips dimmed down.
Now, 1.8 watts at 12V is .15A = 150mA for each strip, right?

What components do I use between the Arduino and these if I want to avoid damaging both parts? I will get a couple of 3021 BuckPucks for some other experiments, but is this "overkill" just to run up to 4 of these strips?

I also have some ULN2003A, can I connect that to PWM and run a constant current source such as http://www.dealextreme.com/details.dx/sku.13557?


retrolefty

You can just use a simple NPN power transistor to switch all those led assemblies at the same time. Either just with on and off commands using digitalWrite() commands or vary the brightness by using a PWM supported output pin and using the analogWrite(pin, value) command. A TIP120 is a cheap popular choice of switching transistor. Wire it's emitter to ground, it's base wired to a series 500-1k ohm resistor with the other end of the resistor wired to the output pin. Wire all the +12vdc wires of the led assemblies together and then to your 12vdc source voltage. Then wire all the - leads of the led assemblies together and then wire it to the collector of the transistor. Finally run a wire from arduino ground pin to the - terminal of your +12vdc power source. The power source must be rated for the total current of all the led assemblies totaled.

Lefty

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