Switching 12V  LED stripe with brightness control?

Hi all,

after playing around a bit with my Arduino, I finally found something with building with it. In my new flat, I'd like to create a nice little background lighting for the combined home cinema screen/DVD storage area..

What I've got here are LED strips I bought with an order in Hong Kong which were pretty cheap, but they can be split every few LEDs and all the parts run on a 12V power supply.

Now I've got two questions which might have been answered a couple of times, but I wasn't able to find any relevant threads:

  1. How would I go about switching those stripes on and off? As far as I read, a relay or optocoupler could do the trick, but I'm not sure about the specs needed for that. What would I have to look for to be able to trigger it from the Arduino and have it switch on a 12V circuit? Same goes for the optocoupler which might last longer(no moving parts) and maybe it's also quieter..

  2. Is it possible to dim the LED stripes or do they have to be specially designed for that? I could think of some nice effects if it were possible to slowly fade the lights on and off. But that would rule out the relay, wouldn't it? Because it would only switch the 12V supply on and off.

Regards, Andre

You could use transistors.

Transistors provide solid state switching, and can adjust their output based on the electricity being applied to its "Base" (from an Arduino PWM pin).

I think Grumpy_Mike might have a page on his site somewhere about relays, but I can't find it.

Here's his site: http://www.thebox.myzen.co.uk/

Good luck!

For the archives, this is the page: http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

It shows how to switch a 12V power supply on and off from the Arduino.

But it wouldn't allow me to control the brightness of the LED, unless I used something like PWM, but I'm scared it might stress the power supply too much or doesn't it?

Another question would be: What specs should I look out for when buying the transistor?

Check here for one relatively simple way of doing it:

http://genericnerd.blogspot.com/2009/05/arduino-mood-light-controller.html

Wonderful, exactly what I was looking for and 1.23EUR for 7 switches on that ULN2003 surely isn't expensive :-)

Thanks a lot.