I have a RGB LED strip (Common +) that I want to drive using a controller that expects the strip to also have a W (White) channel.

So what I am basicly looking for: As soon as the controllers W output is HIGH I want all three R, G and B inputs on the strip to be driven HIGH.

How would I realize this? I could insert diode's between the RGB lines and connect the W output of the controller to all three strip inputs, but then I would have a voltage loss.

  • \$\begingroup\$ You only care about a voltage drop if you're running with a constant voltage supply. Most LED supplies are constant current. However, because of that you won't be able to run parallel LEDs (R/G/B) off one (W) output safely. \$\endgroup\$ – Majenko Feb 24 '15 at 13:20

Just use 3 diodes to pull the R, G, B lines LOW when the white channel turns on. I'm going to assume that your LED strips run from a 12V rail. Because the voltage drop across the resistors inside the strip is fairly small, I'd suggest using Schottky diodes. MBR140 is good for 1 Amp continuous but you may need larger diodes depending upon how much your channel current is.

Simply connect the cathodes of all 3 diodes together and to the (W) output of your controller, connect each of the anodes to the same point as the R, G, B outputs of your controller.

  • \$\begingroup\$ Thanks, I am going to order some and have a look at it, will report back! \$\endgroup\$ – peterrus Feb 25 '15 at 12:49

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