I tried the transistor. It doesn't work. Plus the fact that the strip needs constant voltage in order to store the data. Each tm1803 has 24 bits of memory. Just like regular ram, the memory is reset when power is lost.

Unfortunately no. That would be too easy. A pwm's max voltage is 5v but the strip needs 12v in order to run properly. I am exploring different options. If the op amp doesn't work I will be attempting to try a digital pot.

Start Here: http://arduino.cc/en/Tutorial/Midi. It may give you ideas on using a standard midi port with the arduino.
From there you can start playing with using the Arduino to receive midi codes from the controller through an analog pin.Look at this Instractable: http://www.instructables.com/id/Send-and-Receive-MIDI-with-Arduino/.

Finally you can write your code that takes the midi codes and values and responds with the correct display ion the led strip.

You need an led driver. It is a similar thing to controlling an LED cube that has 125 (5x5x5 cube) or more leds using an arduino. Start your searching there.

Sorry. Away from home. The change in the voltage can change how bright the leds are by changing the input voltage. I attached a pot to the 12 volt wire for the strip and changing the resistance changed the brightness.

Is there a way that the 0-12 voltage can be a smoother line.

I attached an image of the graph.

Basically the blue line is the input voltage and the red is the output. The gain is 2.4.
For example when the blue line is at 5v the red is at 12v and when the blue is at 0v the red is also at 0v. All of the values in-between are proportional between the red and blue lines with a gain of 2.4. Can an Op-amp be used to accomplish this?

Alright. I'm back. So I bought a generic op amp and am following one of the schematics for voltage scaling but it is making the voltage smaller instead of larger. Can anyone tell me how to scale a 0-5v signal to a 0-12v signal using an op amp?

After some more research and tinkering, I think that I will end up using an op-amp to scale the voltage from a 0-5 range to the 0-12 volt range I need.

Yes but if the signal on the input is a low bit for longer than 20 microseconds it sends a reset code. This is the issue I had before. For instance if I had a color 0xFFFFFF, extracting the RGB components, multiplying them by the correct brightness scale and then concatenating them together took too long and therefore sent a reset signal to the chips.

If you have another idea on how to adjust the color, I would be more than happy to hear it.

Here is the "sendColor" function that I have in my code

void sendStrip(uint32_t data){

  int i;
  unsigned long j = 0x800000;
 
  for(i = 0; i < 24; i++)
  {
    if (data & j)
      {
      OnBit;
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");   
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      OffBit;
    }
    else
    {
      OnBit;
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");
      __asm__("nop\n\t");   
      OffBit;
    }

    j >>= 1;
  }
}

OnBit sends a high value to the analog pin
OffBit sends a low value to the analog pin

The groups of "nop"s are delay functions that send the bits to the ic.

Here is the LED strip's documentation as well:

http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/2760249_PM_EN.pdf

alright. Ill have access to a new board tomorrow. Ill see if the PWM and led strip work together. I am thinking that if the power is off for too long, the strip will reset(uses a tm1803 led driver). Im also looking into using a mosfet as a variable resistor.

Crossroads: in reply to your post, the tm1803 has 3 output channels meaning a single ic can control 3 single color leds or 1 RGB led. In my case, its the latter of the two meaning that any change in signal needs to be applied 3 times, once for each color channel. Since Im building an audio visualizer, the brightness changes every loop and since the tm1803 is time based, the calculations to change the color is too slow for the strip to be correctly set to a color sequence (trust me because I did this just before I blew the capacitor on my Uno).

The code is already written. Unfortunately I fried my Uno when I was testing a different idea. Do I use a capacitor in conjunction with the transistor to keep a steady,variable voltage going to the led strip? If so, how much (Again, new to circuit building).

The Transistor seems like a good idea. The 1 meter strip I have has the capability of lighting up individual lights instead of the whole strip being one color. It uses a TM1803 chip to control the led colors. The only problem is that if power is disconnected, the whole strip resets. Is there a way to maintain a constant power to the strip using a transistor connected to PWM?

I have an RGB LED strip from Radio Shack and I am making a visualizer. I am new to circuit building (not programming) and am trying to figure out how to dim the LED strip with one of the digital or analog pins. The only issue is that the strip requires 12vDC to run properly and if I recall correctly, the max for any one of the pins is 5vDC. I have looked at JFETs, Digital POTs, or making a jerry-rigged one by combining a flat led with a photo-resistor. My question is: How can I control a 12v current (I would like to be able to control the output voltage from between 0-12 volts) using a 5v pwm signal.

Thanks