I have an Arduino Mega that I used to control the output of a series of LED based on the color in front of a camera. The arrangement is shown in this Dropbox link:https://www.dropbox.com/s/ynbtwewrc8o4yc6/ArduinoCameraLED.bmp. Basically the micro-controller gets the RGB value of the image passed (range 0-255) to it by the camera and used this RGB value to set the color display by the RGB LED strips.
Now there are two problems I have:
 With the help of three MOSFETs, pointed to with arrow in the link, the LEDs are powered from the Vin of the Arduino, the problem is, as the number of the LED strips increases, the brightness gets worse (normal right?). Is there a way to power the LEDs from outside the Arduino and still be controllable by the Arduino?
 To improve the brightness, I went for this LED amplifier:http://www.usledsupply.com/shop/rgb-mini-amplifier-ttl.html. Which really gives a better brightness with the number of strips that I have, but there are two problems. ---[2.1]The output of that LED amplifer is in the range 0-100%, with 0 being the brightness and 100% being the dimmest. But the RGB outputted by the camera, which Arduino will pass through the amplifier is in the range 0-255, where 255 is the brightest. The question is, how do I cast the values from 0-255 to 100-0? Everything works fine without the camera.
---[2.2] I observed that the response of the LED to the change of image in front of the camera is terribly slowed (as if there is no response) with this amplifier, compared to my initial arrangement with bare-bone MOSFETs. What could be wrong?
Apology for the long questions. Any help will be very much appreciated. Thanks to you all in advance.