Concept: To design a light that mimics a color if shown to it. Design: lamp driver. LEDs are very efficient as they only emit one frequency of light, and because of this the light produced could be perceived as flat and lifeless. Instead i used tungsten bulbs because unlike LEDs they aren’t flat and lifeless. Because the Arduino cannot provide enough current to power a tungsten bulb without damaging the Arduino chip, I had to use transistors to turn a separate power source on to power the bulbs. This also meant that the lamp wouldn’t draw too much current from the laptop. To do this i connected the pwm pins to base of the transistors, and grounded the transistors to the Arduino’s ground in series with diodes to prevent current flowing back through the tungsten bulbs from the Arduino. Because i used the pwm pins i could dim the bulbs the same way one can dim LEDs in the Arduino code.colour sensor. Because I wanted the lamp to detect colors and mimic them, I prototyped a simple color sensor. To do this i connected three light dependent resistors (LDR’s) to the analog inputs of the Arduino, with a 10kohm resistor between them and ground to create a light-dependent voltage divider. I covered each of the LDR’s with a piece of red, green, and blue transparent plastic respectively. This meant that when light of a certain color fell on the LDR’s, it would be absorbed and measured differently by each of them, respective to color. Thus, a color value could be interpreted from the LDR’s and replicated with the tungsten bulbs.notes. At the moment, the color sensor only works effectively when a piece of cellophane is held over the sensor to color the light. In further development a lens could be used to focus images onto the color sensor, thus obtaining a more accurate color value.
September 5, 2007