{"id":268,"date":"2013-08-04T05:44:00","date_gmt":"2013-08-04T05:44:00","guid":{"rendered":"http:\/\/dbbd.sg\/blog\/uncategorized\/simple-colour-changing-ambient-lamp-arduino-3-led\/"},"modified":"2021-05-14T14:18:10","modified_gmt":"2021-05-14T14:18:10","slug":"simple-colour-changing-ambient-lamp-arduino-3-led","status":"publish","type":"post","link":"https:\/\/dbbd.sg\/blog\/2013\/08\/simple-colour-changing-ambient-lamp-arduino-3-led\/","title":{"rendered":"Simple Colour-changing Ambient Lamp (Arduino + 3 LED)"},"content":{"rendered":"

\"P8034922\"<\/p>\n

In this continuation of posts on learning to do the most basic of things with the Arduino, the next experiment I made was a colour-changing lamp with 3 different LEDs. I followed this simple instructable<\/a> but edited slightly. I noticed there were lots of “#define” in the instructable – it seems that #define<\/b> is something from C that is for defining a constant. What is the difference between using #define and int to define which pins each LED is controlled via? Well in practice nothing much seems to be different except the conceptual difference is that #define is for defining a CONSTANT whereas technically speaking an int would be initialising a VARIABLE that can be changed later on in the program, although in this case we don’t really intend to change the pin number. But we could, if we wanted to.<\/p>\n

Things with # in front of them like #include<\/b> and #define<\/b> are preprocessed before the program compiles. Also, apparently #define does not take up any program space, whereas int is stored as variable in RAM. For more info see this wiki entry on C Preprocessor<\/a>.<\/p>\n

Colour Changing Lamp<\/h1>\n

For this you’ll need: an arduino uno, 4 jumper wires, 3 LEDs of different colour, and 3 x 330ohm resistors<\/p>\n

int delayTime = 2;\r\nint maxBrightness = 255;\r\nint redPin = 9;\r\nint greenPin = 10;\r\nint bluePin = 11;\r\nint red = 0;\r\nint green = 170;\r\nint blue = 170;<\/pre>\n
\/\/ Indicates whether a color will be incrementing (1) or decrementing (0) in brightness
\nint incR = 1;
\nint incG = 1;
\nint incB = 0;<\/p>\n
void transition()
\n{
\nif (red >= maxBrightness)
\nincR = 0;
\nelse if (red <= 0)
\nincR = 1;
\nif (green >= maxBrightness)
\nincG = 0;
\nelse if (green <= 0)
\nincG = 1;
\nif (blue >= maxBrightness)
\nincB = 0;
\nelse if (blue <= 0)
\nincB = 1;<\/p>\n
if (incR)
\nred++;
\nelse
\nred–;
\nif(incG)
\ngreen++;
\nelse
\ngreen–;
\nif(incB)
\nblue++;
\nelse
\nblue–;
\n}<\/p>\n
void setColor()
\n{
\nanalogWrite(redPin, red);
\nanalogWrite(greenPin, green);
\nanalogWrite(bluePin, blue);
\n}<\/p>\n
void setup()
\n{
\n\/\/ do nothing
\n}<\/p>\n
void loop()
\n{
\ntransition();
\nsetColor();
\ndelay(delayTime);
\n}<\/p>\n
\"ambientled_bb\"