With this gadget, you can visualize the additive color mixing of red, green, and blue. Pressing the button changes the color of the LED underneath. The gadget can be attached to a whiteboard using the magnets. Power is supplied via a USB-C connector.

Material:

• Arduino Nano with USB-C connector.
• LED-RGB-Strip with three LEDs (35mm between the LEDs)
• three buttons (12mm x 12mm)
• cables
• 5x magnet(height: 2mm, radius: 3 mm)

Connections to the Arduino:

Button 1: D5 and GND
Button 2: D4 and GND
Button 3: D3 and GND
LED Strip: 5V, D10 and GND

Arduino Code:

'#include
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(3,10,NEO_GRB + NEO_KHZ800);
int buttons[] = {5,4,3};
int colors[] = {0,0,0};

void setup() {
pixels.begin();
pinMode(buttons[0], INPUT);
pinMode(buttons[1], INPUT);
pinMode(buttons[2], INPUT);
digitalWrite(buttons[0],HIGH);
digitalWrite(buttons[1],HIGH);
digitalWrite(buttons[2],HIGH);
pixels.setPixelColor(0,pixels.Color(0,0,0));
pixels.setPixelColor(1,pixels.Color(0,0,0));
pixels.setPixelColor(2,pixels.Color(0,0,0));
pixels.show();
}

void loop() {
for (int i=0; i<sizeof(buttons);i++){
if(digitalRead(buttons[i]) == LOW){
colors[i]++;
if(colors[i] == 4){colors[i] = 0;}
switch(colors[i]){
case 0:pixels.setPixelColor(i,pixels.Color(0,0,0));break;
case 1:pixels.setPixelColor(i,pixels.Color(255,0,0));break;
case 2:pixels.setPixelColor(i,pixels.Color(0,255,0));break;
case 3:pixels.setPixelColor(i,pixels.Color(0,0,255));break;
}
pixels.show();
while(digitalRead(buttons[i]) == LOW){
delay(10);
}
}
}
}