Make your own £5 ambient TV backlight

After clearing out some junk, which included an old halogen desk lamp, I was thinking about putting in an LED light behind the PC monitor.

Then I remembered I’d bought a ring of 24 RGB LEDs from Aliexpress last year & hadn’t used it in a project.

I also had a spare Arduino Nano, and all the things I’d need to allow me to hook up a dial (potentiometer) for the light level, and button to cycle through different colour modes.

Here’s a quick video of it in action..

Parts

LED Ring – £2
Arduino Nano – £1.75
Breadboard & bits – £1.25

Wiring it up

It’s an easy one to wire up.. I took a few basic examples and mashed them together to get what I wanted from the design.

I’m not an electronics expert, and approached this like I approach software development; write it in manageable/testable chunks, which I can implement and test individually, then bolt it all together.

fritz-led-ring

The code for the project is pretty simple.. I think the most complicated bit is handling the button, which needed debounce functionality.

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
#include <avr/power.h>
#endif
#define PIN 6 // pin on the Arduino is connected to the LED ring
#define NUMPIXELS 24 // Number of pixels on the LED ring
#define POT_PIN 0 // Potentiometer pin
#define BUTTON_PIN 2 // Button pin
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
int showType = 0;
bool oldState = HIGH;
void setup() {
pinMode(BUTTON_PIN, INPUT_PULLUP); // Declare pushbutton as input
pixels.begin(); // This initializes the NeoPixel library.
}
void loop() {
// Read the potentiometer value and translate to how many pixels we want to illuminate
int value = analogRead(POT_PIN);
value = map(value, 0, 1023, 0, 25);
// Switch colours if the button is pressed
bool newState = digitalRead(BUTTON_PIN);
if (newState == LOW && oldState == HIGH) {
delay(20); // Short delay to debounce button.
// Check if button is still low after debounce.
newState = digitalRead(BUTTON_PIN);
if (newState == LOW) {
// Cycle through different colour schemes
showType++;
if (showType > 8) showType=0;
}
}
oldState = newState; // Set the last button state to the old state.
uint32_t color = pixels.Color(255,255,255); // default to white when first booted
if (showType==1) color = pixels.Color(0,0,255); // blue
if (showType==2) color = pixels.Color(0,255,0); // green
if (showType==3) color = pixels.Color(255,0,0); // red
if (showType==4) color = pixels.Color(0,127,255);
if (showType==5) color = pixels.Color(255,127,0);
if (showType==6) color = pixels.Color(255,0,127);
if (showType==7) color = pixels.Color(0,255,255);
if (showType==8) color = pixels.Color(127,127,255);
// Illuminate X pixels depending on how far the potentiometer is turned
for(int i=0;i<NUMPIXELS;i++){
if (i<value) {
pixels.setPixelColor(i, color);
} else {
pixels.setPixelColor(i, pixels.Color(0,0,0)); // Don't show anything
}
}
pixels.show(); // This sends the updated pixel configuration to the hardware.
}

And here are a few pictures of it in place behind the PC monitor..

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